Introduction to Engineering materials

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An basic introduction to engineering materials and phase diagrams followed by clear under standing of Fe-c phase diagram

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ENGINEERING MATERIALS AND METALLURGY autonomous:

ENGINEERING MATERIALS AND METALLURGY autonomous For fourth SEMESTER(II YEAR) PREPARED BY S.ARAVINDHA BALAJI ASSISTANT PROFESSOR DEPARTMENT OF MECHANICAL ENGINEERING SONA COLLEGE OF TECHNOLOGY SALEM:636005

ENGINEERING MATERIALS AND METALLURGY:

ENGINEERING MATERIALS AND METALLURGY Application of EMAM(In Industry): Steel industry( e.g. steel plants, (SAIL) Essar steels, jindal steel ltd.(JSW)) Pipe maufacturing industry, Plastic industry. Some jewelry industry(Grades of the gold) Manufacturing industry. 1/5/2013 2 SAB-AP/MECH SONACT

ENGINEERING MATERIALS AND METALLURGY:

ENGINEERING MATERIALS AND METALLURGY OBJECTIVE Knowledge on the structure Properties of the materials Treatment Testing and applications of metals and non-metallic materials Suitable materials for various engineering application 1/5/2013 3 SAB-AP/MECH SONACT

ENGINEERING MATERIALS AND METALLURGY:

ENGINEERING MATERIALS AND METALLURGY Review (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.

ENGINEERING MATERIALS AND METALLURGY:

ENGINEERING MATERIALS AND METALLURGY Review (Not for Exam) Grain size ASTM grain size number 1/5/2013 5 SAB-AP/MECH SONACT

ENGINEERING MATERIALS AND METALLURGY:

ENGINEERING MATERIALS AND METALLURGY UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS Constitution 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. 1/5/2013 6 SAB-AP/MECH SONACT

ENGINEERING MATERIALS AND METALLURGY:

ENGINEERING MATERIALS AND METALLURGY UNIT:II HEAT TREATMENT Definition- Full annealing, stress relief, recrystallisation and spheroidizing-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 . 1/5/2013 7 SAB-AP/MECH SONACT

ENGINEERING MATERIALS AND METALLURGY:

ENGINEERING MATERIALS AND METALLURGY UNIT:III MECHANICAL PROPERTIES AND TESTING Mechanism 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. 1/5/2013 8 SAB-AP/MECH SONACT

ENGINEERING MATERIALS AND METALLURGY:

ENGINEERING MATERIALS AND METALLURGY UNIT:IV FERROUS AND NON FERROUS METALS Effect 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. 1/5/2013 9 SAB-AP/MECH SONACT

ENGINEERING MATERIALS AND METALLURGY:

ENGINEERING MATERIALS AND METALLURGY UNIT V NON-METALLIC MATERIALS Polymers-Types of polymer, commodity and Engineering 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. 1/5/2013 10 SAB-AP/MECH SONACT

ENGINEERING MATERIALS AND METALLURGY:

ENGINEERING MATERIALS AND METALLURGY 1/5/2013 11 SAB-AP/MECH SONACT Metals and alloys Ceramics and glasses Polymers Engineering Materials Application Structures Machines Devices Each category of engineering application requires material from any or all of these three group of materials

ENGINEERING MATERIALS AND METALLURGY:

ENGINEERING MATERIALS AND METALLURGY Organic polymers Plastics, Pvc,PTFE, polyethylene Fibers:Terylene,nylon,cotton, natural, and synthetic rubbers , leathers 1/5/2013 12 SAB-AP/MECH SONACT Metals and alloys Steels, aluminum, copper, silver ,gold, Brasses,, bronze s, maganin invar, super alloys boron rare earth magnetic alloys Ceramic and glasses Mgo, cds, Al 2O3, S iC, BaTio 3,Silica, soda-time-glass, Concrete, cement ferrites and garnets ceramic superconductors Glass fiber- reinforced plastics Si, Ge, GaAs, Boride-reinforced steel Metal-reinforced plastics

ENGINEERING MATERIALS AND METALLURGY:

ENGINEERING MATERIALS AND METALLURGY Structure: The internal structure of a material, simply called the structure. 1/5/2013 13 SAB-AP/MECH SONACT

Non-Metallic Materials::

Non-Metallic Materials: PE (polyethylene) PP (Polypropylene) PS(Polystyrene) PMMA(Polymethyl methacrylate) PET(Polyethylene teraphthalate) PC(Polycarbonates) PA(Polyamides) ABS(Acryknitrile-Butadiene-styrene) PI(Polyimide) 1/5/2013 14 SAB-AP/MECH SONACT

Non-Metallic Materials::

Non-Metallic Materials: PAI( Polyamideimide) PPO(Polyphenylene oxide) PPS(Polyphenylene sulphide) PEEK(Polyether ether ketone) PTFE(Polytetra fluoro ethylene) 1/5/2013 15 SAB-AP/MECH SONACT

ENGINEERING MATERIALS AND METALLURGY:

ENGINEERING MATERIALS AND METALLURGY UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS Constitution 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. 1/5/2013 16 SAB-AP/MECH SONACT

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS:

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS CONSTITUTION - establishment, foundation, creation, formation, structure, organization, charter, bill. 1/5/2013 17 SAB-AP/MECH SONACT

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS:

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS SOME TECHNICAL TERMS AND 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 1/5/2013 18 SAB-AP/MECH SONACT

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS:

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 3.COMPONENTS: The elements present in the system are called component. A system may consist of two or more components. 1/5/2013 19 SAB-AP/MECH SONACT

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS :

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS CONSTITUTION OF ALLOYS: 4.ALLOY: 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) 1/5/2013 20 SAB-AP/MECH SONACT

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS:

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS Alloy find very wide application in the industry than pure metals. 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. 1/5/2013 21 SAB-AP/MECH SONACT

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS:

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS Mechanical properties 1. Tensile strength 2. Yield point 3. Hardness are improved by alloying. 1/5/2013 22 SAB-AP/MECH SONACT

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS:

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS CLASSIFICATION OF ALLOYS 1/5/2013 23 SAB-AP/MECH SONACT CLASSIFICATION OF ALLOYS Pure metals Solid Solution Intermediate phase

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS:

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS Alloy can be either a single phase or a mixture of phases. A phases is anything which is homogeneous and physically distinct. In solid state alloys of three are three possible phase. 1/5/2013 24 SAB-AP/MECH SONACT

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS:

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS If an alloy has a single phase, it could be either a solid solution or an intermediate phase. If the alloy is a mixture it could be composed of any combination of the above three phases. 1/5/2013 25 SAB-AP/MECH SONACT

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS:

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS The major element which is large in amount is called base metal or parent 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). 1/5/2013 26 SAB-AP/MECH SONACT

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS:

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 5. MIXTURE: It is a material more than one phase. 1/5/2013 27 SAB-AP/MECH SONACT

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS:

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 1/5/2013 28 SAB-AP/MECH SONACT SOLID SOLUTION Substitutinal Solid solution Interstitial solid solution Disordered (or) Random Ordered (or) regular

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS:

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS Solid solutions: 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. 1/5/2013 29 SAB-AP/MECH SONACT

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS:

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS A solid solution may be defined as a solid that consist of two or more elements 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. 1/5/2013 30 SAB-AP/MECH SONACT

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS:

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS 2. Solvent: Solvent constitutes the major portion of the solution. Both the solute and the solvent can be solid, liquid or gas. 1/5/2013 31 SAB-AP/MECH SONACT

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS:

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS Solid solution: Simply a solution in the solid state. 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. 1/5/2013 32 SAB-AP/MECH SONACT

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS:

UNIT:I CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS space lattice: Space lattice is defined as an array of points in three dimensions in which every point has surroundings identical to that every other point in the array. 1/5/2013 33 SAB-AP/MECH SONACT

Solid solution:

Solid solution Case: In certain cases, the solidification of an 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. 1/5/2013 34 SAB-AP/MECH SONACT

Solid solution:

Solid solution In such a case we have a solid metal in which the 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 distorted form of one of the constituent metals. 1/5/2013 35 SAB-AP/MECH SONACT

Solid solution:

Solid solution Soildsolution are conductors, but not so good as the pure metals on which they are based. Some 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) 1/5/2013 36 SAB-AP/MECH SONACT

Substitutional solid solution:

Substitutional solid solution 1/5/2013 37 SAB-AP/MECH SONACT Solute Atoms SOLVENT OR MATRIX ATOMS solute-Atom of Metal-B Solvent-Atoms of zinc Metal-A zinc (Solute ) Copper(Solvent) Disordered substitutinal solid solution(random,)

Substitutional solid solution:

Substitutional solid solution Ordered subsitutional solid solution 1/5/2013 38 SAB-AP/MECH SONACT Solute Atoms SOLVENT OR MATRIX ATOMS

Substitutional solid solution:

Substitutional solid solution In substitutional solid solution, there is a direct 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); 1/5/2013 39 SAB-AP/MECH SONACT

Substitutional solid solution:

Substitutional solid solution The alloy is said to be in a disordered condition if 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. 1/5/2013 40 SAB-AP/MECH SONACT

Substitutional solid solution:

Substitutional solid solution An ordered subsititutional solid solution is shown fig Cu-Zn, Al-Cu, α -Brass are some examples of ordered structures. 1/5/2013 41 SAB-AP/MECH SONACT

Interstitial solid solution:

Interstitial solid solution The four elements hydrogen, carbon, nitrogen, and boron have such small diameters that they can occupy the empty spaces (Interstices) in the crystal lattices of many metals. 1/5/2013 42 SAB-AP/MECH SONACT

Interstitial solid solution:

Interstitial solid solution 1/5/2013 43 SAB-AP/MECH SONACT Solvent or matrix atoms Solute atoms INTERSTITIAL SOLID SOLUTION CARBON (solute) IRON ( SOLVENT)

Interstitial solid solution:

Interstitial solid solution Interstitial solid solution usually have a limited composition range and are generally considered of secondary importance, but there are a few instances worthy of special attention. 1/5/2013 44 SAB-AP/MECH SONACT

Interstitial solid solution:

Interstitial solid solution The interstitial solution of carbon in iron 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. 1/5/2013 45 SAB-AP/MECH SONACT

Interstitial solid solution:

Interstitial solid solution Interstitial nitrogen is useful not only in nirtriding process but also as an important factor in maintaining 18Cr-8Ni Stainless steel in the austenitic condition. 1/5/2013 46 SAB-AP/MECH SONACT

HUME - ROTHERY’S RULES OF SOLID SOLUBILITY :

HUME - ROTHERY’S RULES OF SOLID SOLUBILITY 1/5/2013 47 SAB-AP/MECH SONACT Hume - Rothery’s Rules of solid solubility

Hume - Rothery’s Rules of solid solubility:

Hume - Rothery’s Rules of solid solubility 1/5/2013 48 SAB-AP/MECH SONACT Hume - Rothery’s Rules of solid solubility

Interstitial solid solution:

Interstitial solid solution HUME –ROTHERY’S RULES OF SOLID SOLUBILITY The solubility limit of solute in solvents depends on various factors. These were stated by Hume- rothery and are as follows: Critical structure factor (or) Crystal structure: Metals that have the same crystal stucture (Lattice structure) have a greater solubility. 1/5/2013 49 SAB-AP/MECH SONACT

Interstitial solid solution:

Interstitial solid solution 2. Relative atomic size factor(or) size factor: The solid solution will tend to form if the 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 than 8% 1/5/2013 50 SAB-AP/MECH SONACT

Interstitial solid solution:

Interstitial solid solution 3. Chemical affinity factor (or) Electronegativity : Formulation of solid solution is 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. 1/5/2013 51 SAB-AP/MECH SONACT

Interstitial solid solution:

Interstitial solid solution 4. Relative valency factor(or)valence: A metal that has a higher valency will 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. 1/5/2013 52 SAB-AP/MECH SONACT

Interstitial solid solution:

Interstitial solid solution In some alloys both interstitial and 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. 1/5/2013 53 SAB-AP/MECH SONACT

Possibilities of solid solutions:

Possibilities of solid solutions There are three possible solid solutions based on 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. 1/5/2013 54 SAB-AP/MECH SONACT

Possibilities of solid solutions:

Possibilities of solid solutions 2. Saturated solid solution: If the solvent is dissolving limiting amount of solute, it is called saturated solid solution. 1/5/2013 55 SAB-AP/MECH SONACT

Possibilities of solid solutions:

Possibilities of solid solutions 3. Supersaturated solid solution: If the solvent is dissolving more of solute that it should, under equilibrium, it is called supersaturated solid solution. 1/5/2013 56 SAB-AP/MECH SONACT

PHASE DIAGRAM:

PHASE DIAGRAM Types of phase diagram 1. Isomorphous 2. Eutectoid system 3. Eutectic system 4.Peritectic system 5. Peritectroid reactions 1/5/2013 57 SAB-AP/MECH SONACT

PHASE DIAGRAM:

PHASE DIAGRAM Phase Diagrams Phase diagrams are graphical representation of what phases are present in an alloy system at various Temperatures, pressures, and compositions. 1/5/2013 58 SAB-AP/MECH SONACT

PHASE DIAGRAM:

PHASE DIAGRAM (or) A phase diagram is a map showing the 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 . 1/5/2013 59 SAB-AP/MECH SONACT

Why should phase diagrams be studied?:

Why should phase diagrams be studied? The phase diagrams can answer the following important questions: What condition is the material in? Is the composition uniform throughout ? If not, how much of each component is present? 1/5/2013 60 SAB-AP/MECH SONACT

Why should phase diagrams be studied?:

Why should phase diagrams be studied? Is something present that may give undesired properties? What will happen if temperature is increased or decreased; pressure is changed or composition is varied? 1/5/2013 61 SAB-AP/MECH SONACT

Why should phase diagrams be studied?:

Why should phase diagrams be studied? Phase diagrams are used by engineers and scientists to understand and to predict many aspects of the behavior of materials. 1/5/2013 62 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams Components System Alloy Solid solution Solute Solution 1/5/2013 63 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams 6. Solvent 7. Phase 8. Equilibrium 9. Solubility limit 10.Degrees of freedom 1/5/2013 64 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams The various terms used in the study of phase 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. 1/5/2013 65 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams 2. SYSTEM: The system has two meanings in this context i . System: May refer to a specific body of material under consideration. For Eg: A ladle of molten steel is referred as a system. 1/5/2013 66 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams (ii)system: May also refer to the series of possible alloys consisting of the same components. For example, the Iron-Carbon system. 1/5/2013 67 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams A system having one components is called a Unary system, and the system having two, three and four components are known as Binary, ternary and quaternary systems, respectively. 1/5/2013 68 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams 3. ALLOY: An alloy is a mixture of two or more metals or a metal (metals) and a non-metal (non-metals). 1/5/2013 69 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams 4.SOLID SOLUTION: It is a solid that consist of two or more elements atomically dispersed in a single-phase structure. 1/5/2013 70 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams 5. SOLUTE SOLUTION: It is the minor part of the solution or the material which is dissolved. 1/5/2013 71 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams 6. SOLVENT: The material which contributes the major portion of the solution. 1/5/2013 72 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams 7. PHASE: A phase may be defined as a homogenous portion of a system that has uniform physical and chemical characteristics. 1/5/2013 73 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams 8. EQUILIBRIUM: Equilibrium is said to exit when enough time is allowed for all possible reactions to be completed. 1/5/2013 74 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams The equilibrium state refers to the characteristics of the system that remain constant indefinitely. Equilibrium occurs when the free energy of the system is at its minimum value. 1/5/2013 75 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams The term phase equilibrium refers to equilibrium as it applies to systems in which more than one phase may exist. 1/5/2013 76 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams 9. SOLUBILITY LIMIT: It is the maximum concentration of solute that may be added without forming a new phase. 1/5/2013 77 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams NOTE: The addition of solution in excess of the solubility limit results in the formation of another solid solution or compound. 1/5/2013 78 SAB-AP/MECH SONACT

Terminology used in phase diagrams:

Terminology used in phase diagrams 10. DEGREES OF FREEDOM: 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. 1/5/2013 79 SAB-AP/MECH SONACT

What is meant by the term phase? :

What is meant by the term phase? A phase may be a portion of matter which is homogenous A phase may be defined as any physical distinct homogenous and mechanically separable portion of a substance. 1/5/2013 80 SAB-AP/MECH SONACT

What is meant by the term phase?:

What is meant by the term phase? In Layman’s term, a phase requires a unique structure, uniform composition, and well-defined boundaries or interfaces Examples: A pure substance such as water is a single phase. 1/5/2013 81 SAB-AP/MECH SONACT

What is meant by the term phase?:

What is meant by the term phase? The pure substance water can exist in solid, 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. 1/5/2013 82 SAB-AP/MECH SONACT

What is meant by the term phase?:

What is meant by the term phase? Thus the salt- water solution forms a single phase as shown if fig(b) If more salt is added into water, then we have two different phases as shown if fig(c) 1/5/2013 83 SAB-AP/MECH SONACT

What is meant by the term phase?:

What is meant by the term phase? A Single phase system is also termed as “homogeneous system” 1/5/2013 84 SAB-AP/MECH SONACT

What is meant by the term phase?:

What is meant by the term phase? System composed of two or more phases are termed as mixtures or heterogeneous systems’. Fig (d) Most metallic alloys, ceramic, polymers, and composite are heterogenous. 1/5/2013 85 SAB-AP/MECH SONACT

ILLUSTRATION OF PHASES :

ILLUSTRATION OF PHASES WATER(2) ILLUSTRATION OF PHASES: (A) Three forms of water: 1) Ice 2)water 3) water vapour are each a phase. 1/5/2013 86 SAB-AP/MECH SONACT WATER ICE (1) WATER VAPOUR(3)

ILLUSTRATION OF PHASES :

ILLUSTRATION OF PHASES salt (b) Salt and water have unlimited solubility (Homogeneous solution)- from a single phase 1/5/2013 87 SAB-AP/MECH SONACT •

ILLUSTRATION OF PHASES :

ILLUSTRATION OF PHASES (C) Salt and water have limited solubility (Heterogenous solution)-from two distinct phases 1/5/2013 88 SAB-AP/MECH SONACT Saturated brine Excess salt

ILLUSTRATION OF PHASES :

ILLUSTRATION OF PHASES 1/5/2013 89 SAB-AP/MECH SONACT OIL WATER OIL AND WATER HAVE VIRTUALLY NO SOLUBILITY FROM TWO DISTINCT PHASES

PHASE DIAGRAM OF PURE SUBSTANCE:

PHASE DIAGRAM OF PURE SUBSTANCE One- Component Phase diagram 1/5/2013 90 SAB-AP/MECH SONACT

PHASE DIAGRAM OF PURE SUBSTANCE:

PHASE DIAGRAM OF PURE SUBSTANCE 1/5/2013 91 SAB-AP/MECH SONACT

PHASE DIAGRAM OF PURE SUBSTANCE:

PHASE DIAGRAM OF PURE SUBSTANCE A pure substance such as water can exist in solid, liquid, or vapour phases, depending on the condition of temperature and pressure 1/5/2013 92 SAB-AP/MECH SONACT

PHASE DIAGRAM OF PURE SUBSTANCE:

PHASE DIAGRAM OF PURE SUBSTANCE The phase relationships may be represented on a pressure- temperature (PT) diagram, known as a one-component (or unary) phase diagram, for the H 2O System. 1/5/2013 93 SAB-AP/MECH SONACT

PHASE DIAGRAM OF PURE SUBSTANCE:

PHASE DIAGRAM OF PURE SUBSTANCE The phase diagram is composed of regions of 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. 1/5/2013 94 SAB-AP/MECH SONACT

PHASE DIAGRAM OF PURE SUBSTANCE:

PHASE DIAGRAM OF PURE SUBSTANCE Liquid and vapour phase exist along the vapourisation line and liquid and solid phases along the freezing line, shows in figure. These lines are also known as Two phase equilibrium lines. 1/5/2013 95 SAB-AP/MECH SONACT

PHASE DIAGRAM OF PURE SUBSTANCE:

PHASE DIAGRAM OF PURE SUBSTANCE The point “O” is know as Triple point. 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. 1/5/2013 96 SAB-AP/MECH SONACT

PHASE DIAGRAMS :

PHASE DIAGRAMS The properties of an alloy depend on nature, amount, size, distribution and orientation of the phases. A phase is the chemically and structurally homogeneous portion of the microstructure. 1/5/2013 97 SAB-AP/MECH SONACT

PHASE DIAGRAMS:

PHASE DIAGRAMS It has the following characteristics 1. Same structure throughout. 2. Roughly the same composition and properties throughout. 3. Definite interface between the phase and surrounding. 1/5/2013 98 SAB-AP/MECH SONACT

J.W. GIBBS ( Josiah Willard Gibbs):

J.W. GIBBS ( Josiah Willard Gibbs) 1/5/2013 99 SAB-AP/MECH SONACT

J.W. GIBBS( Josiah Willard Gibbs):

J.W. GIBBS( Josiah Willard Gibbs) JOSIAH WILLARD GIBBS PROPOSAL (OR) J.W. GIBBS LAW (OR) GIBB’S PHASE RULE (or) PHASE RULE 1/5/2013 100 SAB-AP/MECH SONACT

GIBBS PHASE RULE:

GIBBS PHASE RULE J.W. Gibbs, American physicist derived an equation which established relationship in a system between the number of phases, The number of degree of freedom and the number of components. 1/5/2013 101 SAB-AP/MECH SONACT

GIBB’S PHASE RULE:

GIBB’S PHASE RULE The phase rule indicates the phases that exists at equilibrium. The Gibb’s phase rule satisfies the following relation: P+F=C+n 1/5/2013 102 SAB-AP/MECH SONACT

GIBB’S PHASE RULE:

GIBB’S PHASE RULE P- Number of phases that exist in a system under certain conditions. C - Number of components in the system. n- It represents the number of variables, examples: Temperature, pressure and concentration. 1/5/2013 103 SAB-AP/MECH SONACT

GIBB’S PHASE RULE:

GIBB’S PHASE RULE F- Degree of freedom. It is the number of 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. 1/5/2013 104 SAB-AP/MECH SONACT

GIBB’S PHASE RULE:

GIBB’S PHASE RULE In most studies the pressure is constant 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 1/5/2013 105 SAB-AP/MECH SONACT

USES OF PHASE RULE:

USES OF PHASE RULE The phase rule predicts maximum number of phases present in the alloy under equilibrium conditions at any point of diagram. If the number of phases are known, one can determine the degree of freedom using phase rule. 1/5/2013 106 SAB-AP/MECH SONACT

USES OF PHASE RULE:

USES OF PHASE RULE Thus the phase rule is useful to know whether the temperature or pressure or both variables can be changed without changing the structure of the alloy. 1/5/2013 107 SAB-AP/MECH SONACT

ILLUSTRATION OF THE USE OF THE PHASE RULE:

ILLUSTRATION OF THE USE OF THE PHASE RULE Let us consider the application of gibbs phase rule to the phase diagram of water system 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 1/5/2013 108 SAB-AP/MECH SONACT

THE USE OF THE PHASE RULE:

THE USE OF THE PHASE RULE The number of degree of freedom can be 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. 1/5/2013 109 SAB-AP/MECH SONACT

THE USE OF THE PHASE RULE:

THE USE OF THE PHASE RULE Note: Since the variables temperature or pressure cannot be changed and still keep the three phases of coexistence. The triple point is called an invariant point. 1/5/2013 110 SAB-AP/MECH SONACT

THE USE OF THE PHASE RULE:

THE USE OF THE PHASE RULE Case 2: Next consider a point along liquid-solid freezing curve P=2 Then for water system C=1 Applying the phase rule, we get: F=1- 2+ 2 F=1 (one degree of freedom) 1/5/2013 111 SAB-AP/MECH SONACT

THE USE OF THE PHASE RULE:

THE USE OF THE PHASE RULE This means that one variable ( Temperature or pressure) can be changed independently and still maintain a system with two coexisting phases. 1/5/2013 112 SAB-AP/MECH SONACT

THE USE OF THE PHASE RULE:

THE USE OF THE PHASE RULE Case:3 Now consider a point on the phase 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 1/5/2013 113 SAB-AP/MECH SONACT

THE USE OF THE PHASE RULE:

THE USE OF THE PHASE RULE F=1-1+2 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. 1/5/2013 114 SAB-AP/MECH SONACT

THE USE OF THE PHASE RULE:

THE USE OF THE PHASE RULE Note: In many application (especially for most binary alloy) the pressure is kept constant at 1 atmosphere. In this case Gibbs phase rule is modified as F=C-P+1 1/5/2013 115 SAB-AP/MECH SONACT

THE USE OF THE PHASE RULE:

THE USE OF THE PHASE RULE The above equation is known as condensed phase rule. This equation can be applied to most of the binary phase diagram. 1/5/2013 116 SAB-AP/MECH SONACT

OBJECTIVE TYPE QUESTIONS:

OBJECTIVE TYPE QUESTIONS 1. -----------May be visualized as forming from a centre of freezing, or nucleus, which is composed of a small group of atoms oriented into one of the common crystal patterns. Crystal 1/5/2013 117 SAB-AP/MECH SONACT

OBJECTIVE TYPE QUESTIONS:

OBJECTIVE TYPE QUESTIONS 2.Perfect crystal of proper external shape can be obtained only if crystallisation develops under conditions when degree of ----------------is very slight and the metal has a very high purity. 1/5/2013 118 SAB-AP/MECH SONACT

Micro-Constituents OF Iron-Carbon Alloys:

Micro-Constituents OF Iron-Carbon Alloys There are different micorscope constituents of Iron-Carbon alloys exit. The study of these micro-constituents is essential in order to understand iron-iron carbide (Fe-Fe3C) equilibrium phase diagram. 1/5/2013 119 SAB-AP/MECH SONACT

Various Micro-Constituents of Iron-Carbon Alloys are::

Various Micro-Constituents of Iron-Carbon Alloys are: 1. Ferrite 2.Austenite 3.Cementite 4.Pearlite 5.Ledeburite 6.Martensite 1/5/2013 120 SAB-AP/MECH SONACT

Various Micro-Constituents of Iron-Carbon Alloys are::

Various Micro-Constituents of Iron-Carbon Alloys are: 7. Troosite 8. Sorbite, and 9.Bainite 1/5/2013 121 SAB-AP/MECH SONACT

Various Micro-Constituents of Iron-Carbon Alloys are::

Various Micro-Constituents of Iron-Carbon Alloys are: Ferrite (or α -Iron) 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. 1/5/2013 122 SAB-AP/MECH SONACT

Ferrite:

Ferrite 1/5/2013 123 SAB-AP/MECH SONACT

Various Micro-Constituents of Iron-Carbon Alloys are::

Various Micro-Constituents of Iron-Carbon Alloys are: Maximum solubility of carbon in iron is 0.025% carbon 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 1/5/2013 124 SAB-AP/MECH SONACT

Various Micro-Constituents of Iron-Carbon Alloys are::

Various Micro-Constituents of Iron-Carbon Alloys are: 2. Austenite (or γ -Iron) Austenite is a primary solid solution based on γ iron having FCC structure. This is also an interstitial solid solution of carbon in iron  1/5/2013 125 SAB-AP/MECH SONACT

Austenite:

Austenite 1/5/2013 126 SAB-AP/MECH SONACT

Austenite:

Austenite It is also a non-magnetic (paramagnetic) Austentite has a greater electrical resistance and coefficient of expansion than ferrite. 1/5/2013 127 SAB-AP/MECH SONACT

Cementite:

Cementite Cementite is the name given to the carbide of iron(Fe 3 c). It is the hard, brittle, intermetallic compound of iron with 6.69% of carbon. 1/5/2013 128 SAB-AP/MECH SONACT

Cementite:

Cementite The hardness and brittleness of cast iron is believed to be due to the presence of the cementite. It is Magnetic below 250°c 1/5/2013 129 SAB-AP/MECH SONACT

Cementite:

Cementite 1/5/2013 130 SAB-AP/MECH SONACT

Pearlite:

Pearlite Pearlite is the eutectoid mixture of ferrite (87.5%) and cementite (12.5%). It is formed when austenite decomposes during cooling. It contains 0.8% of carbon 1/5/2013 131 SAB-AP/MECH SONACT

Pearlite:

Pearlite 1/5/2013 132 SAB-AP/MECH SONACT

Pearlite Lamellar-Pearlite beaded bag:

Pearlite Lamellar-Pearlite beaded bag 1/5/2013 133 SAB-AP/MECH SONACT

Pearlite:

Pearlite It consist of alternate thin layers (or lamellae) of 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. 1/5/2013 134 SAB-AP/MECH SONACT

Pearlite:

Pearlite The properties of pearlite is midway between ferrite and cementite. It is relatively strong, hard and ductile. 1/5/2013 135 SAB-AP/MECH SONACT

Ledeburite:

Ledeburite Ledeburite is the eutectic mixture of austenite( γ -Iron) and cementite (Fe 3C) 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. 1/5/2013 136 SAB-AP/MECH SONACT

Ledeburite:

Ledeburite Pig iron, the most important engineering material, is ledeburite. 1/5/2013 137 SAB-AP/MECH SONACT

Ledeburite:

Ledeburite 1/5/2013 138 SAB-AP/MECH SONACT

Ledeburite:

Ledeburite 1/5/2013 139 SAB-AP/MECH SONACT

Martensite:

Martensite Martensite is the super saturated solid solution 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. 1/5/2013 140 SAB-AP/MECH SONACT

Martensite:

Martensite It is very hard more brittle and low ductility properties. There is an increase in specific volume during formation of martensite from austenite. 1/5/2013 141 SAB-AP/MECH SONACT

Martensite:

Martensite As a result internal stresses are set up in the materials leading to the formation of minute cracks. 1/5/2013 142 SAB-AP/MECH SONACT

Martensite (red and yellow martensite. Green: austenite):

Martensite (red and yellow martensite. Green: austenite) 1/5/2013 143 SAB-AP/MECH SONACT

Troostite:

Troostite Troosite is the mixture of radial lamella of ferrite and cementite. In fact, it differs from pearlite only in the degree of fitness. This constituents is also known as troostite pearlite. 1/5/2013 144 SAB-AP/MECH SONACT

Troostite:

Troostite It is the microstructure consisting ferrite and finely divided cementite, produced on tempering martensite below 450 °C 1/5/2013 145 SAB-AP/MECH SONACT

Troostite:

Troostite It is formed by the decomposition of austenite when cooled at a rate slower than that which will yield a martensitic structure and faster than that which will produce a sorbitic structure. 1/5/2013 146 SAB-AP/MECH SONACT

Troostite:

Troostite It has hardness intermediate between martensite and sorbite. 1/5/2013 147 SAB-AP/MECH SONACT

Troostite:

Troostite 1/5/2013 148 SAB-AP/MECH SONACT

Sorbite:

Sorbite Sorbite is the microstructure consisting ferrite, and finely divided cementite, produced on tempering martensite above 450°C 1/5/2013 149 SAB-AP/MECH SONACT

Sorbite:

Sorbite This constituents is also known as sorbitic pearlite. It is formed by the decomposition of austenite when cooled at a rate slower than that which will produce a pearlitic structure 1/5/2013 150 SAB-AP/MECH SONACT

Sorbite:

Sorbite Though sorbitic steel is slightly less ductile than pearlite steel, its tensile and yield strength are high. The sorbite steels are often known as Toughened steels. 1/5/2013 151 SAB-AP/MECH SONACT

Sorbite:

Sorbite 1/5/2013 152 SAB-AP/MECH SONACT

Sorbite:

Sorbite Note: 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. 1/5/2013 153 SAB-AP/MECH SONACT

Sorbite:

Sorbite Troosite has fine pearlite And sorbite has medium pearlite 1/5/2013 154 SAB-AP/MECH SONACT

Bainite:

Bainite Bainite is a decomposition product of austenite, 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. 1/5/2013 155 SAB-AP/MECH SONACT

Bainite:

Bainite Lower bainite provides high mechanical 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. 1/5/2013 156 SAB-AP/MECH SONACT

Bainite:

Bainite 1/5/2013 157 SAB-AP/MECH SONACT

Iron/Carbon alloy Phase Diagram:

Iron/Carbon alloy Phase Diagram 1/5/2013 158 SAB-AP/MECH SONACT

PowerPoint Presentation:

1/5/2013 159 SAB-AP/MECH SONACT

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