Laboratory work on material science 1. Protective material science.docx - Collection of practical and laboratory work on material science
1st semester
1. "Analysis of the crystalline structure of metals and alloys" (No. 1, workshop 2). 2 s.
2. "Test materials for hardness" (No. 10, workshop 2). 1 s.
3. "Testing for stretching samples" (№11, workshop 2; or "mechanical properties of structural materials", a separate file). 2 s.
4. "Determination of the shock viscosity of the material" (No. 12, workshop 2). 1 s.
5. "Fractographic analysis of the destruction of metal materials" (No. 9, workshop 2). 1 s.
6. "The influence of cold plastic deformation and temperature of recrystallization on the structure and properties of metals" (No. 4, workshop 1). 2 s.
7. "Thermal analysis of alloys" (No. 1, workshop 1). Part 1 - Constructing a diagram of the state of the "zinc-tin" system by the thermal method. Part 2 - Analysis of dual alloys status diagrams: perform an individual task under paragraph 5 to the "Report Content". 2 s.
8. "Macroscopic analysis (macroanalysis) of the structure of metallic materials" (No. 2, workshop 2). 1 s.
9. "Microscopic analysis (microanalysis) of the structure of metallic materials" (No. 3, workshop 2). 1 s.
2nd semester
1 (10). "Microscopic analysis of metals and alloys. The structure of carbon steel "(No. 2, workshop 1) or similar work No. 7" Investigation of the structure of carbon steels in an equilibrium state by microanalysis ", workshop 2). Practical part: Students look at the MM-7 microscope of the structure of four alloys of iron-carbon: technical iron, doevtectoid, eutectoid and zaletetoid alloys. Make schematic sketches, signed structural components, an example of steel grade is given, for a deetectoid alloy, the carbon content formula is calculated. 1 s. + t. 2 (11). "The diagram of the state of iron-carbon. Structure, properties and use of iron "No. 3 of workshop 1) or similar work No. 8" Investigation of the structure of carbonous castoffs by microanalysis "from the workshop 2). Practical part: Students look at the MIM-7 microscope structure of three cast irons: gray cast iron with fine graphite graphite on a pearlite basis, high-strength cast iron on ferrito-pearly-based and deetectic white cast iron. Unfortunately, no more. Also make sketches, they write the names of cast iron and structural components. 1 s. + t. 3 (12). "The influence of the cooling rate on the hardness of carbon steel" No. 20 of the workshop 2). Practical part: Four samples of steel U8. One is exposed to annealing, the second - normalization, the third - quenching in oil, fourth - quenching in water. Hardness is measured, a graph of hardness dependence on the cooling rate is built. Cooling speed values \u200b\u200bare taken from the table in laboratory work. 2 s.
4 (13). "Hardening carbon steels" No. 5 of the workshop 1). Practical part: Three samples from steels 20, 45, U9 are hardened in water, one sample of steel 45 is hardened in oil. Measure hardness to (HRB) and after (HRC) quenching. The convene table is determined by hardness in HB units. According to the results, two graphics are built: hb \u003d f (% c) and hrc \u003d f (Vochl.). 2 s. + t.
5 (14). "Vacation of steel" No. 6 of the workshop 1) or similar work No. 18 "Vacation of carbon steel" from the workshop 2). The practical part: practicer 1) is carried out low (200ºС), medium (400ºС) and high (600ºС) vacation of tempered samples made of steel 45 and low leave (200ºС) of the tempered sample from steel U9. Measure hardness. Build a graph HRC \u003d F (Totp.). According to Workshop 2), there is a low, medium and high vacation of tempered samples from steel U8. 2 s. + t.
6 (15). "Annealing and normalization of steel" No. 7 of the workshop 1). Practical part: two samples of steel 45. With one is carried out isothermal annealing, with the second - normalization. 2 s. + t.
7 (16). "Chemical-thermal processing of steel" No. 8 from the workshop 1. 1 s.
8 (17). "The effect of alloying elements on the calcination of steel, defined by the mechanical injection molding" No. 21 of the workshop 2. 2 s.
9 (18). "Classification, marking and application of structural materials." Practical part: Students receive a card on which five brands describe in detail each. 1 s.
Laboratory work number 1
Laboratory work on the course "Materials Science"
S semester
1. "Analysis of the crystalline structure of metals and alloys" (No. 1, workshop 2). 2 s.
2. "Test materials for hardness" (No. 10, workshop 2). 1 s.
3. "Testing for stretching samples" (№11, workshop 2; or "mechanical properties of structural materials", a separate file). 2 s.
4. "Determination of the shock viscosity of the material" (No. 12, workshop 2). 1 s.
5. "Fractographic analysis of the destruction of metal materials" (No. 9, workshop 2). 1 s.
6. "The influence of cold plastic deformation and temperature of recrystallization on the structure and properties of metals" (No. 4, workshop 1). 2 s.
7. "Thermal analysis of alloys" (No. 1, workshop 1). Part 1 - Constructing a diagram of the state of the "zinc-tin" system by the thermal method. Part 2 - Analysis of dual alloys status diagrams: perform an individual task under paragraph 5 to the "Report Content". 2 s.
8. "Macroscopic analysis (macroanalysis) of the structure of metallic materials" (No. 2, workshop 2). 1 s.
9. "Microscopic analysis (microanalysis) of the structure of metallic materials" (No. 3, workshop 2). 1 s.
S semester
1 (10). "Microscopic analysis of metals and alloys. The structure of carbon steel "(No. 2, workshop 1) or similar work No. 7" Investigation of the structure of carbon steels in an equilibrium state by microanalysis ", workshop 2). Practical part: Students look at the MM-7 microscope of the structure of four alloys of iron-carbon: technical iron, doevtectoid, eutectoid and zaletetoid alloys. Make schematic sketches, signed structural components, an example of steel grade is given, for a deetectoid alloy, the carbon content formula is calculated. 1 s. + t.
2 (11). "The diagram of the state of iron-carbon. Structure, properties and use of iron "No. 3 of workshop 1) or similar work No. 8" Investigation of the structure of carbonous castoffs by microanalysis "from the workshop 2). Practical part: Students look at the MIM-7 microscope structure of three cast irons: gray cast iron with fine graphite graphite on a pearlite basis, high-strength cast iron on ferrito-pearly-based and deetectic white cast iron. Unfortunately, no more. Also make sketches, they write the names of cast iron and structural components. 1 s. + t.
3 (12). "The influence of the cooling rate on the hardness of carbon steel" No. 20 of the workshop 2). Practical part: Four samples of steel U8. One is exposed to annealing, the second - normalization, the third - quenching in oil, fourth - quenching in water. Hardness is measured, a graph of hardness dependence on the cooling rate is built. Cooling speed values \u200b\u200bare taken from the table in laboratory work. 2 s.
4 (13). "Hardening carbon steels" No. 5 of the workshop 1). Practical part: Three samples from steels 20, 45, U9 are hardened in water, one sample of steel 45 is hardened in oil. Measure hardness to (HRB) and after (HRC) quenching. The convene table is determined by hardness in HB units. According to the results, two graphics are built: hb \u003d f (% c) and hrc \u003d f (Vochl.). 2 s. + t.
5 (14). "Vacation of steel" No. 6 of the workshop 1) or similar work No. 18 "Vacation of carbon steel" from the workshop 2). The practical part: practicer 1) is carried out low (200ºС), medium (400ºС) and high (600ºС) vacation of tempered samples made of steel 45 and low leave (200ºС) of the tempered sample from steel U9. Measure hardness. Build a graph HRC \u003d F (Totp.). According to Workshop 2), there is a low, medium and high vacation of tempered samples from steel U8. 2 s. + t.
6 (15). "Annealing and normalization of steel" No. 7 of the workshop 1). Practical part: two samples of steel 45. With one is carried out isothermal annealing, with the second - normalization. 2 s. + t.
7 (16). "Chemical-thermal processing of steel" No. 8 from the workshop 1. 1 s.
8 (17). "The effect of alloying elements on the calcination of steel, defined by the mechanical injection molding" No. 21 of the workshop 2. 2 s.
9 (18). "Classification, marking and application of structural materials." Practical part: Students receive a card on which five brands describe in detail each. 1 s.
Laboratory work number 1
Analysis of the crystalline structure
Metals and alloys
Purpose of work:
To get acquainted with the types of crystalline lattices of metals and alloys, defects of the crystalline structure and the types of solid solutions.
Devices, Materials and Tools
Models of the main types of crystalline lattices of metals and solid solutions.
Brief theoretical information
Atomic crystalline structure of metals. Metals under normal conditions have a crystalline structure, a distinctive feature of which is a certain mutual periodic arrangement of atoms, spreading out to arbitrarily long distances. This arrangement of atoms is called long-term order. Thus, under the atomic crystal structure, the mutual arrangement of atoms (ions) is understood, which exists in a real crystal. To describe the atomic crystal structure, the concept of a spatial or crystal lattice is used. The crystal metal grid is an imaginary spatial grid, in the nodes of which atoms (ions) are located, between which free electrons are moving. The electrostatic forces of attraction between ions and electrons balance the pushing force between ions. Thus, the positions of atoms are such that the minimum energy of the interaction between them is ensured, and, consequently, the sustainability of the entire aggregate.
The minimum crystal volume, which gives an idea of \u200b\u200bthe atomic structure of the metal throughout the volume, is called elementary crystal cell. Clean metals have one of the following species of the crystal lattice: the system-centering (BCC), the GRAnetsentarized (HCC) and hexagonal dense-packed (GPU) (Fig. 1).
BCC lattice have, for example, A-iron, lithium, vanadium, tungsten, molybdenum, chrome, tantalum; HCC Grid - Aluminum, G-iron, Copper, Gold, Nickel, Platinum, Lead, Silver. GPU lattice have magnesium, zinc, beryllium, cadmium, cobalt, a-titanium.
Coordinate directions (crystallographic axes). In the crystallographic axis system, the form of an elementary cell of the spatial grid can be described using three coordinate angles A, B and G between crystallographic axes and three lattice parameters a, b, s.
For elementary cells of cubic lattices OCC (Fig. 1a) and the ICC (Fig. 1b), the equality of the angles A \u003d B \u003d G \u003d 90 ° and the equality of the lattice parameters a \u003d b \u003d s.For the GPU lattice (Fig. 1B) are characterized by the values \u200b\u200bof the angles A \u003d B \u003d 90 ° and G \u003d 120 ° and the equality of the two lattice parameters a \u003d b s.
To describe atomic planes and directions, crystallographic symbols are used in the crystal. To determine the symbols of the planes, use the plane to indicate on segments. To do this, choose a coordinate system so that the coordinate axes I, II, III are parallel with the three intersecting edges of the crystal (Fig. 2). As a rule, the first crystallographic axis is directed to the observer, the second is horizontally, the third is oriented upwards. The plane A 1 in 1 C 1 cuts off on the coordinate axes of the segments equal to the parameters of the lattice OA 1 \u003d A, s 1 \u003d B, OS 1 \u003d s. The plane A 1 in 1 s 1 is called single. The parameters of the lattice A, B, C are taken for axial units.
To determine the crystallographic indexes of the plane and 2 to 2 C 2, it is necessary:
Find the parameters of a given plane, i.e. segments in axial units, cut off by this plane on the coordinate axes;
Record the ratio of the three fractions whose numerators are the parameters of the unit plane A 1 in 1 C 1, and the denominators are the parameters of the predetermined plane A 2 in 2 C 2, i.e. 1 / OA 2: 1 / s 2: 1 / OS 2;
Create the resulting ratio to the ratio of three integers mutually simple numbers, i.e. bring the fraraty to common denominator, reduce, if possible, on a general factor, and denominator to discard.
The resulting three integers and mutually simple numbers denoted by h, k, l are called the indices of the atomic plane. The totality of indexes is called a symbol of the atomic plane, which is customary to enter into parentheses and record (HKL). If the plane crosses the coordinate axes in a negative quarter, then the "-" sign is installed above the index. If the plane is considered parallel to one of the crystallographic axes, the index corresponding to this axis is zero. Figure 3 shows examples of indication of planes in a cubic elementary cell of the BRASE.
Symbols should be read by numbers, for example, (100) as 1, 0, 0. The characters of parallel planes coincide. Consequently, the plane symbol describes an infinitely large family of parallel atomic planes, which are structurally equivalent. Atomic planes of one family are located apart from each other at an equal interplanar distance d.
Atomic planes of different families can be non-parallel, but identical by the location of atoms and the interpositive distance d. Such planes are combined and denoted by a symbol (HKL). Thus, in cubic crystals in one set of planes, whose indices differ only in signs and location in the symbol. For example, a combination of atomic planes (100) includes six families: (100), (͞100), (010), (0 ͞10), (001), (00͞1).
The symbol of the crystallographic direction is determined by three mutually simple numbers (indexes) U, V, W, which are proportional to the coordinates of the radius-vector R, which connects the origin of the coordinates (initial node) with the nearest node of the crystal lattice in the specified direction. Indexes enclose in square brackets and write. If the direction does not pass through the origin of the coordinate (initial node), it must mention it to mentally move in parallel or move the origin and coordinate axes so that the direction takes place through the origin.
Figure 4 shows examples of the indication of crystallographic directions in a cubic crystal.
Position the origin of the coordinates at the point about. Then, for example, point from has coordinates 0, 0, 1; Symbol of direction oS. -. Reads separately - "Zero-Zero direction is one." Point e. has coordinates ½; ½; one; Symbol of direction oE -. To determine the direction of the direction aU, mentally transfer it in parallel to myself to the point about; Then the coordinates of the point in - ͡͞1, 1, 0; Direction symbol - [͞110]. When the direction changes to the opposite, indexes are changed to opposite, for example, and (see Figure 1.5). Parallel directions have the same symbols and are combined into the family. Families of identical, but non-parallel directions form a totality, which is denoted
In hexagonal crystals to indicate planes, mostly four-way coordinate system are used. Examples of planes indicating in a hexagonal crystal are shown in Figure 5.
The fourth coordinate axis of OU lies in the horizontal plane and is located on the bisector between the negative semi-axes (-H) and (-Y). The plane symbol consists of four indexes and recorded (HKIL). Three of them (H, K and L) are calculated from the reverse values \u200b\u200bof segments cut off by the plane under consideration on three crystallographic axes (OX), (OY), (OZ), and the fourth index I.calculated by the ratio:
h + K + i \u003d 0 (1)
For example, if H \u003d 1; k \u003d 1, l \u003d 0, then using the ratio (1), you can find the fourth index: i \u003d - (H + K) \u003d - (1 +1) \u003d -2. The plane symbol is written as (11͞20). This is the closest plane in Figure 6. The fourth index i is used when it is necessary to designate identical planes, and not used in the calculation of interplanar distances, angles between planes and directions. Therefore, instead of a complete record of a plane symbol, for example, (11͞20), sometimes used (11.0), i.e. Instead of index I put a point. The family and the combination of identical planes are determined similarly to families and aggregates in cubic crystals.
To describe crystallographic directions in hexagonal crystals, both three-axis and four-axis symbols are used. Three-axle symbols are determined by the coordinates of the specified radius-vector (as in cubic crystals).
Between four directions indexes there is a ratio:
r 1 + R 2 + R 3 \u003d 0 (2)
For the transition from triaxial characters to four-axle, relations are used:
r 1 \u003d 2U -V; R 2 \u003d 2V - U; R 3 \u003d -U - V; R 4 \u003d 3W (3)
Examples of the indication of crystallographic directions in a hexagonal crystal are shown in Figure 6.
In addition to the geometrical characteristics of the crystal, the concepts are used in physical material: the number of atoms on the cell N, the coordination number (CC) and the filling coefficient η.
Under the number of atoms on the cell N, I understand the number of atomic volumes per elementary cell of the BRAS. We will take the volume of one atom per unit. For example, consider the volume center-centered cell, which is formed by 9 atoms, 8 of which are located in the cube vertices, and 1 in the center of Cuba. Each atom at the top belongs to both eight adjacent cells, therefore, one cell belongs to 1/8 of each of the 8 atoms: 1/8. 8 \u003d 1; Atom in the center of Cuba fully belongs to the cell. Thus, the system-centered cell is formed by two atomic volumes, that is, the cell accounts for two atoms.
Under the coordination number (CC), the number of atoms that are equal and the lowest distance from this atom are understood. The higher the coordination number, the greater the density of the packing of atoms. So, in a centrified cubic lattice KC \u003d 8; In the grazenrized and hexagonal grilles Kch \u003d 12.
The filling coefficient η is called pronounced in percentage of the volume V A, occupied by atoms in the cell, to the volume of the entire cell V:
η \u003d (V A / V) ∙ 100% (4)
The coordination number (QC) and the filling coefficient η characterize the density of the packing of atoms in the elementary cell of the metal crystal. The most dense packaging of atoms is implemented in the granetable and hexagonal cells of the Brav.
Defects of the crystalline structure . The real crystal differs from the ideal presence of defects of the crystalline structure, which affect, often decisive, on the macroscopic properties of crystalline bodies. By geometric features, defects are divided into three groups:
Point (zermet);
Linear (one-dimensional);
Surface (two-dimensional).
Spot defects They have dimensions in all directions from one to four atomic diameters. Divided into own and impurity.
Your own point defects include: vacancies formed by removing an atom (ion) from its normal position in the crystal lattice node, and interstitial atoms - the main metal atoms located in the interstillers of the crystal lattice. An impurity belongs to the atoms of another (or other) elements dissolved in the main grille on the principle of substitution or introduction.
Figure 7 shows in a two-dimensional model of the vacancy crystal, its own interstitial atom and impurity atoms of substitution and implementation.
The most common vacancies are the most common. Two mechanisms for occurrence of vacancies are known: Schottky mechanism - at the outlet of the atom on the outer surface or the surface of the pore or cracks inside the crystal under the action of heat fluctuations, and the mechanism of Frankel - when it is formed inside the Crystal lattice, the "own interstitial atom is a vacancy" during deformation, irradiation of metals ionizing Radiations: fast electrons, γ - rays. In real crystals, vacancies are constantly formed and disappeared under the action of thermal fluctuations. The activation energy of the vacancy is approximately 1 eV, an interstitial atom - from 3 to 10 eV.
With increasing temperature, the equilibrium concentration of point defects in the crystal increases. With plastic deformation, irradiation, quenching the number of point defects increases sharply, which leads to a violation of their equilibrium concentration by several orders.
The impurity substitution atoms migrate the same as the main atoms - by the vacancy mechanism. The impurity deployment atoms have small sizes and therefore, in contrast to large intrinsic interstitial atoms, can migrate through the voids between the atoms of the crystal lattice.
Point defects have a big impact on the mechanism and kinetics of creep processes, long-term destruction, the formation of diffusion porosity, decarburization, graphitization and other processes associated with the transfer of atoms in the volume of substance, as well as physical properties: electrical resistance, density.
Linear defects Miles (several atomic diameters) in two directions and have a greater length comparable to a crystal length in the third. Linear defects include dislocations, chains of vacancies and interstitial atoms.
Dislocations are divided into two main types: edge and screw.
The edge dislocation can be represented if the vertically mentally split the perfect crystal, say with a cubic primitive lattice, and insert an extra short atomic layer in it, called extlospa. The extlospility can also be obtained by a shift of one part of the crystal relative to the other. Extraplosity, acting as a wedge, bends the lattice around its lower edge inside the crystal (Fig. 8).
The area of \u200b\u200bimperfection around the edge of the extraplicity is called the edge dislocation. Strong distortions of the crystal lattice are concluded as if inside the "pipe" with a diameter of two to ten atomic diameters, the axis of which is the edge of extliateness. Already, macroscopic character, and in the two other directions (on the diameter of the "pipe") are very small in the line of the extrapremeness of imperfection. If the extlospility is located in the upper part of the crystal, the dislocation associated with it is called positive and denoted (┴); If the extlospility is located at the bottom, the dislocation is negative and denoted (┬).
Under the action of an external applied voltage, the edge dislocation can be moved by sliding according to certain crystallographic planes and directions. PRESENTAL SLOGE ON THE TRAINED PLAYS. The combination of the slip plane and the direction of sliding is called the sliding system. For each type of crystal lattice, their sliding systems are characteristic. So, in crystals with a granetable cubic lattice, this plane of the aggregate (111) and the direction of the aggregate<110> (Cu, Al, Ni), with a large-centered cubic lattice - (110) (α-Fe, Mo, Nb), (211) (Ta, W, α-FE), (321) (CR, α-FE) and<111>, with hexagonal tight-packed - (0001),<11͞20> (Zn, Mg, BE), (1͞100), (10͞11),<11͞20> (Ti), (11͞22),<1͞213> (Ti). The stress required for the shift is called critical shift or rocking. Moreover, only a small group of atoms is involved in the displacement on both sides of the slip plane. Figure 9 shows the slip diagram of the edge dislocation through the crystal.
The final stage of sliding is the yield of the edge dislocation (extliate) to the surface of the crystal. At the same time, the upper part of the crystal is shifted relative to the bottom to one interatomic distance in the direction of the shift. Such movement is an elementary act of plastic deformation. Sliding is a conservative movement that is not associated with the transfer of mass of matter. The direction and value of the shift when moving the edge dislocation are characterized by the Burgers vector b.and its power, respectively. Direction of moving the edge dislocation parallel to the vector of Burgers.
In addition to slip, the edge dislocation can be moved by the overwriting, which is carried out diffusion and is a thermally activated process. Positive overwriting is carried out when the chain of atoms from the edge of the extlospility is moved to neighboring vacancies or interstices, i.e. The extlospility is shortened on one interatomic distance and the edge dislocation goes into the upper plane of slip, parallel to the first. The negative carriage occurs when the edge of the extlospility is completed atomic close by the addition of interstitial or adjacent atoms, and the edge dislocation goes into the lower plane of sliding. The overwhelming is non-consistent movement, i.e. happens with the transfer of mass. The velocity speed depends on both temperature and the concentration of point defects.
Screw dislocation, as well as edge, can be created using a shift. Represent the crystal in the form of a stack of horizontal parallel atomic planes. We mentally make a non-looked incision in the crystal (Fig. 10a) and shifted, for example, the right side down (along the plane of the ABSD) per interplanstone distance (Fig. 10b).
The screw dislocation is divided into the right (Fig. 10b), when when moving from the upper plane to the bottom of the dislocation line, you need to be bypassed clockwise, and the left, when when moving from the upper plane to the bottom of the dislocation line, you need to bypass counterclockwise (if relative to the ABSD plane shift down the left part of the crystal). The line of the screw dislocation is always parallel to the Burgers vector (Fig. 11).
The screw dislocation, in contrast to the edge, is not related to a certain shift plane, therefore it can be moved by sliding in any crystallographic plane containing a dislocation line and a shift vector (Fig. 12). The direction of movement of the screw deployment is always perpendicular to the vector of the Burgers. As a result of sliding both the edge and screw dislocation, a step is formed on the surface of the crystal, equal to the module of the vector of Burgers b. (Fig. 12).
Dislocations are present in all crystals. Thus, in non-deformed metals, the dislocation density is 10 6 -10 8 cm -2; In homeopolar crystals - 10 4 cm -2. With an external voltage, equal to the critical cleathing τ kr \u003d 10 -5 g, where G is the modulus of elasticity of the material, dislocations come into motion, i.e. plastic deformation begins. In the process of plastic deformation, the density of dislocations increases. For example, in deformed metals, the dislocation density is 10 10 -10 12 cm -2; in homeopolar crystals up to 10 8 cm -2. Obstacles for moving dislocations serve various types of barriers (particles of the second phase, point defects, grain boundaries, etc.). In addition, as the number of dislocations increases, they begin to accumulate, beyond the balls and interfere with other moving dislocations. As the degree of deformation τ increases, the Kyrgyz Republic increases, i.e., to continue the deformation process, an increase in external voltage is required, which to a certain extent determines the strengthening of the material.
Surface defects. Surface defects include grain boundaries (submersens) (Fig. 13). Surface defects are two-dimensional, i.e., macroscopic sizes in two directions and atomic in the third direction. The boundaries are called small, if the rationalization of crystalline lattices of neighboring grains does not exceed 10 °, and high-thoughts (larger) with greater reversal.
The small borders can be formed by systems of both edge and screw dislocations of different orientation and with different vectors of the Burgers. The small borders arise with the growth of melt crystals, with plastic deformation, etc. The dislocation of the small border attracts point defects due to elastic interaction with them. Migration of the small border is carried out only diffusion. Therefore, point defects concentrated in the cross-border zone in several interatomic distances, inhibit this process and stabilize the substructure.
The highly kili boundaries were found much earlier than small and the "oldest" species of the defects of the crystalline structure. It is believed that the high-aged border is a layer of 2-3 atomic diameters with a layer in which atoms occupy some intermediate positions in relation to the correct positions of the adjusting grain gratings. Such a position of atoms provides minimal potential energy in the boundary layer, so sufficiently stable.
Nature and behavior of both small and high-body boundaries with power and temperature effects affect the mechanical properties of the material.
The task
1. The plane in the cubic crystal cuts off on the coordinate axes of the segments, equal to A; 2B; from. Determine the crystallographic plane indices (HKL).
2. Build a spatial image of the planes (on the example of the cube) having crystallographic indexes (110); (111); (112); (321); (1͞10); (͞111); (͞1͞1͞1).
3. Determine the direction of the direction passing through the points (0, V / 3, C / 3).
4. Build the spatial image of the following directions in Cuba; ; ; [100]; ; ; ; ; ; ; [͞111]; ; ; [͞1͞11]; [͞111]; ; [͞1͞1͞1]; ; .
5. Count the number of atoms in the cell and the coordination number for the BCC and the ICC and the GPU lattices.
Control questions
1. How many types of elementary cells are BVE today? Which of them are most characteristic of metals?
2. What are crystallographic symbols? Describe the scheme for determining the symbol of the atomic plane in the crystal.
3. What types of point defects exist in crystals? What distances are the distortion caused by a point defect?
4. How does the vacancy concentration change when the temperature is raised?
5. Why are dislocations called linear defects?
6. According to what sign of dislocation is divided into edges and screws?
7. What is the Burgers vector? What is the power of the Burgers vector?
8. How is the Burgers vector in relation to the line of the regional and screw deployment?
9. What is superficial defects?
10. What are the physical properties of crystalline solids affect the defects of the crystal structure?
Laboratory work number 2.
Federal Agency for Education State Educational Institution of the Higher vocational education
"South Russian State University of Economics and Service" (GOU VPO "YURGUES")
MATERIALS SCIENCE
Technology of structural materials
Laboratory workshop
for students of specialties 190601, 190603, 200503, 260704
full-time and correspondence forms of training
Mine GOU VPO "YURGUES"
UDC 620.1 (076.5) BBK 30.3y73
Compilers:
k.T.N., Associate Professor of the Department "Applied Mechanics and Machine Designation"
Yu.E. Damn
k.T., Art. Lecturer of the Department "Applied Mechanics and Machine Design"
S.N. Baybara
Reviewers:
ph.D., Professor, Head. Department "Technical operation of cars"
SOUTH. Sapronov
k.T.N., Professor of the Department "Technology of leather products, standardization and certification"
M341 Materials Science: Technology of structural materials: Laboratory workshop / Compilers Yu.E. Damn, S.N. Baybara. - Shakhty: GOU VPO "YURGUES", 2010. - 71 p.
Using a laboratory workshop will consolidate lecture material, provide independent study individual didactic units of discipline, successful performance of test and independent tasks.
Designed for students of specialties 190601, 190603, 200503, 260704 full-time and correspondence forms of training.
UDC 620.1 (076.5) BBK 30.3y73
Access mode K. electronic analogue Print edition: http://www.libdb.sssu.ru
© GOU VPO "South Russian stateuniversity of Economics and Service, 20 10
Preface ................................................... .......................................... | |
Laboratory work number 1.Studying the crystallization process | |
Laboratory work number 2.Learning macro and microstructure | |
metals and alloys ............................................... ........................................ | |
Laboratory work number 3.Study of status diagrams | |
double alloys ................................................ ........................................... | |
Laboratory work number 4.Study of phase transformations | |
according to the condition of the state of iron cementite ............................................ ...... | |
Laboratory work number 5.Methods for measuring hardness of metals ...... | |
Laboratory work number 6.The effect of thermal processing | |
on the mechanical properties of structural steel .................................... | |
Laboratory work number 7.Formation of blanks casting | |
in sandy forms ................................................. .......................................... | |
Laboratory work number 8.Study of electric methods | |
metal welding ................................................ ............................................ | |
Laboratory work number 9.Study of manufacturing methods | |
products from plastics ..................................................... ..................................... | |
Bibliographic list ................................................ .......... |
Preface
The future specialist is a graduate of the highest educational institution It is necessary to work in rapidly changing production conditions. Already now the technology update cycle in some industries shorter than the training period at the Institute or University. Therefore, the preparation of new type specialists who can quickly adapt to new working conditions of enterprises is one of the main tasks of the university.
Laboratory workshops, as a form of training sessions, maximally contributes to the intensification of the mental activity of students and developing their creative skills in the practice of knowledge gained.
The proposed laboratory work will allow students deeper to study the theoretical provisions of the course "Materials science", to obtain practical skills to study the structure and properties of metal machine-building materials, assess the effect on the structure and properties of metals of various types of thermal processing.
The implementation of laboratory work in conditions of a sharp reduction in the volume of readable lectures often does not coincide with the procedure for presenting the lecture course. Therefore, each work contains general theoretical information that will facilitate independent training of a student to fulfill work, contributing to the conscious conduct and understanding the results obtained.
Laboratory workshop was prepared in accordance with the requirements of the State Discipline "Materials Science. TKM "for students of machine-building specialties of higher educational institutions.
Laboratory work number 1 Study of the process of crystallization of metals and alloys
Objective: Study of the process of transition of metal materials (metals and alloys) from liquid in solid aggregate state, taking into account influence external factors, as well as the study of the structure of the steel ingot.
1. Give a brief characteristic of metals, alloys and processes of their crystallization.
2. Get acquainted with the device of the biological microscope.
3. To monitor the crystallization of the salts from the oversaturated aqueous solutions.
4. Draw, observing the crystallization of the drop, the most characteristic zones and give explanations. Fraction size - 50 mm circle.
5. Draw longitudinal and transverse cuts of the steel ingot. Give an explanation for the presence of three zones in the slope.
6. Develop a written report on work.
General information from theory
1. Brief characteristic of metals and alloys
Metals and alloys are essential structural materials widely used in the technique. Metals besides gloss and plasticity are inherent in high thermal conductivity and electrical conductivity.
The preparation of chemically pure metals is associated with significant difficulties, and the values \u200b\u200bof their mechanical characteristics are not high. In this regard, metal alloys are used in the technique everywhere.
Alloys are complex substances that include several metals or metals and non-metals. Metal alloys have marked above properties of pure metals.
Metal materials in solid aggregate state have a crystalline structure in which positively charged ions are located in a strictly defined manner, periodically repeated in three dimensions of space. Since alloys are usually obtained by metallurgical technology, the solid state is preceded by liquid. The transition of a substance from a liquid state in solid is called
crystallization.
2. Crystallization of metals and alloys
Crystallization proceeds under conditions when the system proceeds to a thermodynamically more stable state with less free energy. Under the free energy F understand that part of the internal energy of the system, which can be turned into work. With increasing temperature, the free energy of liquid and solid states of the metal decreases (see Fig. 1.1).
Free Energy F.
state
state |
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T kr | ||||||
T pl |
||||||
Temperature, | ||||||
Figure 1.1 - change in the free energy of liquid and solid states depending on temperature
Upon reaching the equilibrium temperature T S, the free energy of liquid and solid states is equal, and therefore at this temperature neither the crystallization process nor the melting process cannot completely flow.
To develop the crystallization process, it is necessary to create such conditions under which the free energy of the solid phase will be less than the free energy of the liquid phase. As can be seen from the graph shown in Figure 1.1, this is possible only with some overexposition of the alloy.
Degree of supercoolingcalled the difference between the equilibrium (theoretical) and the actual crystallization temperatures
T TS TKR.
For the development of the melting process you need some degree of overheating alloy
T TPL TS.
The degree of hypothermia is measured in degrees Celsius and depends on the rate of cooling, nature and purity of the melt. The greater the cooling rate, the greater the degree of hypothermia. The cleaner the melt, the greater its stability and, therefore, more degree of hypothermia.
The presence of undisposed particles in the melt accelerates the crystallization process, grinds grain. Research D.K. Chernova was revealed that crystallization begins with the formation of crystalline embryos (crystallization centers) and continues in the conditions of growth of their number and sizes.
The number of centers of crystallization (Ch.TS.) and the speed of their growth (S.R.) depends on the degree of hypothermia. With an increase in the degree of hypothermia, the number of crystallization centers increases and their growth rate increases; With the definable degree of hypothermia, the maximum occurs.
However, metals and alloys, which in a liquid state, a small tendency to supercooling, cannot be cooled to such temperatures at which the number of crystallization centers and crystal growth rate would reach a maximum. Therefore, for metals, the curves "Ch.TS." and "S.R." Out of the small degrees of supercooling (solid curves in Figure 1.2).
S.R.
T ST
The degree of supercooling T, with
Figure 1.2 - The effect of the degree of supercooling on the number of crystallization centers and crystal growth rate
For the degree of overcooling, the speed of formation of crystallization centers and their growth are small, therefore the crystallization process proceeds slowly, and large is large (as few crystallization centers are formed in a unit of volume of the liquid phase).
For the degree of supercooling, the T significantly increased both the rate of the nucleation of crystallization centers and the speed of their growth, therefore the crystallization process will flow much faster than with degree of hypothermia, and since the number of crystallization centers in a unit volume increases, the small one increases.
Thus, changing the degree of hypothermia, you can get crystallites (grain) of various sizes. Many alloy properties depend on the grain. In practice, the grinding of grain in alloys is also achieved by modifying, i.e. Introduction to the melt dispersed particles of modifiers that become additional crystallization centers.
The process of crystallization of metals and alloys is similar to the process of crystallization of salts from aqueous solutions. In this case, the formation of crystals becomes possible to observe with a biological microscope at room temperatures as water evaporates, which is convenient and safe.
3. The structure of the metal ingot
The crystals in the process of solidification of the metal can have a different form depending on the cooling rate, character and amount of impurities. Most often, branched or tree crystals are formed in the crystallization process, called dendrites. Initially, long branches are formed, the so-called first-order axes (the main axes of dendrita). Simultaneously with the lengthening of the first-order axes, they are branched and grow perpendicular to them the same second-order branches. In turn, the axes of the third order are originated on the second order axes, etc.
- zone of small grain; |
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- zone of columnar crystals; |
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- zone of uniform crystals; |
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- Shrinking sink; |
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- Gas bubbles, emptiness, |
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shrinking loaf |
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Figure 1.3 - Fragment of the steel ingot of calm steel
The crystallization of the liquid metal begins at the surface of a colder form and is initially occurred in the thin layer adjacent to the surface of a strongly supercooled fluid. This leads to the formation of a very narrow zone of small ne-oriented green on the surface of the ingot.
The second zone is located outside the ingot zone 1 - the area of \u200b\u200bthe columnar crystals. The growth of these crystals is in the direction of heat removal, and since all crystals grow at the same time, then the columnal (elongated) crystals are obtained, the growth of which continues until there is a directional heat removal. In case of strong overheating and rapid cooling, the area of \u200b\u200bthe columnar crystallites can fill the entire volume of the ingot.
This type of crystallization is called transcrystallization.In the inside of the ingot, zone 3 is formed, consisting of equilibly different oriented dendritic crystals, larger due to the low cooling rate (due to the decrease). Since the liquid metal has a greater specific volume than solid, then in the toysto ingot, which freezes the latter turn, the emptiness is formed - shrinkage sink. It is usually surrounded by the most contaminated metal containing micro and macropores, gas bubbles and other defects. The crystallization of the ingot zones, as well as the dendritis axes, does not occur simultaneously, therefore the metal of the ingot has heterogeneity by chemical composition - zonal and dendritic bait.
4. Equipment and samples
To observe the process of crystallization of salt, biological microscopes are used. The microscope tripod is a steady base to which the other parts of the microscope are attached: a tube, a condenser holder, a revolving nozzle with lenses, eyepiece. As a rule, the microscope is equipped with several lenses of different zooms placed on a turret nozzle, which allows you to move the lenses into the working position. The study of the sample is usually starting with the smallest increase with the largest field of view. Interesting details are considered using lenses with a great increase.
The schematic diagram of the biological microscope is presented in Figure 1.4.
- mirror;
- Sample table;
- Seld glass;
- a drop of salt solution;
- lens;
- microscope tube;
- eyepiece;
- eye observer.
Figure 1.4 - Schematic diagram of biological microscope
The microscope regulation is as follows. Turning glass 2 to the light source, achieve the most bright lighting in the eyepiece 8. Then it is set to the slide 4 with a drop of 5 salt solutions on the table 3 so that the edge of the drop can be observed. The focal length setting is produced by lowering / raising the subject table 3 relative to the tube 7, seeking a clear image of the edge of the drop in the eyepiece 8.
5. Procedure for performing work
Having studied the theoretical part and reading the task to work, students proceed to observing the crystallization process. To do this, the biological microscope is issued and the slim glass with a throttle aquatic solution crash salt. After regulating the microscope, the glass is installed on the microscope's subject table and observe the beginning of the crystallization process at the edge of the drop. As water evaporates, crystals will grow and in the following drops of drops. The conditionally studied process can be divided into three periods. The first is the crystallization of salt at the edge of the drop, where the amount of water is the smallest. During this period, the edge of the drops are formed small crystals of the correct form, since the hypothermia causes the formation of a large number of crystallization centers. During the second period, large columnar crystals are formed. The direction of their axes is normal to the edges of the drop. During this period, there is a high growth rate of crystals and a limited number of crystallization centers. During the third period, tree (dendritic) crystals are formed. At the same time, the amount of water in a drop is insignificant and evaporation of it from the middle part goes quickly.
Federal State Budgetary Educational Institution of Higher Education
"Volga State University of Water Transport"
Perm branch
E.A. . Sazonov
MATERIALS SCIENCE
Collection of practical and laboratory work
26.02.06 "Operation of ship electrical equipment and automation means"
23.02.01 "Organization of transportation and transport management" (by type)
PERMIAN
2016
Introduction
Methodical recommendations for the implementation of laboratory and practical work on the study discipline "Materials science" are intended for secondary vocational education students in the specialty26.02.06 "Operation of ship electrical equipment and automation means"
In this methodical manual The instructions for the implementation of practical and laboratory work on the topics of the discipline are given, the topics and the content of laboratory and practical work, the forms of control for each topic and recommended literature are given.
As a result of the development of this educational discipline The student must be able to:
˗ perform mechanical testing of sample materials;
˗ use physico-chemical methods of research of metals;
˗ Use reference tables to determine the properties of materials;
˗ Choose materials for professional activities.
As a result of the development of this academic discipline, the student should know:
˗ The main properties and classification of materials used in professional activities;
˗ Name, labeling, properties of the material being processed;
˗ Rules for the use of lubricating and cooling materials;
˗ Basic information on metals and alloys;
˗ Basic information about non-metallic, gaskets,
Sealing and electrical materials, steel, their classification.
Laboratory and practical work will allow you to form practical skills of work, professional competencies. They are included in the structure of the study of the educational discipline of "Materials Science", after studying the topic: 1.1. "Basic information about metals and alloys", 1.2 "iron-carbon alloys", 1.3 "non-ferrous metals and alloys".
Laboratory and practical work are an element of educational discipline and are evaluated by the criteria under:
The rating "5" is set by the student if:
˗ The subject of work corresponds to the specified, the student shows systemic and complete knowledge and skills on this issue;
˗ The work is executed in accordance with the recommendations of the teacher;
˗ The scope of work corresponds to the specified;
˗ The work is performed exactly in the deadlines specified by the teacher.
The rating "4" is set by the student if:
˗ The subject of work corresponds to the specified, the student allows small inaccuracies or some errors in this matter;
˗ The work is framed with inaccuracies in the design;
˗ The scope of work corresponds to the specified or slightly less;
˗ The work is handed over to the deadlines specified by the teacher, or later, but not more than 1-2 days.
The rating "3" is set to the student if:
˗ The subject of the work corresponds to the specified, but there are no significant elements on the maintenance of the work or the subjects are setlined illogical, the main content of the question is not clearly presented;
˗ The work is framed with errors in the design;
˗ The volume of work is significantly less than the specified;
˗ The work is handed over with a delay in the timing of 5-6 days.
The rating "2" is set by the student if:
˗ not disclosed the main theme of work;
˗ The work is not framed in accordance with the requirements of the teacher;
˗ The scope of work does not correspond to the specified;
˗ The work is handed over with a delay in more than 7 days.
Laboratory and practical work on their content have a specific structure, we propose to consider it: the course of work is given at the beginning of each practical and laboratory work; When performing practical work, students are tasked, which is indicated at the end of the work (item "Task for students"); When performing laboratory work, a report is drawn up by execution, the content of the report is indicated at the end of the laboratory work (the "Content of the Report").
When performing laboratory and practical work, students are implemented by certain rules, consider them below: laboratory and practical work are carried out during training sessions; It is allowed to finalize laboratory and practical work at home; It is allowed to use additional literature when performing laboratory and practical work; Before performing laboratory and practical work, it is necessary to explore the main theoretical provisions on the subject matter under consideration.
Practical work number 1
"The physical properties of metals and the methods of studying them"
purpose of work : To study the physical properties of metals, methods for their definition.
Progress:
Theoretical part
Physical properties include: density, melting (melting point), thermal conductivity, thermal expansion.
Density - the amount of substance contained in a unit of volume. This is one of the most important characteristics of metals and alloys. By density, metals are divided into the following groups:lungs (density no more than 5 g / cm 3 ) - magnesium, aluminum, titanium, etc.;heavy - (density from 5 to 10 g / cm 3 ) - iron, nickel, copper, zinc, tin, etc. (this is the most extensive group);very heavy (density of more than 10 g / cm 3 ) - Molybdenum, tungsten, gold, lead, etc. Table 1 shows the values \u200b\u200bof the density of metals.
Table 1
Metal density
The melting point is the temperature at which the metal moves from the crystalline (solid) state into a liquid with the absorption of heat.
The melting point of metals is in the range from -39 ° C (mercury) to 3410 ° C (tungsten). The melting point of most metals (with the exception of alkaline) is high, but some "normal" metals, such as tin and lead, can be melted on a conventional electrical or gas stove.
Depending on the melting point, the metal is subdivided into the following groups:legomethal (Melting point does not exceed 600 o. C) - zinc, tin, lead, bismuth, etc.;mid-slight (from 600. o. From up to 1600. o. C) - they include almost half of metals, including magnesium, aluminum, iron, nickel, copper, gold;refractory (more than 1600. o. C) - tungsten, molybdenum, titanium, chrome, etc. When administered to the metal additives, the melting point is usually reduced.
table 2
Melting and boiling point of metals
The thermal conductivity is the ability of the metal with one or another speed to carry out heat when heated.
Electrical conductivity - metal ability to carry out an electric current.
Thermal expansion is the ability of metal to increase its volume when heated.
The smooth surface of the metals reflects a large percentage of light - this phenomenon is called a metal glitter. However, in a powder condition, most metals lose their glitter; Aluminum and magnesium, however, retain their shine and in powder. The most well reflect the light of aluminum, silver and palladium - mirrors produce from these metals. For the manufacture of mirrors, it is sometimes used and rhodium, despite its extremely high price: thanks much greater than that of silver or even palladium, hardness and chemical resistance, the rhodium layer can be much thinner than the silver.
Methods of research in materials science
The main methods of research in metal and materials science are: Frame, macrostructure, microstructure, electron microscopy, X-ray research methods. Consider their features in more detail.
1. Fravel - the easiest and most affordable method of evaluation inner structure Metals. The method of evaluating breaks, despite its apparent rudeness assessment of the quality of the material, is used quite widely in various industries of production and scientific research. Evaluation of the breakfast in many cases can characterize the quality of the material.
The break can be crystalline or amorphous. The amorphous break is characteristic of materials that does not have a crystalline structure, such as glass, rosin, vitreous slags.
Metal alloys, including steel, cast iron, aluminum, magnesium alloys, zinc and its alloys give a grainy, crystalline break.
Each line of crystalline breakfast is the plane of the cleansing of individual grains. Therefore, the break shows us the size of the metal grain. Studying steel, it can be seen that the grain size can fluctuate in very wide limits: from several centimeters in cast, slowly cooled, steel to thousandth fractions of a millimeter in properly discharged and hardened steel. Depending on the grain size, the break can be a large-crystalline and fine-crystalline. Usually the fine-crystalline fracture corresponds to more high quality Metal alloy.
In the event that the destruction of the test sample passes with the preceding plastic deformation, the grains in the plane of the breakformation are deformed, and the break no longer reflects the inner crystalline structure of the metal; In this case, the break is called fibrous. Often in one sample, depending on the level of its plasticity, fibrous and crystalline sections can be in the break. Often, according to the ratio of the spoughness area, occupied by the crystalline sections under these test conditions, the quality of the metal is estimated.
The fragile crystalline break can be obtained by destroying the grains or sliding planes crossing the grains. In the first case, the break is called intercrystalline, in the second transcrystalline. Sometimes, especially with very fine grains, it is difficult to determine the nature of the break. In this case, the break is studied using a magnifying glass or a binocular microscope.
Recently, the metallic studies in the fractographic study of fractures on metallographic and electron microscopes has been developing. At the same time, they find the new advantages of the old method of studies in metal and research of breakfast, applying the concept of fractal dimensions to such studies.
2. Macrotructure - is the following method for researching metals. The macrostructure study is to study the plane of the section of the product or sample in the longitudinal, transverse or any other directions after etching, without the use of magnifying devices or with a magnifying glass. The advantage of macrostructural research is that with the help of this method you can explore the structure directly by the whole casting or ingot, forgings, stamping, etc. With this method of research, the internal defects of the metal can be found: bubbles, emptiness, cracks, slag inclusions, investigate the crystalline casting structure, study the inhomogeneity of the crystallization of the ingot and its chemical heterogeneity (likvation).
With the help of sulfur fingerprints on the photo paper on Bauman, the unevenness of the sulfur distribution on the cross-section of ingots is determined. Great importance This research method has in the study of forged or stamped billets to determine the direction of fibers in the metal.
3. The microstructure is one of the main methods in metallothing is a study of a metal microstructure on metallographic and electron microscopes.
This method allows you to study the microstructure of metal objects with large zooms: from 50 to 2000 times on an optical metallographic microscope and from 2 to 200 thousand times on an electron microscope. The study of the microstructure is performed on polished sandings. The presence of non-metallic inclusions, such as oxides, sulphides, small slag inclusions, and other inclusions, differ from the nature of the base metal are studied on net-shaped polishers.
The microstructure of metals and alloys is studied on the injuries. The etching is usually produced by weak acids, alkalis or other solutions, depending on the nature of the metal of the grind. The etching effect is that it dissolves different structural components in different ways, painting them into different colors or colors. The borders of the grains, differing from the main solution, have a robe usually different from the base and stands out on the sluff in the form of dark or light lines.
The polyhedra of grains visible under the microscope are sections of grains with a surface of the grind. Since this section is random and can take place at different distances from the center of each individual grain, the difference in the size of polyhedra does not correspond to valid differences in grain sizes. The closest grain largest grains are the closest to the actual size of the grain.
When etching a sample consisting of homogeneous crystalline grains, such as a pure metal, a homogeneous solid solution, etc., often differently treated surfaces of different grains are observed.
This phenomenon is explained by the fact that grains of various crystallographic orientation are emerging on the surface of the sandpaper, as a result of which the degree of acid exposure for these grains is different. Some grains look shiny, others are strongly treated, darken. This darkening is associated with the formation of various etching figures, differently reflecting light rays. In the case of alloys, individual structural components form a microrelief on the surface of a sandpaper, which has sections with different slope of individual surfaces.
Normally located areas reflect the greatest amount of light and turn out to be the most light. Other sites are darker. Often the contrast in the image of the grainy structure is not associated with the structure of the grain surface, but with the relief of the borders of the grains. In addition, various shades of structural components may be the result of the formation of films formed by the interaction of the etcher with structural components.
Using a metallographic study, you can perform a qualitative identification of structural components of alloys and a quantitative study of microstructures of metals and alloys, firstly, by comparing with well-known microsowing structures and, secondly, special methods of quantitative metallography.
The magnitude of the grain is determined. The method of visual assessment consisting in the fact that the microstructure under consideration is approximately estimated by the points of standard scales according to GOST 5639-68, GOST 5640-68. According to the relevant tables, the area of \u200b\u200bone grain and the amount of grains per 1 mm is determined for each score. 2 and 1 mm 3 .
The method of calculating the amount of grains per unit surface of the sandpaper by appropriate formulas. If S is an area on which the number of grains N, and M - an increase in the microscope, then average value grains in the cross section of the surface of the grind
Determination of phase composition. The alloy phase composition is more often evaluated by eye or by comparing structure with standard scales.
The approximate method of quantitative determination of the phase composition can be carried out by the method of sequentially by calculating the length of segments occupied by different structural components. The ratio of these segments corresponds to the volume content of individual components.
The point is A.A. Glagolev. This method is carried out by assessing the number of points (points of intersection of the ocular mesh of the microscope) entering the surface of each structural component. In addition, the method of quantitative metallography is produced: determining the value of the surface of the phase and grains; determining the number of particles in volume; Determination of the orientation of grains in polycrystalline samples.
4. Electronic microscopy. The electronic microscope is in recent importance in metallographic studies. Undoubtedly, he owns a big future. If the resolution of the optical microscope reaches the values \u200b\u200b0.00015 mm \u003d 1500 A, then the resolution ability of electron microscopes reaches 5-10 A, i.e. a few hundred times more than optical.
On the electron microscope, thin films (replicas) removed from the surface of the shelf or directly studying thin metal films obtained by the refinement of a massive sample.
The most need to use electron microscopy of the study of processes associated with the release of excess phases, for example, the decay of the implicated solid solutions with thermal or deformation aging.
5. X-ray research methods. One of the most important methods in establishing the crystallographic structure of various metals and alloys is x-ray structural analysis. This research method makes it possible to determine the nature of the mutual arrangement of atoms in crystalline bodies, i.e. Solve the task that is not available or an ordinary nor electron microscope.
The basis of X-ray structural analysis is the interaction between the X-ray rays and the atoms of the body under study lie on their way, thanks to which the latter becomes like new sources of X-rays, being centers of their scattering.
Scattering rays atoms can be like to reflect these rays from the atomic planes of the crystal according to the laws of geometric optics.
X-rays are reflected not only from the planes lying on the surface, but also from the depths. Reflecting from several equally oriented planes, the reflected ray is enhanced. Each plane of the crystal lattice gives its bundle of reflected waves. Having obtained a certain alternation of reflected X-ray beams at certain angles, calculate the interplanar distance, crystallographic indices of reflective planes, ultimately, the shape and size of the crystal lattice.
Practical part
Content of the report.
1. The report needs to specify the name, work goal.
2. List the main physical properties of metals (with definitions).
3. Fix in the notebook of Table 1-2. Make conclusions on tables.
4. Fill in table: "Basic research methods in materials science."
Rengenianresearch methods
Practical work number 2
Topic: "Study of status diagrams"
Purpose of work: Familiarization of students with basic types of status diagrams, their main lines, points, their meaning.
Progress:
1. Increase the theoretical part.
Theoretical part
The status diagram is graphic image The states of any alloy of the system being studied depending on the concentration and temperature (see cris. 1)
Fig.1 of the status diagram
Status diagrams show stable states, i.e. States that under these conditions have a minimum of free energy, and therefore it is also called the equilibrium diagram, as it shows which equilibrium phases exist under these conditions.
Construction of the status diagrams is most often carried out using thermal analysis. As a result, a series of cooling curves are obtained at which at temperatures of phase transformations, the inflection points and temperature stops are observed.
Temperatures corresponding to phase transformations are called critical points. Some critical points They have names, for example, the points corresponding to the beginning of the crystallization are called dots of liquidus, and the end of crystallization - solidus points.
By cooling curves, the composition of the composition is built in the coordinates: along the abscissa axis - the concentration of components, along the axis of the ordinate temperature. The concentration scale shows the content of the component V. The main lines are the licoity lines (1) and solidus (2), as well as the lines corresponding to phase transformations in the solid state (3, 4).
According to the state diagram, you can determine the temperatures of phase transformations, changing the phase composition, approximately, the alloy properties, types of processing that can be used for alloy.
Below are various types of status diagrams:
Fig.2. Frame diagram with unlimited solubility
components in solid state (a); Curves cooling typical
alloys (b)
Analysis of the obtained diagram (Fig. 2).
1. Number of components: K \u003d 2 (components A and B).
2. Number of phases: F \u003d 2 (liquid phase L, solid crystals)
3. The main lines of the chart:
aCB is a line of liquidus, above this line of alloys are in a liquid state;
aDB - Solidus line, below this line alloys are in solid state.
Fig.3. Diagram of the state of alloys with the absence of solubility of components in a solid state (A) and cooling curves of alloys (b)
Analysis of the status diagram (Fig. 3).
1. Number of components: K \u003d 2. (components A and B);
2. Number of phases: f \u003d 3. (component crystals, component crystals in, liquid phase).
3. The main lines of the chart:
the line of solidus ECF, parallel to the axis of concentrations tends to the axes of the components, but does not reach them;
Fig. 4. Diagram of the state of alloys with limited solubility of components in a solid state (A) and cooling curves of typical alloys (b)
Analysis of the status diagram (Fig. 4).
1. Number of components: K \u003d 2 (components A and B);
2. The number of phases: F \u003d 3 (liquid phase and crystals of solid solutions (a solution of component in component A) and (component solution A in component B));
3. The main lines of the chart:
the line of liquidus ACB consists of two branches converging at one point;
the line of solidus ADCFB consists of three sites;
dM - line of the limiting concentration of component in in component A;
fn - line of the limiting concentration of component A in component V.
Practical part
Task for students:
1. Record the name of the work and its goal.
2. Record what is a status diagram.
Answer the questions:
1. How is the status diagram build?
2. What can I define the status diagram?
3. What names have the basic points of the chart?
4. What is indicated in the diagram on the abscissa axis? Ortinity axes?
5. What are the main lines of the diagram?
Options for options:
Students respond to the same questions differently are drawings for which it is necessary to answer. 1 Option gives answers in Figure 2, 2 options gives answers in Figure 3, option 3 gives answers in Figure 4. The figure must be fixed in the notebook.
1. What is the name of the diagram?
2. Name how many components are involved in the formation of alloy?
3. What letters indicate the main lines of the chart?
Practical work number 3
Topic: "Studying Castows"
Purpose of work: introduction of students with marking and the area of \u200b\u200bapplication of castoffs; Formation of the ability to decipher the brands of cast iron.
Progress:
Theoretical part
Cast iron differs from steel: in composition - a higher carbon content and impurities; According to technological properties - higher casting properties, a small ability to plastic deformation, is almost not used in welded structures.
Depending on the state of carbon in the cast iron distinguish: white cast iron - carbon in associated condition in the form of cementite, in the breakfast has white and metal glitter; Gray cast iron - all carbon or most is in a free state in the form of graphite, and in the associated state there are no more than 0.8% carbon. Because of the large amount of graphite, its break is gray; A half-carbon part is in a free state in the form of graphite, but at least 2% of carbon is in the form of cementite. Little is used in the technique.
Depending on the form of graphite and the conditions for its formation, the following groups of castoffs distinguish: gray - with lamellar graphite; high-strength - with spherical graphite; Dusty - with florid graphite.
Graphite inclusions can be considered as an appropriate form of emptiness in the structure of cast iron. About such defects during loading, voltages are concentrated, the value of which is the greater that the sharp defect. It follows that graphite inclusions of the plate shape to the maximum measurement of the metal. A more favorable flaky shape, and the optimal is a spherical form of graphite. Plasticity depends on the form in the same way. The presence of graphite most sharply reduces resistance at rigid loading methods: a blow; gap. Resistance to compression is reduced.
Gray cast iron
Gray cast iron is widely used in mechanical engineering, as it is easily processed and has good properties. Depending on the strength, gray cast iron is divided into 10 grades (GOST 1412).
Gray cast irons with a small stretch resistance have a sufficiently high compression resistance. The structure of the metallic base depends on the amount of carbon and silicon.
Considering the small resistance of the castings of gray cast iron by stretching and shock loads, this material should be used for parts that are subjected to compressive or bending loads. In the machine tool, these are basic, body parts, brackets, gear wheels, guides; In the automotive - cylinder blocks, piston rings, camshafts, clutch discs. Castings made of gray cast iron are also used in electrical storage, for the manufacture of consumer goods.
Marking of gray castoffs: indicated by the index of the sch (gray cast iron) and the number that shows the value of the strength of the strength multiplied by 10 -1 .
For example: Mount 10 gray cast iron, tensile strength of 100 MPa.
Matchy cast iron
Good properties in castings are ensured if the process of graphitization does not occur during crystallization and cooling of castings in the form. To prevent graphitization, cast iron should have a reduced carbon and silicon content.
There are 7 stamps of forging cast iron: three with ferritic (KCh 30 - 6) and four with pearlite (KCh 65 - 3) base (GOST 1215).
For mechanical and technological properties, maversea cast iron occupies an intermediate position between the gray cast iron and steel. The disadvantage of the forging cast iron compared with high strength is the limitation of the wall thickness for casting and the need for annealing.
Dake cast iron castings are used for parts operating at shock and vibratory loads.
Carter gearboxes, hubs, hooks, staples, clamps, couplings, flanges are manufactured from ferritic castons.
From pearlite castors characterized by high durability, sufficient plasticity, forks of cardan shafts, links and rollers of the conveyor chains, brake pads are made.
Marking of the forging cast iron: indicated by the CC index (forging cast iron) and numbers. The first number corresponds to the limit of tensile strength, multiplied by 10 -1 , The second number is a relative elongation.
For example: KC 30-6 - Dake cast iron, tensile strength of 300MP, relative elongation is 6%.
High-strength cast iron
Get these cast iron from gray, as a result of magnesium modification or cerium. Compared to gray cast iron, mechanical properties increase, it is caused by the absence of unevenness in the distribution of stresses due to the spherical shape of graphite.
These cast iron have a high liquid procession, linear shrinkage - about 1%. Foundry voltages in castings are slightly higher than for gray cast iron. Due to the high modulus of elasticity, a highly high cutting processability. Have a satisfactory weldability.
From high-strength cast iron, thin-walled castings are made (piston rings), rugs forging hammer, beds and frames of presses and rolling mills, molds, cutters, tops.
Castings of crankshafts weighing up to 2..3 t, instead of forged shafts made of steel, have a higher cyclic viscosity, completely well-sensitive to external voltage concentrators, have better antifriction properties and significantly cheaper.
Marking of high-strength cast iron: denoted by the index of RF (high-strength cast iron) and the number that shows the value of the strength of the strength multiplied by 10 -1 .
For example: HF 50 - high-strength cast iron with a tensile strength of 500 MPa.
Practical part
Task for students:
1. Enter the name of the work, its goal.
2. Describe the production of cast iron.
3. Requires the table:
3. High passcast iron
Practical work number 4
Topic: "Study of carbon and alloyed structural steels"
Purpose of work:
Progress:
1. Consider with the theoretical part.
2. Complete the tasks of the practical part.
Theoretical part
Steel is an iron alloy with carbon, in which carbon is contained in an amount of 0 -2.14%. Steel are the most common materials. Have good technological properties. Products are obtained as a result of pressure and cutting processing.
Quality depending on the content of harmful impurities: sulfur and phosphorus steel are divided into steel:
˗ Ordinary quality, content up to 0.06% sulfur and up to 0.07% phosphorus.
˗ Qualitative - up to 0.035% sulfur and phosphorus each separately.
˗ High quality - up to 0.025% sulfur and phosphorus.
˗ Special-quality, up to 0.025% phosphorus and up to 0.015% sulfur.
The deoxidation is the process of removing oxygen from steel, that is, according to the degree of deoxidation, there are: calm steel, i.e., completely stretched; Such steel are denoted by the letters "SP" at the end of the brand (sometimes letters are lowered); Boiling steel - weakly stretched; marked with the letters "KP"; semi-deval steel, occupying an intermediate position between the two previous; Denotee "PS".
Steel of ordinary quality is also divided into supplies of 3 groups: steel of group A is supplied to consumers for mechanical properties (such steel may have an increased sulfur content or phosphorus); Steel group B - by chemical composition; Steel group B - with guaranteed mechanical properties and chemical composition.
Construction steel are designed for the manufacture of structures, parts of machinery and appliances.
So in Russia and in the CIS countries (Ukraine, Kazakhstan, Belarus, etc.), the alphanumeric designation of steel and alloys and alloys, which, according to GOST, are conditionally indicated by the names of the elements and methods of steel, and the numbers are conditionally designated Elements. To date, international standardization organizations have not developed a unified stool marking system.
Marking of structural carbon steels
ordinary quality
˗ Indicate according to GOST 380-94 letters "ST" and the conditional number of the brand (from 0 to 6), depending on the chemical composition and mechanical properties.
˗ The higher the carbon content and the strength properties of steel, the greater its number.
˗ The letter "g" after the number of the brand indicates the increased content of manganese in steel.
˗ Before the brand indicate a group of steel, and the group "A" in the designation of the brand has become not placed.
˗ To indicate the category of steel to the mark designation, the number at the end of the corresponding category is added, the first category is usually not indicated.
For example:
˗ St1kp2 - carbon steel of ordinary quality, boiling, brand 1, second category, comes to consumers for mechanical properties (group A);
˗ ESTA - carbon steel of ordinary quality with increased manganese content, calm, brand 5, first category with guaranteed mechanical properties and chemical composition (group B);
˗ Eggs - carbon steel of ordinary quality, the number of the brand 0, group B, the first category (steel stamps of St0 and BST0 according to the degree of deoxidation are not separated).
Marking of structural carbon high-quality steels
˗ In accordance with GOST 1050-88, these steel are marked with two-digit numbers showing the average carbon content in the hundredths of percent: 05; 08; 10 ; 25; 40, 45, etc.
˗ For calm steels, the letters at the end of their names are not added.
For example, 08kp, 10ps, 15, 18kp, 20, etc.
˗ The letter G in brand began to indicate an increased maintenance of manganese.
For example: 14g, 18g, etc.
˗ The most common group for the manufacture of machine parts (shafts, axles, bushings, gear wheels, etc.)
For example:
˗ 10 - structural carbon high-quality steel, with carbon content of about 0.1%, calm
˗ 45 - structural carbon high-quality steel, with carbon content of about 0.45%, calm
˗ 18 KP - structural carbon high-quality steel with a carbon content of about 0.18% boiling
˗ 14G - structural carbon high-quality steel with a carbon content of about 0.14%, calm, with a high content of manganese.
Marking of alloyed structural steels
˗ In accordance with GOST 4543-71, the name of such steels consist of numbers and letters.
˗ The first figures of the brand indicate the average carbon content in steel in hundredths of interest.
˗ Letters indicate the main alloying elements included in the steel.
˗ The numbers after each letter denote the approximate percentage content of the corresponding element, rounded to an integer, when the alloying element is content up to 1.5%, the number is not specified during the corresponding letter.
˗ Letter A at the end of the brand indicates that steel high quality (with a reduced sulfur and phosphorus content)
˗ N - Nickel, X - Chrome, K - Cobalt, M - Molybdenum, V - Wolfram, T - Titan, D - Copper, G - Manganese, C - Silnic.
For example:
˗ 12х2Н4A - structural alloy steel, high quality, with carbon content of about 0.12%, chromium about 2%, nickel about 4%
˗ 40Khn - structural alloy steel, with carbon content of about 0.4%, chromium and nickel to 1.5%
Marking of other groups of structural steels
Spring steel.
˗ The main distinguishing feature of these steels - the carbon content in them should be about 0.8% (in this case, the elastic properties appear in the steels)
˗ Springs and springs are made of carbon (65.70,75,80) and alloyed (65С2, 50HGS, 60C2 chops, 55 hgr) structural steels
˗ These steel doped with elements that increase the limit of elasticity - silicon, manganese, chrome, tungsten, vanadium, boron
For example: 60C2 - Steel structural carbon spring-spring with a carbon content of about 0.65%, silicon about 2%.
Ball bearing steel
GOST 801-78 marked with the letters "Shx", after which the chromium content is indicated in the decisions of the percentage.
˗ For steels subjected to electric shielding, the letter W is added also at the end of their names through the dash.
For example: SHH15, SHH20SG, SHH4-sh.
˗ Of them produce parts for bearings, they are also used to make parts operating under high loads.
For example: SHH15 - steel structural ball bearing with a carbon content of 1%, chromium 1.5%
Automatic Steel.
GOST 1414-75 begin with the letter A (automatic).
˗ If the steel is doped with lead, then its name begins with the letters of the AU.
˗ To reflect the content in the steels of the remaining elements, the same rules are used as for alloyed structural steels. For example: A20, A40G, AC14, AC38HMM
For example: AC40 - steel structural machine, with a carbon content of 0.4%, lead 0.15-0.3% (not specified in the brand)
Practical part
Task for students:
2. Record the main signs of labeling all groups of structural steels (ordinary quality, high-quality steels, alloyed structural steels, spring-spring steels, ball bearings, automatic steels), with examples.
Options for options:
Decry the stamps and write down the scope of the specific brand (i.e., for the manufacture of which it is intended)
Practical work number 5
Topic: "Study of carbon and alloyed tool steels"
Purpose of work: familiarization of students with labeling and the area of \u200b\u200bapplication of structural steels; Formation of the ability to decipher the marking of structural steels.
Progress:
1. Consider with the theoretical part.
2. Complete the task of the practical part.
Theoretical part
Steel is an iron alloy with carbon, in which carbon is contained in an amount of 0-2.14%.
Steel are the most common materials. Have good technological properties. Products are obtained as a result of pressure and cutting processing.
The advantage is the ability to obtain the desired complex of properties, changing the composition and type of processing.
Depending on the purpose of the steel is divided into 3 groups: structural, instrumental and special-purpose steel.
Quality depending on the content of harmful impurities: sulfur and phosphorus steel are divided into: ordinary quality steel, content up to 0.06% sulfur and up to 0.07% phosphorus; high-quality - up to 0.035% sulfur and phosphorus each separately; high quality - up to 0.025% sulfur and phosphorus; Comprehensive, up to 0.025% phosphorus and up to 0.015% sulfur.
Instrumental steel are designed for the manufacture of various tools, both for manual processing and mechanical.
The presence of a wide range of steel and alloys manufactured in different countriesThe need to identify them, however, so far there is no uniform marking system steels and alloys, which creates certain difficulties for metal trading.
Marking of carbonaceous tool steels
˗ Steel data in accordance with GOST 1435-90 are divided into high-quality and high quality.
˗ Qualitative steel are denoted by the letter in (carbon) and a digit indicating the average carbon content in steel, in tenths of the percentage.
For example: U7, U8, U9, U10. U7 - carbon tool steel with a carbon content of about 0.7%
˗ In the designation of high quality steels, the letter A (U8A, U12A, etc.) is added. In addition, the letter G may be present in the notation of both high-quality and high-quality carbonaceous tools, indicating the increased content in the manganese steel.
For example: U8g, U8Ga. U8A - carbon tool steel with a carbon content of about 0.8%, high quality.
˗ Made a tool for handmade (chisel, kerner, diaper, etc.), mechanical work at low speeds (drills).
Marking of alloyed tool steels
˗ The rules for the designation of instrumental alloy steel according to GOST 5950-73 are mainly the same as for structural alloyed.
The difference lies only in numbers indicating the mass fraction of carbon in steel.
˗ The percentage of carbon is also indicated at the beginning of the name of steel, in tenths of interest, and not in hundredths, as for structural alloyed steels.
˗ If in the instrumental doped steel, the carbon content is about 1.0%, then the corresponding digit at the beginning of its name is usually not indicated.
We give examples: Steel 4x2V5MF, HBH, HVF.
˗ 9x5VF - alloyed tool steel, with carbon content of about 0.9%, chromium about 5%, vanadium and tungsten up to 1%
Tighted labeling (high-speed)
tool steels
˗ Denote by the letter "P", the figure following it indicates the percentage of tungsten in it: Unlike the alloyed steels in the names of high-speed steel, the percentage of chromium does not indicate, because It is about 4% in all steels, and carbon (it is proportional to the content of vanadium).
˗ The letter F showing the presence of vanadium is indicated only if the content of vanadium is more than 2.5%.
For example: P6M5, P18, P6 M5F3.
˗ Usually from these steels produce a high-performance tool: drills, cutters, etc. (for cheaper only work part)
For example: P6M5K2 - high-speed steel, with a carbon content of about 1%, tungsten about 6%, chromium about 4%, vanadium to 2.5%, molybdenum about 5%, cobalt about 2%.
Practical part
Task for students:
1. Record the name of the work, its goal.
2. Record the basic principles of labeling of all groups of instrumental steels (carbon, alloyed, high-alloyed)
Options for options:
1. Decipher the stamps and write down the scope of the specific brand (i.e., for the manufacture of which it is intended).
Practical work number 6
Topic: "Study of copper-based alloys: brass, bronze"
Purpose of work: Acquaintance of students with labeling and field of application of non-ferrous metals - copper and alloys based on it: brass and bronze; Formation of the ability to decipher labeling brass and bronze.
Recommendations for students:
Progress:
1. Consider with the theoretical part.
2. Complete the task of the practical part.
Theoretical part
Brass
Brass can be in their composition up to 45% zinc. The increase in zinc content up to 45% leads to an increase in the strength of up to 450 MPa. Maximum plasticity takes place when zinc content is about 37%.
According to the method of manufacturing products, brass deformable and foundry are distinguished.
The deformable brass is marked with the letter L, followed by a number indicating the copper content in percentages, for example, in brass L62 contains 62% of copper and 38% zinc. If, besides copper and zinc, there are other elements, then their initial letters are set (O - Tin, C - Lead, Z - Iron, F - Phosphorus, MC - Manganese, A - Aluminum, C - Zinc).
The number of these elements is denoted by the corresponding numbers after the number indicating the copper content, for example, the alloy LAG60-1-1 contains 60% of copper, 1% aluminum, 1% iron and 38% zinc.
Brass have good corrosion resistance, which can be enhanced by an additionally adding tin. Brass LO70 -1 Rack against corrosion in sea water And called "Sea Brass". The addition of nickel and iron increases the mechanical strength of up to 550 MPa.
Foundry brass are also marked with the letter L, after the letter notation of the main alloying element (zinc) and each subsequent is the digit, indicating its averaged content in the alloy. For example, brass Lz23A6Zh3MC2 contains 23% zinc, 6% aluminum, 3% iron, 2% manganese. The brand of the Lz16K4 brand has the best liquid process. Foundry brass includes brass type LS, LK, LA, LAW, LJs. Foundry brass are not inclined to the bait, have a concentrated shrinkage, castings are obtained with high density.
Brass are a good material for structures that work under negative temperatures.
Bronze
Copper alloys with other elements other than zinc are called bronze. Bronze is divided into deformable and foundry.
When labeling deformable bronze in the first place, the letters of the BR are set, then the letters indicating which elements, except copper, are included in the alloy. After the letters are numbers, showing the contents of the composition components. For example, Brand Brof10-1 means that 10% tin is included in the bronze, 1% f o ozfora, the rest is copper.
The casting bronze marking also begins with the letters of the BR, then the letter designations of the alloying elements are indicated and the figure indicates its averaged content in the alloy. For example, bronze bro3c12С5 contains 3% tin, 12% zinc, 5% lead, the rest is copper.
Tin bronze When fusing copper with tin, solid solutions are formed. These alloys are very prone to liquor due to the large thermal interval of crystallization. Due to the fusion of alloys with a tin content above 5% is favorable for parts of the sliding bearings: the soft phase provides good old worker, solid particles create wear resistance. Therefore, tin bronze are good antifriction materials.
Tin bronze have a low bulk shrinkage (about 0.8%), so used in artistic casting. The presence of phosphorus provides good liquid process. Tin bronze is divided into deformable and foundry.
In the deformable bronze, the tin content should not exceed 6%, to provide the required plasticity, Brof6.5-0.15. Depending on the composition of the deformable bronze differ in high mechanical, anti-corrosion, antifriction and elastic properties, and are used in various industries. From these alloys, rods, pipes, ribbon, wire are made.
Practical part
Task for students:
1. Release the name and purpose of the work.
2. Requires the table:
Namealloy, It
definition
Maintenance
properties
alloy
Example
marking
Decoding
brands
Region
applications
Practical work number 7
Topic: "Study of aluminum alloys"
Purpose of work: familiarization of students with marking and the area of \u200b\u200bnon-ferrous metals - aluminum and alloys based on it; Studying the features of the use of aluminum alloys depending on their composition.
Recommendations for students: Before proceeding to perform the practical part of the task, carefully read theoretical provisions, as well as lectures in your workbook on this topic.
Progress:
1. Consider with the theoretical part.
2. Complete the task of the practical part.
Theoretical part
The principle of labeling aluminum alloys. At the beginning indicates the type of alloy: d - alloys of the type of duralumin; A - technical aluminum; AK -KOV aluminum alloys; In - high strength alloys; Al - casting alloys.
The continuous alloy number is indicated. The conditional number follows the designation characterizing the state of the alloy: m - soft (implanted); T - thermally processed (hardening plus aging); N-funded; P - semi-finished.
According to the technological properties of the alloys are divided into three groups: deformable alloys, non-refined heat treatment; deformable alloys strengthened by heat treatment; Foundry alloys. The methods of powder metallurgy produce sintered aluminum alloys (CAC) and sintered aluminum powder alloys (SAP).
Deformable casting alloys that are not hardened by heat treatment.
Aluminum strength can be raised by doping. In alloys, not hardened by heat treatment, manganese or magnesium are introduced. Atoms of these elements significantly increase its strength, reducing plasticity. The alloys are indicated: with manganese - AMC, with magnesium - AMG; After the element designation indicates its content (AMG3).
Magnesium acts only as a complementar, manganese strengthens and increases corrosion resistance. Alloy strength increases only as a result of strain in cold condition. The greater the degree of deformation, the more significant the strength is growing and the plasticity is reduced. Depending on the degree of hardening, the alloys of muggy and semi-finished (AMG3P) differ.
These alloys are used for the manufacture of various welded tanks for fuel, nitric and other acids, low and medium-wide structures. Deformable alloys, strengthened heat treatment.
Such alloys include duralumin (complex alloys of aluminum systems - copper - magnesium or aluminum - copper - magnesium - zinc). They have reduced corrosion resistance, to increase which manganese is introduced. Duralumins are usually undergoing temperatures of 500 about With and natural aging, which is preceded by a two-, three-hour incubation period. The maximum strength is achieved through 4.5 days. The widespread use of Duralumin is found in aircraft engineering, automotive, construction.
High strength aging alloys are alloys, which, in addition to copper and magnesium, contain zinc. B95 alloys, B96 have a strength of about 650 MPa. The main consumer is aircraft (covering, stringers, spars).
Forging aluminum alloys AK, AK8 are used for the manufacture of forgings. Forgings are made at a temperature of 380-450 about C, exposed to quench the temperature of 500-560 about C and aging at 150-165 about C for 6 hours.
Nickel, iron, titanium, which increase the recrystallization temperature and heat resistance to 300 are additionally introduced into the aluminum alloys. about FROM.
Pistons, blades and discs of axial compressors, turbojet engines are manufactured.
Foundry alloys
Foundry alloys include alloys of the aluminum system - silicon (silhoins) containing 10-13% silicon. Additive to the silum of magnesium, copper contributes to the effect of hardening the casting alloys during aging. Titanium and zirconium crushed grain. Manganese increases anticorrosive properties. Nickel and iron increase heat resistance.
Foundry alloys are marked with al2 to al20. Silhounds are widely used for the manufacture of cast details of devices and other medium - and low-loaded parts, including thin-walled castings of complex shape.
Practical part
Task for students:
1. Record the name and purpose of the work.
2. Fill in the table:
Namealloy, It
definition
Maintenance
properties
alloy
Example
marking
Decoding
brands
Region
applications
Laboratory work number 1
Topic: "Mechanical properties of metals and methods for studying (hardness)"
Purpose of work:
Progress:
1. Consider with theoretical positions.
2. Complete the task of the teacher.
3.Cill the report in accordance with the task.
Theoretical part
The hardness is called the ability of the material to resist the penetration of another body into it. When testing on hardness, the body introduced into the material and called an indenter must be more solid, to have certain sizes and shape should not receive residual deformation. Hardness tests can be static and dynamic. The first type includes testing by the method of indulgence, to the second - by the method of shockproof. In addition, there is a method for determining the hardness of the scarring - sclerometry.
By the value of metal hardness, you can make an idea of \u200b\u200bits properties. For example, the higher the hardness determined by the pressure of the tip, the less the plasticity of the metal, and vice versa.
The instrumental test tests are that an indenter (diamond, from hardened steel, solid alloy), having a ball, cone or pyramid form, is pressed into the sample under the action of the load. After removing the load on the sample, the imprint remains measuring the magnitude of which (diameter, depth or diagonal) and comparing it with the size of the indenter and the load value, can be judged by the metal hardness.
The hardness is determined on special devices - hardness. The most often hardness is determined by the methods of Brinell (GOST 9012-59) and Rockwell (GOST 9013-59).
There are general requirements for the preparation of samples and testing with these methods:
1. The surface of the sample must be clean, without defects.
2. Samples must be a certain thickness. After receiving the imprint on the reverse side of the sample should not be traces of deformation.
3. The sample must lie on the table rigidly and steadily.
4. The load should act perpendicular to the surface of the sample.
Determination of Brinell Hardness
The hardness of the brine metal is determined by indulging in the sample of the tempered steel ball (Fig. 1) with a diameter of 10; 5 or 2.5 mm and expressed by the number of HB hardness obtained by the division of the applied load P in H or kgf (1H \u003d 0.1 kgf) on the surface area formed on the sample print F in mm
Brinell Hardness HB. expressed by the attitude of the appointed loadF. To SquareS. Spherical surface of the imprint (wells) on the measured surface.
HB. = , (MPa),
where
S. - Square spherical surface of the imprint, mm 2 (expressed throughD. andd.);
D. - the diameter of the ball, mm;
d. - the diameter of the imprint, mm;
Load valueF. , Sharch diameterD. And the duration of the excerpt under the load τ is chosen according to Table 1.
Figure 1. Scheme measurement of hardness by the method of Brinell.
a) Paving the ball into the test metal
F.D. - Bulb diameter,d. ref - the diameter of the imprint;
b) Measurement of the magnetic print diameter (in the pictured.\u003d 4.2 mm).
Table 1.
Select the diameter of the ball, load and excerpt under load depending
from hardness and sample thickness
More than 6.6…3
less than 3.
29430 (3000)
7355 (750)
1840 (187,5)
Less than 1400.
more than 6.
6…3
less than 3.
9800 (1000)
2450 (750)
613 (62,5)
Non-ferrous metals and alloys (copper, brass, bronze, magnesium alloys, etc.)
350-1300
more than 6.
6…3
less than 3.
9800 (1000)
2450 (750)
613 (62,5)
30
Non-ferrous metals (aluminum, bearing alloys, etc.)
80-350
more than 6.
6…3
less than 3.
10
5
2,5
2450 (250)
613 (62,5)
153,2 (15,6)
60
Figure 2 shows a diagram of a lever device. The sample is installed on the subject table 4. Rotating flywheel 3, screw 2 raise the sample to contact it with a ball 5 and further to complete compression of the spring 7, put on the spindle 6. The spring creates a pre-load on the ball equal to 1 kN (100 kgf) that Provides a steady position of the sample during loading. Thereafter, the electric motor 13 and through the worm gear of the gearbox 12, the connecting rod 11 and the system of the levers of 8.9, located in the hardware body 1 with loads 10 creates a given full load on the ball. On the test sample, a ball imprint is obtained. After unloading the device, the sample is removed and determined by the diameter of the imprint of a special magnifying glass. For the calculated diameter of the imprint, the average arithmetic value of measurements in two mutually perpendicular directions are taken.
Figure 2. Brinell Device Scheme
According to the above formula, using the measured diameter of the imprint, the number of HB hardness is calculated. The number of hardness depending on the diameter of the received imprint can also be found along tables (see the table of hardness numbers).
When measuring hardness with a ball with a diameter d \u003d 10.0 mm under the load F \u003d 29430 H (3000 kgf), with a shutter speed τ \u003d 10 C - the number of hardness is written as follows:HB. 2335 MPa or old designation NV 238 (in kgf / mm 2 )
When measuring the hardness of the brinell, you must remember the following:
You can experience materials with hardness no more than 4,500 MPa, since with greater hardness of the sample there is an unacceptable deformation of the ball itself;
In order to avoid puzzle, the minimum sample thickness should be at least tenfold the imprint depth;
The distance between the centers of two adjacent prints should be at least four diameters of the imprint;
The distance from the center of the print to the side surface of the sample must be at least 2.5d..
Determination of hardness by Rockwell
According to the Rockwell method, the hardness of the metals is determined by indulge in the test sample of the hardened steel ball with a diameter of 1,588 mm or a diamond cone with an angle at the top of 120 about Under the action of two consistently accompanying loads: a preliminary p0 \u003d 10 kgf and a general p equal to the amount of preliminary P0 and the main P1 loads (Fig. 3).
Rockwell hardnessHr. It is measured in conditional dimensionless units and is determined by the formulas:
Hr. c. \u003d - when pressing a diamond cone
Hr. in \u003d - when indulging the steel ball,
where 100.– the number of divisions of the black scale C, 130 is the number of fission of the red scale into the dial of the indicator, measuring the depth of indulgence;
h. 0 - Depth of indulgence of a diamond cone or a ball under the action of preload. MM.
h. - Depth of indulgence of a diamond cone or ball under the action of a total load, mm
0.002 - the price of dividing the scale of the dial of the indicator (moving a diamond cone when measuring hardness by 0.002 mm corresponds to the movement of the arrow of the indicator on one division), mm
The type of tip and the load value is selected according to Table 2, depending on the hardness and thickness of the test sample. .
Rockwell hardness number (Hr.) It is a measure of the depth of indenter indentation and is expressed in conventional units. Over the unit of hardness adopted a dimensionless value corresponding to axial movement by 0.002 mm. The number of rockell hardness is directly directly arrow on the scale or in the indicator after automatic removal of the main load. The hardness of the same metal, determined by various methods, is expressed by various units of hardness.
For example,HB. 2070, Hr. c. 18 orHr. in 95.
Figure 3. Rockwell hardness measurement scheme
table 2
IN
Hr. IN
Steel Ball
981 (100)
0,7
25…100
on the scale B.
from 2000 to 7000 (hardened steel)
FROM
Hr. FROM
Diamond cone.
1471 (150)
0,7
20…67
on the scale of C.
From 4000 to 9000 (parts subjected to cementation or nitrogenation, solid alloys, etc.)
BUT
Hr. BUT
Diamond cone.
588 (60)
0,4
70…85
on the scale B.
Rockwell method is characterized by simplicity and high performance, ensures the preservation of the high-quality surface after the test, allows you to test metals and alloys, both low and high hardness. This method is not recommended for alloys with an inhomogeneous structure (gray, damp and high-strength cast iron, antifriction bearing alloys, etc.).
Practical part
Content of the report.
Specify the name of the work, its goal.
Answer the questions:
1. What is called hardness?
2. What is the essence of the definition of hardness?
3. What 2 methods for determining hardness do you know? What is their difference?
4. How to prepare a sample to the test?
5. How to explain the absence of a universal method for determining hardness?
6. Why of many mechanical characteristics of materials most often determine hardness?
7. Fix in the notebook the scheme for determining the hardness of the brinnal and Rockwell.
Laboratory work number 2
Topic: "Mechanical properties of metals and methods for studying (strength, elasticity)"
Purpose of work: Examine the mechanical properties of metals, methods for studying them.
Progress:
1. Consider with theoretical positions.
2. Complete the task of the teacher.
3.Cill the report in accordance with the task.
Theoretical part
The main mechanical properties are strength, elasticity, viscosity, hardness. Knowing mechanical properties, the constructor reasonably selects the corresponding material that ensures the reliability and durability of the structures in their minimum mass.
Mechanical properties determine the behavior of the material during deformation and destruction from the action of external loads. Depending on the loading conditions, mechanical properties can be determined at:
1. Static loading - the load on the sample increases slowly and smoothly.
2. Dynamic loading - the load increases at high speed, has a shock.
3. Re-alternating or cyclic loading - the load in the process of testing is repeatedly varied in magnitude or in size and direction.
To obtain comparable results, the samples and methods for carrying out mechanical tests are grunting. With a static tensile test: GOST 1497 receives the characteristics of strength and plasticity.
Strength - the ability of the material to resist deformations and destruction.
Plasticity is the ability of the material to change its dimensions and shape under the influence of external forces; Measure plasticity - the value of residual deformation.
A device that determines strength and plasticity is a discontinuous machine that records the tensile diagram (see Fig. 4) expressing the relationship between the elongation of the sample and the active load.
Fig. 4. Tensile diagram: A - absolute, b - relative.
The OA site on the diagram corresponds to the elastic deformation of the material when the law of the thread is observed. The voltage corresponding to the elastic limit deformation at point A is called the proportionality limit.
The limit of proportionality is the greatest tension, until the achievement of which is the law of the throat.
At stresses above the proportionality limit, uniform plastic deformation occurs (elongation or narrowing of the section).
Point B - the limit of elasticity - the highest voltage, until the achievement of which residual deformation does not occur in the sample.
The CD platform is a flow pad, it corresponds to the yield limit - this voltage at which the deformation increases in the sample without increasing the load (the material "flows").
Many steel grades, non-ferrous metals have a pronounced fluidity platform, so the conditional yield strength is set for them. The conditional yield strength is a voltage that corresponds to the residual deformation of 0.2% on the initial length of the sample (alloy steel, bronze, duralumin and other materials).
The point in corresponds to the limit strength (a local refinement appears on the sample - neck, the formation of the refinement is characteristic of plastic materials).
The tensile strength is the maximum voltage that can withstand the sample to permission (time resistance).
Over the point in the load falls (due to the elongation of the neck) and the destruction occurs at the point K.
Practical part.
Content of the report.
1. Specify the name of the work, its goal.
2. What mechanical properties do you know? What methods do the mechanical properties of materials are determined?
3. Write down the definition of concepts strength and plasticity. What methods do they define? What is the name of the device that determines these properties? With what properties are defined?
4. Secure the absolute tension diagram of the plastic material.
5. After the diagram, specify the names of all points and sections of the diagram.
6. What limit is the main characteristic when choosing a material for the manufacture of any product? Justify the answer.
7. What materials are more reliable in work fragile or plastic? Justify the answer.
Bibliography
Main:
Adakin A.M., Zuev V.M. Materials science (metalworking). - M.: OITs "Academy", 2009 - 240 p.
Adakin A.M., Zuev V.M. Materials and technology materials. - M.: Forum, 2010 - 336 p.
Chumachenko Yu.T. Materials science and plot (NGOs and SPO). - Rostov N / D.: Phoenix, 2013 - 395 s.
Additional:
Zhukovets I.I. Mechanical tests of metals. - M.: Horsis.Shk., 1986. - 199 p.
Lakhtin Yu.M. Basics of materials science. - M.: Metallurgy, 1988.
Lakhtin Yu.M., Leontiev V.P. Materials Science. - M.: Mechanical Engineering, 1990.
Electronic resources:
1. Materials Magazine. (Electronic resource) - the form of access http://www.nait.ru/journals/index.php?p_journal_id\u003d2.
2. Materials Science: Educational resource, Access form http: // www.supermetalloved / narod.ru.
3. Market Steel. (Electronic resource) - WWW.SPLAV.Kharkov.com access form.
4. Federal Center for Information and Educational Resources. (Electronic resource) - the form of access www.fcior.ru.
