Laboratory work on materials science. Brief theoretical information
Questions for the exam for the 2nd year of the Faculty of IM
Questions for the exam for 1st year undergraduates of IM
Laboratory works
Laboratory journals for the course "Materials Science"
(For laboratory work, students need to have a printed version of the laboratory journals with them)
Laboratory work on the course "Materials Science"
Laboratory work on the course "Materials Science"
The main educational and educational-methodical literature on the disciplines read at the department
Cycle Materials Science
1. Bogodukhov S.I., Kozik E.S. Materials Science. Textbook for universities. - M .: Mashinostroenie, 2015 .-- 504 p.
2. Solntsev Yu.P., Pryakhin E.I. Materials Science. Textbook for universities. - SPb .: KHIMIZDAT, 2007 .-- 784 p.
3. Arzamasov V.B., Cherepakhin A.A. Materials Science. Textbook. - M .: Examination, 2009 .-- 352 p.: Ill.
4. Oskin V.A., Baikalova V.N., Karpenkov V.F. Workshop on Materials Science and Technology of Structural Materials: Tutorial for universities (ed. Oskin V.A., Baikalova V.N.). - M .: KolosS, 2007 .-- 318 p .: ill.
5. Materials science and technology of metals: textbook for universities / G.P. Fetisov and others - 6th ed., Add. - M .: graduate School, 2008 .-- 878 p.
6. Materials science and technology of metals: a textbook for universities in machine-building specialties / G.P. Fetisov, M.G. Karpman and others - M .: Higher school, 2009 .-- 637 p.
7. Medvedeva M.L., Prygaev A.K. A notebook on materials science. Methodical manual - M .: Publishing Center of the Russian State University of Oil and Gas named after THEM. Gubkina, 2010, 90 p.
8. Efimenko L.A., Elagina O.Yu., Prygaev A.K., Vyshemirsky E.M., Kapustin O.E., Muradov A.V. Promising and traditional pipe steels for the construction of gas and oil pipelines. Monograph. - M .: Logos, 2011, 336 p.
9. Prygaev A.K., Kurakin I.B., Vasiliev A.A., Krivosheev Yu.V. Justification of the choice of structural materials and the development of modes of their heat treatment for the manufacture of machine parts and equipment for the oil and gas industry. Methodical manual for course work on the discipline "Materials Science" - M .: Russian State University of Oil and Gas named after IM Gubkina, 2015
10. Fektistov G.P., Karpman M.G., Miatyukhin V.M. and other Materials science and technology of materials. - M .: Higher school, 2000
11. Gulyaev A.P. Materials Science. - M .: Metallurgy, 1986
12. Efimenko L.A., Prygaev A.K., Elagina O.Yu. Metallurgy and heat treatment of welded joints. Tutorial. - M .: Logos, 2007 .-- 455 p.: Ill.
13. Methodical guidelines for laboratory work on the course "Materials Science" part 1 and part 2, - M .: Russian State University of Oil and Gas, 2000
14. Trofimova G.A. Methodical guidelines for laboratory works "Construction and analysis of thermomechanical curves for amorphous polymers" and "Determination of mechanical properties of plastics and rubbers." - Moscow: Russian State University of Oil and Gas named after I.M. Gubkin, 1999
Cycle Corrosion and protection of oil and gas equipment
1. Semenova I.V., Florianovich G.M., Khoroshilov A.V. Corrosion and corrosion protection. - M: Fizmatlit, 2010 .-- 416 p.
2. Medvedeva M.L. Corrosion and equipment protection in oil and gas processing. Tutorial. Moscow: FSUE Publishing House "Oil and Gas" Russian State University of Oil and Gas named after I.M. Gubkina, 2005 .-- 312 p .: ill.
3. Medvedeva M.L., Muradov A.V., Prygaev A.K. Corrosion and protection of main pipelines and reservoirs: Textbook for universities of oil and gas profile. - M .: Publishing Center of the Russian State University of Oil and Gas named after I.M. Gubkina, 2013 .-- 250 p.
4. Sorokin G.M., Efremov A.P., Saakiyan L.S. Corrosion-mechanical wear of steels and alloys. -M .: Oil and Gas, 2002
Cycle Tribology
1. Sorokin G.M., Malyshev V.N., Kurakin I.B. Tribology of steels and alloys: Textbook for universities. - M .: Russian State University Oil and Gas named after I.M. Gubkina, 2013 .-- 383 p .: ill.
2. Sorokin G.M., Kurakin I.B. System analysis and complex criteria for the strength of steels. - M .: Nedra Publishing House LLC, 2011. - 101 p.
3. Sorokin G.M. Tribology of steels and alloys. M .: Nedra, 2000
4. Vinogradov V.N., Sorokin G.M. Mechanical wear of steels and alloys: Textbook for universities. - M .: Nedra, 1996 .-- 364 p .: ill.
5. Vinogradov V.N., Sorokin G.M. Wear resistance of steels and alloys: Textbook for universities. - M .: Oil and gas, 1994 .-- 417 p .: ill. 246.
Theme:Study of the crystallization process of metals
Purpose of work: to study the mechanism of crystallization of metals, the energy conditions of the crystallization process.
Work order
1. Study theoretical information.
2. In a notebook for practical work, answer in writing the control questions.
Theoretical information
The general property of metals and alloys is their crystalline structure, which is characterized by a certain arrangement of atoms in space. To describe the atomic-crystal structure, the concept of a crystal cell is used - the smallest volume, the translation of which in all dimensions can fully reproduce the structure of the crystal. In a real crystal, atoms or ions are brought close to each other to a state of direct contact, but for simplicity they are replaced by schemes where the centers of attraction of atoms or ions are depicted by dots; The cells most typical for metals are shown in Fig. 1.1.
Figure 1.1. Types of crystal lattices and the arrangement of atoms in them:
a) face-centered (FCC), b) body-centered (BCC), c) hexagonal close-packed (GSC)
Any substance can be in three aggregate states: solid, liquid and gaseous, and the transition from one state to another occurs at a certain temperature and pressure. Most technological processes occur at atmospheric pressure, then phase transitions are characterized by the temperature of crystallization (melting), sublimation and boiling (evaporation).
With an increase in the temperature of a solid, the mobility of atoms in the nodes of the crystal cell increases, and their vibration amplitude increases. When the melting temperature is reached, the energy of the atoms becomes sufficient to leave the cell - it collapses with the formation of a liquid phase. Melting point is an important physical constant of materials. Among metals, mercury has the lowest melting point (-38.9 ° C), and the highest is tungsten (3410 ° C).
The opposite picture takes place when the liquid is cooled with its further solidification. In the vicinity of the melting point, groups of atoms are formed, packed into cells, as in a solid. These groups are centers (nuclei) of crystallization, and then a layer of crystals grows on them. Upon reaching the same melting point, the material passes into a liquid state with the formation of a crystal lattice.
Crystallization is the transition of a metal from a liquid to a solid state at a certain temperature. According to the law of thermodynamics, any system tends to go into a state with a minimum value of free energy - a composite internal energy that can be isothermally converted into work. Therefore, the metal solidifies when there is less free energy in the solid state and melts when there is less free energy in the liquid state.
The crystallization process consists of two elementary processes: the nucleation of crystallization centers and the growth of crystals from these centers. As noted above, at a temperature close to crystallization, the formation of a new structure, a crystallization center, begins. With an increase in the degree of supercooling, the number of such centers increases, around which crystals begin to grow. At the same time, new crystallization centers are formed in the liquid phase; therefore, an increase in the solid phase occurs simultaneously both due to the emergence of new centers and due to the growth of existing ones. The total crystallization rate depends on the course of both processes, and the rates of nucleation of centers and crystal growth depend on the degree of supercooling ΔТ. In fig. 1.2 schematically shows the crystallization mechanism.
Rice. 1.2. Crystallization mechanism
Real crystals are called crystallites, they have an irregular shape, which is explained by their simultaneous growth. Crystallization nuclei can be fluctuations of the base metal, impurities and various solid particles.
The grain sizes depend on the degree of supercooling: at small values of ΔТ, the crystal growth rate is high, therefore, an insignificant amount of large crystallites is formed. An increase in ΔТ leads to an increase in the rate of nucleation, the number of crystallites increases significantly, and their sizes decrease. However, the main role in the formation of the metal structure is played by impurities (non-metallic inclusions, oxides, deoxidation products) - the more there are, the smaller the grain sizes. Sometimes the metal is modified on purpose - the deliberate introduction of impurities in order to reduce the grain size.
In the formation of the crystal structure, the direction of heat removal plays an important role, because the crystal grows faster in this direction. The dependence of the growth rate on the direction leads to the formation of branched tree-like crystals - dendrites (Fig. 1.3).
Rice. 1.3 Dendritic crystal
During the transition from a liquid to a solid state, selective crystallization always takes place - first of all, the purer metal hardens. Therefore, the grain boundaries are more enriched in impurities, and the heterogeneity of the chemical composition within the dendrites is called dendritic liquation.
In fig. 1.4. shows the structure of a steel ingot, in which it is possible to distinguish 3 characteristic zones: fine-grained 1, a zone of columnar crystals 2 and a zone of equilibrium crystals 3. Zone 1 consists of a large number of crystals not oriented in space, formed under the influence of a significant temperature difference between the liquid metal and cold walls.
Rice. 1.4. Steel ingot structure
After the formation of the outer zone, the conditions for heat removal deteriorate, hypothermia decreases and fewer crystallization centers appear. Crystals begin to grow from them in the direction of heat removal (perpendicular to the walls of the mold), forming zone 2. In zone 3 there is no clear direction for heat removal, and the nuclei of crystallization in it contain foreign particles displaced during the crystallization of the previous zones.
Control questions
1. In what states of aggregation can material exist?
2. What is called a phase transformation of the first kind?
3. What process is called crystallization, to what type of phase transformation does it belong?
4. Describe the crystallization mechanism of the metal and the conditions necessary for its start.
5. What is the cause of the dendritic shape of the crystals?
6. Describe the structure of the metal ingot
Laboratory works on the course "Materials Science"
Th semester
1. "Analysis of the crystal structure of metals and alloys" (No. 1, workshop 2). 2 h.
2. "Testing materials for hardness" (No. 10, workshop 2). 1 h.
3. "Testing of samples in tension" (No. 11, workshop 2; or "Mechanical properties of structural materials", a separate file). 2 h.
4. "Determination of the impact strength of the material" (No. 12, workshop 2). 1 h.
5. "Fractographic analysis of the destruction of metallic materials" (No. 9, workshop 2). 1 h.
6. "Influence of cold plastic deformation and recrystallization temperature on the structure and properties of metals" (No. 4, workshop 1). 2 h.
7. "Thermal analysis of alloys" (No. 1, workshop 1). Part 1 - construction of a state diagram of the "zinc-tin" system by the thermal method. Part 2 - analysis of the diagrams of the state of binary alloys: perform an individual task under item 5 in the "Content of the report". 2 h.
8. "Macroscopic analysis (macroanalysis) of the structure of metallic materials" (No. 2, workshop 2). 1 h.
9. "Microscopic analysis (microanalysis) of the structure of metallic materials" (No. 3, workshop 2). 1 h.
Th 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 the method of microanalysis ", workshop 2). Practical part: students look at the structure of four iron-carbon alloys using a MIM-7 microscope: technical iron, hypoeutectoid, eutectoid and hypereutectoid alloys. They make schematic sketches, sign the structural components, give an example of a steel grade, for a hypoeutectoid alloy, the carbon content is calculated using the formula. 1 h. + t.
2 (11). “Iron-carbon status diagram. The structure, properties and application of cast irons "No. 3 from the workshop 1) or a similar work No. 8" Investigation of the structure of carbon cast irons by the microanalysis method "from the workshop 2). Practical part: students look at the structure of three cast irons on the MIM-7 microscope: gray cast iron with fine-lamellar graphite on a pearlite base, ductile iron on a ferrite-pearlite base and hypoeutectic white cast iron. Unfortunately, no more. They also make sketches, write the names of cast irons and structural components. 1 h. + t.
3 (12). "The influence of the cooling rate on the hardness of carbon steel" No. 20 from the workshop 2). Practical part: four samples from U8 steel. One is annealed, the second is normalized, the third is oil quenched, and the fourth is water quenched. The hardness is measured, a graph of the dependence of the hardness on the cooling rate is plotted. Cooling rates are taken from a table in laboratory work. 2 h.
4 (13). "Quenching of carbon steels" No. 5 from workshop 1). Practical part: three samples of steel 20, 45, U9 are quenched in water, one sample of steel 45 is quenched in oil. The hardness is measured before (HRB) and after (HRC) hardening. The conversion table is used to determine the hardness in HB units. Based on the results, two graphs are built: HB = f (% C) and HRC = f (Vcool.). 2 h. + t.
5 (14). "Vacation of steel" No. 6 from the workshop 1) or similar work No. 18 "Vacation of carbon steel" from the workshop 2). Practical part: according to workshop 1), low (200 ° C), medium (400 ° C) and high (600 ° C) tempering of hardened specimens from steel 45 and low tempering (200 ° C) of a hardened specimen from steel U9 are carried out. Measure the hardness. Build a graph HRC = f (Tamp.). According to workshop 2), low, medium and high tempering of hardened samples from U8 steel is carried out. 2 h. + t.
6 (15). "Annealing and normalization of steel" No. 7 from workshop 1). Practical part: two samples of steel 45. Isothermal annealing is carried out with one, and normalization with the second. 2 h. + t.
7 (16). "Chemical heat treatment of steel" No. 8 from workshop 1. 1 h.
8 (17). "The influence of alloying elements on the hardenability of steel, determined by the method of end hardening" No. 21 from workshop 2. 2 h.
9 (18). "Classification, labeling and use of construction materials." Practical part: students receive a card with five stamps, describe each in detail. 1 h.
Laboratory work No. 1
ANALYSIS OF THE CRYSTALLINE STRUCTURE
METALS AND ALLOYS
Purpose of work:
Get acquainted with the types of crystal lattices of metals and alloys, crystal structure defects and types of solid solutions.
Devices, materials and tools
Models of the main types of crystal lattices of metals and solid solutions.
Brief theoretical information
Atomic crystal structure of metals. Metals under normal conditions have a crystalline structure, distinctive feature which is a certain mutual periodic arrangement of atoms, spreading over arbitrarily large distances. This arrangement of atoms is usually called long-range order. Thus, the atomic-crystal structure is understood as the mutual arrangement of atoms (ions) that exists in a real crystal. To describe the atomic-crystal structure, the concept of a spatial or crystal lattice is used. The crystal lattice of a metal is an imaginary spatial grid, at the nodes of which atoms (ions) are located, between which free electrons move. The electrostatic forces of attraction between ions and electrons balance the repulsive forces between ions. Thus, the positions of the atoms are such that the minimum interaction energy between them is ensured, and, consequently, the stability of the entire aggregate.
The minimum volume of a crystal that gives an idea of the atomic structure of a metal in the entire volume is called elementary crystal cell. Pure metals have one of the following types of crystal lattice: body-centered (bcc), face-centered (fcc) and hexagonal close-packed (hcp) (Fig. 1).
The bcc lattice is, for example, a-iron, lithium, vanadium, tungsten, molybdenum, chromium, tantalum; FCC lattice - aluminum, g-iron, copper, gold, nickel, platinum, lead, silver. The hcp lattice has magnesium, zinc, beryllium, cadmium, cobalt, a-titanium.
Coordinate directions (crystallographic axes). In the system of crystallographic axes, the shape of the unit cell of the spatial lattice can be described using three coordinate angles a, b, and g between the crystallographic axes and three lattice parameters a, b, c.
The unit cells of cubic lattices of bcc (Fig.1a) and fcc (Fig.1b) are characterized by the equality of the angles a = b = g = 90 ° and the equality of the lattice parameters a = b = c. The hcp lattice (Fig.1c) is characterized by the values of the angles a = b = 90 ° and g = 120 ° and the equality of the two lattice parameters a = b c.
Crystallographic symbols are used to describe atomic planes and directions in a crystal. To determine the symbols of the planes, use the method of indexing the plane by line segments. For this, a coordinate system is selected so that the coordinate axes I, II, III are parallel to the three intersecting edges of the crystal (Fig. 2). As a rule, the first crystallographic axis is directed towards the observer, the second is horizontal, and the third is oriented upward. Plane А 1 В 1 С 1 cuts off at coordinate axes segments equal in size to the lattice parameters ОА 1 = a, ОВ 1 = b, OC 1 = c. The plane A 1 B 1 C 1 is called a single plane. Lattice parameters a, b, c are taken as axial units.
To determine the crystallographic indices of the plane А 2 В 2 С 2, it is necessary:
Find the parameters of a given plane, i.e., the segments in axial units, cut off by this plane on the coordinate axes;
Write down the ratio of three fractions, the numerators of which are the parameters of the unit plane А 1 В 1 С 1, and the denominators are the parameters of the given plane А 2 В 2 С 2, i.e. 1 / ОА 2: 1 / ОВ 2: 1 / ОВ 2;
Reduce the resulting ratio to the ratio of three integers coprime numbers, that is, reduce the fractions to common denominator, reduce, if possible, by a common factor, and discard the denominator.
The resulting three integers and coprime numbers, denoted by h, k, l, are called the indices of the atomic plane. The set of indices is called the symbol of the atomic plane, which is usually enclosed in parentheses and written (hkl). If the plane intersects the coordinate axes in a negative quarter, then a "-" sign is placed above the index. If the plane under consideration is parallel to one of the crystallographic axes, then the index corresponding to this axis is zero. Figure 3 shows examples of the indexing of planes in the Bravais cubic unit cell.
The symbols should be read numerically, for example (100) as 1, 0, 0. The symbols for the parallel planes are the same. Consequently, the plane symbol describes an infinitely large family of parallel atomic planes that are structurally equivalent. Atomic planes of one family are located from each other at an equal interplanar distance d.
Atomic planes of different families can be non-parallel, but identical in the arrangement of atoms and interplanar distance d. Such planes are combined and denoted by the symbol (hkl). So, in cubic crystals, one set includes families of planes, the indices of which differ only in signs and location in the symbol. For example, the set of atomic planes (100) includes six families: (100), (͞100), (010), (0 ͞10), (001), (00͞1).
The symbol of the crystallographic direction is determined using three coprime numbers (indices) u, v, w, which are proportional to the coordinates of the radius vector R connecting the origin (starting site) with the nearest crystal lattice site in a given direction. Indices are enclosed in square brackets and written down. If the direction does not pass through the origin (starting node), then it must be mentally transferred parallel to itself or move the origin and coordinate axes so that the direction passes through the origin.
Figure 4 shows examples of crystallographic directions indication in a cubic crystal.
Place the origin at the point O... Then, for example, the point with has coordinates 0, 0, 1; direction symbol wasps-. It is read separately - "direction zero - zero - one". Point e has coordinates ½; ½; 1; direction symbol oh-. To define a direction symbol aw, mentally transfer it parallel to itself to the point O; then the coordinates of the point v- ͡͞1, 1, 0; direction symbol is [͞110]. When the direction is reversed, the signs of the indices are reversed, for example, and (see Figure 1.5). Parallel directions have the same symbols and are combined into families. Families of identical but non-parallel directions form a set, which is denoted by
In hexagonal crystals, a four-axis coordinate system is mainly used to indicate planes. Examples of plane indexing in a hexagonal crystal are shown in Figure 5.
The fourth coordinate axis OU lies in the horizontal plane and is located along the bisector between the negative semiaxes (-ОХ) and (-ОY). The plane symbol consists of four indices and is written (hkil). Three of them (h, k and l) are calculated from the reciprocal values of the 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 = 0 (1)
For example, if h = 1; k = 1, l = 0, then, using relation (1), we can find the fourth index: i = - (h + k) = - (1 +1) = -2. The plane symbol is written as (11͞20). This is the plane closest to us in Figure 6. The fourth index i is used when it is necessary to designate identical planes, and is not used when calculating interplanar distances, angles between planes and directions. Therefore, instead of completely writing the plane symbol, for example, (11͞20), sometimes (11.0) is used, i.e. instead of the index i, they put a period. Families and assemblies of identical planes are defined similarly to families and assemblies in cubic crystals.
To describe the crystallographic directions in hexagonal crystals, both triaxial and four-axial symbols are used. Triaxial symbols are determined by the coordinates of a given radius vector (as in cubic crystals).
There is a relationship between the four-axis directional indices:
r 1 + r 2 + r 3 = 0 (2)
To switch from three-axis symbols to four-axis symbols, the following ratios are used:
r 1 = 2u –v; r 2 = 2v - u; r 3 = -u - v; r 4 = 3w (3)
Examples of indication of crystallographic directions in a hexagonal crystal are shown in Figure 6.
In addition to the geometric characteristics of a crystal, physical materials science uses the following concepts: the number of atoms per cell n I, the coordination number (CN) and the filling factor η.
By the number of atoms per cell n I mean the number of atomic volumes per Bravais unit cell. Let's take the volume of one atom per unit. As an example, consider a body-centered cell, which is formed by 9 atoms, 8 of which are located at the vertices of the cube, and 1 in the center of the cube. Each atom in a vertex belongs to eight neighboring cells at the same time, therefore, 1/8 of each of the 8 atoms belongs to one cell: 1/8. 8 = 1; the atom in the center of the cube belongs entirely to the cell. Thus, a body-centered cell is formed by two atomic volumes, i.e., there are two atoms per cell.
Coordination number (CN) is understood as the number of atoms located at the same and the smallest distance from a given atom. The higher the coordination number, the higher the packing density of atoms. So, in a body-centered cubic lattice, CN = 8; in face-centered and hexagonal lattices, CN = 12.
The filling factor η is the percentage ratio of the volume V a occupied by atoms in a cell to the volume of the entire cell V i:
η = (V a / V i) ∙ 100% (4)
The coordination number (CN) and the filling factor η characterize the packing density of atoms in the unit cell of a metal crystal. The densest packing of atoms is realized in the face-centered and hexagonal Bravais cells.
Crystalline defects . A real crystal differs from an ideal one by the presence of crystal structure defects, which influence, often decisively, the macroscopic properties of crystalline bodies. Geometrically, defects are divided into three groups:
Point (zero-dimensional);
Linear (one-dimensional);
Surface (two-dimensional).
Point defects have dimensions in all directions from one to four atomic diameters. They are subdivided into own and impurity.
Intrinsic point defects include: vacancies formed when an atom (ion) is removed from its normal position in a crystal lattice site, and interstitial atoms - the atoms of the base metal located in interstitial sites of the crystal lattice. Impurity atoms include atoms of other (or other) elements, dissolved in the main lattice according to the principle of substitution or insertion.
Figure 7 shows, in a two-dimensional model of the crystal, vacancies, an intrinsic interstitial atom, and substitutional and interstitial impurity atoms.
The most common are vacancies. There are two known mechanisms for the emergence of vacancies: the Schottky mechanism - when an atom leaves the outer surface or the surface of a pore or crack inside a crystal under the influence of thermal fluctuations, and the Frenkel mechanism - when a pair of "intrinsic interstitial atom - vacancy" forms inside the crystal lattice during deformation, irradiation of metals with ionizing radiation: fast electrons, γ - rays. In real crystals, vacancies are constantly formed and disappear under the influence of thermal fluctuations. The activation energy for the formation of a vacancy is approximately 1 eV, for an interstitial atom, from 3 to 10 eV.
With increasing temperature, the equilibrium concentration of point defects in the crystal increases. During plastic deformation, irradiation, and quenching, the number of point defects increases sharply, which leads to a violation of their equilibrium concentration by several orders of magnitude.
Substitutional impurity atoms migrate in the same way as the main atoms - by the vacancy mechanism. Impurity interstitial atoms are small and therefore, in contrast to large intrinsic interstitial atoms, they can migrate over the voids between the atoms of the crystal lattice.
Point defects have a great influence on the mechanism and kinetics of creep processes, long-term fracture, the formation of diffusion porosity, decarburization, graphitization, and other processes associated with the transfer of atoms in the bulk of a substance, as well as on physical properties: electrical resistance, density.
Linear defects are small (several atomic diameters) in two directions and have a large extent, comparable to the length of the crystal, in the third. Linear defects include dislocations, chains of vacancies, and interstitial atoms.
Dislocations are divided into two main types: edge and screw.
An edge dislocation can be imagined by mentally splitting a perfect crystal vertically, say, with a primitive cubic lattice, and inserting an extra short atomic layer called an extraplane into it. Extra-plane can also be obtained by shifting one part of the crystal relative to the other. The extraplane, acting like a wedge, bends the lattice around its bottom edge inside the crystal (Fig. 8).
The area of imperfection around the edge of the extraplane is called an edge dislocation. Strong distortions of the crystal lattice are enclosed, as it were, inside a "pipe" with a diameter of two to ten atomic diameters, the axis of which is the edge of the extraplane. Along the extraplane line, the imperfections are macroscopic, while in the other two directions (along the "pipe" diameter) they are very small. If the extraplane is located in the upper part of the crystal, then the dislocation associated with it is called positive and denoted by (┴); if the extraplane is located in the lower part, then the dislocation is called negative and denoted by (┬).
Under the action of an external applied stress, an edge dislocation can slide along certain crystallographic planes and directions. The predominant sliding occurs along close-packed planes. The combination of the sliding plane and the sliding direction is called the sliding system. Each type of crystal lattice is characterized by its own slip systems. Thus, in crystals with a face-centered cubic lattice, these are the planes of the set (111) and the directions of the set<110>(Cu, Al, Ni), with a body-centered cubic lattice - (110) (α-Fe, Mo, Nb), (211) (Ta, W, α-Fe), (321) (Cr, α-Fe) and<111>, with hexagonal close-packed - (0001),<11͞20>(Zn, Mg, Be), (1͞100), (10͞11),<11͞20>(Ti), (11͞22),<1͞213>(Ti). The stress required for shear is called critical shear or shear stress. Moreover, at each moment of time, only a small group of atoms participates in the displacement on both sides of the slip plane. Figure 9 shows a diagram of the sliding of an edge dislocation through a crystal.
The final stage slip is the exit of an edge dislocation (extraplane) on the surface of the crystal. In this case, the upper part of the crystal is shifted relative to the lower one by one interatomic distance in the direction of shear. Such movement is an elementary act of plastic deformation. Glide is a conservative movement that is not associated with the transfer of mass of matter. The direction and magnitude of the shear during the displacement of the edge dislocation are characterized by the Burgers vector b and its power, respectively. The direction of displacement of the edge dislocation is parallel to the Burgers vector.
In addition to sliding, an edge dislocation can move by crawling, which is carried out by a diffusion path and is a thermally activated process. Positive climb occurs when a chain of atoms from the edge of the extraplane moves to neighboring vacancies or interstices, i.e. the extraplane is shortened by one interatomic distance and the edge dislocation passes into the upper slip plane parallel to the first one. Negative climb occurs when the edge of the extraplane is completed by an atomic row due to the attachment of interstitial or neighboring atoms, and the edge dislocation passes into the lower slip plane. Crawling is a non-conservative movement, i.e. occurs with mass transfer. The creep rate depends on both the temperature and the concentration of point defects.
A screw dislocation, like an edge dislocation, can be created using a shift. Let's imagine a crystal in the form of a stack of horizontal parallel atomic planes. Let us mentally make a blind notch in the crystal (Fig. 10a) and move, for example, the right part downward (along the ABCD plane) by one interplanar distance (Fig. 10b).
A screw dislocation is subdivided into the right (Fig.10b), when moving from the upper plane to the lower line of the dislocation must be bypassed clockwise, and the left, when, when moving from the upper plane to the lower dislocation line, it is necessary to bypass counterclockwise (if relative to the plane ABCD move down the left side of the crystal). The screw dislocation line is always parallel to the Burgers vector (Fig. 11).
A screw dislocation, in contrast to an edge dislocation, is not associated with a specific shear plane; therefore, it can slide by sliding in any crystallographic plane containing a dislocation line and a shear vector (Fig. 12). The direction of movement of the screw dislocation is always perpendicular to the Burgers vector. As a result of sliding of both edge and screw dislocations, a step is formed on the crystal surface with a height equal in magnitude to the Burgers vector b(fig. 12).
Dislocations are present in all crystals. So, in undeformed metals the density of dislocations is 10 6 -10 8 cm -2; in homeopolar crystals - 10 4 cm -2. With an external stress equal to the critical shear stress τ cr = 10 -5 G, where G is the elastic modulus of the material, the dislocations start to move, that is, plastic deformation begins. In the process of plastic deformation, the dislocation density 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. Various kinds of barriers (second-phase particles, point defects, grain boundaries, etc.) serve as obstacles for moving dislocations. In addition, as the number of dislocations increases, they begin to accumulate, become entangled in tangles, and interfere with other moving dislocations. As the degree of deformation increases, τcr increases, i.e., to continue the deformation process, an increase in external stress is required, which, to a certain extent, determines the hardening of the material.
Surface defects. Surface defects include grain boundaries (subgrains) (Fig. 13). Surface defects are two-dimensional, that is, they are macroscopic in two directions and atomic in the third direction. The boundaries are called low-angle, if the misorientation of the crystal lattices of neighboring grains does not exceed 10 °, and high-angle (high-angle) with a greater misorientation.
Low-angle boundaries can be formed by systems of both edge and screw dislocations of different orientations and with different Burgers vectors. Low-angle boundaries arise during the growth of crystals from a melt, during plastic deformation, etc. Dislocations of a low-angle boundary attract point defects due to elastic interaction with them. The migration of the low-angle boundary is carried out only by diffusion. Therefore, point defects, concentrated in the near-boundary zone at several interatomic distances, inhibit this process and stabilize the substructure.
High-angle boundaries were found much earlier than low-angle ones and are the “oldest” type of crystal structure defects. It is believed that the high-angle boundary is a layer 2-3 atomic diameters thick, in which the atoms occupy some intermediate positions with respect to the correct positions of the lattice sites of neighboring grains. This position of the atoms provides the minimum potential energy in the boundary layer, therefore, it is quite stable.
The nature and behavior of both low-angle and high-angle boundaries under force and temperature influences the mechanical properties of the material.
Exercise
1. A plane in a cubic crystal cuts off segments equal to a on the coordinate axes; 2c; with. Determine the crystallographic indices of the plane (hkl).
2. Build a spatial image of planes (for example, a cube) with crystallographic indices (110); (111); (112); (321); (1͞10); (͞111); (͞1͞1͞1).
3. Define the symbol for the direction passing through the points (0, in / 3, s / 3).
4. Build a spatial image of the following directions in a cube; ; ; [100]; ; ; ; ; ; ; [͞111]; ; ; [͞1͞11]; [͞111]; ; [͞1͞1͞1]; ; ...
5. Count the number of atoms in a cell and the coordination number for bcc and fcc and hcp lattices.
Control questions
1. How many types of Bravais unit cells are known today? Which of them are most typical for metals?
2. What are crystallographic symbols? Describe the scheme for determining the symbol of the atomic plane in a crystal.
3. What types of point defects exist in crystals? What are the distances covered by the distortion caused by the point defect?
4. How does the concentration of vacancies change with increasing temperature?
5. Why are dislocations called linear defects?
6. On what basis are dislocations subdivided into edge and screw ones?
7. What is the Burgers vector? What is the cardinality of the Burgers vector?
8. How is the Burgers vector directed in relation to the line of edge and screw dislocations?
9. What are surface defects?
10. What are the physical properties of crystalline solids Are crystal structure defects affected?
Laboratory work No. 2
1st semester
1. "Analysis of the crystal structure of metals and alloys" (No. 1, workshop 2). 2 h.
2. "Testing materials for hardness" (No. 10, workshop 2). 1 h.
3. "Testing of samples in tension" (No. 11, workshop 2; or "Mechanical properties of structural materials", a separate file). 2 h.
4. "Determination of the impact strength of the material" (No. 12, workshop 2). 1 h.
5. "Fractographic analysis of the destruction of metallic materials" (No. 9, workshop 2). 1 h.
6. "Influence of cold plastic deformation and recrystallization temperature on the structure and properties of metals" (No. 4, workshop 1). 2 h.
7. "Thermal analysis of alloys" (No. 1, workshop 1). Part 1 - construction of a state diagram of the "zinc-tin" system by the thermal method. Part 2 - analysis of the diagrams of the state of binary alloys: perform an individual task under item 5 in the "Content of the report". 2 h.
8. "Macroscopic analysis (macroanalysis) of the structure of metallic materials" (No. 2, workshop 2). 1 h.
9. "Microscopic analysis (microanalysis) of the structure of metallic materials" (No. 3, workshop 2). 1 h.
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 the method of microanalysis ", workshop 2). Practical part: students look at the structure of four iron-carbon alloys using a MIM-7 microscope: technical iron, hypoeutectoid, eutectoid and hypereutectoid alloys. They make schematic sketches, sign the structural components, give an example of a steel grade, for a hypoeutectoid alloy, the carbon content is calculated using the formula. 1 h. + t. 2 (11). “Iron-carbon status diagram. The structure, properties and application of cast irons "No. 3 from the workshop 1) or a similar work No. 8" Investigation of the structure of carbon cast irons by the microanalysis method "from the workshop 2). Practical part: students look at the structure of three cast irons on the MIM-7 microscope: gray cast iron with fine-lamellar graphite on a pearlite base, ductile iron on a ferrite-pearlite base and hypoeutectic white cast iron. Unfortunately, no more. They also make sketches, write the names of cast irons and structural components. 1 h. + t. 3 (12). "The influence of the cooling rate on the hardness of carbon steel" No. 20 from the workshop 2). Practical part: four samples from U8 steel. One is annealed, the second is normalized, the third is oil quenched, and the fourth is water quenched. The hardness is measured, a graph of the dependence of the hardness on the cooling rate is plotted. Cooling rates are taken from a table in laboratory work. 2 h.
4 (13). "Quenching of carbon steels" No. 5 from workshop 1). Practical part: three samples of steel 20, 45, U9 are quenched in water, one sample of steel 45 is quenched in oil. The hardness is measured before (HRB) and after (HRC) hardening. The conversion table is used to determine the hardness in HB units. Based on the results, two graphs are built: HB = f (% C) and HRC = f (Vcool.). 2 h. + t.
5 (14). "Vacation of steel" No. 6 from the workshop 1) or similar work No. 18 "Vacation of carbon steel" from the workshop 2). Practical part: according to workshop 1), low (200 ° C), medium (400 ° C) and high (600 ° C) tempering of hardened specimens from steel 45 and low tempering (200 ° C) of a hardened specimen from steel U9 are carried out. Measure the hardness. Build a graph HRC = f (Tamp.). According to workshop 2), low, medium and high tempering of hardened samples from U8 steel is carried out. 2 h. + t.
6 (15). "Annealing and normalization of steel" No. 7 from workshop 1). Practical part: two samples of steel 45. Isothermal annealing is carried out with one, and normalization with the second. 2 h. + t.
7 (16). "Chemical heat treatment of steel" No. 8 from workshop 1. 1 h.
8 (17). "The influence of alloying elements on the hardenability of steel, determined by the method of end hardening" No. 21 from workshop 2. 2 h.
9 (18). "Classification, labeling and use of construction materials." Practical part: students receive a card with five stamps, describe each in detail. 1 h.
Laboratory work No. 1
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FEDERAL STATE BUDGET EDUCATIONAL
INSTITUTION OF HIGHER EDUCATION
"VOLGA STATE UNIVERSITY OF WATER TRANSPORT"
PERM BRANCH
E.A. Sazonova
MATERIALS SCIENCE
COLLECTION OF PRACTICAL AND LABORATORY WORKS
methodological recommendations for the implementation of laboratory and practical
works for middle students vocational education specialties
02.26.06 "Operation of ship electrical equipment and automation equipment"
02.23.01 "Organization of transportation and transport management" (by type)
PERMIAN
2016
Introduction
Methodical recommendations for laboratory and practical work
on the academic discipline "Materials Science" are intended for students of secondary
vocational education in the specialty
02.26.06 "Operation of the ship
electrical equipment and automation equipment "
In this methodological manual instructions on how to perform
practical and laboratory work on the topics of the discipline, topics and content are indicated
laboratory and practical work, control forms for each topic and recommended
literature.
These recommendations contribute to the development of general and professional
competencies, gradual and purposeful development of cognitive abilities.
As a result of mastering this academic discipline, the student should be able to:
˗
perform mechanical tests of material samples;
˗
use physicochemical methods for the study of metals;
˗
use reference tables to determine material properties;
˗
choose materials for the implementation of professional activities.
As a result of mastering this academic discipline, the student should know:
˗
basic properties and classification of materials used in
professional activity;
˗
name, marking, properties of the processed material;
˗
rules for the use of lubricants and cooling materials;
˗
basic information about metals and alloys;
˗
basic information about non-metallic, cushioning,
sealing and electrical materials, steel, their classification.
Laboratory and practical work will allow you to form practical skills
work, professional competence. They are included in the structure of the study of the educational
discipline "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 is an element of educational
disciplines and are assessed according to the criteria presented below:
A grade "5" is given to a student if:
˗
the subject of the work corresponds to the given one, the student shows systemic and complete
knowledge and skills on this issue;
˗
the work is framed in accordance with the recommendations of the teacher;
˗
the amount of work corresponds to the given;
˗
the work was done exactly on time specified by the teacher.
A grade of "4" is given to a student if:
˗
the subject of the work corresponds to the given one, the student admits small
inaccuracies or some errors in this matter;
˗
the work is framed with inaccuracies in the design;
˗
the amount of work corresponds to the given one or slightly less;
˗
the work was completed within the time specified by the teacher, or later, but no more than 12
day.
Grade "3" is given to a student if:
2
the topic of the work corresponds to the given one, but there are no significant
elements of the content of the work or topics are presented illogically, not clearly presented
the main content of the question;
˗
the work is framed with design errors;
˗
the amount of work is much less than the specified one;
˗
the work was delivered with a delay of 56 days.
Grade "2" is given to a student if:
˗
the main topic of the work has not been disclosed;
˗
the work is not framed in accordance with the teacher's requirements;
˗
the volume of work does not correspond to the given;
˗
the work was delivered with a delay of more than 7 days.
Laboratory and practical work in their content has a certain
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 perform
the task, which is indicated at the end of the work (item "Assignment for students"); at
the performance of laboratory work, a report is drawn up on its implementation, the content of the report
indicated at the end of the laboratory work (paragraph "Contents of the report").
˗
When performing laboratory and practical work, students perform
certain rules, consider them below: laboratory and practical work
performed during training sessions; final design allowed
laboratory and practical work at home; allowed to use
additional literature when performing laboratory and practical work; front
performing laboratory and practical work, it is necessary to study the basic
theoretical provisions on the issue under consideration.
3
Practical work No. 1
"Physical properties of metals and methods of their study"
Purpose of the work: to study the physical properties of metals, methods of their determination.
Progress:
Theoretical part
Physical properties include: density, melting (melting point),
thermal conductivity, thermal expansion.
Density is the amount of a 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: light (density no more than 5 g / cm3) magnesium, aluminum, titanium, etc.
heavy (density from 5 to 10 g / cm3) iron, nickel, copper, zinc, tin, etc. (this
the most extensive group); very heavy (density over 10 g / cm3) molybdenum,
tungsten, gold, lead, etc. Table 1 shows the values of the density of metals.
Table 1
metal
Magnesium
Aluminum
Titanium
Zinc
Tin
density g / cm3
Density of metals
metal
1,74
2,70
4,50
7,14
7,29
Iron
Copper
Silver
Lead
Gold
density g / cm3
7,87
8,94
10,50
11,34
19,32
The melting point is the temperature at which the metal passes from
crystalline (solid) state into liquid with heat absorption.
The melting points of metals are in the range of -39 ° C (mercury) to 3410 ° C
(tungsten). Melting point of most metals (excluding alkali)
high, but some "normal" metals, such as tin and lead, can
melt on a conventional electric or gas stove.
Depending on the melting point, the metal is divided into the following
groups: low-melting (melting temperature does not exceed 600 oС) zinc, tin,
lead, bismuth, etc .; medium-melting (from 600 oС to 1600 oС), they include almost
4
half of the metals, including magnesium, aluminum, iron, nickel, copper, gold;
refractory (more than 1600 oС) tungsten, molybdenum, titanium, chromium, etc.
metal additives, the melting point tends to drop.
table 2
metal
Tin
Iron
Copper
Gold
Titanium
Melting and boiling points of metals
Temperature oС
melting
boiling
232
1539
1083
1063
1680
2600
2900
2580
2660
3300
metal
Silver
Magnesium
Zinc
Lead
Aluminum
Temperature oС
melting
boiling
960
650
420
327
660
2180
1100
907
1750
2400
Thermal conductivity - the ability of a metal to conduct
heat when heated.
heating.
Electrical conductivity is the ability of a metal to conduct electric current.
Thermal expansion - the ability of a metal to increase its volume when
The smooth surface of metals reflects a large percentage of light this phenomenon
called a metallic sheen. However, in a powdery state, most
metals lose their luster; aluminum and magnesium, however, retain their luster
and powder. The best reflecting light are aluminum, silver and palladium of these
mirrors are made of metals. Rhodium is sometimes used to make mirrors,
despite its exceptionally high price: due to significantly higher
silver or even palladium, hardness and chemical resistance, the rhodium layer can
be significantly thinner than silver.
Research methods in materials science
The main research methods in metal science and materials science
microstructure, electron microscopy,
are:
X-ray research methods. Consider their features in more detail.
break,
macrostructure,
1. Fracture is the easiest and most affordable way to assess the internal structure
metals. Method for assessing kinks, despite its apparent roughness of the assessment
the quality of the material, it is used quite widely in various industries and
scientific research. Fracture assessment can in many cases characterize quality
material.
The fracture can be crystalline or amorphous. Amorphous fracture is characteristic
for non-crystalline materials such as glass, rosin,
glassy slags.
Metal alloys, including steel, cast iron, aluminum, magnesium
alloys, zinc and its alloys give granular, crystalline fracture.
Each face of a crystalline fracture is a shear plane
single grain. Therefore, the kink shows us the grain size of the metal. Studying the kink
steel, it can be seen that the grain size can vary over a very wide range: from
several centimeters in a cast, slowly cooled down, steel to thousandths
millimeter in properly forged and hardened steel. Depending on the size
grains, fracture can be large-crystalline and fine-crystalline. Usually
fine-crystalline fracture corresponds to more high quality metal
alloy.
5
If the destruction of the test sample proceeds from the previous
plastic deformation, the grains in the fracture plane are deformed, and the fracture is no longer
reflects the internal crystal structure of the metal; in this case kink
called fibrous. Often in one sample, depending on the level of its
plasticity, there can be fibrous and crystalline areas in the fracture. Often on
the ratio of the area of the fracture occupied by the crystalline regions at the given
test conditions evaluate the quality of the metal.
Brittle crystalline fracture can result from fracture along grain boundaries
or along slip planes crossing the grains. In the first case, the break is called
intercrystalline, in the second transcrystalline. Sometimes, especially with very small
grain, it is difficult to determine the nature of the fracture. In this case, the kink is studied using a magnifying glass or
binocular microscope.
Recently, the branch of metal science has been developing in fractographic
the study of fractures on metallographic and electron microscopes. Wherein
find new advantages of the old research method in metal science
research
to such studies of the concept of fractal
dimensions.
applying
break,
2. Macrostructure is the next method for studying metals.
Macrostructural research consists in studying the plane of the section of the product or
sample in longitudinal, transverse or any other directions after etching, without
the use of magnifying devices
Dignity
macrostructural study is the fact that with the help of this
method, you can study the structure directly of the whole casting or ingot, forging,
stamping, etc. With this research method, you can discover internal
metal defects: bubbles, voids, cracks, slag inclusions, investigate
the crystal structure of the casting, to study the inhomogeneity of the crystallization of the ingot and its
chemical heterogeneity (liquation).
help
magnifiers.
at
or
Using sulfur prints of macrosections on photographic paper according to Bauman, it is determined
uneven distribution of sulfur over the section of the ingots. Great importance this method
research has in the study of forged or stamped blanks for
determining the correct direction of the fibers in the metal.
3. Microstructure one of the main methods in metallurgy is
study of metal microstructure on metallographic and electronic
microscopes.
This method makes it possible to study the microstructure of metal objects with large
magnifications: from 50 to 2000 times on an optical metallographic microscope and from
2 to 200 thousand times on an electron microscope. Microstructure research
produced on polished sections. On non-etched thin sections, the presence of
non-metallic inclusions such as oxides, sulfides, fine slag inclusions
and other inclusions that differ sharply from the nature of the base metal.
The microstructure of metals and alloys is studied on etched sections. Etching
usually produced with weak acids, alkalis, or other solutions, depending on
from the nature of the metal of the thin section. The etching action is that it is differently
dissolves various structural components, coloring them in different tones or
colors. Grain boundaries other than the base solution are etched usually
different from the base and stands out on the thin section in the form of dark or light lines.
The polyhedra of grains visible under the microscope are sections of grains
surface of the thin section. Since this section is random and can take place at different
distances from the center of each individual grain, the difference in the sizes of the polyhedra is not
corresponds to the actual differences in grain size. The closest value to
6
the actual grain size is the largest grain.
When etching a sample consisting of homogeneous crystalline grains,
for example, pure metal, homogeneous solid solution, etc. is often observed
differently etched surfaces of different grains.
This phenomenon is explained by the fact that grains emerge on the surface of the microsection, having
different crystallographic orientations, as a result of which the degree of exposure
acids for these grains are different. Some grains look shiny, others
strongly etched, darken. This darkening is associated with the formation of various
etched figures, differently reflecting light rays. In the case of alloys, separate
structural components form a microrelief on the surface of a thin section, which has
areas with different slopes of individual surfaces.
Normal areas reflect the most light and
turn out to be the lightest. Other areas are darker. Often the contrast in
the image of the grain structure is associated not with the structure of the surface of the grains, but with
relief at the grain boundaries. In addition, various shades of structural components
can be the result of the formation of films formed during the interaction
etchant with structural components.
With the help of metallographic examination, it is possible to carry out a high-quality
identification of structural components of alloys and quantitative study of microstructures
metals
studied
microcomponents of structures and, secondly, by special methods of quantitative
metallography.
first, by comparison
with well-known
alloys,
and
The grain size is determined. By the method of visual assessment, consisting in the fact that
considered microstructure, approximately estimated by points of standard scales
according to GOST 563968, GOST 564068. According to the corresponding tables, for each point
the area of one grain and the number of grains per 1 mm2 and in 1 mm3 are determined.
By counting the number of grains per unit surface of a thin section by
corresponding formulas. If S is the area on which the number of
grains n, and M magnification of the microscope, then average value grains in the cross-section of the surface
thin section
Determination of the phase composition. The phase composition of the alloy is often assessed by eye or
by comparing the structure with standard scales.
An approximate method for the quantitative determination of the phase composition can be
carried out by the secant method with the calculation of the lengths of the segments occupied by different
structural components. The ratio of these segments corresponds to the volumetric
the content of individual components.
Point method A.A. Glagoleva. This method is carried out by evaluating
the number of points (points of intersection of the eyepiece reticle of the microscope) falling on
surface of each structural component. In addition, by the method of quantitative
metallography produce: determination of the size of the interface between phases and grains;
determination of the number of particles in the volume; determination of grain orientation in polycrystalline
samples.
4. Electronic
microscopy. Big
in metallographic
research has recently found an electron microscope. Undoubtedly, he
a great future belongs. If the resolution of the optical microscope
reaches values of 0.00015 mm = 1500 A, then the resolution of electronic
microscopes reaches 510 A, i.e. several hundred times more than optical.
meaning
An electron microscope is used to study thin films (replicas),
taken from the surface of a thin section or direct study of thin metal
films obtained by thinning a massive sample.
7
Most in need of electron microscopy
studies of processes associated with the release of excess phases, for example, decay
supersaturated solid solutions during thermal or strain 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. To solve the task,
not accessible to either a conventional or an electron microscope.
X-ray structural analysis is based on the interaction between
X-rays and the atoms of the investigated body lying in their path, thanks to
to which the latter become, as it were, new sources of X-rays,
being the centers of their dispersion.
The scattering of rays by atoms can be likened to the reflection of these rays from atomic
crystal planes according to the laws of geometric optics.
X-rays are reflected not only from planes lying on
surface, but also from deep. Reflecting from several equally oriented
planes, the reflected beam is amplified. Each plane of the crystal lattice
gives its own beam of reflected waves. Having received a certain alternation of reflected
beams of X-rays at certain angles, calculate the interplanar
distance, crystallographic indices of reflecting planes, ultimately,
the shape and size of the crystal lattice.
Practical part
Content of the report.
1. It is necessary to indicate the title and purpose of the work in the report.
2. List the basic physical properties of metals (with definitions).
3. Record Table 12 in the notebook. Draw conclusions from the tables.
4. Fill in the table: "Basic research methods in materials science".
Method name
What is being studied
Method essence
Devices,
for research
the necessary
Break
Macrostructure
Microstructure
Electronic
microscopy
X-rays
research methods
8
Practical work number 2
Topic: "Exploring state diagrams"
Purpose of work: familiarizing students with the main types of state diagrams,
their main lines, points, their meaning.
Progress:
1. Learn the theoretical part.
Theoretical part
A state diagram is a graphical representation of a state
any alloy of the system under study, depending on concentration and temperature (see Fig.
1)
9
Fig. 1 Status diagram
State diagrams show steady states, i.e. states that
under these conditions have a minimum of free energy, and therefore it is also
is called an equilibrium diagram, since it shows which, under given conditions
there are equilibrium phases.
The construction of state diagrams is most often carried out using
thermal analysis. As a result, a series of cooling curves is obtained, in which at
at temperatures of phase transformations, inflection points and temperature
stop.
Temperatures corresponding to phase transformations are called critical.
dots. Some critical points have names, for example, points corresponding to
the beginning of crystallization is called liquidus points, and the end of crystallization is called
solidus.
The cooling curves are used to construct a composition diagram in the coordinates: along the abscissa axis
concentration of components, temperature on the ordinate axis. The concentration scale shows
content of component B. The main lines are liquidus (1) and solidus lines
(2), as well as lines corresponding to phase transformations in the solid state (3, 4).
The phase diagram can be used to determine the temperatures of phase transformations,
a change in the phase composition, approximately, the properties of the alloy, the types of processing that
can be used for alloying.
Below are the different types of state diagrams:
10
Fig. 2. State diagram of alloys with unlimited solubility
components in solid state (a); cooling curves of typical
alloys (b)
Analysis of the resulting diagram (Fig. 2).
1. Number of components: K = 2 (components A and B).
2. Number of phases: f = 2 (liquid phase L, crystals of solid solution
3. The main lines of the diagram:
acb - liquidus line, above this line the alloys are in a liquid state;
adb - solidus line, below this line alloys are in solid state.
Fig. 3. State diagram of alloys with no solubility of components in
solid state (a) and cooling curves of alloys (b)
Analysis of the state diagram (Fig. 3).
2. Number of phases: f = 3 (crystals of component A, crystals of component B, liquid phase).
3. The main lines of the diagram:
11
the solidus line ecf, parallel to the concentration axis tends to the axes of the components, but
does not reach them;
Rice. 4. Diagram of the state of alloys with limited solubility of the components in
solid state (a) and cooling curves of typical alloys (b)
Analysis of the state diagram (Fig. 4).
1. Number of components: K = 2 (components A and B);
2. Number of phases: f = 3 (liquid phase and crystals of solid solutions
B in component A) and
(solution of component A in component B));
(component solution
3. The main lines of the diagram:
line liquidus acb, consists of two branches, converging at one point;
solidus line adcfb, consists of three sections;
dm is the line of the limiting concentration of component B in component A;
fn is the line of the limiting concentration of component A in component B.
Practical part
Assignment for students:
1. Write down the title of the job and its purpose.
2. Write down what a status diagram is.
Answer the questions:
1. How is the state diagram built?
2. What can be determined from the state diagram?
3. What are the names of the main points of the diagram?
4. What is indicated on the chart along the abscissa? Y-axis?
5. What are the main lines of the diagram called?
Assignment by options:
Students answer the same questions, the drawings are different, according to
who need to answer. Option 1 gives answers to Figure 2, Option 2 gives answers to
Figure 3, option 3 gives answers to Figure 4. The figure must be recorded in a notebook.
1. What is the name of the diagram?
2. What are the components involved in the formation of the alloy?
12
3. What letters represent the main lines of the diagram?
Practical work number 3
Topic: "Studying cast irons"
cast irons; the formation of the ability to decipher the grades of cast iron.
Progress:
Theoretical part
Cast iron differs from steel: its composition has a higher carbon content and
impurities; by technological properties, higher casting properties, low
the ability to plastic deformation, almost never used in welded structures.
Depending on the state of carbon in cast iron, they are distinguished: white cast iron -
carbon in a bound state in the form of cementite, in a fracture it has a white color and
metallic luster; gray cast iron - all or most of the carbon is in
free state in the form of graphite, and in the bound state is no more than 0.8
% carbon. Due to the large amount of graphite, its fracture is gray in color;
half - part of the carbon is in a free state in the form of graphite, but
not less than 2% of carbon is in the form of cementite. Little is used in technology.
Depending on the form of graphite and the conditions of its formation, the following are distinguished:
cast iron groups: gray with lamellar graphite; high-strength with spherical
graphite; malleable with flaky graphite.
Graphite inclusions can be viewed as corresponding to the shape of the void
in the structure of cast iron. Stresses are concentrated near such defects during loading,
the value of which is the greater, the sharper the defect. Hence it follows that graphite
lamellar inclusions soften the metal to the maximum extent. More
the flaky shape is favorable, and the spherical shape of the graphite is optimal.
Plasticity depends on shape in the same way. The presence of graphite is most dramatic
reduces resistance in case of hard loading methods: shock; break. Resistance
the compression decreases a little.
Gray cast irons
Gray cast iron is widely used in mechanical engineering, as it is easy
processed and has good properties. Depending on the strength, gray
cast iron is subdivided into 10 grades (GOST 1412).
Gray cast irons with low tensile strength have a sufficiently high
compression resistance. The structure of the metal base depends on the amount of carbon and
silicon.
Given the low resistance of gray iron castings to tensile and
shock loads, use this material for parts that
are subjected to compressive or bending loads. In machine tool building, these are basic,
body parts, brackets, gear wheels, guides; in the automotive industry blocks
cylinders, piston rings, camshafts, clutch discs. Castings from
gray cast iron are also used in electrical engineering, for the manufacture of goods
consumer consumption.
Marking of gray cast irons: indicated by the index СЧ (gray cast iron) and the number,
which shows the value of the tensile strength multiplied by 101.
13
For example: SCH 10 - gray cast iron, tensile strength 100 MPa.
Malleable cast iron
Good properties of castings are ensured if during crystallization and
cooling of castings in the mold does not occur the graphitization process. To
prevent graphitization, cast irons must have a reduced carbon content and
silicon.
There are 7 grades of malleable cast iron: three with ferritic (KCH 30 6) and four with
pearlite (KCH 65 3) base (GOST 1215).
In terms of mechanical and technological properties, ductile iron occupies
intermediate position between gray iron and steel. The disadvantage of ductile iron
compared with high strength is the limitation of the wall thickness for the casting and
the need for annealing.
Ductile iron castings are used for parts operating under shock and
vibration loads.
Ferritic cast iron is used to make gearbox housings, hubs, hooks, brackets,
clamps, couplings, flanges.
From pearlitic cast irons, characterized by high strength, sufficient
plasticity, forks of cardan shafts, links and rollers of conveyor chains are made,
brake pads.
Malleable iron marking: designated by the KCH index (malleable cast iron) and
numbers. The first number is the tensile strength multiplied by
101, the second number is the elongation.
For example: KCH 306 - ductile iron, tensile strength 300MPa,
elongation 6%.
Ductile iron
These cast irons are obtained from gray ones, as a result of modification with magnesium or
cerium. Compared with gray cast irons, the mechanical properties are improved, this
caused by the absence of uneven stress distribution due to the spherical
forms of graphite.
These cast irons have high fluidity, linear shrinkage of about 1%.
Foundry stresses in castings are slightly higher than for gray cast iron. Izza
high modulus of elasticity, sufficiently high machinability. Possess
satisfactory weldability.
Thin-walled castings (piston rings) are made of high-strength cast iron,
forging hammers, beds and frames of presses and rolling mills, molds,
tool holders, faceplates.
Castings of crankshafts weighing up to 2..3 t, instead of forged steel shafts,
have a higher cyclic viscosity, are insensitive to
external
stress concentrators, have better antifriction properties and
much cheaper.
Ductile iron marking: indicated by the HF index (ductile
cast iron) and a number that indicates the tensile strength value multiplied by 101.
For example: VCh 50 - ductile cast iron with ultimate tensile strength
500 MPa.
Assignment for students:
1. Write down the title of the work, its purpose.
Practical part
14
2. Describe the production of pig iron.
3.Fill in the table:
Cast iron properties
Cast iron marking
Cast iron application
Cast iron name
1.Grey cast irons
2 malleable irons
3.High strength
cast irons
Topic: "Study of carbon and alloy structural steels"
Practical work number 4
Purpose of work: familiarization of students with marking and scope
decoding marking
shaping
skills
steels;
structural
structural steels.
Progress:
1. Get acquainted with the theoretical part.
2. Complete the tasks of the practical part.
Theoretical part
Steel is an alloy of iron with carbon, in which carbon is contained in the amount of 0
2.14%. Steels are the most common materials. Have good
cutting.
composition and type of processing.
subdivided into steels:
˗
Ordinary quality, content up to 0.06% sulfur and up to 0.07% phosphorus.
˗
Quality up to 0.035% sulfur and phosphorus each separately.
˗
High quality up to 0.025% sulfur and phosphorus.
˗
Especially high quality, up to 0.025% phosphorus and up to 0.015% sulfur.
Deoxidation is the process of removing oxygen from steel, that is, according to the degree of its
deoxidation, exist: calm steels, that is, completely deoxidized; such steel
designated by the letters "cn" at the end of the stamp (sometimes the letters are omitted); boiling steels -
slightly deoxidized; marked with the letters "kp"; half-dead steels occupying
intermediate position between the two previous ones; denoted by the letters "ps".
Steel of ordinary quality is also subdivided by supply into 3 groups: steel
group A is supplied to consumers in terms of mechanical properties (such steel can
have a high content of sulfur or phosphorus); steel of group B - by chemical
composition; steel of group B - with guaranteed mechanical properties and chemical
composition.
Structural steels are intended for the manufacture of structures, machine parts
and appliances.
So in Russia and in the CIS countries (Ukraine, Kazakhstan, Belarus, etc.)
the alphanumeric designation system for steel grades and
15
˗
room.
˗
become.
˗
steel is not put.
˗
˗
˗
˗
˗
˗
˗
alloys, where, according to GOST, letters conventionally denote the names of elements and methods
smelting steel, and in numbers
- the content of the elements. Until now
international standardization organizations have not developed a unified labeling system
steels.
Marking of structural carbon steels
ordinary quality
Designated in accordance with GOST 38094 with the letters "St" and the conditional number of the brand (from 0 to 6) in
depending on the chemical composition and mechanical properties.
The higher the carbon content and strength properties of steel, the more it
The letter "G" after the brand number indicates an increased content of manganese in
The steel group is indicated in front of the brand, and the group "A" in the brand designation
To indicate the category of steel, a number at the end is added to the grade designation
corresponding to a category, the first category is usually not indicated.
For example:
˗
St1kp2 carbon steel of ordinary quality, boiling, grade No. 1,
the second category, supplied to consumers by mechanical properties (group A);
VSt5G carbon steel of ordinary quality with increased
manganese content, calm, grade No. 5, first category with guaranteed
mechanical properties and chemical composition (group B);
ВСт0 carbon steel of ordinary quality, grade number 0, group B,
the first category (steel grades St0 and Bst0 are not divided according to the degree of deoxidation).
Marking of quality structural carbon steels
In accordance with GOST 105088, these steels are marked with two-digit numbers,
showing the average carbon content in hundredths of a percent: 05; 08; ten ; 25;
40, 45, etc.
˗
For quiescent steels, no letters are added at the end of their names.
For example, 08kp, 10ps, 15, 18kp, 20, etc.
˗
The letter G in a steel grade indicates a high content of manganese.
For example: 14G, 18G, etc.
˗
The most common group for the manufacture of machine parts (shafts, axles,
bushings, gears, etc.)
For example:
˗
10 - structural carbon quality steel, with carbon content
about 0.1%, calm
about 0.45%, calm
45 - structural carbon quality steel, with carbon content
18 kp - structural carbon quality steel containing
carbon about 0.18%, boiling
˗
14G - structural carbon quality steel with carbon content
about 0.14%, calm, with a high content of manganese.
Alloy structural steels marking
˗
In accordance with GOST 454371, the names of such steels consist of numbers and letters.
˗
The first digits of the brand indicate the average carbon content in steel in hundredths
fractions of a percent.
˗
The letters indicate the main alloying elements included in the steel.
˗
The numbers after each letter indicate the approximate percentage
of the corresponding element, rounded to the nearest whole number, with the alloying content
16
˗
˗
˗
˗
˗
˗
Marking of other groups of structural steels
Spring steel.
˗
The main distinguishing feature of these steels is that the carbon content in them must
be about 0.8% (in this case, elastic properties appear in steels)
Springs and springs are made of carbon (65,70,75,80) and alloyed
(65S2, 50HGS, 60S2HFA, 55HGR) of structural steels
These steels are alloyed with elements that increase the elastic limit - silicon,
manganese, chromium, tungsten, vanadium, boron
For example: 60S2 - structural carbon steel spring-loaded with
carbon content about 0.65%, silicon about 2%.
GOST 80178 is marked with the letters "ШХ", after which the content is indicated
Ball bearing steels
˗
chromium in tenths of a percent.
For steels subjected to electroslag remelting, the letter Ш is added
also at the end of their names, separated by a dash.
For example: ШХ15, ШХ20СГ, ШХ4Ш.
˗
They are used to make parts for bearings, they are also used for manufacturing
parts operating under high loads.
For example: ШХ15 - structural steel ball bearing containing
carbon 1%, chromium 1.5%
˗
GOST 141475 begin with the letter A (automatic).
˗
If the steel is alloyed with lead, then its name begins with the letters
Automatic steels
AC.
element up to 1.5%, the figure behind the corresponding letter is not indicated.
The letter A at the end of the grade indicates that the steel is high quality (with
low sulfur and phosphorus content)
˗
H - nickel, X - chromium, K - cobalt, M - molybdenum, B - tungsten, T - titanium, D
- copper, G - manganese, C - silicon.
For example:
˗
12Х2Н4А - structural alloy steel, high quality, with
carbon content about 0.12%, chromium about 2%, nickel about 4%
40ХН - structural alloy steel, with a carbon content of about 0.4%,
chromium and nickel up to 1.5%
To reflect the content of other elements in steels, the same
rules as for alloyed structural steels. For example: A20, A40G, AC14,
AS38HGM
For example: АС40 - automatic structural steel with carbon content
0.4%, lead 0.150.3% (not specified in the brand)
Practical part
Assignment for students:
2. Write down the main signs of marking of all groups of structural steels
(ordinary quality, high quality steels, alloyed structural steels,
spring-loaded
steels, ball bearing steels, automatic steels), with
examples.
Assignment by options:
1.
Decipher the steel grades and write down the area of application of a specific
brand (i.e. what it is intended for the manufacture)
17
No. Task for option 1
St0
1
BST3Gps
2
08
3
40
4
18Х2Н4МА
5
30HGSA
6
70
7
55S2A
8
9
50HFA
10 ШХ4Ш
11
A40
Task for option 2
St3
VSt3ps
10
45
12ХН3А
38HMYUA
85
60S2X2
55S2
SHX20
A11
Practical work number 5
Topic: "Study of carbon and alloy tool steels"
Purpose of work: familiarization of students with marking and scope
decoding marking
shaping
skills
structural
structural steels.
steels;
Progress:
1. Get acquainted with the theoretical part.
2. Complete the assignment of the practical part.
Steel is an alloy of iron with carbon, in which carbon is contained in the amount of 0
Theoretical part
2,14%.
Steels are the most common materials. Have good
technological properties. Products are obtained as a result of pressure treatment and
cutting.
The advantage is the ability to obtain the desired set of properties by changing
composition and type of processing.
Depending on the purpose, steels are divided into 3 groups: structural,
instrumental and special steel.
Quality depending on the content of harmful impurities: sulfur and phosphorus steel
subdivided into: steels of ordinary quality, sulfur content up to 0.06% 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; especially high quality, up to 0.025%
phosphorus and up to 0.015% sulfur.
Tool steels are designed for the manufacture of various tools,
for both manual processing and mechanical.
Availability of a wide range of manufactured steels and alloys manufactured in
different countries, made it necessary to identify them, however, until now
time, there is no single system for marking steels and alloys, which creates
certain difficulties for the metal trade.
Marking of carbon tool steels
˗
These steels in accordance with GOST 143590 are divided into high-quality and
high quality.
18
Quality steels are designated by the letter U (carbon) and a number indicating
average carbon content in steel, in tenths of a percent.
For example: U7, U8, U9, U10. U7 - carbon tool steel with
carbon content about 0.7%
The letter A is added to the designation of high-quality steels (U8A, U12A and
etc.). In addition, in the designations of both high-quality and high-quality
carbon tool steels, the letter G may be present, indicating
increased content of manganese in steel.
For example: U8G, U8GA. U8A - carbon tool steel with
carbon content of about 0.8%, high quality.
They make a tool for manual work (chisel, center punch, scribe, etc.),
mechanical work at low speeds (drills).
Alloy Tool Steels Marking
Designation rules for tool alloy steels in accordance with GOST 595073 in
basically the same as for structural alloy.
The difference lies only in the numbers indicating the mass fraction of carbon in
become.
˗
˗
˗
˗
˗
˗
The percentage of carbon is also indicated at the beginning of the name.
steel, in tenths of a percent, and not in hundredths, as for structural alloy
steels.
˗
If in the tool alloy steel the carbon content is
about 1.0%, then the corresponding figure at the beginning of its name is usually not indicated.
Let's give examples: steel 4X2V5MF, KhVG, KhVCh.
˗
9Х5ВФ - alloyed tool steel, with a carbon content of about
0.9%, chromium about 5%, vanadium and tungsten up to 1%
High-alloy (high-speed) marking
tool steels
Designated by the letter "P", the following figure indicates the percentage
the content of tungsten in it: Unlike alloy steels in the names
high-speed steels do not indicate the percentage of chromium, because it amounts to
about 4% in all steels, and carbon (it is proportional to the vanadium content).
˗
The letter F, indicating the presence of vanadium, is indicated only if
the vanadium content is over 2.5%.
For example: R6M5, R18, R6 M5F3.
˗
Usually, high-performance tools are made from these steels: drills,
cutters, etc. (to reduce the cost, only the working part)
For example: R6M5K2 - high-speed steel, with a carbon content of about 1%,
tungsten about 6%, chromium about 4%, vanadium up to 2.5%, molybdenum about 5%, cobalt
about 2%.
Practical part
Assignment for students:
1. Write down the title of the work, its purpose.
2. Write down the basic principles of marking all groups of tool steels
(carbon, alloyed, high-alloyed)
Assignment by options:
1. Decipher the steel grades and write down the area of application of a particular grade
(i.e. what it is intended to manufacture).
19
No. Task for option 1
1
2
3
4
5
6
U8
U13A
NS
HVSG
P18
R6M5
Task for option 2
U9
U8A
9XC
CVH
P6
R6M5F3
Practical work number 6
Topic: "Study of copper-based alloys: brass, bronze"
Purpose of work: familiarization of students with marking and scope
non-ferrous metals - copper and alloys based on it: brass and bronze; shaping
the ability to decipher the marking of brass and bronze.
Recommendations for students: before starting the practical
parts of the assignment, carefully read the theoretical provisions, as well as lectures
in your workbook on this topic.
Progress:
1. Get acquainted with the theoretical part.
2. Complete the assignment of the practical part.
Theoretical part
Brass
Brass can contain up to 45% zinc. Content enhancement
zinc up to 45% leads to an increase in ultimate strength up to 450 MPa. Maximum
plasticity takes place at a zinc content of about 37%.
According to the method of manufacturing products, deformable and foundry brass are distinguished.
Deformable brasses are marked with the letter L followed by a number,
showing the percentage of copper, for example, brass L62 contains 62% copper
and 38% zinc. If, in addition to copper and zinc, there are other elements, then they are put
initial letters (O tin, C lead, F iron, P phosphorus, Mts manganese, A
aluminum, zinc zinc).
The number of these elements is indicated by the corresponding numbers after the number,
showing the copper content, for example, the LAZh6011 alloy contains 60% copper, 1%
aluminum, 1% iron and 38% zinc.
Brasses have good corrosion resistance which can be improved
additionally with tin additive. Brass LO70 1 corrosion resistant in seawater
20
and is called "marine brass". The addition of nickel and iron increases the mechanical
strength up to 550 MPa.
Cast brasses are also marked with the letter L, after the letter designation
the main alloying element (zinc) and each subsequent number is put,
indicating its average content in the alloy. For example, brass ЛЦ23А6Ж3МЦ2
contains 23% zinc, 6% aluminum, 3% iron, 2% manganese. The best
brass of the LTs16K4 brand possesses fluidity. Foundry brasses include brasses
type ЛС, ЛК, ЛА, ЛАЖ, ЛАЖМЦ. Cast brasses are not prone to liquation, have
concentrated shrinkage, castings are obtained with high density.
Brass is a good material for structures operating under
negative temperatures.
Alloys of copper with elements other than zinc are called bronzes. Bronze
Bronze
are subdivided into wrought and casting.
When marking deformable bronzes, the letters Br are put in the first place, then
letters indicating which elements, other than copper, are included in the alloy. After the letters go
numbers showing the content of the components in the float. For example, brand BROF101
means that bronze contains 10% tin, 1% phosphorus, the rest is copper.
Cast bronzes also begin with the letters Br, then indicate
letter designations of alloying elements and a number is put indicating it
average content in the alloy. For example, bronze BrO3Ts12S5 contains 3% tin, 12
% zinc, 5% lead, the rest is copper.
Tin bronzes When copper and tin are fused, solid solutions are formed. These
alloys are very prone to segregation due to the large temperature range
crystallization. Due to segregation, alloys with a tin content above 5% are
favorable for parts such as plain bearings: the soft phase provides
good running-in, solid particles create wear resistance. That's why
pewter bronzes are good anti-friction materials.
Tin bronzes have a low volumetric shrinkage (about 0.8%), therefore
used in artistic casting. The presence of phosphorus ensures good
fluidity. Tin bronzes are subdivided into wrought and cast ones.
In deformable bronzes, the tin content should not exceed 6%, for
ensuring the required plasticity, BrOF6,50,15. Depending on the composition
deformable bronzes are distinguished by high mechanical, anti-corrosion,
anti-friction and elastic properties, and are used in various industries
industry. Bars, pipes, tape, wire are made of these alloys.
Practical part
Assignment for students:
1. Write down the title and purpose of the work.
2.Fill in the table:
Name
alloy, its
definition
The main
properties
alloy
Example
markings
Decryption
stamps
Region
application
21
Practical work number 7
Topic: "Study of aluminum alloys"
Purpose of work: familiarization of students with marking and scope
non-ferrous metals - aluminum and alloys based on it; study of application features
aluminum alloys depending on their composition.
Recommendations for students:
before proceeding
the practical part of the assignment, carefully read the theoretical provisions, and
See also lectures in your workbook on this topic.
Progress:
1. Get acquainted with the theoretical part.
2. Complete the assignment of the practical part.
Theoretical part
Principle of marking aluminum alloys. At the beginning, the type of alloy is indicated: D
duralumin type alloys; And technical aluminum; AK malleable aluminum
alloys; In high-strength alloys; AL casting alloys.
Further, the conditional number of the alloy is indicated. The conditional number is followed by
designation characterizing the state of the alloy: M soft (annealed); T
thermally treated (hardening plus aging); N cold-worked; NS -
semi-standardized.
According to their technological properties, alloys are divided into three groups: wrought
alloys not hardened by heat treatment; wrought alloys, hardenable
heat treatment; foundry alloys. Powder metallurgy methods
produce sintered aluminum alloys (SAS) and sintered aluminum powder
alloys (SAP).
Wrought cast alloys not hardened by heat treatment.
The strength of aluminum can be increased by alloying. Into alloys not hardened
heat treatment, introduce manganese or magnesium. The atoms of these elements are essentially
increase its strength, reducing plasticity. Alloys are indicated: with manganese AMts,
with magnesium AMg; after the designation of the element, its content is indicated (AMg3).
Magnesium acts only as a hardener, manganese hardens and increases
corrosion resistance. The strength of alloys increases only as a result of deformation
in a cold state. The greater the degree of deformation, the more it grows
22
strength and plasticity decreases. Depending on the degree of hardening, a distinction is made between
cold-worked and semi-worked alloys (AMg3P).
These alloys are used for the manufacture of various welded fuel containers,
nitric and other acids, low and medium loaded structures. Deformable
heat-hardened alloys.
These alloys include duralumin (complex alloys of aluminum
copper magnesium or aluminum copper magnesium zinc). They have a reduced
corrosion resistance, to increase which manganese is introduced. Duralumin
usually undergo hardening at a temperature of 500 ° C and natural aging, which
preceded by a two to three hour incubation period. Maximum strength
reached after 4.5 days. Duralumin is widely used in aircraft construction,
automotive industry, construction.
High-strength aging alloys are alloys that, in addition to copper and
magnesium contain zinc. Alloys B95, B96 have a tensile strength of about 650 MPa.
The main consumer is aircraft construction (skin, stringers, spars).
at
Forging aluminum alloys AK, AK8 are used for the manufacture of forgings.
temperature of 380-450 ° C, are hardened from
Forgings
temperature 500-560 ° C and aging at 150-165 ° C for 6 hours.
manufactured
Nickel, iron, titanium are additionally introduced into the composition of aluminum alloys, which
increase the temperature of recrystallization and heat resistance up to 300 ° C.
Pistons, blades and disks of axial compressors, turbojets
engines.
Casting alloys
Casting alloys include alloys of the aluminum-silicon system (silumins),
containing 1013% silicon. Additive to silumin magnesium, copper contributes to the effect
hardening of casting alloys during aging. Titanium and zirconium grind the grain.
Manganese improves anti-corrosion properties. Nickel and iron increase
heat resistance.
Casting alloys are marked from AL2 to AL20. Silumins are widely used
for the manufacture of cast parts for devices and other medium and lightly loaded
details, including thin-walled castings of complex shape.
Practical part
Assignment for students:
1. Write down the title and purpose of the work.
2. Fill in the table:
Name
alloy, its
definition
The main
properties
alloy
Example
markings
Decryption
stamps
Region
application
23
Laboratory work No. 1
Topic: "Mechanical properties of metals and methods of their study (hardness)"
Progress:
1. Become familiar with the theoretical provisions.
2. Complete the instructor's assignment.
3. Make a report according to the assignment.
Theoretical part
are called
material
Hardness
ability
resist
penetration of another body into it. In hardness tests, a body embedded in
material and called an indenter must be harder, have certain
size and shape, should not receive permanent deformation. Hardness tests
can be static and dynamic. The first type includes tests
by the indentation method, to the second by the impact indentation. Besides,
There is a method for determining the hardness by scratching, sclerometry.
By the value of the hardness of the metal, you can get an idea of the level of its
properties. For example, the higher the hardness determined by the pressure of the tip, the
less ductility of the metal, and vice versa.
The indentation hardness test consists in the fact that a sample under
the action of the load is pressed in the indenter (diamond, hardened steel, hard
alloy), in the form of a ball, cone or pyramid. After removing the load on
the sample remains an imprint, measuring the value of which (diameter, depth or
diagonal) and comparing it with the dimensions of the indenter and the magnitude of the load, one can judge
about the hardness of the metal.
Hardness is determined using special hardness testers. Most often
hardness is determined by Brinell (GOST 901259) and Rockwell (GOST 901359) methods.
There are general requirements for sample preparation and testing
by these methods:
1. The surface of the sample must be clean and free from defects.
2. Samples must be of a certain thickness. After receiving the print on
the reverse side of the sample should not show any signs of deformation.
3. The sample should be firm and stable on the table.
4. The load should act perpendicular to the surface of the sample.
Determination of Brinell hardness
The Brinell hardness of the metal is determined by indentation into a sample of a hardened
24
steel ball (Fig. 1) with a diameter of 10; 5 or 2.5 mm and are expressed by the number of hardness
HB obtained by dividing the applied load P in N or kgf (1N = 0.1 kgf) by
surface area of the imprint formed on the sample F in mm
The Brinell hardness number HB is expressed by the ratio of the applied load F
to the area S of the spherical surface of the indentation (hole) on the measured surface.
HB =
, (Mpa),
D − √D2 − d2
πD¿
F
S = 2F
¿
where
F - load, N;
S is the area of the spherical surface of the imprint, mm2 (expressed in terms of D and d);
D is the diameter of the ball, mm;
d - indentation diameter, mm;
The value of the load F, the diameter of the ball D and the holding time under
load
τ
, are selected according to table 1.
Figure 1. Scheme of hardness measurement by the Brinell method.
a) Scheme of pressing the ball into the test metal
F load, D - ball diameter, dop - indent diameter;
b) Measurement of the indentation diameter with a loupe (in the figure d = 4.2 mm).
Table 1.
Selection of ball diameter, load and load holding depending on
on the hardness and thickness of the sample
Diameter
ball D,
mm
Thickness
test subject
sample, mm
Material
Black metals
Interval
hardness in
units
Brinell,
MPa
14004500
more than 6
6…3
less than 3
more than 6
6…3
10
5
2,5
10
5
Less than 1400
Excerpt
under
load
with
, τ
10
Load
F, N (kgf)
29430
(3000)
7355 (750)
1840
(187,5)
9800
(1000)
25
Non-ferrous metals
and alloys (copper,
brass, bronze,
magnesium alloys
and etc.)
3501300
Non-ferrous metals
(aluminum,
bearing
alloys, etc.)
80350
less than 3
more than 6
6…3
less than 3
more than 6
6…3
less than 3
2,5
10
5
2,5
10
5
2,5
2450 (750)
613 (62,5)
9800
(1000)
2450 (750)
613 (62,5)
2450 (250)
613 (62,5)
153,2
(15,6)
30
60
Figure 2 shows a diagram of a lever device. The sample is set on
stage 4. Rotating the handwheel 3, lift the sample with the screw 2 until it touches
it with the ball 5 and further until the full compression of the spring 7, put on the spindle 6. The spring
creates a preload on the ball equal to 1 kN (100 kgf), which provides
stable position of the specimen during loading. Then include
electric motor 13 and through the worm gear of the gearbox 12, the connecting rod 11 and the system of levers
8.9, located in the housing 1 of the hardness tester with weights 10 creates a given full load
on the ball. A spherical impression is obtained on the test piece. After unloading the device
the sample is removed and the diameter of the print is determined with a special magnifier. For the calculated diameter
print take average arithmetic value measurements in two mutually
perpendicular directions.
Figure 2. Diagram of the Brinell device
Using the above formula, using the measured indentation diameter,
the hardness number HB is calculated. Hardness number depending on the diameter obtained
indentation can also be found in tables (see table of hardness numbers).
When measuring hardness with a ball with a diameter of D = 10.0 mm under a load of F = 29430 N
HB 2335 MPa or over
= 10 s - the number of hardness is written as follows:
τ
(3000 kgf), with shutter speed
old designation HB 238 (in kgf / mm2)
When measuring Brinell hardness, keep in mind the following:
1.
It is possible to test materials with a hardness of not more than HB 4500 MPa, since at
greater hardness of the sample, an unacceptable deformation of the ball itself occurs;
2.
To avoid punching, the minimum sample thickness should not be
less than ten times the depth of the print;
26
3.
4.
four diameters of the print;
not less than 2.5 d.
The distance between the centers of two adjacent prints must be at least
The distance from the center of the indentation to the lateral surface of the sample should be
Determination of Rockwell hardness
According to the Rockwell method, the hardness of metals is determined by indentation into the test
sample of a hardened steel ball with a diameter of 1.588 mm or a diamond cone with an angle at
the top
loads:
preliminary P0 = 10 kgf and total P equal to the sum of preliminary P0 and
main P1 loads (Fig. 3).
two consecutively
attached
action
120o under
Rockwell hardness number HR is measured in conventional dimensionless units and
HRc = 100−
determined by the formulas:
h − h0
0.002 - when pressing the diamond cone
h − h0
0.002 - when a steel ball is pressed in,
HRv = 130−
where 100 is the number of divisions of the black scale C, 130 is the number of divisions of the red scale B
the dial of the indicator measuring the indentation depth;
h0 is the depth of indentation of the diamond cone or ball under the action of
preload. Mm
h is the depth of indentation of the diamond cone or ball under the action of the total load,
mm
0.002 - the value of the scale division of the indicator dial (movement of the diamond cone
when measuring the hardness of 0.002 mm corresponds to the movement of the indicator arrow by
one division), mm
Tip type and load value are selected according to table 2, depending on
hardness and thickness of the test piece. ...
The Rockwell hardness number (HR) is a measure of the indentation depth of the indenter and
expressed in conventional units. The unit of hardness is taken as a dimensionless value,
corresponding to an axial displacement of 0.002 mm. Rockwell hardness number
indicated directly by an arrow on the C or B scale of the indicator after the automatic
removing the main load. The hardness of the same metal, determined by different
methods are expressed in various units of hardness.
For example, HB 2070, HRc 18 or HRb 95.
Figure 3. Scheme of Rockwell hardness measurement
27
View
tip
ika
General
load F,
N (kgf)
Minimum
thickness
sample
Designation
hardness on
Rockwell
scale
Number
firmly
sti
V
WITH
A
HRB
Steel
ball
981 (100)
Hrs
Diamonds
th cone
1471 (150)
HRA
Diamonds
th cone
588 (60)
0,7
0,7
0,4
table 2
The limits
measurements
in units
Rockwell
25…100
on the B scale
20…67
on the C scale
70…85
on the B scale
The limits
measurements
hardness
sample in
units
Brinell, NV
500 to 2300
(unhardened
steel colored
metals and their
alloys
from 2000 to 7000
(hardened
become)
4000 to
9000 (details
exposed
cementation or
nitriding,
hard alloys
and etc.)
The Rockwell method is distinguished by its simplicity and high productivity, provides
preservation of a high-quality surface after testing, allows you to test metals and
alloys, both low and high hardness. This method is not recommended for
alloys with a heterogeneous structure (gray cast irons, malleable and high-strength,
antifriction bearing alloys, etc.).
Practical part
Content of the report.
Answer the questions:
1. What is called hardness?
2. What is the essence of hardness determination?
3. What 2 methods of hardness determination do you know? What is the difference between them?
4. How should a sample be prepared for testing?
5. How can you explain the lack of a universal method for determining hardness?
6. Why, of the many mechanical characteristics of materials, the most common
determine the hardness?
7. Record in a notebook the scheme for determining the hardness according to Brinell and Rockwell.
28
Laboratory work No. 2
Topic: "Mechanical properties of metals and methods of their study (strength, elasticity)"
Purpose of the work: to study the mechanical properties of metals, methods of their study.
Progress:
1. Become familiar with the theoretical provisions.
2. Complete the instructor's assignment.
3. Make a report according to the assignment.
Theoretical part
The main mechanical properties are strength, elasticity, toughness,
the designer reasonably chooses
hardness.
appropriate material that ensures the reliability and durability of structures when
their minimum mass.
Knowing the mechanical properties,
Mechanical properties determine the behavior of the material during deformation and
destruction from the action of external loads. Depending on loading conditions
mechanical properties can be determined when:
1. Static loading, the load on the sample increases slowly and smoothly.
29
2. Under dynamic loading, the load increases at a high speed, has
shock character.
3. Repeatedly alternating or cyclic loading the load in the process
the test varies many times in magnitude or in magnitude and direction.
To obtain comparable results, samples and procedures
mechanical tests are regulated by GOSTs. In a static test on
tensile: GOST 1497 obtain the characteristics of strength and ductility.
Strength is the ability of a material to resist deformation and destruction.
Plasticity is the ability of a material to change its size and shape under
the influence of external forces; the measure of plasticity is the amount of permanent deformation.
The device that determines strength and ductility is a tensile testing machine,
which records the stress-strain diagram (see Fig. 4) expressing the relationship between
specimen elongation and acting load.
Rice. 4. Stretch diagram: a - absolute, b - relative.
Section oa in the diagram corresponds to the elastic deformation of the material when
Hooke's law is respected. Stress corresponding to elastic limit deformation
at point a is called the proportionality limit.
The proportional limit is the highest voltage before reaching
which Hooke's law is valid.
At voltages above the proportional limit, a uniform
plastic deformation (lengthening or narrowing of the section).
Point b - elastic limit - the highest stress, before reaching which in
no permanent deformation occurs in the sample.
The cd area is the yield point, it corresponds to the yield point - this is
stress at which an increase in deformation occurs in the sample without an increase
loads (material "flows").
Many grades of steel, non-ferrous metals do not have a pronounced area
yield strength, therefore, a conditional yield point is set for them. Conditional
yield stress is the stress that corresponds to permanent deformation
equal to 0.2% of the original length of the sample (alloy steel, bronze, duralumin and
other materials).
Point B corresponds to the ultimate strength (a local
thinning is a neck, the formation of thinning is characteristic of plastic materials).
30
Tensile strength is the maximum stress that a sample can withstand.
before resolution (temporary tensile strength).
Behind point B, the load falls (due to neck elongation) and destruction
occurs at point K.
The practical part.
Content of the report.
1. Indicate the title of the work, its purpose.
2. What mechanical properties do you know? What methods are used to determine
mechanical properties of materials?
3. Write down the definition of strength and ductility. What methods
are they determined? What is the name of the device that determines these properties? WITH
with what properties are defined?
4. Record the absolute tensile diagram of the plastic material.
5. After the diagram, specify the names of all points and sections of the diagram.
6. What is the limit is the main characteristic when choosing a material for
making any product? Justify the answer.
7. What materials are more reliable in work, brittle or ductile? Answer
justify.
Bibliography
Main:
1.
Adaskin A.M., Zuev V.M. Materials science (metalworking). - M .: OITs
"Academy", 2009 - 240 p.
FORUM, 2010 - 336 p.
2.
3.
Adaskin A.M., Zuev V.M. Materials science and technology of materials. - M .:
Chumachenko Yu.T. Materials science and plumbing (NGO and SPO). -
Rostov n / a: Phoenix, 2013 - 395 p.
Additional:
1.
Zhukovets I.I. Mechanical testing of metals. - M .: Higher school, 1986. -
199 p.
2.
3.
Lakhtin Yu.M. Fundamentals of Materials Science. - M .: Metallurgy, 1988.
Lakhtin Yu.M., Leontyeva V.P. Materials Science. - M .: Mechanical Engineering, 1990.
31
Electronic resources:
1. Journal "Materials Science". (Electronic resource) - access form
http://www.nait.ru/journals/index.php?p_journal_id=2.
2. Materials science: educational resource, access form http: //
steels.
(Electronic
resource)
–
the form
access
www.supermetalloved / narod.ru.
3.
Vintage
www.splav.kharkov.com.
4. Federal Center for Information and Education Resources. (Electronic
resource) - access form www.fcior.ru.
32
