LEARNING OBJECTIVES PREFACE

Transcription

1 LEARNING OBJECTIVES PREFACE Accreditation standards, as mandated by many engineering accreditation organizations, now include outcome assessment components. Often one of these components includes the delineation of detailed educational objectives, and, in addition, some means of evaluating whether or not these objectives have been achieved by the students. One way of addressing this issue is for instructors in departments of engineering to incorporate learning objectives in their course offerings. To this end we decided to include learning objectives both in the textbook and this instructors guide. There appear on the first page of each of the textbook chapters several learning objectives, general in nature, that are relevant to that chapter's content. Furthermore, we have included in this section of the Instructors Guide, a detailed list of objectives for each of the 24 chapters. We believe that, in addition, to providing outcome assessment criteria, these objectives will also help the instructor to organize the course subject material and also give direction to the classroom presentations; in addition, objectives allow the instructor to ascertain whether or not the intended course goals have been achieved. When distributed to and used by the students, their studying becomes more focused and effective, and preparation for examinations is facilitated.

2 CHAPTER 1 INTRODUCTION LEARNING OBJECTIVES 1. List six different property classifications of materials that determine their applicability. 2. Define what is meant by a structural element of a material, and then cite two structural elements. 3. (a) Cite the four components that are involved in the design, production, and utilization of materials. (b) Now, briefly describe the interrelationships between these components. 4. Cite three criteria that are important in the materials selection process. 5. (a) List the three primary classifications of solid materials, and then cite the distinctive chemical feature of each. (b) In addition, note the other three types of materials, and, for each, its distinctive feature(s). 1

3 CHAPTER 2 ATOMIC STRUCTURE AND INTERATOMIC BONDING LEARNING OBJECTIVES 1. Name the two atomic models cited, and note the differences between them. 2. Describe the important quantum-mechanical principle that relates to electron energies. 3. (a) Name the four electron quantum numbers. (b) For a specific electron, note what each of its quantum numbers determines. 4. Write a definition of the Pauli exclusion principle. 5. Cite the general characteristics of the elements that are arrayed in each column of the periodic table. 6. Write the equation that relates energy and force. 7. (a) Schematically plot attractive, repulsive, and net energies versus interatomic separation for two atoms or ions. (b) Now note on this plot the equilibrium separation and the bonding energy. 8. (a) Briefly describe ionic, covalent, metallic, hydrogen, and van der Waal's bonds. (b) Now note what materials exhibit each of these bonding types. 9. Given the chemical formula for a material, be able to cite what bonding type(s) is (are) possible. 10. Given the electronegativities of two elements, compute the percent ionic character of the bond that forms between them. 11. Define what is meant by the term "molecule". 2

4 CHAPTER 3 THE STRUCTURE OF CRYSTALLINE SOLIDS LEARNING OBJECTIVES 1. Give a definition of a crystalline solid. 2. Describe the difference between crystalline and noncrystalline materials. 3. Give a brief definition of a unit cell. 4. Schematically diagram face-centered cubic, body-centered cubic, and hexagonal closepacked unit cells. 5. Given the atomic radius of an atom that forms into a face-centered cubic crystal structure as well as the metal's atomic weight, compute its density. 6. Given the atomic radius of an atom that forms into a body-centered cubic crystal structure as well as the metal's atomic weight, compute its density. 7. (a) Explain what is meant by coordination number and atomic packing factor. (b) Cite the atomic packing factors and coordination numbers for body-centered cubic, face-centered cubic, and hexagonal close-packed crystal structures. 8. Briefly define polymorphism (or allotropy). 9. Distinguish between crystal system and crystal structure. 10. Recognize and also give the lattice parameter relationships for all seven crystal systems- -i.e., cubic, hexagonal, tetragonal, rhombohedral, orthorhombic, monoclinic, and triclinic. 11. Given a unit cell and three direction indices, draw the direction represented by these indices referenced to this unit cell. 12. Given a direction that has been drawn referenced to a unit cell, specify its direction indices. 13. Given a unit cell and the Miller indices for a plane, draw the plane represented by these indices referenced to this unit cell. 14. Given a plane that has been drawn referenced to a unit cell, specify its Miller indices. 15. For hexagonal crystals, be able to convert both directional and planar indices from the three-axes scheme to the four-axes (Miller Bravais) scheme. 16. Given the unit cell for some crystal structure, be able to draw the atomic packing arrangement for a specific crystallographic plane. 17. Define both linear and planar atomic densities. 3

5 18. For a given crystal structure, be able to determine the linear density for a specified crystallographic direction. 19. For a given crystal structure, be able to determine the planar density for a specified crystallographic plane. 20. (a) Draw the packing of a close-packed plane of spheres (atoms). (b) Describe how both hexagonal close-packed and face-centered cubic crystal structures may be generated by the stacking of close-packed planes. (c) Cite which planes in both hexagonal close-packed and face-centered cubic structures are close-packed. 21. Briefly cite the difference between single crystals and polycrystalline materials. 22. Give definitions for isotropy and anisotropy. 23. Define grain boundary. 24. Briefly describe the phenomenon of diffraction. 25. Given the angle at which an x-ray diffraction peak occurs, as well as the x-ray wavelength and order of reflection, compute the interplanar spacing for the crystallographic planes that are responsible for the diffraction peak. 26. For crystals having cubic symmetry, given the lattice parameter (i.e., unit cell edge length), compute the interplanar spacing for a set of crystallographic planes of specified Miller indices. 4

6 CHAPTER 4 IMPERFECTIONS IN SOLIDS LEARNING OBJECTIVES 1. Describe both vacancy and self-interstitial crystalline defects. 2. Given the density and atomic weight for some material, as well as Avogardo's number, compute the number of atomic sites per cubic meter 3. For some material, given the number of atomic sites per cubic meter, the energy required for vacancy formation, and, in addition, the value for the gas constant, compute the number of vacancies at some specified temperature. 4. Define what is meant by the term "alloy". 5. State the two types of solid solutions, and provide a brief written definition and/or schematic diagram of each. 6. State the criteria for the formation of each of substitutional and interstitial solid solutions. 7. Given the atomic radii of host and impurity atoms, as well as their crystal structures, electronegativities, and valences, determine if solid solutions that form are (a) substitutional with appreciable solubility, (b) substitutional with limited solubility, or (c) interstitial. 8. Given the masses and atomic weights of two or more elements in a metal alloy, compute the weight percent and atomic percent of each element. 9. (a) Given the composition (in weight percent) and atomic weights for two elements in an alloy, determine the composition in atom percent. (b) Make a composition conversion from atom percent to weight percent. 10. Given the atomic weights and densities for two elements in an alloy: (a) Determine the average density when the composition is specified in weight percent. (b) Determine the average density when the composition is specified in atom percent. 11. Given the atomic weight for each of two elements in an alloy: (a) Determine the average atomic weight when the composition is specified in weight percent. (b) Determine the average atomic weight when the composition is specified in atom percent. 12. For each of edge, screw, and mixed dislocations: (a) describe and make a drawing of the dislocation; 5

7 (b) note the location of the dislocation line; and (c) indicate the direction along which the dislocation line extends. 13. (a) Describe the atomic structure within the vicinity of a grain boundary. (b) Make a distinction between high- and low-angle grain boundaries. (c) Explain how a low-angle tilt boundary is formed by an array of edge dislocations. 14. Describe the arrangement of atoms in the vicinity of a twin boundary. 15. Define the terms microstructure and microscopy. 16. Explain what preparations are necessary for observation of the grain structure of a polycrystalline material with an optical microscope. 17. Name and briefly describe the operations of both types of electron microscopes. 18. In general terms, briefly explain how scanning probe microscopes operate. 19. Given a photomicrograph of a polycrystalline material, as well as the magnification, determine the grain size using intercept and ASTM methods. 6

8 CHAPTER 5 DIFFUSION LEARNING OBJECTIVES 1. Give a brief definition of diffusion. 2. Explain the terms interdiffusion and self-diffusion. 3. (a) List and briefly describe the two atomic mechanisms of diffusion. (b) Indicate which type of diffusion occurs more rapidly, and then explain why this is so. 4. Given the mass of material diffusing through a cross-sectional area over a specified time period, compute the diffusion flux. 5. Define the terms concentration profile and concentration gradient. 6. Make a distinction between steady-state and nonsteady-state diffusion. 7. For steady-state diffusion through a metal sheet, determine the diffusion flux given values for the diffusion coefficient, the sheet thickness, and the concentrations of diffusing species at both surfaces. 8. Cite the driving force for steady-state diffusion. 9. Write Fick's second law in equation form. 10. For diffusion into a semi-infinite solid and when the concentration of diffusing species at the surface is held constant, compute the concentration at some position after a specified time given the following: (a) the pre-diffusion concentration in the solid, (b) the surface composition, and (c) the value of the diffusion coefficient of the diffusing species. Also, assume that a tabulation of error function values (similar to Table 5.1) is available. 11. Cite two factors that influence diffusion rate (i.e., the magnitude of the diffusion coefficient). 12. Given the pre-exponential, D o, the activation energy, the absolute temperature, and the gas constant, be able to compute the value of the diffusion coefficient. 13. Given a plot of logarithm of the diffusion coefficient (to the base 10) versus the reciprocal of absolute temperature, determine values for the diffusion coefficient's pre-exponential and activation energy. 7

9 CHAPTER 6 MECHANICAL PROPERTIES OF METALS LEARNING OBJECTIVES 1. List three factors that should be considered in designing laboratory tests to assess the mechanical characteristics of materials for service use. 2. Given the tensile load on a specimen and its original and instantaneous cross-sectional dimensions, be able to compute the engineering stress and the true stress. 3. Given the original and instantaneous lengths of a specimen which is being loaded in tension, be able to compute the engineering strain and the true strain. 4. Given the magnitude of a tensile stress that is applied parallel to the specimen axis, compute the magnitudes of normal and shear stresses on a plane that is oriented at some specified angle relative to the specimen end-face. 5. Distinguish between elastic and plastic deformations, both by definition, and in terms of behavior on a stress-strain plot. 6. Compute the elastic modulus from a stress-strain diagram. 7. Given the elastic modulus and either elastic engineering stress or strain, be able to compute the other (strain or stress). 8. For a material that exhibits nonlinear elastic behavior, be able to compute tangent and secant moduli from its stress-strain diagram. 9. State what is occurring on an atomic level as a material is elastically deformed. 10. Briefly explain how the shape of a material's force versus interatomic separation curve influences its modulus of elasticity. 11. Given the cross-sectional area of a specimen over which a shear forced of specified magnitude acts, and, in addition, the resulting shear strain, be able to compute the shear modulus. 12. Define anelasticity. 13. Given Poisson's ratio and the elastic strain in the direction of the applied load (i.e., axial strain), be able to compute the elastic strain in the lateral (or perpendicular) direction. 14. Cite typical value ranges of modulus of elasticity and Poisson's ratio for metallic materials. 15. Given values of modulus of elasticity and Poisson's ratio for an isotropic material, estimate the value of its shear modulus. 8

10 16. Given an engineering stress-strain diagram estimate the proportional limit, and then determine the yield strength (0.002 strain offset) and the tensile strength. 17. Schematically sketch the stress-strain behavior for a material that displays distinct upper and lower yield points, and then explain how the yield strength is determined. 18. Given the stress-strain behavior for two metals, be able to distinguish which is stronger. 19. For a cylindrical specimen of a ductile material that is deformed in tension, describe how the specimen's profile changes in moving through elastic and plastic regimes of the stress-strain curve, to the point of fracture. 20. Explain why engineering stress decreases with increasing engineering strain past the tensile strength point. 21. Cite typical yield and tensile strength ranges for metal alloys. 22. Give a brief definition of ductility, and schematically sketch the engineering stress-strain behaviors for both ductile and brittle materials. 23. Given the original and fracture dimensions of a specimen deformed in tension, be able to determine its ductility in terms of both percent elongation and percent reduction of area. 24. Cite which tensile parameters are sensitive (and also which are insensitive) to any prior deformation, the presence of impurities, and/or any heat treatment. 25. Cite how elastic modulus, tensile and yield strengths, and ductility change with increasing temperature. 26. Give brief definitions of and the units for modulus of resilience and toughness (static). 27. Given yield strength and modulus of elasticity values for some material, compute its modulus of resilience. 28. Given the stress-strain behavior for two metals, determine which is the most resilient and which is the toughest. 29. Given values of the constants K and n in the equation relating plastic true stress and true strain, be able to compute the true stress necessary to produce some specified true strain. 30. Schematically plot both the tensile engineering stress-strain and true stress-strain behaviors for the same material and then explain the difference between the two curves. 31. Describe the phenomenon of elastic recovery using a stress-strain plot. 32. Determine the elastic strain recovered for some material, given its stress-strain plot and the total strain to which a specimen has been subjected. 9

11 33. Define hardness in a one- or two-sentence statement. 34. Cite three reasons why hardness tests are performed more frequently than any other mechanical test on metals. 35. Name the two most common hardness-testing techniques that are used in the U.S., and give two differences between them. 36. Name and briefly describe the two different microhardness testing techniques. Now cite situations for which these techniques are generally used. 37. Cite three precautions that should be taken when performing hardness tests in order to insure accurate readings. 38. Schematically diagram tensile strength versus hardness for a typical metal. 39. Cite five factors that can lead to scatter in measured data. 40. Given a series of data values that have been collected, be able to compute both the average and the standard deviation. 41. Given the yield strength of a ductile material, be able to compute the working stress. 10

12 CHAPTER 7 DISLOCATIONS AND STRENGTHENING MECHANISMS LEARNING OBJECTIVES 1. Describe edge dislocation motion by the translation of an extra half-plane of atoms as atomic bonds are repeatedly and successively broken and then reformed. 2. Briefly describe how plastic deformation occurs by the movement of both edge and screw dislocations in response to applied shear stresses. 3. Distinguish between edge and screw dislocations in terms of the direction of line motion in response to an applied shear stress. 4. Define dislocation density and cite its units. 5. Given a drawing of atom positions around an edge dislocation, locate regions of compressive and tensile strains that are created in the crystal due to the presence of the dislocation. 6. Name and describe the kind of lattice strains that are found in the vicinity of a screw dislocation. 7. Define slip system. 8. Specify the characteristics of a slip system for some crystal structure. 9. Specify the slip systems for face-centered cubic and body-centered cubic crystal structures. 10. Explain, in terms of slip systems, why body-centered cubic and hexagonal close-packed metals ordinarily experience a ductile-to-brittle transition with decreasing temperature, while face-centered cubic metals do not experience such a transition. 11. Define resolved shear stress and critical resolved shear stress. 12. Compute the resolved shear stress on a specified plane given the value of the applied tensile stress, as well as 1) the angle between the normal to the slip plane and the applied stress direction, and 2) the angle between the slip and stress directions. 13. Describe the nature of plastic deformation, in terms of dislocation motion, for a single crystal that is pulled in tension. 14. Briefly explain how the grain structure of a polycrystalline metal is altered when it is plastically deformed. 15. Briefly describe, from an atomic perspective, how plastic deformation results from the formation of mechanical twins. 11

13 16. Cite two differences between deformation by slip and deformation by twinning. 17. Explain why and describe how the yield strength of a metal is related to the ability of dislocations to move. 18. Describe how grain boundaries impede dislocation motion and why a metal having small grains is stronger than one having large grains. 19. Given a plot of yield strength versus d -1/2 (d being the average grain size), be able to determine the values of σ o and k y, and also the yield strength at a specified value of d. 20. Briefly describe the phenomenon of solid-solution strengthening. 21. Briefly explain solid-solution strengthening for substitutional impurity atoms in terms of lattice strain interactions with dislocations. 22. Describe the phenomenon of strain hardening (or cold-working) in terms of 1) changes in mechanical properties, and 2) stress-strain behavior. 23. Given the original and deformed cross-sectional dimensions of a metal specimen that has been cold-worked, compute the percent cold work. 24. Schematically plot tensile strength, yield strength, and ductility versus percent cold work for a metal specimen. 25. Briefly describe the phenomenon of strain hardening in terms of dislocations and strain field interactions. 26. Cite three characteristics/properties that become altered when a metal is plastically deformed. 27. Briefly describe the changes that take place as a metal experiences recovery. 28. Briefly describe what occurs during the process of recrystallization, in terms of both the alteration of microstructure and mechanical characteristics of the material. 29. Cite the driving force for recrystallization. 30. Make a schematic plot of how the room temperature tensile strength and ductility vary with temperature (at a constant heat-treating time) in the vicinity of the recrystallization temperature, for a metal that was previously cold-worked. 31. Define recrystallization temperature. 32. Name two factors that influence the recrystallization temperature of a metal or alloy, and then note how they influence the recrystallization temperature. 33. Make a distinction between hot-working and cold-working. 34. Describe a procedure that may be used to reduce the cross-sectional area of a cylindrical specimen, given its original and deformed radii, and, in addition, the required strength and ductility after deformation. 12

14 35. Describe the phenomenon of grain growth from both microscopic and atomic level perspectives. 36. Cite the driving force for grain growth. 37. For some polycrystalline material, given a value for the diameter exponent (n), and, in addition, the grain diameters at two different times at an elevated temperature, be able to compute the following: 1) the original grain diameter, and 2) the grain diameter after yet another time. 13

15 CHAPTER 8 FAILURE LEARNING OBJECTIVES 1. Cite the three usual causes of failure. 2. (a) Cite the two modes of fracture and the differences between them. (b) Note which type of fracture is preferred, and give two reasons why. 3. Describe the mechanism of crack propagation for both ductile and brittle modes of fracture. 4. Describe the two different types of fracture surfaces for ductile metals, and, for each, cite the general mechanical characteristics of the material. 5. Briefly describe the mechanism of crack formation and growth in moderately ductile materials. 6. Briefly describe the macroscopic fracture profile for a material that has failed in a brittle manner. 7. Name and briefly describe the two crack propagation paths for polycrystalline brittle materials. 8. Explain why the strengths of brittle materials are much lower than predicted by theoretical calculations. 9. Given the magnitude of an applied tensile stress, and the length and tip radius of a small crack which axis is perpendicular to the direction of the applied stress, compute the maximum stress that may exist at the crack tip. 10. Cite the conditions that must be met in order for a brittle material to experience fracture. 11. Briefly state why sharp corners should be avoided in designing structures that are subjected to stresses. 12. For some material, given values of the modulus of elasticity and specific surface energy, and the length of an internal crack, be able to compute the critical stress for propagation of this crack. 13. Define critical strain energy release rate, and cite an equation for its determination. 14. Describe/illustrate the three different crack displacement modes. 15. Describe the conditions of plane stress and plane strain. 16. In a brief statement define fracture toughness and also specify its units. 14

16 17. Make distinctions between stress intensity factor, fracture toughness, and plane strain fracture toughness. 18. Given plane strain fracture toughness and yield strength values for a material, compute the minimum plate thickness for the condition of plane strain. 19. Given the plane-strain fracture toughness of a material, the length of the longest surface crack, and the value of Y, compute the critical (or design) stress. 20. Determine whether or not a flaw of critical length is subject to detection given the resolution limit of the detection apparatus, the maximum applied tensile stress, the plane strain fracture toughness of the material, as well as a value for the scale parameter (Y). 21. Name three factors that are critical relative to a metal experiencing a transition from ductile to brittle fracture. 22. Name and briefly describe the two techniques that are used to measure impact energy (or notch toughness) of a material. 23. Make a schematic plot of the dependence of impact energy on temperature for a metal that experiences a ductile-to-brittle transition. 24. Note which types of materials do, and also those which do not, experience a ductile-tobrittle transition with decreasing temperature. 25. Cite two measures that may be taken to lower the ductile-to-brittle transition temperature in steels. 26. Define fatigue and specify the conditions under which it occurs. 27. Name and describe the three different stress-versus-time cycle modes that lead to fatigue failure. 28. Given a sinusoidal stress-versus-time curve, be able to determine the stress amplitude and mean stress. 29. (a) Briefly describe the manner in which tests are performed to generate a plot of fatigue stress versus the logarithm of the number of cycles. (b) Note three in-service conditions should be replicated in a fatigue test. 30. Schematically plot the fatigue stress as a function of the logarithm of the number of cycles to failure for both materials which do and which do not exhibit a fatigue limit. For the former, label the fatigue limit. 31. Given a fatigue plot for some material: (a) for some particular stress level, determine the maximum number of cycles allowable before failure (i.e., the fatigue lifetime); 15

17 (b) for some specified number of cycles, determine the fatigue strength. 32. Briefly describe the two stages of crack propagation in polycrystalline materials which may ultimately lead to fatigue failure. 33. Describe the two differently types of fatigue surface features, and cite the conditions under which they occur. 34. Given σ max and σ min, and, for a particular material, initial and critical crack lengths, and, in addition, values for the Y, A, and m parameters, estimate the fatigue lifetime. 35. Cite five measures that may be taken to improve the fatigue resistance of a metal. 36. Describe thermal fatigue failure, and note how it may be prevented. 37. Describe corrosion fatigue, and then cite five measures that may be taken to prevent it. 38. Define creep and specify the conditions under which it occurs. 39. Make a schematic sketch of a typical creep curve, and then note on this curve the three different creep stages. 40. Given a creep plot for some material, determine (a) the steady-state creep rate, and (b) the rupture lifetime. 41. Given the absolute melting temperature of a metal, estimate the temperature at which creep becomes important. 42. Schematically sketch how the creep behavior of a material changes with increasing temperature and increasing load (or stress). 43. Make schematic plots showing how the rupture life and steady-state creep rate for a material are represented as functions of stress and temperature. 44. Cite the general mathematical expression for the dependence of steady-state creep rate on both applied stress and temperature. 45. Given a Larson-Miller master plot of creep data for some material, determine the rupture life at a given temperature and stress level. 16

18 CHAPTER 9 PHASE DIAGRAMS LEARNING OBJECTIVES 1. Define phase. 2. Name three important microstructural characteristics for multiphase alloys. 3. Cite three factors that affect the microstructure of an alloy. 4. Briefly explain the concept of phase equilibrium. 5. Briefly define metastable in terms of microstructure. 6. (a) Schematically sketch simple isomorphous and eutectic phase diagrams. (b) On these diagrams label the various phase regions. (c) Also label liquidus, solidus, and solvus lines. 7. Given a binary phase diagram, the composition of an alloy, its temperature, and assuming that the alloy is at equilibrium, determine: (a) what phase(s) is (are) present; (b) the composition(s) of the phase(s); and (c) the mass fraction(s) of the phase(s). 8. Given mass fractions and densities for both phases of a two-phase alloy, determine the phase volume fractions. 9. Using an isomorphous phase diagram, explain the phenomenon of coring for the nonequilbrium solidification of an alloy that belongs to this isomorphous system. 10. Given a binary phase diagram, locate the temperatures and compositions of all eutectic reactions, and then write the reactions for either heating or cooling. 11. Given a binary eutectic phase diagram, for an alloy of specified composition the microstructure of which consists of both primary and eutectic microconstituents, do the following: (a) compute the mass fractions of both microconstituents; and (b) sketch and label a schematic drawing of the microstructure. 12. Define microconstituent, and then cite two examples. 13. Given a binary phase diagram, determine the solubility limit of one of the elements in one phase at some given temperature. 14. Explain the following terms: (a) terminal solid solution, (b) intermediate solid solution, and (c) intermetallic compound. 17

19 15. For some given binary phase diagram, do the following: (a) locate the temperatures and compositions of all eutectoid, peritectic, and congruent phase transformations; and (b) write reactions for all these transformations for either heating or cooling. 16. Write the Gibbs phase rule in its most general form, and explain each term in the phase rule equation. 17. Apply Gibbs phase rule in single- and two-phase regions, as well as on isotherm lines for binary phase diagrams. 18. Name the crystal structures for both ferrite (α-iron) and austenite (γ-iron). 19. Give the composition of iron carbide, Fe 3 C, and also the maximum solubility of carbon in both α-ferrite and austenite phases. 20. Specify the temperature and composition at which the eutectoid reaction occurs, and write this eutectoid reaction for either heating or cooling. 21. Cite the three types of ferrous alloys on the basis of carbon content, and then note the composition range for each. 22. Briefly describe the pearlite structure, and then calculate the relative amounts of the two phases in this structure. 23. Given the composition of an iron-carbon alloy containing between wt% C and 2.11 wt% C, be able to (a) determine whether it is a hypoeutectoid or hypereutectoid alloy; (b) specify the proeutectoid phase; (c) compute the mass fractions of the proeutectoid phase and pearlite; and (d) make a schematic diagram of the microstructure. 24. Given the composition of an Fe-C-M alloy (where M represents a metallic element other than iron--e.g., Cr, Ni, Mo, etc.), and a plot of the eutectoid composition versus the concentration of element M, be able to determine (a) the proeutectoid phase, and (b) the approximate mass fractions of proeutectoid and pearlite microconstituents. 18

20 CHAPTER 10 PHASE TRANSFORMATIONS IN METALS LEARNING OBJECTIVES 1. Cite the two distinct steps that are involved in the formation of particles of a new phase. 2. Make a schematic fraction transformation-versus-logarithm of time plot for a typical solidsolid transformation, and then note nucleation and growth regions on the curve. 3. For some solid-solid reaction, given values of the constants k and n, compute the fraction transformation after a specified time. 4. Given a fraction transformation-versus-logarithm of time curve at some temperature, be able to determine the overall rate of the transformation. 5. Define the terms supercooling and superheating. 6. Explain how an isothermal transformation diagram for some alloy is generated from a series of isothermal fraction transformation-versus-logarithm of time curves. 7. Describe the difference in microstructure for fine and coarse pearlites, and then explain this difference in terms of the isothermal temperature range over which each transforms. 8. Briefly describe the microstructures of upper and lower bainites and of spheroidite. 9. Briefly describe martensite in terms of its crystal structure and its microstructures. 10. Describe the difference between thermally activated and athermal transformations, and then cite one example of each transformation. 11. Describe the heat treatment that is necessary to produce martensite, and explain why it forms instead of pearlite or bainite. 12. Given the isothermal transformation diagram for some iron-carbon alloy and also a specific isothermal heat treatment, be able to describe the microstructure that will result. The microstructure may consist of austenite, a proeutectoid phase, fine pearlite, coarse pearlite, spheroidite, bainite, and/or martensite. 13. Given a continuous cooling transformation diagram for some particular alloy and a specific cooling curve, describe the resulting microstructure that exists at room temperature. 14. Define what is meant by the critical cooling rate, and given a continuous cooling transformation diagram, schematically plot the critical cooling curve. 19

21 15. Describe or diagram how alloying elements other than carbon alter the continuous cooling transformation diagram for a steel. Now explain, in terms of this alteration, why alloying elements make a steel more "heat-treatable." 16. Schematically diagram how tensile strength, hardness, and ductility vary with carbon content for steels having microstructures consisting of fine and coarse pearlite, and spheroidite. Also, explain why hardness and strength increase with increasing carbon content. 17. Explain briefly why fine pearlite is harder than coarse pearlite, which in turn is harder than spheroidite. 18. Qualitatively compare the mechanical characteristics of bainite and iron-carbon alloys that have other microstructures. 19. Cite two reasons why martensite is so hard and brittle. 20. Describe the microstructure of tempered martensite. 21. Describe the heat treatment that is necessary to produce tempered martensite. 22. Compare the properties of martensite and tempered martensite, and also explain the properties of tempered martensite in terms of its microstructure. 23. Schematically plot how hardness depends on tempering time at constant temperature, and briefly explain this behavior. 24. Schematically plot how yield strength, tensile strength, and ductility depend on tempering temperature (at constant tempering time), and then explain this behavior. 25. (a) Describe the phenomenon of temper embrittlement. (b) Note what procedures cause it to occur (b) List measures that may be taken to prevent it. 26. Describe briefly and qualitatively the procedure necessary to transform one steel microstructure into another (e.g., bainite to spheroidite). 20

22 CHAPTER 11 THERMAL PROCESSING OF METAL ALLOYS LEARNING OBJECTIVES 1. State the purposes of and describe the procedures for the following heat treatments: process annealing, stress relief annealing, normalizing, full annealing, and spheroidizing. 2. Define hardenability. 3. Describe the Jominy end-quench test. 4. Make a schematic sketch of a typical hardenability curve (label both vertical and horizontal axes), and then briefly explain the shape of the curve. 5. (a) On the same plot, schematically sketch hardenability curves for two different alloys-- one of which is more hardenable than the other. (b) Explain the difference in shape of these two curves. 6. For the quenching of a steel specimen, briefly explain why quenching medium type and degree of agitation influence the rate of specimen cooling. 7. Generate a hardness profile for a cylindrical steel specimen that has been austenitized and then quenched, given the hardenability curve for the specific alloy, as well as quenching rate-versus-bar diameter curves at several radial positions for the quenching medium used. 8. Using a phase diagram, describe the two heat treatments (solution and precipitation) that are involved in the precipitation hardening of a binary alloy. Explain why each heat treatment is carried out and describe changes in microstructure that occur during each heat treatment. 9. (a) Schematically plot how the room temperature yield and tensile strengths, and hardness depend on the logarithm of time for a precipitation heat treatment at constant temperature. (b) Explain the general shape of these curves in terms of the mechanism of precipitation hardening (i.e., dislocation-precipitate particle interactions). 10. Cite two necessary requirements for an alloy to be precipitation hardenable. 21

23 CHAPTER 12 METAL ALLOYS LEARNING OBJECTIVES 1. Cite three reasons why ferrous alloys are used extensively as engineering materials, and also three of their major limitations. 2. (a) Name and describe four forming operations that are used to shape metal alloys. (b) Cite the general mechanical characteristics of materials that are subjected to these forming operations. 3. (a) Name and describe four casting techniques. (b) Cite three circumstances for which casting is the preferred fabrication mode. 4. Describe the powder metallurgical forming process, and note two reasons why it is used. 5. (a) Briefly describe the process of welding, and note reasons why it is used. (b) Cite four potential problems that may be encountered with the formation of a heat affected zone in the vicinity of a weld junction. 6. Define what is meant by a plain carbon steel, and cite three typical applications. 7. Recognize the four digit AISI/SAE designation for both plain carbon and low alloy steels, and from such determine the carbon content. 8. Name three other types of steels and, for each, cite compositional differences, distinctive properties, and typical uses. 9. Specify the three classes of stainless steels. 10. Cite two differences between cast irons and steels. 11. (a) Name the four major cast iron types. (b) For each type draw and label a schematic diagram of the microstructure, and give a general description of its mechanical characteristics. 12. Cite the distinguishing features for both wrought and cast alloys. 13. Name seven different types of nonferrous alloys, and for each, cite its distinctive physical and mechanical characteristics, and, in addition, list at least three typical applications. 22

24 CHAPTER 13 STRUCTURES AND PROPERTIES OF CERAMICS LEARNING OBJECTIVES 1. Make a distinction between cations and anions. 2. Cite two features of the component ions that determine the crystal structure of a ceramic material. 3. Sketch (or describe) unit cells for sodium chloride, cesium chloride, zinc blende, fluorite, and perovskite crystal structures. 4. Given the chemical formula for a ceramic compound, the ionic radii of its component ions, and, using Table 13.4, determine the crystal structure. 5. For a ceramic material which crystal structure may be generated from the stacking of close-packed planes of anions, given which type of interstitial positions (tetrahedral or octahedral) are occupied with cations, do the following: (a) specify what fraction of these sites are filled, and (b) note the occupied interstitial positions between two close-packed planes drawn as stacked one upon the other. 6. For an ionic compound having one of the crystal structures discussed in this chapter, be able to compute its density given the atomic weights of the constituent elements, the unit cell edge length, and Avogadro's number. 7. Given the unit cell for some ceramic crystal structure, be able to sketch the ionic/atomic packing of a specified crystallographic plane. 8. Draw and describe the basic structural unit for the silicate ceramics. 9. Schematically diagram the atomic structure of a silica glass. 10. Sketch (or describe) the following: (a) a unit cell for the diamond cubic crystal structure, (b) the atomic structure of graphite, and (c) the structure of a C 60 fullerene molecule. 11. Name and describe eight different ionic point defects that are found in ceramic compounds (including Schottky and Frenkel defects). 12. Define the term electroneutrality, and note what part it plays in the formation of ionic point defects in ceramic materials. 13. Define stoichiometric, and cite one example of a nonstoichiometric material. 23

25 14. Note two ways in which an ionic compound can be made to be nonstoichiometric. 15. (a) Given a substitutional impurity ion, determine whether or not it will render an ionic compound nonstoichiometric. (b) If the host material does become nonstoichiometric, ascertain what kind(s) of defect(s) form, and how many form for every substitutional impurity ion. 16. Note three requirements that must be met in order for there to be significant solid solubility of one ionic compound in another. 17. Cite the differences in room temperature mechanical characteristics for metals and ceramics. 18. Briefly explain why there is normally significant scatter in the fracture strength for identical specimens of the same ceramic material. 19. Note the reason why ceramic materials are stronger in compression than in tension. 20. Give three reasons why the stress-strain characteristics of ceramic materials are determined using transverse bending tests rather than tensile tests. 21. Given the cross-sectional dimensions of a rectangular ceramic rod bent to fracture using a three-point loading technique, as well as the distance between support points, and the fracture load, compute the flexural strength. 22. Given the radius of a cylindrical ceramic rod that is bent to fracture using a three-point loading technique, as well as the distance between support points, and the fracture load, compute the flexural strength. 23. Briefly describe the mechanism by which plastic deformation occurs for each of crystalline and noncrystalline ceramic materials. 24. On the basis of slip considerations, briefly explain why crystalline ceramic materials are so brittle. 25. Briefly define viscosity and cite the units in which it is expressed. 26. For a porous ceramic, do the following: (a) Given the modulus of elasticity for the nonporous material, compute E for a specified volume fraction of porosity. (b) Given values of the experimental σ o and n constants, calculate the flexural strength at some given P. 24

26 CHAPTER 14 APPLICATIONS AND PROCESSING OF CERAMICS LEARNING OBJECTIVES 1. List the three primary ingredients of a soda-lime glass. 2. Cite the two prime assets of glass materials. 3. (a) Schematically plot specific volume versus temperature for both crystalline and noncrystalline ceramics. (b) On this graph indicate melting and glass-transition temperatures. 4. (a) Schematically sketch a plot of the temperature dependence of the viscosity of a glass. (b) Now note how the curve changes with increasing impurity additions. 5. Name and briefly describe four forming methods that are used to fabricate glass pieces. 6. Briefly explain why thermal stresses are established in glass pieces as they are cooled. 7. (a) Briefly describe the procedure that is used to thermally temper glass pieces. (b) Now explain the mechanism by which thermal tempering increases strength. 8. Define devitrification. 9. (a) Briefly describe the process by which glass-ceramics are produced. (b) Note two properties of these materials that make them superior to glass. 10. Name the two types of clay products, and then give two examples of each. 11. Cite the two roles that clay minerals play in the fabrication of ceramic bodies. 12. Name and briefly describe the two techniques that are used to fabricate clay products. 13. Briefly explain what processes occur during the drying and firing of clay-based ceramic ware. 14. (a) Define vitrification. (b) Note the role this process plays in the development of strength of a ceramic body. 15. For the refractory ceramics do the following: (a) Cite three important requirements that normally must be met by this group of materials. (b) For each of the four classifications discussed, cite the primary ingredients and typical applications. 16. For the abrasive ceramics do the following: 25

27 (a) Cite three important requirements that normally must be met by this group of materials. (b) Name four different ceramic materials that are commonly used as abrasives. (c) Cite the three different forms of abrasives. 17. Name and briefly describe the three ceramic powder pressing techniques that were discussed in this chapter. 18. Briefly describe and diagram the process of sintering as it occurs for powder particle aggregates. 19. Describe the tape casting process. 20. Briefly describe the process by which portland cement is produced. 21. Briefly explain the mechanism by which cement hardens when water is added. 22. Briefly explain the role of cement in a concrete mix. 23. List three advanced ceramic applications, and, for each, the required material characteristics. 26

28 CHAPTER 15 POLYMER STRUCTURES LEARNING OBJECTIVES 1. Define the term isomerism. 2. Describe a typical polymer molecule in terms of its chain structure, and, in addition, how the molecule may be generated by repeating mer units. 3. Draw mer structures for polyethylene, polyvinyl chloride, polytetrafluoroethylene, polypropylene, and polystyrene. 4. Distinguish between a homopolymer and a copolymer. 5. Distinguish between bifunctional and trifunctional mer units. 6. For some homopolymer, given its mer chemical formula, its several molecular weight ranges, and, for each range, the number and weight fractions, be able to compute: (a) the number-average and weight-average molecular weights, and (b) the number-average and weight-average degrees of polymerization. 7. For a copolymer, given its mer chemical formulas, the atomic weights of the constituent atoms, and the fraction of each mer type, be able to compute the average mer molecular weight. 8. Cite two features of polymer chains that restrict their ability to rotate and bend. 9. Name and briefly describe the four general types of molecular structures found in polymers. 10. Distinguish between head-to-tail and head-to-head configurations. 11. Name and briefly describe: (a) the three types of stereoisomers, (b) the two kinds of geometrical isomers, and (c) the four types of copolymers. 12. Draw the following chemical repeat units: acrylonitrile, butadiene, chloroprene, cisisoprene, isobutylene, and dimethylsiloxane. 13. (a) Briefly describe the crystalline state in polymeric materials. (b) Cite the main difference between the crystalline state in polymers and in metallic materials. 27

29 14. Given the density of a polymer specimen, as well as densities for totally crystalline and totally amorphous materials of the same polymer, be able to compute the percent crystallinity. 15. Cite how the degree of crystallinity in a polymer material is affected by polymer chemistry, by characteristics of the polymer structure, and for the various copolymers. 16. Briefly describe the structure of a chain-folded polymer crystallite. 17. Briefly describe and diagram the spherulitic structure for a semicrystalline polymer. 28

30 CHAPTER 16 CHARACTERISTICS, APPLICATIONS, AND PROCESSING OF POLYMERS LEARNING OBJECTIVES 1. (a) Schematically plot the three different characteristic types of stress-strain behavior for polymeric materials. (b) Now note which type(s) of polymer(s) display(s) each of these behaviors. 2. Make a comparison of the general mechanical properties of plastics and elastomeric materials with metals and ceramics. 3. Cite three effects on the mechanical characteristics of a polymer as its temperature is increased, or as the deformation strain rate is decreased. 4. Briefly describe the mechanism by which semicrystalline polymers elastically deform. 5. Describe/sketch various stages in the plastic deformation of a semicrystalline (spherulitic) polymer. 6. Briefly describe the effects of annealing on a semicrystalline polymer that has been permanently deformed. 7. (a) Describe the macroscopic tensile deformation (i.e., specimen profile) of a cylindrical dog-bone specimen of a typical ductile plastic to fracture. (b) Correlate this behavior with the stress-strain plot. 8. Discuss the influence of the following factors on polymer tensile modulus and/or strength: (a) molecular weight, (b) degree of crystallinity, (c) extent of crosslinking, (d) predeformation, and (e) the heat treating undeformed materials. 9. Briefly describe, from a molecular perspective, (a) crystallization, (b) melting, and (c) the glass transition for polymeric materials. 10. For polymer crystallization, given values of the constants k and n, compute the fraction crystallization after a specified time. 29

31 11. Schematically plot specific volume versus temperature for crystalline, semicrystalline, and amorphous polymers, noting glass-transition and melting temperatures. 12. (a) List four characteristics or structural components of a polymer that affect its melting temperature. (b) Note the manner in which each characteristic/component influences the magnitude of T m. 13. (a) List six characteristics or structural elements of a polymer that influence its glass transition temperature. (b) Now note how each of these characteristics/elements affects the magnitude of T g. 14. Name the two classifications of polymeric materials according to their mechanical characteristics at elevated temperatures. 15. Cite the differences in behavior for thermoplastic and thermosetting polymers, and also the differences in their molecular structures. 16. Define viscoelasticity. 17. (a) Describe the manner in which stress relaxation measurements are conducted. (b) Using the results of a stress relaxation test, briefly explain how the relaxation modulus is determined. 18. (a) On a graph of the logarithm of relaxation modulus versus temperature plot schematic curves for semicrystalline, amorphous, and crosslinked polymers. (b) On this plot note melting and glass transition temperatures. (c) In addition, indicate on this same plot glass, leathery, rubbery, and viscous flow regions. 19. (a) Briefly describe the molecular mechanism by which elastomeric polymers deform elastically. (b) Now cite the driving force for the recoil of an elastomeric material. 20. Note the four criteria that are necessary for a polymer to exhibit elastomeric behavior. 21. (a) Briefly describe the phenomenon of crazing. (b) Note which type of polymers craze. (c) Cite experimental/service conditions that produce crazing in polymeric materials. 22. Briefly describe the mechanisms by which chain reaction and step reaction polymerization processes occur. 23. Name the five types of polymer additives, and, for each, how it modifies the properties. 24. (a) Cite the seven different polymer application types. (b) Note the general characteristics of each of these types 30