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Inroduction to Engineering materials

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Inroduction to Engineering materials

  1. 1. ENGINEERING MATERIALS AND METALLURGY AUTONOMOUSFor fourth SEMESTER(II YEAR) PREPARED BY S.ARAVINDHA BALAJI ASSISTANT PROFESSOR DEPARTMENT OF MECHANICAL ENGINEERING SONA COLLEGE OF TECHNOLOGY SALEM:636005
  2. 2. ENGINEERING MATERIALS AND METALLURGY 1/5/2013Application of EMAM(In Industry): Steel industry( e.g. steel plants, (SAIL) Essar SAB-AP/MECH SONACT steels, jindal steel ltd.(JSW)) Pipe maufacturing industry, Plastic industry. Some jewelry industry(Grades of the gold) Manufacturing industry. 2
  3. 3. ENGINEERING MATERIALS AND METALLURGY 1/5/2013OBJECTIVE SAB-AP/MECH SONACT Knowledge on the structure Properties of the materials Treatment Testing and applications of metals and non-metallic materials Suitable materials for various engineering application 3
  4. 4. ENGINEERING MATERIALS AND METALLURGYReview (Not for Exam) Crystal structure BCC, (Body cubic centre) structure FCC, (Face cubic centre) structure and HCP, (Hexagonal close packing)structure Unit cell Crystallographic planes and directions Miller indices Crystal imperfections for point, line, planar and volume defects.
  5. 5. ENGINEERING MATERIALS AND METALLURGY 1/5/2013Review (Not for Exam) Grain size SAB-AP/MECH SONACT ASTM grain size number 5
  6. 6. ENGINEERING MATERIALS AND METALLURGY 1/5/2013 UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS Constitution of alloys-Solid solution, SAB-AP/MECH SONACT substitutional and interstitial-Phase diagrams, Isomorphous, eutectic, peritectic, and peritectroid reactions, Iron-Iron carbon equilibrium diagram. Classification of steel and cast Iron, Microstructure, Properties and applications. 6
  7. 7. ENGINEERING MATERIALS AND METALLURGY 1/5/2013UNIT:II HEAT TREATMENTDefinition-Full annealing, stress relief, recrystallisation and spheroidizing- SAB-AP/MECH SONACT normalising, hardening and tempering of steel. Isothermal transformation diagrams-cooling curves superimposed on I.T.diagram, CCR-Hardenability, Jominy and quench test- Austempering, Martempering-case hardening- carburising, nitriding, cyaniding, carbonitriding, flame and induction hardening . 7
  8. 8. ENGINEERING MATERIALS AND METALLURGY 1/5/2013UNIT:III MECHANICAL PROPERTIES AND TESTING SAB-AP/MECH SONACTMechanism of plastic deformation, slip and twinning-types of fracture-testing of materials under tension, compression and shear loads- Hardness tests (Brinell, Vickers and Rockwell), Impact test-Izod and charpy, Fatigue and creep tests, fracture toughness tests. 8
  9. 9. ENGINEERING MATERIALS AND METALLURGY 1/5/2013 UNIT:IVFERROUS AND NON FERROUS METALS SAB-AP/MECH SONACTEffect of alloying elements on steel(Mn, Si, Cr, Mo, V, Ti & W) –Stainless and tool steels –HSLA-maraging steels-Cast irons-Grey, White malleable, spheroidal-Graphite, Alloy cast irons, Copper and copper alloys-Brass, Bronze and Cupronickel-Aluminum and Al-Cu alloy- Precipitation hardening-Bearing alloys. 9
  10. 10. ENGINEERING MATERIALS AND METALLURGY 1/5/2013 UNIT V NON-METALLIC MATERIALS SAB-AP/MECH SONACTPolymers-Types of polymer, commodity andEngineering polymers-properties and applications of PE, PP, PS, PVC, PMMA, PET, PC, PA, ABS, PI, PAI, PPO, PPS, PEEK, PTFE Polymer-Urea and Phenol formaldehydes- Engineering ceramics-Introduction to fiber reinforced plastics. 10
  11. 11. ENGINEERING MATERIALS AND METALLURGYEach category of engineering application requires material from any or all of 1/5/2013 these three group of materials Ceramics and PolymersMetals and alloys SAB-AP/MECH SONACT glasses Engineering Materials Application Structures Machines Devices 11
  12. 12. ENGINEERING MATERIALS AND METALLURGY Metals and alloys Steels, aluminum, copper, silverreinforced steel SAB-AP/MECH SONACT d plastics reinforce Metal- ,gold, Brasses,,Si, Ge, GaAs, bronze s, maganin invar, super alloysBoride- boron rare earth magnetic alloys Ceramic and Organic polymers Plastics, glasses Pvc,PTFE, Mgo, cds, polyethylene Fibers:Terylene,nylo Al2O3, n,cotton, S iC, BaTio3,Silica, natural, and soda-time-glass, synthetic rubbers , Concrete, cement leathers ferrites and garnets ceramic superconductors Glass fiber- reinforced 12 plastics 1/5/2013
  13. 13. ENGINEERING MATERIALS AND METALLURGY 1/5/2013Structure: The internal structure of a material, SAB-AP/MECH SONACT simply called the structure. 13
  14. 14. NON-METALLIC MATERIALS: 1/5/2013 PE (polyethylene) PP (Polypropylene) SAB-AP/MECH SONACT PS(Polystyrene) PMMA(Polymethyl methacrylate) PET(Polyethylene teraphthalate) PC(Polycarbonates) PA(Polyamides) ABS(Acryknitrile-Butadiene-styrene) PI(Polyimide) 14
  15. 15. NON-METALLIC MATERIALS: 1/5/2013 PAI( Polyamideimide) PPO(Polyphenylene oxide) SAB-AP/MECH SONACT PPS(Polyphenylene sulphide) PEEK(Polyether ether ketone) PTFE(Polytetra fluoro ethylene) 15
  16. 16. ENGINEERING MATERIALS AND METALLURGY 1/5/2013 UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS SAB-AP/MECH SONACTConstitution of alloys-Solid solution, substitutional and interstitial-Phase diagrams Isomorphous, eutectic, peritectic, and peritectroid reactions, Iron-Iron carbon equilibrium diagram. Classification of steel and cast Iron, Microstructure, Properties and applications. 16
  17. 17. UNIT:ICONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/2013 CONSTITUTION- establishment, foundation, SAB-AP/MECH SONACT creation, formation, structure, organization, charter, bill. 17
  18. 18. UNIT:ICONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/2013SOME TECHNICAL TERMS AND SAB-AP/MECH SONACT DEFINITIONS:1.SYSTEM: It is a combination of phases of one or more components.2.PHASE: It is a Physically and chemically homogenous part of a system under study, one phase is different from the other in structure or composition 18
  19. 19. UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/20133.COMPONENTS: SAB-AP/MECH SONACT The elements present in the system are called component. A system may consist of two or more components. 19
  20. 20. CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/2013CONSTITUTION OF ALLOYS:4.ALLOY: SAB-AP/MECH SONACT An alloy is defined as a combination of two or more elements, of which one of the element should be a metal in major proportion. The others could be metals or non-metals, for eg: Brass (CU-Zn), Steel (Fe-C) 20
  21. 21. UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/2013 Alloy find very wide application in the industry than pure metals. SAB-AP/MECH SONACT Uses of pure metals 1. High electrical conductivity 2. High ductility 3. Corrosion resistance are required.These properties are generally at a maximum value in pure metals. 21
  22. 22. UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/2013 Mechanical properties SAB-AP/MECH SONACT 1. Tensile strength 2. Yield point 3. Hardness areimproved by alloying. 22
  23. 23. UNIT:ICONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/2013 CLASSIFICATION OF ALLOYS CLASSIFICATION OF SAB-AP/MECH SONACT ALLOYS Solid Intermedia Pure metals Solution te phase 23
  24. 24. UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/2013 Alloy can be either a single phase or a mixture SAB-AP/MECH SONACT of phases. A phases is anything which is homogeneous and physically distinct. In solid state alloys of three are three possible phase. 24
  25. 25. UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/2013 If an alloy has a single phase, it could be either a solid solution or an intermediate phase. SAB-AP/MECH SONACT If the alloy is a mixture it could be composed of any combination of the above three phases. 25
  26. 26. UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/2013 Themajor element which is large in amount is called base metal or parent SAB-AP/MECH SONACT metal or solvent. The other element that is lesser in amount is called the alloying element or solute, it is the minor part (such as salt or sugar which is less in amount, being mixed in water- solvent). 26
  27. 27. UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/20135. MIXTURE: It is a material more than one phase. SAB-AP/MECH SONACT 27
  28. 28. UNIT:ICONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/2013 SOLID SOLUTION SAB-AP/MECH SONACT Substitutinal Interstitial Solid solution solid solution Disordered Ordered(or) Random (or) regular 28
  29. 29. UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/2013 Solid solutions: SAB-AP/MECH SONACT A solid solution is the simplest type of alloys. A Solution can be defined as a homogeneous mixture in which the atoms or molecules of one substance are dispersed at random into another substance. 29
  30. 30. UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/2013 A solid solution may be defined as a solid that consist of two or more elements SAB-AP/MECH SONACT atomically dispersed in a single-phase structure. A solid solution is composed of two parts. 1 . Solute: A solute is the minor part of the solution or the material which is dissolved. 30
  31. 31. UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/20132. Solvent: Solvent constitutes the major portion of SAB-AP/MECH SONACT the solution. Both the solute and the solvent can be solid, liquid or gas. 31
  32. 32. UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/2013 Solid solution: Simply a solution in the solid state. SAB-AP/MECH SONACT Solid solution may be defined as a solution In the solid state which consists of two kinds of atoms combined in one type of space lattice. 32
  33. 33. UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/2013 space lattice: Space lattice is defined as an array of SAB-AP/MECH SONACT points in three dimensions in which every point has surroundings identical to that every other point in the array. 33
  34. 34. SOLID SOLUTION 1/5/2013 Case: In certain cases, the solidification of an SAB-AP/MECH SONACT alloy results in the formation of one kind of crystal. In which both metals are present, but they cannot be detected by the microscope Although properties of the crystals are profoundly( deeply,strongly) changed. 34
  35. 35. SOLID SOLUTION 1/5/2013 In such a case we have a solid metal in which the SAB-AP/MECH SONACT interatomic state which existed in the liquid solution has been persevered after solidification, and it is known as a solid solution. In a solid solution the atom occur in a definite geometrical pattern, which is usually a slightly 35 distorted form of one of the constituent metals.
  36. 36. SOLID SOLUTION 1/5/2013 Soildsolution are conductors, but not so good as the pure metals on which they are based. SAB-AP/MECH SONACTSome examples of solid solutions are: Cu-Zn alloys (Brasses) Ni-Cu alloys (Monel metal) Au-Ag alloys(Sterling silver) Fe-Cr-Ni alloys (Certain stainless steels) Fe-C alloys (Steels) 36
  37. 37. SUBSTITUTIONAL SOLID SOLUTION Solute Atoms 1/5/2013 SOLVENT OR SAB-AP/MECH SONACT MATRIX ATOMS solute-Atom of Metal-B Solvent-Atoms of zinc Metal-A 37 zinc(Solute) Copper(Solvent) Disordered substitutinal solid solution(random,)
  38. 38. SUBSTITUTIONAL SOLID SOLUTION Ordered subsitutional solid solution 1/5/2013  SOLVENT OR MATRIX ATOMS SAB-AP/MECH SONACT Solute Atoms 38
  39. 39. SUBSTITUTIONAL SOLID SOLUTION 1/5/2013 In substitutional solid solution, there is a direct SAB-AP/MECH SONACT substitution of one type of atom for another. so that solute atoms(cu) enter the crystal to take positions normally occupied by solvent atoms (e.g., Nickel atoms); 39
  40. 40. SUBSTITUTIONAL SOLID SOLUTION 1/5/2013 The alloy is said to be in a disordered condition if SAB-AP/MECH SONACT in the formation of a substitutional solid solution, the solute atoms do not occupy any specific position but are distributed at random in the lattice structure of the solvent. 40
  41. 41. SUBSTITUTIONAL SOLID SOLUTION 1/5/2013 An ordered subsititutional solid solution is shown SAB-AP/MECH SONACT fig Cu-Zn, Al-Cu, α-Brass are some examples of ordered structures. 41
  42. 42. INTERSTITIAL SOLID SOLUTION 1/5/2013  The four elements hydrogen, carbon, nitrogen, SAB-AP/MECH SONACT and boron have such small diameters that they can occupy the empty spaces (Interstices) in the crystal lattices of many metals. 42
  43. 43. INTERSTITIAL SOLID SOLUTION Solvent or 1/5/2013 matrix atoms Solute atoms SAB-AP/MECH SONACT CARBON (solute) IRON ( SOLVENT) INTERSTITIAL SOLID SOLUTION 43
  44. 44. INTERSTITIAL SOLID SOLUTION 1/5/2013 Interstitial solid solution usually have a limited SAB-AP/MECH SONACT composition range and are generally considered of secondary importance, but there are a few instances worthy of special attention. 44
  45. 45. INTERSTITIAL SOLID SOLUTION 1/5/2013 The interstitial solution of carbon in iron SAB-AP/MECH SONACT constitutes the basis of steel hardening. Very small amount of hydrogen introduced into steels during acid pickling(cleaning), plating, or welding operations causes a Sharpe decrease in ductility, known as hydrogen embrittlement. 45
  46. 46. INTERSTITIAL SOLID SOLUTION 1/5/2013 Interstitial nitrogen is useful not only in SAB-AP/MECH SONACT nirtriding process but also as an important factor in maintaining 18Cr-8NiStainless steel in the austenitic condition. 46
  47. 47. HUME - ROTHERY’S RULES OF SOLID SOLUBILITY 1/5/2013 SAB-AP/MECH SONACTHume - Rothery’s Rules of solid solubility 47
  48. 48. HUME - ROTHERY’S RULES OF SOLID SOLUBILITY 1/5/2013 SAB-AP/MECH SONACTHume - Rothery’s Rules of solid solubility 48
  49. 49. INTERSTITIAL SOLID SOLUTION 1/5/2013HUME –ROTHERY’S RULES OF SOLID SOLUBILITY SAB-AP/MECH SONACT The solubility limit of solute in solvents depends on various factors. These were stated by Hume-rothery and are as follows:1. Critical structure factor (or) Crystal structure: Metals that have the same crystal stucture (Lattice structure) have a greater solubility. 49
  50. 50. INTERSTITIAL SOLID SOLUTION2. Relative atomic size factor(or) size factor: 1/5/2013 The solid solution will tend to form if the SAB-AP/MECH SONACT difference in size of solute and solvent is less than 15%. If the difference is greater than 15% formation of solid solution will be limited. For good solid solubility the difference should be less 50 than 8%
  51. 51. INTERSTITIAL SOLID SOLUTION3. Chemical affinity factor (or) Electronegativity: 1/5/2013 Formulation of solid solution is SAB-AP/MECH SONACT favoured for metals that have less chemical affinity is more, then a compound is formed instead of a solid solution. The metal which are separated in widely in the periodic table are not suitable for making alloys because of their high affinity. 51
  52. 52. INTERSTITIAL SOLID SOLUTION 1/5/20134. Relative valency factor(or)valence: A metal that has a higher valency will SAB-AP/MECH SONACT disslove only a small amount of a lower valency metal, where as the metal with low valency will have good solubility for the higher valency metal. 52
  53. 53. INTERSTITIAL SOLID SOLUTION 1/5/2013 In some alloys both interstitial and SAB-AP/MECH SONACT substitutional solid solution are formed to an appreciable extent. For Eg: A Cr-Ni steel contains interstitially dissolved carbon and substitution ally dissolved chromium, nickel, and minor elements. 53
  54. 54. POSSIBILITIES OF SOLID SOLUTIONS 1/5/2013• There are three possible solid solutions based on SAB-AP/MECH SONACT the amount of their elements. They are:1.Unsaturated solid solution: In the solvent is dissolving small amount of solute as well as at a given temperature and pressure, it is called unsaturated solid solution. 54
  55. 55. POSSIBILITIES OF SOLID SOLUTIONS 1/5/20132. Saturated solid solution: If the solvent is dissolving SAB-AP/MECH SONACT limiting amount of solute, it is called saturated solid solution. 55
  56. 56. POSSIBILITIES OF SOLID SOLUTIONS 1/5/20133. Supersaturated solid solution: If the solvent is dissolving more of solute that it SAB-AP/MECH SONACT should, under equilibrium, it is called supersaturated solid solution. 56
  57. 57. PHASE DIAGRAM 1/5/2013Types of phase diagram SAB-AP/MECH SONACT1. Isomorphous2. Eutectoid system3. Eutectic system4.Peritectic system 575. Peritectroid reactions
  58. 58. PHASE DIAGRAM 1/5/2013 Phase Diagrams SAB-AP/MECH SONACT Phase diagrams are graphical representation of what phases are present in an alloy system at various Temperatures, pressures, and compositions. 58
  59. 59. PHASE DIAGRAM 1/5/2013 (or) A phase diagram is a map showing the SAB-AP/MECH SONACT structure or phase present as the temperature and overall composition of the material are varied. Phase diagrams are also known as equilibrium diagrams or constitutional diagrams. 59
  60. 60. WHY SHOULD PHASE DIAGRAMS BESTUDIED? 1/5/2013 The phase diagrams can answer the following SAB-AP/MECH SONACT important questions: What condition is the material in? Is the composition uniform throughout? If not, how much of each component is present? 60
  61. 61. WHY SHOULD PHASE DIAGRAMS BESTUDIED? 1/5/2013 Is something present that may give undesired SAB-AP/MECH SONACT properties? What will happen if temperature is increased or decreased; pressure is changed or composition is varied? 61
  62. 62. WHY SHOULD PHASE DIAGRAMS BESTUDIED? 1/5/2013 Phase diagrams are used by engineers and SAB-AP/MECH SONACT scientists to understand and to predict many aspects of the behavior of materials. 62
  63. 63. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/20131. Components SAB-AP/MECH SONACT2. System3. Alloy4. Solid solution5. Solute Solution 63
  64. 64. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/20136. Solvent SAB-AP/MECH SONACT7. Phase8. Equilibrium9. Solubility limit10.Degrees of freedom 64
  65. 65. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/2013 The various terms used in the study of phase SAB-AP/MECH SONACT diagrams have been explained below:1. COMPONENT: Component are pure metals and or compounds of which an alloy is composed. Eg: In a copper-zinc brass, the components are CU and Zn. 65
  66. 66. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/20132. SYSTEM: The system has two meanings in this context SAB-AP/MECH SONACTi. System: May refer to a specific body of material under consideration. For Eg: A ladle of molten steel is referred as a system. 66
  67. 67. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/2013 (ii)system: May also refer to the series of possible SAB-AP/MECH SONACT alloys consisting of the same components. For example, the Iron-Carbon system. 67
  68. 68. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/2013 A system having one components is called a SAB-AP/MECH SONACT Unary system, and the system having two, three and four components are known as Binary, ternary and quaternary systems, respectively. 68
  69. 69. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/20133. ALLOY: SAB-AP/MECH SONACT An alloy is a mixture of two or more metals or a metal (metals) and a non-metal (non-metals). 69
  70. 70. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/20134.SOLID SOLUTION: It is a solid that consist of two or SAB-AP/MECH SONACT more elements atomically dispersed in a single- phase structure. 70
  71. 71. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/20135. SOLUTE SOLUTION: It is the minor part of the SAB-AP/MECH SONACT solution or the material which is dissolved. 71
  72. 72. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/20136. SOLVENT: SAB-AP/MECH SONACT The material which contributes the major portion of the solution. 72
  73. 73. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/20137. PHASE: SAB-AP/MECH SONACT A phase may be defined as a homogenous portion of a system that has uniform physical and chemical characteristics. 73
  74. 74. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/20138. EQUILIBRIUM: SAB-AP/MECH SONACT Equilibrium is said to exit when enough time is allowed for all possible reactions to be completed. 74
  75. 75. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/2013 The equilibrium state refers to the SAB-AP/MECH SONACT characteristics of the system that remain constant indefinitely. Equilibrium occurs when the free energy of the system is at its minimum value. 75
  76. 76. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/2013 The term phase equilibrium refers to SAB-AP/MECH SONACT equilibrium as it applies to systems in which more than one phase may exist. 76
  77. 77. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/20139. SOLUBILITY LIMIT: It is the maximum concentration of SAB-AP/MECH SONACT solute that may be added without forming a new phase. 77
  78. 78. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/2013 NOTE: The addition of solution in excess SAB-AP/MECH SONACT of the solubility limit results in the formation of another solid solution or compound. 78
  79. 79. TERMINOLOGY USED IN PHASE DIAGRAMS 1/5/201310. DEGREES OF FREEDOM: SAB-AP/MECH SONACT It is the number of independent variables ( such as temperature, pressure, and composition). That can be changed independently without changing the phase or phases of the system. 79
  80. 80. WHAT IS MEANT BY THE TERM PHASE? 1/5/2013 A phase may be a portion of matter which is SAB-AP/MECH SONACT homogenous A phase may be defined as any physical distinct homogenous and mechanically separable portion of a substance. 80
  81. 81. WHAT IS MEANT BY THE TERM PHASE? 1/5/2013 In Layman’s term, a phase requires a unique SAB-AP/MECH SONACT structure, uniform composition, and well-defined boundaries or interfacesExamples: A pure substance such as water is a single phase. 81
  82. 82. WHAT IS MEANT BY THE TERM PHASE? 1/5/2013 The pure substance water can exist in solid, SAB-AP/MECH SONACT liquid and vapour, each of these states being a single phase, as shown in fig (a) Now consider the effect of adding salt(Nacl) to water. Salt will dissolve in water to give a homogeneous solution. 82
  83. 83. WHAT IS MEANT BY THE TERM PHASE? 1/5/2013 Thus the salt- water solution forms a single SAB-AP/MECH SONACT phase as shown if fig(b) If more salt is added into water, then we have two different phases as shown if fig(c) 83
  84. 84. WHAT IS MEANT BY THE TERM PHASE? 1/5/2013 A Single phase system is also termed as SAB-AP/MECH SONACT “homogeneous system” 84
  85. 85. WHAT IS MEANT BY THE TERM PHASE? 1/5/2013 System composed of two or more phases are SAB-AP/MECH SONACT termed as mixtures or heterogeneous systems’. Fig (d) Most metallic alloys, ceramic, polymers, and composite are heterogenous. 85
  86. 86. ILLUSTRATION OF PHASES WATER VAPOUR(3) 1/5/2013 SAB-AP/MECH SONACT ICE (1) WATER(2) WATER ILLUSTRATION OF PHASES: (A) Three forms of water: 1) Ice 2)water 3) water vapour are each a phase. 86
  87. 87. ILLUSTRATION OF PHASES 1/5/2013 salt SAB-AP/MECH SONACT •(b) Salt and water have unlimited solubility (Homogeneous solution)- from a single phase 87
  88. 88. ILLUSTRATION OF PHASES 1/5/2013 Saturated brine SAB-AP/MECH SONACT Excess salt (C) Salt and water have limited solubility (Heterogenous solution)-from two distinct phases 88
  89. 89. ILLUSTRATION OF PHASES 1/5/2013 SAB-AP/MECH SONACT OIL WATEROIL AND WATER HAVE VIRTUALLY NO SOLUBILITY FROM TWO 89 DISTINCT PHASES
  90. 90. PHASE DIAGRAM OF PURE SUBSTANCE 1/5/2013 One- Component Phase diagram SAB-AP/MECH SONACT 90
  91. 91. PHASE DIAGRAM OF PURE SUBSTANCE 1/5/2013 SAB-AP/MECH SONACT 91
  92. 92. PHASE DIAGRAM OF PURE SUBSTANCE 1/5/2013 A pure substance such as water can exist in SAB-AP/MECH SONACT solid, liquid, or vapour phases, depending on the condition of temperature and pressure 92
  93. 93. PHASE DIAGRAM OF PURE SUBSTANCE 1/5/2013 The phase relationships may be represented on SAB-AP/MECH SONACT a pressure- temperature (PT) diagram, known as a one-component (or unary) phase diagram, for the H2O System. 93
  94. 94. PHASE DIAGRAM OF PURE SUBSTANCE 1/5/2013 The phase diagram is composed of regions of SAB-AP/MECH SONACT pressure and temperature where only a single phase is stable. The line OA indicates the vapourisation line and the line OB indicates the freezing line. 94
  95. 95. PHASE DIAGRAM OF PURE SUBSTANCE 1/5/2013 Liquid and vapour phase exist along the SAB-AP/MECH SONACT vapourisation line and liquid and solid phases along the freezing line, shows in figure. These lines are also known as Two phase equilibrium lines. 95
  96. 96. PHASE DIAGRAM OF PURE SUBSTANCE 1/5/2013 The point “O” is know as Triple point. SAB-AP/MECH SONACT Triple point is the point at which three phases (Solid, liquid, and vapour phases(gas)). of a single material coexit. This triple point of water exists at temperature 0.00980C and at pressure 4.58 mm of Hg. 96
  97. 97. PHASE DIAGRAMS 1/5/2013 The properties of an alloy depend on nature, SAB-AP/MECH SONACT amount, size, distribution and orientation of the phases. A phase is the chemically and structurally homogeneous portion of the microstructure. 97
  98. 98. PHASE DIAGRAMS 1/5/2013 It has the following characteristics 1. Same structure throughout. SAB-AP/MECH SONACT 2. Roughly the same composition and properties throughout. 3. Definite interface between the phase and surrounding. 98
  99. 99. J.W. GIBBS( JOSIAH WILLARD GIBBS) 1/5/2013 SAB-AP/MECH SONACT 99
  100. 100. J.W. GIBBS( JOSIAH WILLARD GIBBS)JOSIAH WILLARD GIBBS PROPOSAL 1/5/2013 (OR) SAB-AP/MECH SONACT J.W. GIBBS LAW (OR) GIBB’S PHASE RULE (or) PHASE RULE 100
  101. 101. GIBBS PHASE RULE 1/5/2013 J.W. Gibbs, American physicist derived an SAB-AP/MECH SONACT equation which established relationship in a system between the number of phases, The number of degree of freedom and the number of components. 101
  102. 102. GIBB’S PHASE RULE 1/5/2013 The phase rule indicates the phases that exists SAB-AP/MECH SONACT at equilibrium. The Gibb’s phase rule satisfies the following relation: P+F=C+n 102
  103. 103. GIBB’S PHASE RULE 1/5/2013 P- Number of phases that exist in a SAB-AP/MECH SONACT system under certain conditions. C-Number of components in the system. n- It represents the number of variables, examples: Temperature, pressure and concentration. 103
  104. 104. GIBB’S PHASE RULE 1/5/2013F- Degree of freedom. It is the number of SAB-AP/MECH SONACT variables such as temperature or pressure or concentration which can be change independently without changing the number of phases that are present in the system. 104
  105. 105. GIBB’S PHASE RULE 1/5/2013 In most studies the pressure is constant SAB-AP/MECH SONACT i.e., 1 atmospheric pressure and hence pressure is not considered a variable. Usually the only variable under consideration is temperature and hence the Gibb’s phase rule becomes; P+F=C+1 105
  106. 106. USES OF PHASE RULE 1/5/2013 The phase rule predicts maximum number of phases present in the alloy under equilibrium SAB-AP/MECH SONACT conditions at any point of diagram. If the number of phases are known, one can determine the degree of freedom using phase rule. 106
  107. 107. USES OF PHASE RULE 1/5/2013 Thus the phase rule is useful to know whether SAB-AP/MECH SONACT the temperature or pressure or both variables can be changed without changing the structure of the alloy. 107
  108. 108. ILLUSTRATION OF THE USE OF THE PHASE RULE 1/5/2013 Let us consider the application of gibbs phase rule to the phase diagram of water system SAB-AP/MECH SONACT Case 1 : Consider a triple point in the diagram. At the triple point, three phases coexist in equilibrium . P=3. Since there is one component (water) in the system C= 1 108
  109. 109. THE USE OF THE PHASE RULE 1/5/2013 The number of degree of freedom can be SAB-AP/MECH SONACT calculated using the Gibbs phase rule as, F=1- 3+2 F=0 (Zero degree of freedom) This means that one of the variables (Temperature or pressure) can be changed at the triple point. 109
  110. 110. THE USE OF THE PHASE RULE 1/5/2013 Note: Since the variables temperature or SAB-AP/MECH SONACT pressure cannot be changed and still keep the three phases of coexistence. The triple point is called an invariant point. 110
  111. 111. THE USE OF THE PHASE RULE 1/5/2013Case 2: Next consider a point along liquid-solid freezing curve SAB-AP/MECH SONACT P=2Then for water system C=1Applying the phase rule, we get: F=1- 2+ 2 F=1 (one degree of freedom) 111
  112. 112. THE USE OF THE PHASE RULE 1/5/2013 This means that one variable SAB-AP/MECH SONACT ( Temperature or pressure) can be changed independently and still maintain a system with two coexisting phases. 112
  113. 113. THE USE OF THE PHASE RULE 1/5/2013 Case:3 Now consider a point on the phase SAB-AP/MECH SONACT diagram of water inside a single phase in this case there will be only one phase present. P=1 , Then for water system, C=1 Now the phase rule gives 113
  114. 114. THE USE OF THE PHASE RULE 1/5/2013 F=1-1+2 SAB-AP/MECH SONACT F=2 ( two degree of freedom) This means that two variables ( Temperature and pressure) can be varied independently and the system will still remain in a single phase. 114
  115. 115. THE USE OF THE PHASE RULE 1/5/2013 Note: In many application (especially for most SAB-AP/MECH SONACT binary alloy) the pressure is kept constant at 1 atmosphere. In this case Gibbs phase rule is modified as F=C-P+1 115
  116. 116. THE USE OF THE PHASE RULE 1/5/2013 The above equation is known as condensed phase SAB-AP/MECH SONACT rule. This equation can be applied to most of the binary phase diagram. 116
  117. 117. OBJECTIVE TYPE QUESTIONS 1/5/20131. -----------May be visualized as forming from a SAB-AP/MECH SONACT centre of freezing, or nucleus, which is composed of a small group of atoms oriented into one of the common crystal patterns. Crystal 117
  118. 118. OBJECTIVE TYPE QUESTIONS 1/5/2013 2.Perfect crystal of proper external shape can be SAB-AP/MECH SONACT obtained only if crystallisation develops under conditions when degree of ----------------is very slight and the metal has a very high purity. 118
  119. 119. MICRO-CONSTITUENTS OF IRON-CARBON ALLOYS 1/5/2013 There are different micorscope constituents of SAB-AP/MECH SONACT Iron-Carbon alloys exit. The study of these micro-constituents is essential in order to understand iron-iron carbide (Fe-Fe3C) equilibrium phase diagram. 119
  120. 120. VARIOUS MICRO-CONSTITUENTS OF IRON-CARBON ALLOYS ARE: 1/5/20131.Ferrite SAB-AP/MECH SONACT2.Austenite3.Cementite4.Pearlite5.Ledeburite 1206.Martensite
  121. 121. VARIOUS MICRO-CONSTITUENTS OF IRON-CARBON ALLOYS ARE: 1/5/20137. Troosite SAB-AP/MECH SONACT8. Sorbite, and9.Bainite 121
  122. 122. VARIOUS MICRO-CONSTITUENTS OF IRON-CARBON ALLOYS ARE: 1/5/20131. Ferrite (or α-Iron) SAB-AP/MECH SONACT Ferrite is a primary solid solution based on α iron having BCC structure. It is Nothing but the interstitial solid solution of carbon in iron. 122
  123. 123. 1/5/2013 SAB-AP/MECH SONACT 123FERRITE
  124. 124. VARIOUS MICRO-CONSTITUENTS OF IRON-CARBON ALLOYS ARE: 1/5/2013 Maximum solubility of carbon in iron is 0.025% carbon SAB-AP/MECH SONACT at 723°C, While its solubility at room temperature is only 0.008%. Ferrite is soft, ductile, and highly Magnetic. It can undergo extensive cold working 124
  125. 125. VARIOUS MICRO-CONSTITUENTS OF IRON-CARBON ALLOYS ARE: 1/5/20132. Austenite(or γ-Iron) SAB-AP/MECH SONACT Austenite is a primary solid solution based on γ iron having FCC structure. This is also an interstitial solid solution of carbon in iron 125
  126. 126. 1/5/2013 SAB-AP/MECH SONACT 126AUSTENITE
  127. 127. AUSTENITE 1/5/2013 It is also a non-magnetic (paramagnetic) SAB-AP/MECH SONACT Austentite has a greater electrical resistance and coefficient of expansion than ferrite. 127
  128. 128. CEMENTITE 1/5/2013 Cementite is the name given to the carbide of SAB-AP/MECH SONACT iron(Fe3c). It is the hard, brittle, intermetallic compound of iron with 6.69% of carbon. 128
  129. 129. CEMENTITE 1/5/2013 The hardness and brittleness of cast iron is SAB-AP/MECH SONACT believed to be due to the presence of the cementite. It is Magnetic below 250°c 129
  130. 130. 1/5/2013 SAB-AP/MECH SONACT 130CEMENTITE
  131. 131. PEARLITE 1/5/2013 Pearlite is the eutectoid mixture of ferrite SAB-AP/MECH SONACT (87.5%) and cementite (12.5%). It is formed when austenite decomposes during cooling. It contains 0.8% of carbon 131
  132. 132. 1/5/2013 SAB-AP/MECH SONACT 132PEARLITE
  133. 133. PEARLITELAMELLAR-PEARLITE BEADED BAG 1/5/2013 SAB-AP/MECH SONACT 133
  134. 134. PEARLITE 1/5/2013 It consist of alternate thin layers (or lamellae) of SAB-AP/MECH SONACT ferrite and cementite shown in fig. The name derives from its lustrous apperance (similar to mother of pearl) when viewed in white light under a microscope. 134
  135. 135. PEARLITE 1/5/2013 The properties of pearlite is midway between SAB-AP/MECH SONACT ferrite and cementite. It is relatively strong, hard and ductile. 135
  136. 136. LEDEBURITE 1/5/2013 Ledeburite is the eutectic mixture of austenite(γ-Iron) and SAB-AP/MECH SONACT cementite (Fe3C) Containing 4.3% carbon. In pure iron-carbon alloy, it forms at 1140 °C. Most of the engineering alloy materials belong to this range of alloy. 136
  137. 137. LEDEBURITE 1/5/2013 Pig iron, the most important engineering SAB-AP/MECH SONACT material, is ledeburite. 137
  138. 138. 1/5/2013 SAB-AP/MECH SONACT 138LEDEBURITE
  139. 139. 1/5/2013 SAB-AP/MECH SONACT 139LEDEBURITE
  140. 140. MARTENSITE 1/5/2013 Martensite is the super saturated solid solution SAB-AP/MECH SONACT of carbon in α-Iron. It is formed when steel is very rapidly cooled from the austenitic state. It exhibits a characteristic acicular or needle like structure. 140
  141. 141. MARTENSITE 1/5/2013 It is very hard more brittle and low ductility SAB-AP/MECH SONACT properties. There is an increase in specific volume during formation of martensite from austenite. 141
  142. 142. MARTENSITE 1/5/2013 As a result internal stresses are set up in the SAB-AP/MECH SONACT materials leading to the formation of minute cracks. 142
  143. 143. MARTENSITE (RED AND YELLOWMARTENSITE. GREEN: AUSTENITE) 1/5/2013 SAB-AP/MECH SONACT 143
  144. 144. TROOSTITE 1/5/2013 Troosite is the mixture of radial lamella of SAB-AP/MECH SONACT ferrite and cementite. In fact, it differs from pearlite only in the degree of fitness. This constituents is also known as troostite pearlite. 144
  145. 145. TROOSTITE 1/5/2013 It is the microstructure consisting ferrite and SAB-AP/MECH SONACT finely divided cementite, produced on tempering martensite below 450 °C 145
  146. 146. TROOSTITE 1/5/2013 It is formed by the decomposition of austenite SAB-AP/MECH SONACT when cooled at a rate slower than that which will yield a martensitic structure and faster than that which will produce a sorbitic structure. 146
  147. 147. TROOSTITE 1/5/2013 It has hardness intermediate between SAB-AP/MECH SONACT martensite and sorbite. 147
  148. 148. 1/5/2013 SAB-AP/MECH SONACT 148TROOSTITE
  149. 149. SORBITE 1/5/2013 Sorbite is the microstructure consisting ferrite, SAB-AP/MECH SONACT and finely divided cementite, produced on tempering martensite above 450°C 149
  150. 150. SORBITE 1/5/2013 This constituents is also known as sorbitic SAB-AP/MECH SONACT pearlite. It is formed by the decomposition of austenite when cooled at a rate slower than that which will produce a pearlitic structure 150
  151. 151. SORBITE 1/5/2013 Though sorbitic steel is slightly less ductile than SAB-AP/MECH SONACT pearlite steel, its tensile and yield strength are high. The sorbite steels are often known as Toughened steels. 151
  152. 152. 1/5/2013 SAB-AP/MECH SONACT 152SORBITE
  153. 153. SORBITE 1/5/2013Note: SAB-AP/MECH SONACT All the pearlite, troosite and sorbite are ferrite- cementite mixtures having lamellar structure. However they are distinguished by their degree of dispersion. Pearlite has corase pearlite. 153
  154. 154. SORBITE 1/5/2013 Troosite has fine pearlite SAB-AP/MECH SONACT And sorbite has medium pearlite 154
  155. 155. BAINITE 1/5/2013 Bainite is a decomposition product of austenite, SAB-AP/MECH SONACT consisting of an aggregate of ferrite and carbide. Bainite is obtained by transformation of pearlite higher temperature ( has a feathery structure) is called upper bainite. 155
  156. 156. BAINITE 1/5/2013 Lower bainite provides high mechanical SAB-AP/MECH SONACT properties and that is why it is extensively used for components of machine and structures. Bainite has hardness in between the hardness of pearlite and martensite. 156
  157. 157. 1/5/2013 SAB-AP/MECH SONACT 157BAINITE
  158. 158. IRON/CARBON ALLOY PHASE DIAGRAM 1/5/2013 SAB-AP/MECH SONACT 158
  159. 159. 1/5/2013 SAB-AP/MECH SONACT 159

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