The document discusses phases, microstructures, and properties in materials. It defines a phase as a region that differs in structure and/or composition from another region. It explains that phase diagrams provide information on the number and types of phases present at different temperatures and compositions, and can show equilibrium solid solubility and temperature ranges for phase changes. Gibb's phase rule relates the number of phases, components, and degrees of freedom in a system. Solid solutions are discussed as single-phase atomic mixtures, including substitutional and interstitial types. The iron-carbon phase diagram is examined in detail, outlining the different phases such as austenite, ferrite, cementite, and eutectic or peritectic
The document discusses various aspects of solidification processes for pure metals and alloys. It covers topics such as solidification curves, grain structure formation, mushy zone formation in alloys, segregation of elements, shrinkage during solidification, and directional solidification techniques. It also discusses the functions and design of gating systems, including elements like pouring basins, sprues, runners, gates, and risers.
The document discusses intermetallic compounds, which are intermediate phases that form between two metals in an alloy system when the solute content exceeds the solid solubility limit. Intermetallics have a fixed stoichiometric composition and crystal structure different from the parent metals. They are very hard and brittle. Examples include Fe3C in steels and Mg2Ni in magnesium-nickel alloys. Intermetallics find use in applications requiring high strength and oxidation resistance at elevated temperatures, such as MoSi2 heating elements and TiAl turbine blades.
This presentation will provide the non-metallurgist with a basic understanding of carbon and low alloy steels. First we'll describe the carbon and low alloy steels by examining the iron-carbon binary phase diagram and understand the basic microstructures as related to carbon content. We'll discuss the nomenclature of the different carbon and alloy steel groups. We will then examine how mechanical properties are influenced through carbon content, alloy additions and heat treatment. We will also discuss the differences in carbon and low alloy steels that are specified as structural steels and high strength-low alloy (HSLA) steels. Finally, we will address the issues of material selection, processing and finishing.
Titanium and its alloys are discussed. Key points include:
- Titanium is the 9th most abundant element on Earth and was discovered in 1791. It has a high strength to weight ratio.
- There are three main types of titanium alloys - commercially pure, alpha/near-alpha, and alpha-beta alloys. Alpha-beta alloys like Ti-6Al-4V are most widely used in aerospace.
- Properties depend on crystal structure and heat treatment. Quenching produces martensite and increases strength while annealing produces different microstructures with varying properties.
Copper and its alloys are discussed. Copper is extracted via both pyrometallurgical and hydrometallurgical methods from ores like chalcopyrite. Blister copper undergoes electrolytic refining to obtain pure copper. Copper alloys include brasses, bronzes, aluminum bronzes, beryllium bronzes and cupro-nickels. These alloys find applications in electrical, automotive and other industries due to copper's high thermal and electrical conductivity.
This document discusses welding metallurgy and the structure of fusion welds. It describes the different zones that make up a typical fusion welded joint, including the fusion zone, weld interface, heat affected zone, and base material. It explains how the microstructure varies across these zones due to melting and solidification processes during welding. Factors like welding parameters, heat input, and joint geometry are described as influencing weld pool shape and grain structure. The concept of thermal severity number is introduced as a way to assess cracking susceptibility based on total plate thickness.
This document discusses dispersion strengthening of composites. It begins with an introduction defining dispersion strengthening as enhancing the strength and hardness of metal alloys through the uniform dispersion of extremely small, insoluble particles within the matrix. It then covers the classification of composites, the mechanism of dispersion strengthening via dislocation pinning, and factors that influence strengthening such as particle size and spacing. A comparison is made between dispersion and precipitation strengthening, noting differences in coherency and temperature stability. Advantages of dispersion strengthening include higher creep resistance and strength retention at high temperatures.
The document discusses microstructures in steels and other alloys. It includes images and descriptions of different microstructures like pearlite, martensite, bainite, and ferrite that form under various cooling conditions from austenite. It also discusses microstructures in cast irons like spheroidal graphite, flake graphite, and ledeburite. The final section discusses sealed quench furnaces and includes images of loads of components prepared for case hardening and quenching treatments.
The document discusses various aspects of solidification processes for pure metals and alloys. It covers topics such as solidification curves, grain structure formation, mushy zone formation in alloys, segregation of elements, shrinkage during solidification, and directional solidification techniques. It also discusses the functions and design of gating systems, including elements like pouring basins, sprues, runners, gates, and risers.
The document discusses intermetallic compounds, which are intermediate phases that form between two metals in an alloy system when the solute content exceeds the solid solubility limit. Intermetallics have a fixed stoichiometric composition and crystal structure different from the parent metals. They are very hard and brittle. Examples include Fe3C in steels and Mg2Ni in magnesium-nickel alloys. Intermetallics find use in applications requiring high strength and oxidation resistance at elevated temperatures, such as MoSi2 heating elements and TiAl turbine blades.
This presentation will provide the non-metallurgist with a basic understanding of carbon and low alloy steels. First we'll describe the carbon and low alloy steels by examining the iron-carbon binary phase diagram and understand the basic microstructures as related to carbon content. We'll discuss the nomenclature of the different carbon and alloy steel groups. We will then examine how mechanical properties are influenced through carbon content, alloy additions and heat treatment. We will also discuss the differences in carbon and low alloy steels that are specified as structural steels and high strength-low alloy (HSLA) steels. Finally, we will address the issues of material selection, processing and finishing.
Titanium and its alloys are discussed. Key points include:
- Titanium is the 9th most abundant element on Earth and was discovered in 1791. It has a high strength to weight ratio.
- There are three main types of titanium alloys - commercially pure, alpha/near-alpha, and alpha-beta alloys. Alpha-beta alloys like Ti-6Al-4V are most widely used in aerospace.
- Properties depend on crystal structure and heat treatment. Quenching produces martensite and increases strength while annealing produces different microstructures with varying properties.
Copper and its alloys are discussed. Copper is extracted via both pyrometallurgical and hydrometallurgical methods from ores like chalcopyrite. Blister copper undergoes electrolytic refining to obtain pure copper. Copper alloys include brasses, bronzes, aluminum bronzes, beryllium bronzes and cupro-nickels. These alloys find applications in electrical, automotive and other industries due to copper's high thermal and electrical conductivity.
This document discusses welding metallurgy and the structure of fusion welds. It describes the different zones that make up a typical fusion welded joint, including the fusion zone, weld interface, heat affected zone, and base material. It explains how the microstructure varies across these zones due to melting and solidification processes during welding. Factors like welding parameters, heat input, and joint geometry are described as influencing weld pool shape and grain structure. The concept of thermal severity number is introduced as a way to assess cracking susceptibility based on total plate thickness.
This document discusses dispersion strengthening of composites. It begins with an introduction defining dispersion strengthening as enhancing the strength and hardness of metal alloys through the uniform dispersion of extremely small, insoluble particles within the matrix. It then covers the classification of composites, the mechanism of dispersion strengthening via dislocation pinning, and factors that influence strengthening such as particle size and spacing. A comparison is made between dispersion and precipitation strengthening, noting differences in coherency and temperature stability. Advantages of dispersion strengthening include higher creep resistance and strength retention at high temperatures.
The document discusses microstructures in steels and other alloys. It includes images and descriptions of different microstructures like pearlite, martensite, bainite, and ferrite that form under various cooling conditions from austenite. It also discusses microstructures in cast irons like spheroidal graphite, flake graphite, and ledeburite. The final section discusses sealed quench furnaces and includes images of loads of components prepared for case hardening and quenching treatments.
The document discusses dislocation theory and behavior in different crystal structures. It covers:
- Observation techniques for dislocations like etching and transmission electron microscopy
- Key concepts like Burgers vector, dislocation loops, and dissociation of dislocations into partial dislocations
- Differences in dislocation behavior in FCC, BCC, and HCP lattices including slip systems and interactions between dislocations
- Stress fields and strain energies of dislocations as well as forces acting on dislocations and between dislocations
- Mechanisms of dislocation motion including glide, cross-slip, and climb that enable plastic deformation.
The document discusses time-temperature-transformation (TTT) diagrams, which show the kinetics of isothermal transformations in steel alloys. TTT diagrams plot temperature versus the logarithm of time and indicate when specific transformations start and end. They show that austenite is stable above the lower critical temperature but unstable below it. Depending on the cooling rate, austenite can transform into pearlite, bainite, or martensite. Slow cooling leads to full pearlite transformation, while very fast cooling results in full martensite formation. TTT diagrams provide information about transformation rates, temperatures, phases, and microstructure sizes.
The document discusses eutectic solidification, where a liquid transforms into two solid phases at a single temperature. It describes how one phase will form via diffusion in the liquid, depleting the local area of one constituent and pushing the composition into the solid phase range. This causes the second phase to form adjacent to the first. The two phases then grow side-by-side in a laminated microstructure. There are two types of eutectic solidification: normal, where the phases form alternate lamellae via diffusion between the phases; and anomalous, where one phase is capable of faceting and forms irregular microstructures sensitive to growth conditions.
This document discusses time-temperature-transformation (TTT) diagrams and continuous cooling transformation (CCT) diagrams. TTT diagrams show the transformation of austenite at constant temperatures over time, indicating what microstructures form during different cooling rates. CCT diagrams track phase changes during continuous cooling at various cooling rates. Both diagrams are important for selecting processing conditions to achieve desired material properties in steels. The document provides detailed explanations of the various microstructures - pearlite, bainite, martensite - that form during austenite decomposition, and how TTT and CCT diagrams can be used to understand their formation.
Austenitic iron is non-magnetic, while ferritic iron is magnetic, due to their different temperatures rather than phases. Magnetism in iron arises from electron spin alignment within atomic zones. Above the Curie temperature, thermal energy disrupts zone formation, eliminating magnetism. The Curie point for iron is near austenite's stability range, but heating ferrite or quenching austenite above the Curie point also removes magnetism, demonstrating it is a temperature not phase effect.
The document discusses the iron-carbon phase diagram and the microstructures of plain carbon steels. It begins by explaining the different phases in the Fe-C system, including ferrite, austenite, cementite, and their crystal structures. It then describes how to properly draw the iron-carbon phase diagram, labeling important curves, temperatures, and carbon percentages. Finally, it illustrates the microstructures that form upon cooling for hypoeutectoid, eutectoid, and hypereutectoid plain carbon steels, such as proeutectoid ferrite, pearlite, and proeutectoid cementite.
Tool steels are high-quality alloy steels developed for shaping other materials. They contain carbon from 0.1-1.6% along with alloying elements like chromium, molybdenum, and vanadium. Tool steels offer better durability, strength, corrosion resistance, and temperature stability compared to other construction steels. They are used in applications involving forming, extrusion, and plastic molding. The document then discusses different types of tool steels categorized based on their intended use and hardening properties.
The document discusses the process of deoxidizing steel. During steelmaking, oxygen dissolves into the liquid steel but not in the solid steel. Deoxidation or "killing" of steel refers to reducing the excess oxygen content before casting to prevent blowholes and inclusions. This is typically done through precipitation deoxidation using elements like aluminum, silicon, and manganese that have a higher affinity for oxygen than iron and form stable oxides. These deoxidizers are chosen based on factors like stability, deoxidizing ability, oxide melting point and density. Aluminum is the most powerful deoxidizer but its oxide alumina must be modified to remain liquid during casting.
The document provides information on the production, properties, and applications of magnesium and magnesium alloys. It discusses the various extraction methods for magnesium including calcination, the Pidgeon process, and the Dow process. It also outlines casting techniques for magnesium alloys such as die casting, squeeze casting, and thixocasting, and describes approaches for grain refinement.
Titanium is named after the Titans, the
powerful sons of the earth in Greek mythology.
• Titanium is the forth abundant metal on
earth crust (~ 0.86%) after aluminium, iron and
magnesium.
Titans
homepage.mac.com
Rutile (TiO2)
mineral.galleries.com
Ilmenite (FeTiO3)
• Not found in its free, pure metal form in
nature but as oxides, i.e., ilmenite (FeTiO3)
and rutile (TiO2).
• Found only in small amount in Thailand...
This document discusses the properties and applications of aluminum and its alloys. It outlines that aluminum is lightweight, corrosion resistant, and electrically and thermally conductive. However, in its pure form aluminum is soft and has a low melting point. The document then discusses how aluminum is commonly alloyed with other metals like copper, magnesium, and manganese to increase its strength and maximum operating temperature. These aluminum alloys have many applications in transportation, infrastructure, consumer goods, and oil and gas due to their high strength to weight ratio and corrosion resistance.
Recrystallization is the process in which deformed grains of the crystal structure are replaced by a new set of stress-free grains that nucleate and grow until all the original grains have been consumed. The process is accomplished by heating the material to temperatures above that of crystallization.
Diffusion bonding is a solid-state welding technique that joins materials together through atomic diffusion without melting. It involves applying high pressure and moderate heat to join carefully cleaned and mated surfaces. Diffusion occurs in two stages - initial metal-to-metal contact formation followed by atomic diffusion and grain growth across the interface to form a complete bond. Various factors like temperature, pressure, time and surface preparation influence the diffusion rate. Common diffusion bonding methods include gas pressure bonding, vacuum fusion bonding and eutectic bonding. Diffusion bonding finds applications in the fabrication of components for industries like aerospace, nuclear and others.
The document discusses several types of engineering ceramics including alumina, silicon carbide, silicon nitride, partially stabilized zirconia, and sialon. It describes their key properties such as hardness, heat resistance, strength, and applications in areas like abrasives, cutting tools, bearings, and high temperature components. Ceramics are brittle but can withstand high temperatures and harsh environments better than metals or polymers.
There are two types of CCT (continuous cooling transformation) diagrams that plot the start, fraction, and finish of transformation temperatures against cooling time or rate. CCT diagrams measure the extent of transformation as a function of cooling time at continuously decreasing temperatures. The main difference from TTT diagrams is that continuous cooling does not allow for bainite formation and always results in pearlite. Properties like hardness and strength depend on the formed microstructure constituents like pearlite, bainite, and martensite, which are affected by factors like carbon content, alloying elements, and grain size.
This document provides an overview of a lecture on aluminium alloys. It discusses the subjects that will be covered, including the production, properties, and applications of aluminium alloys. The production of aluminium is explained, outlining the Bayer process and Hall–Héroult process. The physical properties of aluminium are presented. Methods of extracting aluminium from bauxite and other sources are summarized.
Molten steel is tapped into a ladle and alloying elements are added before being cast into molds. Steel ingots can have square, round, or polygon cross-sections depending on their intended use - squares for rolling, rectangles for flat products, and rounds for tubes. Ingot casting molds are made of cast iron and come in two types - wide end up or narrow end up. As the steel solidifies in the mold, it forms three distinct zones - a thin chill zone against the mold walls, columnar zones of elongated crystals perpendicular to the walls, and an inner equiaxed zone of larger isotropic crystals.
This document provides an overview of phase diagrams and transformations. It discusses:
- Types of phase diagrams including temperature-composition, pressure-temperature diagrams and their significance
- The Gibbs phase rule and how it relates to phase diagrams
- Binary phase diagrams and examples like Cu-Ni
- Equilibrium and non-equilibrium solidification and how they differ in terms of microstructure development
1. Alloys are made of two or more metals to obtain desired properties like strength, toughness, corrosion resistance that pure metals lack.
2. A solid solution is a homogeneous mixture of atoms where solute atoms substitute or fit in the lattice structure of the solvent metal.
3. Cooling curves and phase diagrams are used to understand the solidification process of alloys and predict the phases present at various temperatures and compositions.
DJJ3213 MATERIAL SCIENCE CHAPTER 4 NOTE.pptfieyzaadn
The document discusses material science concepts related to solid solutions and phase diagrams. It begins by describing the stages of grain structure formation during solidification. It then differentiates between base metals and alloys, describing various types of solid solutions like disordered, ordered, and interstitial. Terminologies in phase diagrams are explained, including phases, equilibrium, composition, liquidus, and solidus temperatures. Binary alloy systems containing two components are discussed. Finally, the key aspects of the iron-carbon phase diagram are summarized, including the various phases like ferrite, austenite, cementite, pearlite, and martensite that form at different temperature ranges and carbon concentrations.
The document discusses dislocation theory and behavior in different crystal structures. It covers:
- Observation techniques for dislocations like etching and transmission electron microscopy
- Key concepts like Burgers vector, dislocation loops, and dissociation of dislocations into partial dislocations
- Differences in dislocation behavior in FCC, BCC, and HCP lattices including slip systems and interactions between dislocations
- Stress fields and strain energies of dislocations as well as forces acting on dislocations and between dislocations
- Mechanisms of dislocation motion including glide, cross-slip, and climb that enable plastic deformation.
The document discusses time-temperature-transformation (TTT) diagrams, which show the kinetics of isothermal transformations in steel alloys. TTT diagrams plot temperature versus the logarithm of time and indicate when specific transformations start and end. They show that austenite is stable above the lower critical temperature but unstable below it. Depending on the cooling rate, austenite can transform into pearlite, bainite, or martensite. Slow cooling leads to full pearlite transformation, while very fast cooling results in full martensite formation. TTT diagrams provide information about transformation rates, temperatures, phases, and microstructure sizes.
The document discusses eutectic solidification, where a liquid transforms into two solid phases at a single temperature. It describes how one phase will form via diffusion in the liquid, depleting the local area of one constituent and pushing the composition into the solid phase range. This causes the second phase to form adjacent to the first. The two phases then grow side-by-side in a laminated microstructure. There are two types of eutectic solidification: normal, where the phases form alternate lamellae via diffusion between the phases; and anomalous, where one phase is capable of faceting and forms irregular microstructures sensitive to growth conditions.
This document discusses time-temperature-transformation (TTT) diagrams and continuous cooling transformation (CCT) diagrams. TTT diagrams show the transformation of austenite at constant temperatures over time, indicating what microstructures form during different cooling rates. CCT diagrams track phase changes during continuous cooling at various cooling rates. Both diagrams are important for selecting processing conditions to achieve desired material properties in steels. The document provides detailed explanations of the various microstructures - pearlite, bainite, martensite - that form during austenite decomposition, and how TTT and CCT diagrams can be used to understand their formation.
Austenitic iron is non-magnetic, while ferritic iron is magnetic, due to their different temperatures rather than phases. Magnetism in iron arises from electron spin alignment within atomic zones. Above the Curie temperature, thermal energy disrupts zone formation, eliminating magnetism. The Curie point for iron is near austenite's stability range, but heating ferrite or quenching austenite above the Curie point also removes magnetism, demonstrating it is a temperature not phase effect.
The document discusses the iron-carbon phase diagram and the microstructures of plain carbon steels. It begins by explaining the different phases in the Fe-C system, including ferrite, austenite, cementite, and their crystal structures. It then describes how to properly draw the iron-carbon phase diagram, labeling important curves, temperatures, and carbon percentages. Finally, it illustrates the microstructures that form upon cooling for hypoeutectoid, eutectoid, and hypereutectoid plain carbon steels, such as proeutectoid ferrite, pearlite, and proeutectoid cementite.
Tool steels are high-quality alloy steels developed for shaping other materials. They contain carbon from 0.1-1.6% along with alloying elements like chromium, molybdenum, and vanadium. Tool steels offer better durability, strength, corrosion resistance, and temperature stability compared to other construction steels. They are used in applications involving forming, extrusion, and plastic molding. The document then discusses different types of tool steels categorized based on their intended use and hardening properties.
The document discusses the process of deoxidizing steel. During steelmaking, oxygen dissolves into the liquid steel but not in the solid steel. Deoxidation or "killing" of steel refers to reducing the excess oxygen content before casting to prevent blowholes and inclusions. This is typically done through precipitation deoxidation using elements like aluminum, silicon, and manganese that have a higher affinity for oxygen than iron and form stable oxides. These deoxidizers are chosen based on factors like stability, deoxidizing ability, oxide melting point and density. Aluminum is the most powerful deoxidizer but its oxide alumina must be modified to remain liquid during casting.
The document provides information on the production, properties, and applications of magnesium and magnesium alloys. It discusses the various extraction methods for magnesium including calcination, the Pidgeon process, and the Dow process. It also outlines casting techniques for magnesium alloys such as die casting, squeeze casting, and thixocasting, and describes approaches for grain refinement.
Titanium is named after the Titans, the
powerful sons of the earth in Greek mythology.
• Titanium is the forth abundant metal on
earth crust (~ 0.86%) after aluminium, iron and
magnesium.
Titans
homepage.mac.com
Rutile (TiO2)
mineral.galleries.com
Ilmenite (FeTiO3)
• Not found in its free, pure metal form in
nature but as oxides, i.e., ilmenite (FeTiO3)
and rutile (TiO2).
• Found only in small amount in Thailand...
This document discusses the properties and applications of aluminum and its alloys. It outlines that aluminum is lightweight, corrosion resistant, and electrically and thermally conductive. However, in its pure form aluminum is soft and has a low melting point. The document then discusses how aluminum is commonly alloyed with other metals like copper, magnesium, and manganese to increase its strength and maximum operating temperature. These aluminum alloys have many applications in transportation, infrastructure, consumer goods, and oil and gas due to their high strength to weight ratio and corrosion resistance.
Recrystallization is the process in which deformed grains of the crystal structure are replaced by a new set of stress-free grains that nucleate and grow until all the original grains have been consumed. The process is accomplished by heating the material to temperatures above that of crystallization.
Diffusion bonding is a solid-state welding technique that joins materials together through atomic diffusion without melting. It involves applying high pressure and moderate heat to join carefully cleaned and mated surfaces. Diffusion occurs in two stages - initial metal-to-metal contact formation followed by atomic diffusion and grain growth across the interface to form a complete bond. Various factors like temperature, pressure, time and surface preparation influence the diffusion rate. Common diffusion bonding methods include gas pressure bonding, vacuum fusion bonding and eutectic bonding. Diffusion bonding finds applications in the fabrication of components for industries like aerospace, nuclear and others.
The document discusses several types of engineering ceramics including alumina, silicon carbide, silicon nitride, partially stabilized zirconia, and sialon. It describes their key properties such as hardness, heat resistance, strength, and applications in areas like abrasives, cutting tools, bearings, and high temperature components. Ceramics are brittle but can withstand high temperatures and harsh environments better than metals or polymers.
There are two types of CCT (continuous cooling transformation) diagrams that plot the start, fraction, and finish of transformation temperatures against cooling time or rate. CCT diagrams measure the extent of transformation as a function of cooling time at continuously decreasing temperatures. The main difference from TTT diagrams is that continuous cooling does not allow for bainite formation and always results in pearlite. Properties like hardness and strength depend on the formed microstructure constituents like pearlite, bainite, and martensite, which are affected by factors like carbon content, alloying elements, and grain size.
This document provides an overview of a lecture on aluminium alloys. It discusses the subjects that will be covered, including the production, properties, and applications of aluminium alloys. The production of aluminium is explained, outlining the Bayer process and Hall–Héroult process. The physical properties of aluminium are presented. Methods of extracting aluminium from bauxite and other sources are summarized.
Molten steel is tapped into a ladle and alloying elements are added before being cast into molds. Steel ingots can have square, round, or polygon cross-sections depending on their intended use - squares for rolling, rectangles for flat products, and rounds for tubes. Ingot casting molds are made of cast iron and come in two types - wide end up or narrow end up. As the steel solidifies in the mold, it forms three distinct zones - a thin chill zone against the mold walls, columnar zones of elongated crystals perpendicular to the walls, and an inner equiaxed zone of larger isotropic crystals.
This document provides an overview of phase diagrams and transformations. It discusses:
- Types of phase diagrams including temperature-composition, pressure-temperature diagrams and their significance
- The Gibbs phase rule and how it relates to phase diagrams
- Binary phase diagrams and examples like Cu-Ni
- Equilibrium and non-equilibrium solidification and how they differ in terms of microstructure development
1. Alloys are made of two or more metals to obtain desired properties like strength, toughness, corrosion resistance that pure metals lack.
2. A solid solution is a homogeneous mixture of atoms where solute atoms substitute or fit in the lattice structure of the solvent metal.
3. Cooling curves and phase diagrams are used to understand the solidification process of alloys and predict the phases present at various temperatures and compositions.
DJJ3213 MATERIAL SCIENCE CHAPTER 4 NOTE.pptfieyzaadn
The document discusses material science concepts related to solid solutions and phase diagrams. It begins by describing the stages of grain structure formation during solidification. It then differentiates between base metals and alloys, describing various types of solid solutions like disordered, ordered, and interstitial. Terminologies in phase diagrams are explained, including phases, equilibrium, composition, liquidus, and solidus temperatures. Binary alloy systems containing two components are discussed. Finally, the key aspects of the iron-carbon phase diagram are summarized, including the various phases like ferrite, austenite, cementite, pearlite, and martensite that form at different temperature ranges and carbon concentrations.
The iron-carbon diagram (also called the iron-carbon phase or equilibrium diagram) is a graphic representation of the respective microstructure states depending on temperature (y axis) and carbon content (x axis).
Constitution of alloys – Solid solutions, substitutional and interstitial – phase diagrams, Isomorphous, eutectic, eutectoid, peritectic, and peritectoid reactions, Iron – carbon equilibrium diagram. Classification of steel and cast Iron microstructure, properties and application.
The iron-carbon phase diagram shows the equilibrium phases that exist at different temperatures depending on the carbon content of the alloy. It includes the following phases:
1) Ferrite - a body-centered cubic phase stable at lower temperatures.
2) Austenite - a face-centered cubic phase stable at intermediate temperatures.
3) Cementite - an iron-carbon intermetallic compound.
4) Pearlite - a lamellar structure of ferrite and cementite that forms during slow cooling of eutectoid steel.
5) Martensite - a super-saturated solid solution of carbon in ferrite that forms during rapid quenching.
This document provides an introduction to phase diagrams and phase equilibria. It defines key terms like system, phase, variables, components, alloys, and solid solutions. It describes Gibbs phase rule and how it relates the number of phases, components, and degrees of freedom in a system. It explains Gibbs free energy and how it indicates the thermodynamic stability of phases. It also discusses cooling curves for pure metals, binary solid solutions, eutectic alloys, and off-eutectic alloys. Hume-Rothery rules for solid solubility and interpreting phase diagrams are also summarized.
The document summarizes key aspects of the iron-iron carbide (Fe-Fe3C) phase diagram. It discusses the various phases present in the diagram, including α-ferrite, γ-austenite, δ-ferrite, cementite, and liquid iron-carbon solutions. The maximum solubility of carbon in each phase is specified. Microstructures that form via peritectic, eutectic, and eutectoid reactions are described. The development of microstructures for hypoeutectoid, eutectoid, and hypereutectoid steel compositions is explained. Methods for calculating phase fractions using lever rule are provided, along with example problems.
The document discusses the iron-carbon equilibrium diagram, which shows the different crystal structures of iron alloys at various temperatures and carbon concentrations. It defines the ferrite, austenite, and cementite phases and explains how their proportions change with cooling in hypoeutectoid, eutectoid, and hypereutectoid steel compositions. The key phase changes of peritectic, eutectic, and eutectoid reactions are also summarized along with how the diagram is used to understand the microstructures and properties of steels and cast irons.
The document discusses tensile testing and the properties that can be determined from a tensile test. It explains that a tensile test involves clamping a sample between grips and applying a load while measuring elongation. The stress-strain curve obtained provides important mechanical properties like elastic limit, yield strength, and tensile strength. Yield strength indicates the stress at which permanent deformation begins, while tensile strength is the maximum stress withstood before failure. The test determines how a material responds to applied forces and is important for material selection and design.
TTT curves and CCT curves relation with fatigueSeela Sainath
in this file all failures of materials and how to overcome if the metal bearing sudden load that is fatigue and what are the reasons of failures are discussed here.
The document discusses tensile testing and the properties that can be determined from a tensile test. It explains that a tensile test involves clamping a sample between grips and applying a load while measuring elongation. The stress-strain curve obtained provides important mechanical properties like elastic limit, yield strength, and tensile strength. Yield strength indicates the stress at which permanent deformation begins, while tensile strength is the maximum stress endured before failure. Overall, tensile testing allows direct comparison of a material's strength performance independent of sample size.
1. The document discusses the iron-carbon equilibrium diagram, which shows the different phases of iron as carbon content and temperature vary.
2. It describes the different phases of iron - ferrite, austenite, cementite - and how their crystal structures and carbon solubility change with temperature.
3. Pearlite, an important microstructure in steel, is a lamellar structure composed of alternating layers of ferrite and cementite that forms during a eutectoid reaction when austenite cools below 723°C.
Homework IV - Biomaterials Science
Generally, a phase diagram is a chart used to show conditions (temperature, pressure...) at which different thermodynamic states occur. Where each line represents the transitions between states.
IST - 4th Year - 2nd Semester - Biomedical Engineering.
The document discusses phase diagrams and their classification. It defines a phase diagram as a graph used to show equilibrium conditions between thermodynamically distinct phases. It classifies phase diagrams as unary, binary, ternary and quaternary depending on the number of components involved. Binary phase diagrams are described in more detail, including examples of eutectic, eutectoid, peritectic and peritectoid diagrams. Gibbs' phase rule and its application to phase diagrams is also covered. Homework questions on interpreting phase diagrams and performing equilibrium calculations are provided.
A phase diagram shows the equilibrium conditions between thermodynamically distinct phases at different temperatures and compositions. It plots temperature versus composition. The document discusses unary, binary, ternary and quaternary phase diagrams. It provides details on eutectic, eutectoid, peritectic and peritectoid phase diagrams. Gibbs' phase rule and condensed phase rule are also explained. An example iron-iron carbide binary phase diagram is shown and key areas like the eutectoid point are indicated.
The document discusses the iron-carbon phase diagram. It explains that the diagram shows the different phases that exist in iron-carbon alloys at various temperatures, including ferrite, austenite, cementite, pearlite, and martensite. The key phase transformations on the diagram are the peritectic reaction, eutectic reaction, and eutectoid reaction. The document summarizes how the microstructure of hypoeutectoid, eutectoid, and hypereutectoid steels changes during cooling based on their carbon content.
The document discusses the iron-carbon phase diagram, which maps the equilibrium phases present in iron-carbon alloys at different temperatures and carbon concentrations. It defines various phases including ferrite, austenite, cementite, pearlite, and martensite. The diagram shows three important reactions - the peritectic, eutectic, and eutectoid reactions. It explains how the microstructure of hypoeutectoid, eutectoid, and hypereutectoid steels changes during cooling based on their carbon content. The phase diagram is important for understanding heat treatments of steels and how carbon concentration affects the mechanical properties of different steel grades.
In their simplest form, steels are alloys of Iron (Fe) and Carbon (C). The Fe-C phase diagram is a fairly complex one, but we will only consider the steel and cast iron part of the diagram, up to 6.67% Carbon
The document discusses the iron-carbon phase diagram, which maps the different crystal structures that iron alloys adopt at various temperatures and carbon concentrations. It defines various structures including ferrite, austenite, cementite, pearlite, and martensite. The diagram shows three important reaction lines - the peritectic, eutectic, and eutectoid reactions. It explains how the microstructure of steels with different carbon levels transforms during heating and cooling, resulting in different microstructures like pearlite or ferrite/cementite mixtures. The phase diagram is important for understanding the properties of steels and their heat treatment.
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Heat treatment, phases, microstructures and its properties
1. Malaviya National Institute of Technology Jaipur
Submitted by
Basitti Hitesh
2017PMT5094Submitted to
Dr. V.K.Sharma
Heat Treatment, Phases, Microstructures and its properties
2. Phase
A Phase in a material in terms of its microstructure is a region that differs in
structure and/or composition from another region.
Phase diagram
Phase diagrams are graphical representations from which it is possible to know
number and types of phases present in a material at various temperature,
pressure and composition. The following important information can be obtained
from phase diagrams:
Number and types of phases present at different compositions and
temperatures under slow cooling (equilibrium) conditions.
Equilibrium solid solubility of one element in another.
Temperature at which an alloy starts solidifying undergoing slow cooling and
also the temperature range within which solidification take place.
Temperature at which different phases start melting and regions of stability of
phases in terms of temperature and composition.
3. Gibb’s phase rule:
The Gibb’s phase rule states that P+F=C+2 where
F is the degree of freedom, P is the number of phases and C is the number
of components. Gibb’s phase rule gives an idea on degree of freedom that is
permissible for a given number of components and phases in equilibrium.
Application of Gibb’s phase
rule
Fig. Phase diagram of water system
4. At triple point of water system, three phases are in equilibrium and water is a one
component system.
Now by applying Gibb’s phase rule F=C-P+2, we can write, for invariant
points-
F=1-3+2, i.e., F=0
Hence for this system at triple point, degree of freedom is zero which means
none of the variables viz. temperature and pressure can be changed and still
keeps three phases of coexistence. So triple point is called an invariant point.
Since most binary phase diagrams mainly deals with temperature-composition at
constant pressure at 1 atm, Gibb’s phase rule expressed as P+F=C+1.
5. Concept of solid solution:
An alloy is a mixture of two or more metals or a metal and nonmetal. Alloys
may have simple as well as complex structure. Solid solution is a simple type of
alloy. A solid solution is solid that consists of two or more elements atomically
dispersed in a single phase structure.
In other words, solid solution can be defined as an alloy of two or more metals,
or a metal and a nonmetal which is a single phase atomic mixture. There are
two types of solid solution –
Substitutional Solid Solution
Interstitial Solid Solution
6. Substitutional solid solution: In this type, solute atoms of one element can
substitute parent solvent atoms of another element. In Cu-Ni solid solution, Cu
atoms can replace Ni atoms in crystal lattice. The crystal structure of parent
solvent may remain unchanged, nut lattice may be distorted by the solute
atoms. This happens when there is significant variation in atomic diameters of
parent solvent atom and solute atoms.
7. Hume- Rothery, an English Metallurgist studied various alloy systems
including isomorphous Cu-Ni system and formulated the following
conditions for two elements to have complete solid solubility:
1) The crystal structure of each element of the solid solution must be the
same.
2) The size of the atoms of each of two elements must not differ by more
than 15%.
3) There should not be appreciable difference in electronegativities of the
two elements.
4) The elements should have the same valence.
8. Interstitial Solid Solution: This type of solid solution is formed when solute
atoms enter into the interstices of solvent atom lattice. Hydrogen, Carbon,
Nitrogen and Oxygen atoms are common which form interstitial solid
solutions.
12. The phase composition depending on the temperature and the carbon
content can be read off this dual diagram in which the stable system iron-
graphite (dotted lines) and the meta-stable system iron-carbide (solid lines)
are shown together.
The closeness of the equilibrium lines which correspond to one another
indicates that the difference in the stability of carbide and graphite in the
alloys is not large. Therefore, the carbon may be dissolved in the iron
after solidification or, however, may precipitate in the form of graphite.
Furthermore, it can also occur in the structure in a bound form as iron
carbide (Fe3C) and is dissolved in the α and γ solid solution in both systems.
The eutectic temperature of the iron-graphite reaction is considerably higher
than that of the iron-cementite reaction. In the case of slower cooling, mainly
graphite forms, in the case of accelerated heat dissipation, on the other hand,
mainly cementite. During annealing, graphite may form, reducing
the cementite content. The tendency for graphite to form
from cementite shows that iron or iron-rich solid solutions only form a stable
equilibrium with free carbon (graphite).
Nature of Duality in Fe-Fe3C phase diagram
13. Purpose of the iron-carbon phase diagram?
To know what will be the crystal structure and physical and chemical
properties of iron at known carbon percentage and temperature. provided
that slow and uniform cooling rate is there and no quenching.
14. Different phases present in Iron-Iron carbide system
‘γ’ phase or Austenite:
Interstitial solid solution of carbon in iron of FCC crystal structure having
solubility limit of 2.11 wt.% at 1147⁰C with respect to cementite. The stability of
the phase ranges between 727-1495⁰C and solubility ranges 0-0.77 wt.%C with
respect to alpha ferrite and 0.77-2.11 wt.% C with respect to cementite, at 0
wt.%C the stability ranges from 910-1394⁰C.
α - ferrite:
Interstitial solid solution of carbon in iron of BCC crystal structure (α-iron)
having solubility limit of 0.0218 wt % C at 727⁰C with respect to austenite.
The stability of the phase ranges between low temperatures to 910⁰C, and
solubility ranges 0.008 wt. % C at room temperature to 0.0218 wt%C at 727⁰C
with respect to cementite.
Pearlite:
This phase is a product of eutectoid decomposition of austenite into mixture of
ferrite and cementite (Fe3C).
15. Delta ferrite:
The high-temperature ferrite is labeled delta-iron, even though its crystal
structure is identical to that of alpha-ferrite. The delta-ferrite remains stable
until it melts at 1538 °C. Maximum solubility is 0.1 wt% C at 1495 °C.
Fe3C or Cementite:
Interstitial intermetallic compound of C & Fe with a carbon content of 6.67
wt.% and orthorhombic structure consisting of 12 iron atoms and 4 carbon
atoms in the unit cell. Stability of the phase ranges from low temperatures to
1227°C. This is a chemical compound of high hardness. In steel, it can be
associated with carbides of other elements, such as Mn.
Ledeburite :
Eutectic mixture of austenite and cementite is known as ledeburite.
16. Actually there is no difference in beta phase and alpha phase when we talk
about crystal structure of iron. Beta phase has the same structure as the
alpha phase. The only difference is the magnetic properties which are
absent in beta phase due to the expanded lattice parameter.
Why beta phase is not there in iron carbon phase
diagram?
17. Why is solubility of ‘C’ higher in FCC than in
BCC?
Austenite is having FCC (Face Centred Cubic) structure and Ferrite is
having BCC (Body Centred Cubic) structure.
There are 2 types of interstitial sites octahedral & tetrahedral. In
FCC, octahedral void is significantly larger than tetrahedral void. Whereas in
BCC these are nearly same.
The total open space is shared by more number of sites. Therefore
interstitial gap in BCC is much smaller than that of FCC. This is why carbon
which occupies interstitial site has higher solubility in austenite (FCC).
19. Eutectic reaction:
Liquid↔Solid1+Solid2
Liquid (4.3wt%C) ↔ γ (2.11wt%C) + Fe3C (6.67 wt.%C) at 1147˚C
Liquid-100 wt.% →51.97wt% γ+Fe3C (48.11 wt.%)
The phase mixture of austenite and cementite formed at eutectic temperature
is called ledeburite.
20. Eutectoid reaction:
Solid1↔Solid2+Solid3
γ (0.77wt%C) ↔ α(0.0218 wt.%C) + Fe3C(6.67 wt.%C) at 727 ⁰ C
γ (100 wt.%) →α(89 wt.% ) +Fe3C(11 wt.%)
Typical density: α-ferrite=7.87 g/cm3
Fe3C=7.7 g/cm3
Volume ratio of α-ferrite: Fe3C=7.9:1
21. Sometimes the letters c, e, or r are included:
• Accm — In hypereutectoid steel, the temperature at which the solution of
cementite in austenite is completed during heating.
• Ac1 — The temperature at which austenite begins to form during heating, with
the c being derived from the French chauffant.
• Ac3 — The temperature at which transformation of ferrite to austenite is
completed during heating.
• Aecm, Ae1, Ae3 — The temperatures of phase changes at equilibrium.
• Arcm — In hypereutectoid steel, the temperature at which precipitation of
cementite starts during cooling, with the r being derived from the
French refroidissant.
• Ar1 — The temperature at which transformation of austenite to ferrite or to
ferrite plus cementite is completed during cooling.
• Ar3 — The temperature at which austenite begins to transform to ferrite during
cooling.
• Ar4 — The temperature at which delta-ferrite transforms to austenite during
cooling.
22. A1 = Temperature at which austenite begins to form during heating
A2 = Temperature at which alpha iron becomes non-magnetic
A3 = Temperature at which transformation of alpha iron to austenite is completed
during heating
A4 = Temperature at which austenite transforms to delta ferrite
Am = Temperature at which solutionizing of cementite in austenite is
complete
Critical Temperatures
23. Phase transformations may be classified according to whether or not
there is any change in composition for the phases involved. Those for
which there are no compositional alterations are said to be congruent
transformations. Conversely, for incongruent
transformations, at least one of the phases will experience a change
in composition. Examples of congruent transformations include
allotropic transformations and melting of pure materials. Eutectic and
eutectoid reactions, as well as the melting of an alloy that belongs to an
isomorphous system, all represent incongruent transformations.
Congruent Phase Transformation
24. The microstructure of crystalline materials is defined by the type, structure,
number, shape and topological arrangement of phases and/or lattice
defects .
Elements of microstructure: Point defects, point-defect clusters,
dislocations, stacking faults, grain boundaries, interphase interfaces are
important elements of the microstructure of most materials.
Definition of Microstructure
25. When Fe-alloy of 0.77% of C is cooled
slowly it transforms from single phase
of austenite to pearlite structure, a
lamellar or layered structure of two
phases: ferrite and cementite.
In the micrograph, dark regions
are cementite and bright regions
are ferrite
Microstructure of Eutectoid steel
26. Layered structures are formed
because of redistribution of C
atoms between ferrite (0.022 wt
%) and cementite (6.7 wt %) by
diffusion.
Mechanical properties of
pearlite are in between that of
ferrite (soft) and cementite
(brittle)
Formation of layered structure !
27. Fig. Photomicrographs of (a) α ferrite and (b) austenite (325X)
(copyright 1971 by united states steel corporation)
28. Fig. Photomicrograph of a
eutectoid steel showing the
pearlite microstructure consisting
of alternating layers of α ferrite
(the light phase) and Fe3C (thin
layers most of which appear
dark). 500X. (Reproduced with
permission from metals
handbook, 9th edition, Vol.9,
Metallography and
Microstructures, American
Society for Metals, Materials
park, OH, 1985.)
29. Fig. Schematic representations of
the microstructures for an iron-
carbon alloy of hypoeutectoid
composition C0 (containing less
than 0.76 wt% C) as it is cooled
from within the austenite phase
region to below the eutectoid
temperature.
30. Fig. Photomicrograph of a 0.38 wt% C steel having a microstructure consisting
of pearlite and pro-eutectoid ferrite. 635X. (Photomicrograph courtesy of
Republic Steel Corporation
31. Fig. Schematic
representations of the
microstructures for an iron-
carbon alloy of hyper
eutectroid composition
C1(containing between 0.76
and 2.14 wt% C), as it is
cooled from within the
austenite phase region to
below the eutctoid
temperature
32. Fig. Photomicrograph of a
1.4 wt% C steel having a
microstructure consisting
of a white proeutectoid
cementite network
surrounding the pearlite
colonies. 1000X.
(Copyright 1971 by United
States Steel Corporation
37. MARTENSITIC TRANSFORMATION
• Martensite: austenite quenched to roomtemperature.
• Austenite to martensite does not involve diffusion no activation: athermal
transformation.
• Each atom displaces small (sub-atomic) distance to transform FCC ƴ-Fe (austenite) to
martensite, a Body Centered Tetragonal (BCT) unit cell (like BCC, but one unit cell axis
longer than other two).
• Martensite is metastable - persists indefinitely at room T: transforms to equilibrium
phaseson at elevated temperature
• Sincemartensite is ametastable phase, it does not appear in Fe-Cphase
diagram. The amount of martensite formed is a function of the temperature to
which the sample is quenched and not of time.
• The shear changes the shape of the transforming region:
→ results in considerable amount of shear energy
→ plate-like shape of Martensite
38. The martensitic transformation involves the sudden reorientation of C and
Fe atoms from the FCC solid solution of γ-Fe (austenite) to a body
centered tetragonal (BCT) solid solution (martensite)
Austenite to Martensite
39. Fig. Microstructure of
martensite transformation
in Fe-31wt%Ni-0.02wt%C
transformed by cooling into
liquid nitrogen. Micrograph
obtained by J. R. C.
Guimarães.
40. Martensite is so brittle it needs to be modified for practical applications. Done by heating
to 250-650oC for some time.
Temperedmartensite,extremely fine-grained,well dispersed cementite grains in a
ferrite matrix.
Tempered martensite is more ductile.
Mechanical properties depend upon cementite particle size: fewer, larger
particles means less boundary area and softer, more ductile material - eventual
limit is spheroidite.
Particle size increases with higher tempering temperature and/or longer time
(more carbon diffusion)
Tempered Martensite
41. Tempered martensite is less brittle than martensite; tempered at 594°C.
Tempering reduces internal stresses caused by quenching.
The small particles are cementite; the matrix is α-ferrite. US Steel Corp.
4340 steel
42. Bainite is a Plate-like microstructure that forms in steels at temperatures
of 250–550 °C (depending on alloy content).
First described by E. S. Davenport and Edgar Bain, it is one of the
products that may form when austenite (the face centered cubic crystal
structure of iron) is cooled past a critical temperature.
This critical temperature is 1000 K (727 °C) in plain carbon steels.
Davenport and Bain originally described the microstructure as being similar
in appearance to tempered martensite.
A fine non-lamellar structure, bainite commonly consists of cementite
and dislocation-rich ferrite.
The high concentration of dislocations in the ferrite present in bainite
makes this ferrite harder than it normally would be.
BAINITE