An Introduction to the Properties of Engineering Materials

The engineering designer is always limited by the properties of available materials. Some properties are critically affected by variations in com­ position, in state or in testing conditions, while others are much less so. The engineer must know this if he is to make intelligent use of the data on properties of materials that he finds in handbooks and tables, and if he is to exploit successfully new materials as they become available. He can only be aware of these limitations if he understands how pro­ perties depend on structure at the atomic, molecular, microscopic and macroscopic levels. Inculcating this awareness is one of the chief aims of the book, which is based on a successful course designed to give university engineering students the necessary basic knowledge of these various levels. The material is equivalent to a course of about eighty to a hundred lectures. In the first part of the book the topics covered are mainly fundamental physics. The structure of the atom, considered in non-wave-mechanical terms, leads to the nature of interatomic forces and aggregations of atoms in the three forms-gases, liquids and solids. Sufficient crystallography is discussed to facilitate an understanding of the mechanical behaviour of the crystals. The band theory of solids is not included, but the basic concepts which form a preliminary to the theory-energy levels of electrons in an atom, Pauli's exclusion principle, and so on-are dealt with.

1 | Introduction.- 1.1 The fundamental nature of material properties.- 2 | Atomic Structure.- 2.1 Classification of the elements.- 2.2 Valency.- 2.3 Atomic number.- 2.4 The Bohr-Rutherford atom.- 2.5 The single-electron system.- 2.6 Wave-particle duality.- 2.7 Wave mechanics.- 2.8 Electron states in atoms.- 2.9 Many-electron atoms.- 2.10 Relationship of chemical behaviour to electron structure.- 2.11 X-ray spectra.- 2.12 The bonding between atoms.- 3 | Aggregations of Atoms—The Fluid States.- 3.1 Introduction.- Gases.- 3.2 The behaviour of a gas.- 3.3 Mole.- 3.4 The kinetic theory of gases.- 3.5 Calculation of the pressure of an ideal gas.- 3.6 Energy and velocity of molecules.- 3.7 Maxwellian distribution of velocities.- 3.8 Mean free path.- 3.9 Variation of ? and K with pressure.- 3.10 Deviations from the gas laws.- 3.11 Van der Waals’ equation.- 3.12 The properties of van der Waals’ equation.- 3.13 Comparison of van der Waals’ equation with experiment.- Liquids.- 3.14 The behaviour of liquids.- 3.15 Surface tension.- 3.16 Vapour pressure.- 3.17 Viscosity.- 3.18 Thermal conductivity.- 4 | Aggregations of Atoms—Solids.- 4.1 Introduction.- 4.2 The crystalline state.- 4.3 Space lattices.- 4.4 Crystal systems.- 4.5 Indices of planes.- 4.6 Indices of direction.- 4.7 The common crystal lattices.- 4.8 Face-centred cubic system.- 4.9 Body-centred cubic system.- 4.10 Close-packed hexagonal system.- 4.11 Stacking of close-packed layers.- 4.12 Types of crystal and relation to mechanical properties.- 4.13 Interatomic forces in solids.- 5 | Crystal Growth and Size.- 5.1 Micrographic examination.- 5.2 Formation of liquid drop from vapour.- 5.3 Crystal growth from molten metal.- 5.4 Crystal shapes.- 5.5 Crystal pattern in castings.- 5.6 Grain growth in strain-free solid metal.- 5.7 Grain growth in strained solid metal.- 5.8 Specification of grain size.- 5.9 Growth of single crystals.- 6 | Aggregations of Two Sorts of Atoms—Binary Alloys.- 6.1 Introduction.- 6.2 Mixtures of two liquids.- 6.3 Mixtures in the solid state.- 6.4 Solid solutions.- 6.5 Effect of atomic size.- 6.6 Factors controlling substitutional solid solubility.- 6.7 Intermediate compounds.- 6.8 Formulae of intermediate compounds.- 6.9 Phase.- 7 | Equilibrium Diagrams.- 7.1 Introduction.- 7.2 Equilibrium diagram for two liquids.- 7.3 Rules for interpreting binary equilibrium diagrams.- 7.4 Equilibrium diagram for the case of complete solid insolubility.- 7.5 Cooling curves.- 7.6 Equilibrium diagram for complete solid solubility.- 7.7 Equilibrium diagram for partial solid solubility.- 7.8 Intermediate compounds.- 7.9 Peritectic reaction.- 7.10 Comparison of eutectic and peritectic reactions.- 7.11 Changes occurring below the solidus.- 7.12 Allotropy.- 7.13 Eutectoid reaction.- 7.14 Peritectoid reaction.- 7.15 Ternary equilibrium diagrams.- 7.16 Ternary system with complete solid solubility.- 7.17 Ternary eutectic system.- 7.18 Rules for phase compositions and quantities in a ternary equilibrium diagram.- 8 | The Iron-carbon System.- 8.1 Allotropic forms of pure iron.- 8.2 Solubility of carbon in iron.- 8.3 Cementite and ledeburite.- 8.4 Modifications of allotropic change temperatures.- 8.5 Eutectoid and peritectic decomposition of austenite.- 8.6 Nomenclature of iron-carbon alloys.- 8.7 Microstructures of steels.- 8.8 Phase-transformation diagrams.- 8.9 Nomenclature of change points.- 8.10 Determination of change points.- 8.11 Cast irons.- 9 | Thermal Energy.- 9.1 Kinetic energy of a gas molecule.- 9.2 Specific heat of a gas.- 9.3 Specific heat of a solid.- 9.4 Experimental results for simple substances.- 9.5 Thermal expansion.- 9.6 Stable and metastable states.- 9.7 A simple example of a metastable state.- 9.8 Activation energy.- 9.9 Maxwell-Boltzmann law.- 9.10 Arrhenius’ rate law.- 9.11 Diffusion.- 9.12 Chemical reactions.- 9.13 Thermionic emission.- 10 | The Deformation of Metal Single Crystals.- 10.1 Introduction.- 10.2 Geometry of deformation by slip.- 10.3 Deformation by twinning.- 10.4 Resolved shear stress.- 10.5 Load-extension curves.- 10.6 Relationship of elongation to strain.- 10.7 Shear hardening curves.- 10.8 The nature of slip.- 10.9 Theoretical shear strength.- 10.10 The geometry of dislocations.- 10.11 Strain field around a screw dislocation.- 10.12 Strain field around an edge dislocation.- 10.13 Force on a dislocation line.- 10.14 Forces between dislocations.- 10.15 Tension of a dislocation line.- 10.16 The origin of dislocations.- 11 | The Strengthening of Metals.- 11.1 Introduction.- 11.2 Dislocations and obstacles.- 11.3 Polycrystalline materials.- 11.4 Solid solution alloying.- 11.5 Two phases in equilibrium.- 11.6 Dispersion hardening.- 11.7 Work hardening.- 11.8 Quench hardening.- 11.9 Precipitation hardening.- 11.10 Dispersed oxide hardening.- 12 | Mechanical Testing of Polycrystalline Materials.- 12.1 Introduction.- 12.2 Tensile testing machines.- 12.3 Tensile specimens.- 12.4 Behaviour of materials in tension.- 12.5 Load-extension curve for a ductile material.- 12.6 Yield-point phenomena.- 12.7 The influence of test-piece dimensions.- 12.8 True stress.- 12.9 Logarithmic strain.- 12.10 Ideal plastic material.- 12.11 Other related tests.- 12.12 Compression tests.- 12.13 Hardness tests.- 12.14 Brinell hardness.- 12.15 Diamond pyramid hardness.- 12.16 Rockwell hardness.- 12.17 Relationship of HV to yield stress.- 12.18 Relationship between tensile strength and HV.- 13 | Plastic Flow and Fracture.- 13.1 Introduction.- 13.2 Plastic flow under multi-axial stresses.- 13.3 Ductile fracture.- 13.4 Actual failures of engineering components.- 13.5 Theoretical cohesive strength of a solid.- 13.6 Actual cohesive strength.- 13.7 Griffith equation.- 13.8 Toughness.- 13.9 The influence of the notch.- 13.10 Notch impact tests.- 13.11 Factors of Izod and Charpy tests.- 13.12 Uses of notch tests.- 13.13 Notch brittleness of mild steel.- 13.14 Transition temperatures.- 13.15 Tests on large plates.- 13.16 Casualties due to brittle fracture.- 13.17 The effect of metallurgical factors.- 13.18 Fracture mechanics.- 13.19 Stress intensity factor.- 13.20 Modified Griffith equation.- 13.21 Plane stress and plane strain conditions.- 13.22 Failure modes.- 13.23 Geometrical effects.- 13.24 Determination of KIc.- 13.25 Relationship of design to fracture.- 14 | Fatigue.- 14.1 Failure due to fatigue.- 14.2 Characteristic of fatigue failures.- 14.3 Detection of fatigue cracks.- 14.4 Mechanism of fatigue failure.- 14.5 Fatigue crack growth.- 14.6 Fatigue testing.- 14.7 Fatigue testing machines.- 14.8 Results of fatigue tests.- 14.9 Effect of mean stress.- 14.10 Variation of fatigue limit.- 14.11 Cumulative damage effects.- 14.12 Crack growth rates.- 14.13 Effect of notches.- 14.14 Relation of design to fatigue.- 14.15 Corrosion fatigue.- 15 | Creep.- 15.1 Creep phenomena.- 15.2 Creep testing machines.- 15.3 Characteristics of creep curves.- 15.4 Presentation of creep results.- 15.5 Creep and design.- 15.6 Mechanisms of creep.- 15.7 Deformation mechanism maps.- 15.8 Creep fracture mechanisms.- 15.9 Fracture mechanism maps.- 15.10 Development of creep-resisting alloys.- 15.11 Creep-fatigue interaction.- 16 | Heat Treatment of Steel.- 16.1 Introduction.- 16.2 Transformations on heating.- 16.3 Transformations on cooling.- 16.4 Quenching temperature and rate.- 16.5 Isothermal transformation diagrams.- 16.6 Isothermal transformation diagrams for hypoeutectoid and hypereutectoid steels.- 16.7 Separation of pearlite and bainite knees.- 16.8 Continuous cooling transformation.- 16.9 Retained austenite.- 16.10 Grain size of steel and its effects.- 16.11 Determination of austenite grain size.- 16.12 Tempering.- 16.13 Mechanical property changes with tempering.- 16.14 Special heat treatments.- 16.15 Hardenability.- 16.16 Measurement of hardenability.- 16.17 Cylinder series test.- 16.18 Jominy end-quench test.- 16.19 Relation of ideal critical diameter to end-quenchcurve.- 16.20 Ruling section.- 17 | Alloy Steels.- 17.1 Purposes of alloying.- 17.2 Effect of alloying elements on iron-carbon equilibrium diagram.- 17.3 Effect of alloying elements on isothermal transformation diagram.- 17.4 Effect of alloying elements on tempering.- 17.5 Effect of alloying elements on mechanical properties.- 17.6 Classification of alloy steels.- 17.7 High-tensile structural steels.- 17.8 Alloy steels used in a fully heat-treated condition.- 17.9 Boron steels.- 17.10 Ausformed steels.- 17.11 Maraging steels.- 17.12 Corrosion and heat-resistant steels.- 17.13 Case hardening steels.- 17.14 Tool steels.- 17.15 Steels for cryogenic applications.- 17.16 Special-purpose steels.- 18 | Corrosion.- 18.1 Introduction.- 18.2 Oxidation and reduction.- 18.3 Direct chemical corrosion by dry gases.- 18.4 Growth of oxide layer.- 18.5 The ionization of water.- 18.6 Electrochemical corrosion.- 18.7 Anodic and cathodic reactions.- 18.8 Pourbaix diagrams.- 18.9 Forms of metallic corrosion.- 18.10 Stress corrosion cracking and fracture mechanics.- 18.11 Prevention of corrosion.- 19 | Welding.- 19.1 Nomenclature.- 19.2 Heat distribution in the vicinity of the weld.- 19.3 Metallurgy of weld metal and heat-affected zone.- 19.4 Welds in steel.- 19.5 Welds in non-allotropic materials.- 20 | Inorganic Non-metallic Materials.- 20.1 Introduction.- 20.2 Deformation of crystalline ceramics.- 20.3 Properties and uses of some engineering ceramics.- 20.4 Silicate structures.- 20.5 Vitreous structures.- 20.6 Mechanical behaviour of glasses.- 20.7 Glass-ceramics.- 20.8 Cermets.- 20.9 Fabrication of ceramic articles.- 20.10 Asbestos.- 20.11 Cement and concrete.- 21 | Organic Materials.- 21.1 The nature of organic compounds.- 21.2 Saturated hydrocarbons.- 21.3 Unsaturated hydrocarbons.- 21.4 Aromatic hydrocarbons.- 21.5 Addition polymerization.- 21.6 Condensation polymerization.- 21.7 Relation of mechanical properties to polymer shape.- 21.8 Elastomers.- 21.9 Crystallinity in polymers.- 21.10 Wood.- 21.11 Epoxy resins.- 21.12 Fillers.- 21.13 Plasticizers.- 21.14 Silicones.- 22 | Composites.- 22.1 Introduction.- 22.2 Reinforcing materials for fibrous composites.- 22.3 Manufacture of fibre composites.- 22.4 Elastic properties of a composite.- 22.5 Strength of a fibre composite.- 22.6 Specific stiffness and specific strength.- 22.7 Toughness of fibre composites.- 22.8 Fracture toughness of polyblends.- 23 | The Nucleus.- 23.1 The structure of the nucleus.- 23.2 Isotopes.- 23.3 Mass defect.- 23.4 Nuclear reactions.- 23.5 Rate of radioactive decay.- 23.6 Interaction of radiation with matter.- 23.7 Reaction cross-sections.- 23.8 Radiation damage due to scattering.- 23.9 Radiation damage due to absorption.- 23.10 Conclusion.- Appendix I—Some equilibrium diagrams of interest and importance.- Appendix II—Equilibrium and free energy.- Appendix III—SI units.- Answers to Numerical Questions.