The document discusses heat treatment processes and concepts. It defines heat treatment as operations involving heating, soaking, and cooling to achieve desired microstructures and properties. The major objectives of heat treatment are outlined, such as increasing strength and hardness. Key concepts discussed include the Fe-C phase diagram, phases such as ferrite, austenite, and cementite, and critical temperatures. Common heat treatment processes are also mentioned such as annealing, hardening, and tempering.
The document discusses heat treatment processes and the iron-carbon phase diagram. It describes the various phases in steel like ferrite, austenite, cementite and pearlite. The critical temperatures on the Fe-C diagram are defined, including eutectoid temperature A1 and eutectic temperature A4. Micrographs show the microstructures of allotriomorphic ferrite, pearlite and ledeburite. The objectives of heat treatment like increasing strength and improving properties are mentioned.
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.
Cast iron is an alloy of iron and carbon. It exists in several forms depending on the carbon content and microstructure:
- Gray cast iron has 2-4% carbon present as graphite flakes, giving it a gray color. It has high compressive strength but is brittle. Widely used in machine bases.
- White cast iron has 1.75-2.3% carbon present as cementite, making it very hard and strong but brittle. Used for wear-resistant parts.
- Nodular or spheroidal graphite cast iron has graphite in spherical nodules, making it more ductile. Commonly used for pipes and fittings.
Heat treatment involves heating metals or alloys to specific temperatures, holding for durations, and cooling at controlled rates. This controls microstructure and properties. Key processes include annealing, stress relieving, hardening, tempering, and carburizing. Annealing relieves stresses and strains, improves machinability and ductility. Normalizing refines grains and relieves stresses. Stress relieving reduces stresses without changing microstructure.
The document introduces various steels and the steelmaking process. It discusses how pig iron is produced in a blast furnace and its composition. Steel is an iron alloy with up to 1.5% carbon and other elements that gives a wide range of strengths. The steelmaking process oxidizes carbon in pig iron and modern processes use oxygen. Ladle metallurgy is used to further refine steel. Steel can be cast, rolled, or delivered in other forms for different applications.
The document discusses various heat treatments used for steel, including quenching and tempering, spheroidizing, full annealing, and normalizing. It explains that quenching and tempering steel involves rapidly cooling steel from an austenite phase to form martensite, then reheating it to form tempered martensite which has improved ductility and toughness over martensite. Spheroidizing involves heating steel to just below the eutectoid temperature to form spherical cementite particles for improved machinability.
- Heat treatment is a method used to alter the physical and chemical properties of materials by heating or cooling them to extreme temperatures.
- Common heat treatments for steels include annealing, normalizing, and spheroidizing to produce specific microstructures like pearlite that improve properties like strength and machinability.
- Quenching involves rapidly cooling steel to form hard martensite, while tempering at lower temperatures increases toughness but decreases hardness.
- TTT and CCT diagrams are used to determine the microstructures that form during continuous cooling of steel based on factors like cooling rate. They indicate temperatures for phase transformations like austenite to pearlite or martensite.
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.
The document discusses heat treatment processes and the iron-carbon phase diagram. It describes the various phases in steel like ferrite, austenite, cementite and pearlite. The critical temperatures on the Fe-C diagram are defined, including eutectoid temperature A1 and eutectic temperature A4. Micrographs show the microstructures of allotriomorphic ferrite, pearlite and ledeburite. The objectives of heat treatment like increasing strength and improving properties are mentioned.
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.
Cast iron is an alloy of iron and carbon. It exists in several forms depending on the carbon content and microstructure:
- Gray cast iron has 2-4% carbon present as graphite flakes, giving it a gray color. It has high compressive strength but is brittle. Widely used in machine bases.
- White cast iron has 1.75-2.3% carbon present as cementite, making it very hard and strong but brittle. Used for wear-resistant parts.
- Nodular or spheroidal graphite cast iron has graphite in spherical nodules, making it more ductile. Commonly used for pipes and fittings.
Heat treatment involves heating metals or alloys to specific temperatures, holding for durations, and cooling at controlled rates. This controls microstructure and properties. Key processes include annealing, stress relieving, hardening, tempering, and carburizing. Annealing relieves stresses and strains, improves machinability and ductility. Normalizing refines grains and relieves stresses. Stress relieving reduces stresses without changing microstructure.
The document introduces various steels and the steelmaking process. It discusses how pig iron is produced in a blast furnace and its composition. Steel is an iron alloy with up to 1.5% carbon and other elements that gives a wide range of strengths. The steelmaking process oxidizes carbon in pig iron and modern processes use oxygen. Ladle metallurgy is used to further refine steel. Steel can be cast, rolled, or delivered in other forms for different applications.
The document discusses various heat treatments used for steel, including quenching and tempering, spheroidizing, full annealing, and normalizing. It explains that quenching and tempering steel involves rapidly cooling steel from an austenite phase to form martensite, then reheating it to form tempered martensite which has improved ductility and toughness over martensite. Spheroidizing involves heating steel to just below the eutectoid temperature to form spherical cementite particles for improved machinability.
- Heat treatment is a method used to alter the physical and chemical properties of materials by heating or cooling them to extreme temperatures.
- Common heat treatments for steels include annealing, normalizing, and spheroidizing to produce specific microstructures like pearlite that improve properties like strength and machinability.
- Quenching involves rapidly cooling steel to form hard martensite, while tempering at lower temperatures increases toughness but decreases hardness.
- TTT and CCT diagrams are used to determine the microstructures that form during continuous cooling of steel based on factors like cooling rate. They indicate temperatures for phase transformations like austenite to pearlite or martensite.
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.
The document discusses different types of metals and alloys used in engineering. It describes ferrous metals like steel and cast iron, which are alloys of iron and carbon. It also discusses nonferrous metals like aluminum and copper, as well as superalloys. Key production processes for metals are described, including ironmaking in a blast furnace and steelmaking using basic oxygen or electric arc furnaces. Phase diagrams are introduced to show the different phases that can exist in metal alloys at various temperatures and compositions.
The document discusses the iron-carbon phase diagram and the microstructures that form in steels of different carbon compositions. It defines the key phases - ferrite, austenite, cementite, pearlite - and explains how they form and transform based on the iron-carbon diagram. Specifically, it describes how hypoeutectoid, eutectoid, and hypereutectoid steels will transform as they cool, forming either primary ferrite, pearlite, or primary cementite structures respectively. The document provides detailed information on interpreting the iron-carbon phase diagram.
Topic related to material science and metallurgy, Includes basic information about steel.Also the Iron-Iron Carbon Diagrams and its structures with various features of fe-c diagram.
Austempered ductile iron production properties applicationsSAIFoundry
Austempered ductile iron (ADI) is an engineering material with good mechanical properties due to its unique microstructure of acicular ferrite and carbon-enriched stabilized austenite (ausferrite). The austempering process involves two stages - the first produces ferrite and high-carbon austenite, while the second decomposes austenite and forms carbides. Controlling the austempering time within the "process window" between these stages results in optimum properties. The microstructure and properties depend on factors such as austempering temperature, alloy content, and heat treatment parameters.
This lecture provides an introduction to the metallurgy of precipitation hardening, with a presentation of the fundamental mechanisms involved and illustrations from alloys which form the basis for engineering alloys. The Al-Mg<sub>2</sub>Si system is discussed in some detail because of its commercial importance. The microstructural aspects of precipitation hardening are illustrated by examples, many of which were obtained by electron microscopy; an outline of the background to electron microscopy is given in an appendix. Familiarity with the subject matter covered in earlier lectures 1201, 1202 and 1203 is assumed.
Molybdenum Market Overview of Current & Future SupplyPRABHASH GOKARN
The document discusses the various uses of molybdenum in metals and alloys. Specifically, it describes how molybdenum is used to improve the corrosion resistance and high-temperature strength of stainless steels. It also explains how molybdenum increases the hardenability, reduces temper embrittlement, and improves weldability of alloy steels and cast irons. Common alloys are listed along with their typical molybdenum contents.
This document discusses the development of bulk nanocrystalline steel with exceptionally high strength. It describes how bainite formation through isothermal or continuous cooling transformation can produce a nanocrystalline microstructure in steel. A specific alloy composition is presented that achieves a nanocrystalline microstructure with 20-40nm thick ferrite plates after transforming at 200C for 10 days. This results in an ultrahigh strength of 2.5GPa but maintains good ductility. The technique allows large component manufacturing and is cost effective.
1. The document discusses the Schaeffler diagram, which is used to predict the microstructure of stainless steel welds based on their composition. It also discusses modifications to the diagram by Delong.
2. The M3 concept for developing third generation advanced high strength steels is described, which aims to achieve ultrahigh strength and ductility through a multi-phase, meta-stable, multi-scale microstructure.
3. Quenching and partitioning heat treatments are summarized as a novel method to produce multi-phase steels with significant retained austenite through quenching to form martensite and austenite, followed by an isothermal treatment to partition carbon into the a
The document summarizes key concepts about the iron-carbon phase diagram and microstructures in steels. It describes the various phases in the Fe-Fe3C system, including α-ferrite, γ-austenite, δ-ferrite, and Fe3C cementite. It explains how the microstructure of steels, such as pearlite, depends on the carbon content and cooling rate. Phase transformations like the eutectoid reaction are also summarized.
Chapter 12 discusses ferrous alloys, including steels and cast irons. It covers how heat treatment and alloying can control the microstructure and properties of steels. Special classes of ferrous alloys examined are stainless steels and cast irons. Key topics covered include the designations and classification of steels, simple heat treatments like annealing and normalizing, isothermal heat treatments such as austempering, quench and temper heat treatments that produce martensite and tempered martensite, and the effects of alloying elements on properties.
This document discusses two new aluminum-lithium alloys, 2099 and 2199, for aerospace applications. It summarizes a trade study conducted between Alcoa and Bombardier using these alloys, which highlighted weight and performance benefits when alloys with optimized properties are selected for specific aircraft applications. Testing showed that 2199 plate provided up to 25% lower weight than alternatives for lower wing skins, while 2099 extrusions and 2199 sheet were best for lower wing stringers and fuselage skins, respectively. Properties of 2199 plate compared favorably to the incumbent 2024 alloy, with lower density, better corrosion resistance, and fatigue crack growth performance.
Here are the key steps to design a heat treatment for this application:
1. Determine the critical temperatures (A1, A3) for 1050 steel using the Fe-C phase diagram.
2. Refer to the TTT diagram for 1050 steel to determine the appropriate austenitizing temperature above A3.
3. Determine the appropriate quenching method and quenchant to transform the austenite to martensite for the desired hardness of HRC 23.
4. Determine the appropriate tempering temperature and time based on the TTT diagram to achieve a uniform tempered martensite microstructure.
5. Specify the full heat treatment procedure of austenitizing
This technical presentation summarizes ceramic composites. It begins by defining ceramics and composites. Ceramic composites have higher strength, damage tolerance, and toughness than monolithic ceramics due to reinforcement. Examples of structural ceramic composites in aerospace include rocket engine nozzles and scramjet engines. Case studies show ceramic composite armor provides ballistic impact protection while reducing weight compared to steel. Reinforcements like silicon carbide and matrices like alumina are discussed. In conclusion, ceramic composites are well-suited for applications requiring high-temperature or weight-constrained ballistic impact protection.
This article discusses the metallurgy of cast iron, which varies in composition depending on the type but generally contains 2-4% carbon. It explains that the carbon content and cooling rate determine whether the iron forms gray or white iron. Gray iron has graphite flakes in a matrix and is more ductile, while white iron contains cementite carbides and is very hard and brittle. The article describes different types of cast iron like spheroidal graphite iron and austempered ductile iron, and their microstructures and properties. It also discusses welding repairs for cast iron and challenges due to carbon pickup.
1. The document discusses nickel-based superalloys, which are metallic alloys developed to withstand high temperatures, often up to 70% of their absolute melting temperature. They have excellent creep, corrosion, and oxidation resistance.
2. Key features of nickel-based superalloys include a two-phase microstructure of gamma (γ) and gamma-prime (γ') phases that strengthen the alloy. Precipitation of γ' particles and formation of carbides at grain boundaries further increase the alloy's strength at high temperatures.
3. Alloying elements such as aluminum, titanium, and niobium promote the formation of γ' precipitates while chromium, molybdenum, and tung
Interstitial free (IF) steels were developed in Japan in 1970. They contain very low amounts of carbon (below 30 ppm) due to the addition of stabilizing elements like titanium and niobium that form carbides. This allows for high plasticity and formability. IF steels are used in automotive body parts and deep drawn household appliances due to their low yield strength to tensile strength ratio and ability to be deeply drawn. They are produced through vacuum degassing and stabilization to remove interstitial atoms from the iron lattice.
The document discusses the iron-carbon phase diagram. It describes three important reactions:
1) The eutectic reaction occurs at 4.3% carbon and 1,147°C, where liquid transforms to austenite and cementite.
2) The eutectoid reaction occurs at 0.76% carbon and 727°C, where austenite transforms to ferrite and cementite to form pearlite.
3) The peritectic reaction occurs at 0.16% carbon and 1,493°C, where liquid and delta-ferrite transform to austenite.
The phase diagram is used to explain the microstructures that form in steels with different carbon
2. magnesium, titanium and their alloysRahulRajelli
The document discusses magnesium and its alloys. It provides information on:
1. Common applications of magnesium alloys including in aerospace and automotive industries.
2. The physical and mechanical properties of magnesium such as its hexagonal crystal structure and low density.
3. Commercial magnesium alloys including Mg-Al casting alloys and Mg-Zn-Zr casting alloys.
4. Limitations of magnesium alloys including low strength and corrosion resistance.
Microstructure and Wear Behavior of B4C Particulates Reinforced Al-4.5%Cu All...IOSRJMCE
1) B4C particulates were added to an Al-4.5%Cu alloy matrix using stir casting to produce metal matrix composites (MMCs) with 2% and 4% B4C by weight.
2) Microstructural analysis found the B4C particles were uniformly distributed in the alloy matrix with no clustering or defects.
3) Dry sliding wear tests found the MMCs had lower wear than the unreinforced alloy, with wear resistance increasing with higher B4C content. The MMCs were more resistant to changes in load and sliding speed during wear testing.
The document provides information on heat treatment processes and the fundamentals of heat treatment of metals. It discusses the Fe-C equilibrium diagram and various phases in steel like ferrite, cementite, austenite, and pearlite. It describes the microstructure and properties of these phases. It also covers heat treatment processes like annealing, normalizing, hardening and discusses methods of surface hardening, heat treatment of cast irons and nonferrous metals. Various heat treatment parameters and objectives are defined. Diagrams of phase transformations and microstructures are included.
The document discusses different types of metals and alloys used in engineering. It describes ferrous metals like steel and cast iron, which are alloys of iron and carbon. It also discusses nonferrous metals like aluminum and copper, as well as superalloys. Key production processes for metals are described, including ironmaking in a blast furnace and steelmaking using basic oxygen or electric arc furnaces. Phase diagrams are introduced to show the different phases that can exist in metal alloys at various temperatures and compositions.
The document discusses the iron-carbon phase diagram and the microstructures that form in steels of different carbon compositions. It defines the key phases - ferrite, austenite, cementite, pearlite - and explains how they form and transform based on the iron-carbon diagram. Specifically, it describes how hypoeutectoid, eutectoid, and hypereutectoid steels will transform as they cool, forming either primary ferrite, pearlite, or primary cementite structures respectively. The document provides detailed information on interpreting the iron-carbon phase diagram.
Topic related to material science and metallurgy, Includes basic information about steel.Also the Iron-Iron Carbon Diagrams and its structures with various features of fe-c diagram.
Austempered ductile iron production properties applicationsSAIFoundry
Austempered ductile iron (ADI) is an engineering material with good mechanical properties due to its unique microstructure of acicular ferrite and carbon-enriched stabilized austenite (ausferrite). The austempering process involves two stages - the first produces ferrite and high-carbon austenite, while the second decomposes austenite and forms carbides. Controlling the austempering time within the "process window" between these stages results in optimum properties. The microstructure and properties depend on factors such as austempering temperature, alloy content, and heat treatment parameters.
This lecture provides an introduction to the metallurgy of precipitation hardening, with a presentation of the fundamental mechanisms involved and illustrations from alloys which form the basis for engineering alloys. The Al-Mg<sub>2</sub>Si system is discussed in some detail because of its commercial importance. The microstructural aspects of precipitation hardening are illustrated by examples, many of which were obtained by electron microscopy; an outline of the background to electron microscopy is given in an appendix. Familiarity with the subject matter covered in earlier lectures 1201, 1202 and 1203 is assumed.
Molybdenum Market Overview of Current & Future SupplyPRABHASH GOKARN
The document discusses the various uses of molybdenum in metals and alloys. Specifically, it describes how molybdenum is used to improve the corrosion resistance and high-temperature strength of stainless steels. It also explains how molybdenum increases the hardenability, reduces temper embrittlement, and improves weldability of alloy steels and cast irons. Common alloys are listed along with their typical molybdenum contents.
This document discusses the development of bulk nanocrystalline steel with exceptionally high strength. It describes how bainite formation through isothermal or continuous cooling transformation can produce a nanocrystalline microstructure in steel. A specific alloy composition is presented that achieves a nanocrystalline microstructure with 20-40nm thick ferrite plates after transforming at 200C for 10 days. This results in an ultrahigh strength of 2.5GPa but maintains good ductility. The technique allows large component manufacturing and is cost effective.
1. The document discusses the Schaeffler diagram, which is used to predict the microstructure of stainless steel welds based on their composition. It also discusses modifications to the diagram by Delong.
2. The M3 concept for developing third generation advanced high strength steels is described, which aims to achieve ultrahigh strength and ductility through a multi-phase, meta-stable, multi-scale microstructure.
3. Quenching and partitioning heat treatments are summarized as a novel method to produce multi-phase steels with significant retained austenite through quenching to form martensite and austenite, followed by an isothermal treatment to partition carbon into the a
The document summarizes key concepts about the iron-carbon phase diagram and microstructures in steels. It describes the various phases in the Fe-Fe3C system, including α-ferrite, γ-austenite, δ-ferrite, and Fe3C cementite. It explains how the microstructure of steels, such as pearlite, depends on the carbon content and cooling rate. Phase transformations like the eutectoid reaction are also summarized.
Chapter 12 discusses ferrous alloys, including steels and cast irons. It covers how heat treatment and alloying can control the microstructure and properties of steels. Special classes of ferrous alloys examined are stainless steels and cast irons. Key topics covered include the designations and classification of steels, simple heat treatments like annealing and normalizing, isothermal heat treatments such as austempering, quench and temper heat treatments that produce martensite and tempered martensite, and the effects of alloying elements on properties.
This document discusses two new aluminum-lithium alloys, 2099 and 2199, for aerospace applications. It summarizes a trade study conducted between Alcoa and Bombardier using these alloys, which highlighted weight and performance benefits when alloys with optimized properties are selected for specific aircraft applications. Testing showed that 2199 plate provided up to 25% lower weight than alternatives for lower wing skins, while 2099 extrusions and 2199 sheet were best for lower wing stringers and fuselage skins, respectively. Properties of 2199 plate compared favorably to the incumbent 2024 alloy, with lower density, better corrosion resistance, and fatigue crack growth performance.
Here are the key steps to design a heat treatment for this application:
1. Determine the critical temperatures (A1, A3) for 1050 steel using the Fe-C phase diagram.
2. Refer to the TTT diagram for 1050 steel to determine the appropriate austenitizing temperature above A3.
3. Determine the appropriate quenching method and quenchant to transform the austenite to martensite for the desired hardness of HRC 23.
4. Determine the appropriate tempering temperature and time based on the TTT diagram to achieve a uniform tempered martensite microstructure.
5. Specify the full heat treatment procedure of austenitizing
This technical presentation summarizes ceramic composites. It begins by defining ceramics and composites. Ceramic composites have higher strength, damage tolerance, and toughness than monolithic ceramics due to reinforcement. Examples of structural ceramic composites in aerospace include rocket engine nozzles and scramjet engines. Case studies show ceramic composite armor provides ballistic impact protection while reducing weight compared to steel. Reinforcements like silicon carbide and matrices like alumina are discussed. In conclusion, ceramic composites are well-suited for applications requiring high-temperature or weight-constrained ballistic impact protection.
This article discusses the metallurgy of cast iron, which varies in composition depending on the type but generally contains 2-4% carbon. It explains that the carbon content and cooling rate determine whether the iron forms gray or white iron. Gray iron has graphite flakes in a matrix and is more ductile, while white iron contains cementite carbides and is very hard and brittle. The article describes different types of cast iron like spheroidal graphite iron and austempered ductile iron, and their microstructures and properties. It also discusses welding repairs for cast iron and challenges due to carbon pickup.
1. The document discusses nickel-based superalloys, which are metallic alloys developed to withstand high temperatures, often up to 70% of their absolute melting temperature. They have excellent creep, corrosion, and oxidation resistance.
2. Key features of nickel-based superalloys include a two-phase microstructure of gamma (γ) and gamma-prime (γ') phases that strengthen the alloy. Precipitation of γ' particles and formation of carbides at grain boundaries further increase the alloy's strength at high temperatures.
3. Alloying elements such as aluminum, titanium, and niobium promote the formation of γ' precipitates while chromium, molybdenum, and tung
Interstitial free (IF) steels were developed in Japan in 1970. They contain very low amounts of carbon (below 30 ppm) due to the addition of stabilizing elements like titanium and niobium that form carbides. This allows for high plasticity and formability. IF steels are used in automotive body parts and deep drawn household appliances due to their low yield strength to tensile strength ratio and ability to be deeply drawn. They are produced through vacuum degassing and stabilization to remove interstitial atoms from the iron lattice.
The document discusses the iron-carbon phase diagram. It describes three important reactions:
1) The eutectic reaction occurs at 4.3% carbon and 1,147°C, where liquid transforms to austenite and cementite.
2) The eutectoid reaction occurs at 0.76% carbon and 727°C, where austenite transforms to ferrite and cementite to form pearlite.
3) The peritectic reaction occurs at 0.16% carbon and 1,493°C, where liquid and delta-ferrite transform to austenite.
The phase diagram is used to explain the microstructures that form in steels with different carbon
2. magnesium, titanium and their alloysRahulRajelli
The document discusses magnesium and its alloys. It provides information on:
1. Common applications of magnesium alloys including in aerospace and automotive industries.
2. The physical and mechanical properties of magnesium such as its hexagonal crystal structure and low density.
3. Commercial magnesium alloys including Mg-Al casting alloys and Mg-Zn-Zr casting alloys.
4. Limitations of magnesium alloys including low strength and corrosion resistance.
Microstructure and Wear Behavior of B4C Particulates Reinforced Al-4.5%Cu All...IOSRJMCE
1) B4C particulates were added to an Al-4.5%Cu alloy matrix using stir casting to produce metal matrix composites (MMCs) with 2% and 4% B4C by weight.
2) Microstructural analysis found the B4C particles were uniformly distributed in the alloy matrix with no clustering or defects.
3) Dry sliding wear tests found the MMCs had lower wear than the unreinforced alloy, with wear resistance increasing with higher B4C content. The MMCs were more resistant to changes in load and sliding speed during wear testing.
The document provides information on heat treatment processes and the fundamentals of heat treatment of metals. It discusses the Fe-C equilibrium diagram and various phases in steel like ferrite, cementite, austenite, and pearlite. It describes the microstructure and properties of these phases. It also covers heat treatment processes like annealing, normalizing, hardening and discusses methods of surface hardening, heat treatment of cast irons and nonferrous metals. Various heat treatment parameters and objectives are defined. Diagrams of phase transformations and microstructures are included.
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).
The document discusses the iron-iron carbide diagram and heat treatment processes for steels. It provides details on the phases in the Fe-C diagram including ferrite, cementite, austenite, and pearlite. It also summarizes common heat treatments like full annealing, normalizing, hardening, and tempering. Full annealing involves heating above A3 and furnace cooling to form coarse pearlite for high ductility. Normalizing involves heating above A3 and air cooling to form fine pearlite for improved hardness and ductility. Hardening involves heating above A3 and quenching to form martensite for high strength but brittleness, followed by tempering to improve toughness.
The document discusses heat treatment processes for steel, including purposes, defects, and specific processes. It describes annealing processes like full annealing, subcritical annealing, and spheroidizing annealing. It also covers normalizing to increase strength compared to annealing. Hardening and hardenability of steels are discussed, noting that hardening involves rapid cooling to form martensite for maximum hardness, while hardenability refers to how deep within a steel piece martensite can form during quenching.
The document discusses various types of cast iron, their microstructures, properties, production methods and applications. It describes the microstructures of gray cast iron, white cast iron, ductile cast iron and malleable cast iron. The key types are defined by the form of carbon in the microstructure, such as graphite flakes, nodules or carbide phases. The document also examines the solidification and processing factors that determine the carbon structure.
This document discusses various alloying elements that are added to steel to improve its properties. It explains that alloying elements like manganese, nickel, chromium, molybdenum, and vanadium can increase properties like hardenability, strength, toughness, wear resistance, and corrosion resistance in steel. It provides details on how different alloying elements affect the microstructure and properties of steel, including forming solid solutions, changing phase transformation temperatures, and modifying carbon solubility. Examples of various alloy steels are also summarized, such as stainless steel, tool steel, and high speed steel.
This document provides an overview of material science and engineering concepts related to iron-carbon alloys, including:
- The iron-carbon phase diagram, which shows the different phases that form based on carbon content and temperature. Key phases discussed include austenite, ferrite, pearlite, and cementite.
- The TTT (time-temperature-transformation) diagram, which shows the decomposition of austenite under non-equilibrium conditions based on time and temperature.
- Common heat treatment processes for steels like annealing, hardening, tempering, and their purposes. Hardening involves rapid cooling to form martensite for hardness while tempering reduces brittleness.
Microstructure and chemical compositions of ferritic stainless steelGyanendra Awasthi
This document discusses the microstructure and chemical compositions of ferritic stainless steel. It begins by defining ferrite as the body-centered cubic crystal structure of pure iron that gives steel and cast iron their magnetic properties. It then discusses how adding nickel changes the crystal structure from body-centered cubic to face-centered cubic. The document also examines the different groups of ferritic stainless steels based on their chromium content, from 10-14% chromium to those with over 18% chromium. It notes that ferritic stainless steels have lower strength at temperatures over 600°C but greater resistance to thermal shocks than austenitic stainless steels.
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.
Maraging Steels (Properties, Microstructure & Applications)MANICKAVASAHAM G
Maraging steel is used in aircraft, with applications including landing gear, helicopter undercarriages, slat tracks and rocket motor cases – applications which require high strength-to-weight material.
Maraging steel offers an unusual combination of high tensile strength and high fracture toughness.
Most high-strength steels have low toughness, and the higher their strength the lower their toughness.
The rare combination of high strength and toughness found with maraging steel makes it well suited for safety-critical aircraft structures that require high strength and damage tolerance.
This experiment investigates the heat treatment of steel through examining microstructures, hardness testing, and relating microstructure to hardness. Six steel specimens are subjected to different heat treatments - including austenitizing, quenching, and tempering - and their microstructures and hardness measured. The goals are to understand how heat treating alters steel microstructure and properties like hardness, and examine sources of error and relationships between different hardness tests.
This experiment investigates the heat treatment of steel through examining microstructures, hardness testing, and relating microstructure to hardness. Six steel specimens are subjected to different heat treatments - including austenitizing, quenching, and tempering - and their microstructures and hardness measured. The goals are to understand how heat treating alters steel microstructure and properties like hardness, and examine sources of error and relationships between different hardness tests.
various types of steel basically low carbon steels and alloy steels and how the alloying elements alter the various properties of steels , a detailed study & analysis
Maraging steels are carbon-free iron alloys that are strengthened through precipitation hardening rather than carbon content. They contain additions of nickel, cobalt, molybdenum, titanium, and aluminum. Maraging steels are heat treated through solution treatment to form a martensitic structure, followed by aging to precipitate hardening intermetallic compounds within the martensite. This provides maraging steels with ultra-high strength even at elevated temperatures, along with excellent toughness. Common applications include aerospace components, ordnance, and tooling due to their combination of high strength, corrosion resistance, and fatigue endurance.
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.
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Part1
1. Heat Treatment
R. Manna
Assistant Professor
Centre of Advanced Study
Department of Metallurgical Engineering
Institute of Technology
Banaras Hindu University
Varanasi-221 005, India
rmanna.met@itbhu.ac.in
Tata Steel-TRAERF Faculty Fellowship Visiting Scholar
Department of Materials Science and Metallurgy
University of Cambridge
Pembroke Street, Cambridge, CB2 3QZ
rm659@cam.ac.uk
2. HEAT TREATMENT
Fundamentals
Fe-C equilibrium diagram. Isothermal and continuous
cooling transformation diagrams for plain carbon and
alloy steels. Microstructure and mechanical properties of
pearlite, bainite and martensite. Austenitic grain size.
Hardenability, its measurement and control.
Processes
Annealing, normalising and hardening of steels,
quenching media, tempering. Homogenisation.
Dimensional and compositional changes during heat
treatment. Residual stresses and decarburisation.
2
3. Surface Hardening
Case carburising, nitriding, carbonitriding, induction and flame
hardening processes.
Special Grade Steels
Stainless steels, high speed tool steels, maraging steels, high strength
low alloy steels.
Cast irons
White, gray and spheroidal graphitic cast irons
Nonferrous Metals
Annealing of cold worked metals. Recovery, recrystallisation and grain
growth. Heat treatment of aluminum, copper, magnesium, titanium and
nickel alloys. Temper designations for aluminum and magnesium alloys.
Controlled Atmospheres
Oxidizing, reducing and neutral atmospheres. 3
4. Suggested Reading
R. E. Reed-Hill and R. Abbaschian: Physical Metallurgy
Principles, PWS , Publishing Company, Boston, Third Edition.
Vijendra Singh: Heat treatment of Metals, Standard Publishers
Distributors, Delhi.
Anil Kumar Sinha: Physical Metallurgy Handbook, McGraw-
Hill Publication.
H. K. D. H. Bhadeshia and R. W. K. Honeycombe: Steels-
Microstructure and Properties, Butterworth-Heinemann, Third
Edition, 2006
R. C. Sharma: Principles of Heat Treatment of Steels, New Age
International (P) Ltd. Publisher.
Charlie R. Brooks: Heat Treatment: Structure and Properties of
Nonferrous Alloys, A. S. M. Publication. 4
5. Definition of heat treatment
Heat treatment is an operation or combination of operations
involving heating at a specific rate, soaking at a temperature
for a period of time and cooling at some specified rate. The
aim is to obtain a desired microstructure to achieve certain
predetermined properties (physical, mechanical, magnetic or
electrical).
5
6. Objectives of heat treatment (heat treatment processes)
The major objectives are
• to increase strength, harness and wear resistance (bulk hardening,
surface hardening)
• to increase ductility and softness (tempering, recrystallization
annealing)
• to increase toughness (tempering, recrystallization annealing)
• to obtain fine grain size (recrystallization annealing, full
annealing, normalising)
• to remove internal stresses induced by differential deformation by
cold working, non-uniform cooling from high temperature during
casting and welding (stress relief annealing) 6
7. • to improve machineability (full annealing and normalising)
• to improve cutting properties of tool steels (hardening and
tempering)
• to improve surface properties (surface hardening, corrosion
resistance-stabilising treatment and high temperature
resistance-precipitation hardening, surface treatment)
• to improve electrical properties (recrystallization, tempering,
age hardening)
• to improve magnetic properties (hardening, phase
transformation)
7
8. Fe-cementite metastable phase diagram (Fig.1) consists of
phases liquid iron(L), δ-ferrite, γ or austenite, α-ferrite and
Fe3C or cementite and phase mixture of pearlite
(interpenetrating bi-crystals of α ferrite and cementite)(P) and
ledeburite (mixture of austenite and cementite)(LB).
Solid phases/phase mixtures are described here.
8
10. δ ferrite:
Interstitial solid solution of carbon in iron of body centred
cubic crystal structure (Fig .2(a)) (δ iron ) of higher lattice
parameter (2.89Å) having solubility limit of 0.09 wt% at
1495°C with respect to austenite. The stability of the phase
ranges between 1394-1539°C.
Fig.2(a): Crystal structure of ferrite
This is not stable at room temperature in plain carbon steel.
However it can be present at room temperature in alloy steel
specially duplex stainless steel.
10
11. γ phase or austenite:
Interstitial solid solution of carbon in iron of face centred cubic
crystal structure (Fig.3(a)) having solubility limit of 2.11 wt% at
1147°C with respect to cementite. The stability of the phase ranges
between 727-1495°C 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 910-1394°C.
Fig.3(a ): Crystal structure of austenite is shown at right
side. 11
12. Fig. 3(b): Polished sample held at austenitisation temperature.
Grooves develop at the prior austenite grain boundaries due to the
balancing of surface tensions at grain junctions with the free
surface. Micrograph courtesy of Saurabh Chatterjee.
12
13. α-ferrite:
Interstitial solid solution of carbon in iron of body centred
cubic crystal structure (α iron )(same as Fig. 2(a)) having
solubility limit of 0.0218 wt % C at 727°C with respect to
austenite.
The stability of the phase ranges between low temperatures to
910°C, and solubility ranges 0.00005 wt % C at room
temperature to 0.0218 wt%C at 727°C with respect to
cementite.
There are two morphologies can be observed under
equilibrium transformation or in low under undercooling
condition in low carbon plain carbon steels. These are
intergranular allotriomorphs (α)(Fig. 4-7) or intragranular
idiomorphs(αI) (Fig. 4, Fig. 8)
13
14. Fig. 4: Schematic diagram of grain boundary allotriomoph
ferrite, and intragranular idiomorph ferrite.
14
15. Fig.5: An allotriomorph of ferrite in a sample which is partially
transformed into α and then quenched so that the remaining γ
undergoes martensitic transformation. The allotriomorph grows
rapidly along the austenite grain boundary (which is an easy
diffusion path) but thickens more slowly. 15
16. Fig.6: Allotriomorphic ferrite in a Fe-0.4C steel which is slowly
cooled; the remaining dark-etching microstructure is fine
pearlite. Note that although some α-particles might be identified
as idiomorphs, they could represent sections of allotriomorphs.
Micrograph courtesy of the DOITPOMS project. 16
17. Fig.7: The allotriomorphs have in this slowly cooled low-
carbon steel have consumed most of the austenite before the
remainder transforms into a small amount of pearlite.
Micrograph courtesy of the DoITPOMS project. The shape of
the ferrite is now determined by the impingement of particles
which grow from different nucleation sites.
17
18. Fig. 8: An idiomorph of ferrite in a sample which is partially
transformed into α and then quenched so that the remaining γ
undergoes martensitic transformation. The idiomorph is
crystallographically facetted.
18
19. There are three more allotropes for pure iron that form under
different conditions
ε-iron:
The iron having hexagonal close packed structure. This forms
at extreme pressure,110 kbars and 490°C. It exists at the centre
of the Earth in solid state at around 6000°C and 3 million
atmosphere pressure.
FCT iron:
This is face centred tetragonal iron. This is coherently
deposited iron grown as thin film on a {100} plane of copper
substrate
Trigonal iron:
Growing iron on misfiting {111} surface of a face centred
cubic copper substrate. 19
20. 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
Fig.9(a): Orthorhombic crystal structure of cementite. The purple
atoms represent carbon. Each carbon atom is surronded by eight iron
atoms. Each iron atom is connected to three carbon atoms.
20
21. Fig.9(b): The pearlite is resolved in some regions where the
sectioning plane makes a glancing angle to the lamellae. The
lediburite eutectic is highlighted by the arrows. At high temperatures
this is a mixture of austenite and cementite formed from liquid. The
austenite subsequently decomposes to pearlite.
Courtesy of Ben Dennis-Smither, Frank Clarke and Mohamed Sherif
21
22. Critical temperatures:
A=arret means arrest
A0= a subcritical temperature (<A1) = Curie temperature of
cementite=210°C
A1=Lower critical temperature=eutectoid temperature=727°C
A2=Curie temperature of ferrite=768/770°C
A3=upper critical temperature=γ+α /γ phase field boundary
=composition dependent=910-727°C
A4=Eutectic temperature=1147°C
A5=Peritectic temperature=1495°C
22
23. Acm=γ/γ+cementite phase field boundary=composition dependent =727-
1147°C
In addition the subscripts c or r are used to indicate that the temperature is
measured during heating or cooling respectively.
c=chaffauge means heating, Ac
r=refroidissement means cooling, Ar
Types/morphologies of phases in Fe-Fe3C system
Cementite=primary (CmI), eutectic (Cmeu), secondary (CmII)(grain
boundary allotriomophs, idiomorphs), eutectoid (Cmed) and tertiary(CmIII).
Austenite= austenite(γ)(equiaxed), primary (γI), eutectic (γeu), secondary
(γII) (proeutectoid),
α-ferrite=ferrite (α) (equiaxed), proeutectoid or primary (grain boundary
allotriomorphs and idiomorphs)(αI), eutectoid(αeu) and ferrite (lean in
carbon) (α’).
Phase mixtures
Pearlite (P) and ledeburite(LB)
23
24. Fig.10: δ-ferrite in dendrite form in as-cast Fe-0.4C-
2Mn-0.5Si-2 Al0.5Cu, Coutesy of S. Chaterjee et al.
M. Muruganath, H. K. D. H. Bhadeshia
Important Reactions
Peritectic reaction
Liquid+Solid1↔Solid2
L(0.53wt%C)+δ(0.09wt%C)↔γ(0.17wt%C) at 1495°C
Liquid-18.18wt% +δ-ferrite 81.82 wt%→100 wt% γ
24
25. Fig.11: Microstructure of white cast iron containing
massive cementite (white) and pearlite etched with 4%
nital, 100x. After Mrs. Janina Radzikowska, Foundry
Research lnstitute in Kraków, Poland
Eutectic reaction
Liquid↔Solid1+Solid2
Liquid (4.3wt%C) ↔ γ(2.11wt%C) + Fe3C (6.67wt%C) at 1147˚C
Liquid-100 wt% →51.97wt% γ +Fe3C (48.11wt%)
The phase mixture of austenite and cementite formed at eutectic
temperature is called ledeburite.
25
26. Fig. 12: High magnification view (400x) of the white cast iron
specimen shown in Fig. 11, etched with 4% nital. After Mrs.
Janina Radzikowska, Foundry Research lnstitute in Kraków,
Poland
26
27. Fig. 13: High magnification view (400x) of the white cast
iron specimen shown in Fig. 11, etched with alkaline sodium
picrate. After Mrs. Janina Radzikowska, Foundry Research
lnstitute in Kraków, Poland
27
28. Eutectoid reaction
Solid1↔Solid2+Solid3
γ(0.77wt%C) ↔ α(0.0218wt%C) + Fe3C(6.67wt%C) at 727°C
γ (100 wt%) →α(89 wt% ) +Fe3C(11wt%)
Typical density
α ferrite=7.87 gcm-3
Fe3C=7.7 gcm-3
volume ratio of α- ferrite:Fe3C=7.9:1
28
29. Fig. 14: The process by which a colony of pearlite
evolves in a hypoeutectoid steel.
29
30. Fig. 15 : The appearance of a pearlitic
microstructure under optical microscope.
30
31. Fig. 16: A cabbage filled with water analogy of the three-
dimensional structure of a single colony of pearlite, an
interpenetrating bi-crystal of ferrite and cementite.
31
32. Fig. 17: Optical micrograph showing colonies
of pearlite . Courtesy of S. S. Babu.
32
34. Fig.19: Optical micrograph of extremely fine
pearlite from the same sample as used to
create Fig. 18. The individual lamellae cannot
now be resolved.
34
35. Evolution of microstructure (equilibrium cooling)
Sequence of evolution of microstructure can be described by
the projected cooling on compositions A, B, C, D, E, F.
At composition A
L δ+L δ δ+γ γ γ+αI α α’+CmIII
At composition B
L δ+L L+γI γ αI +γ αI+ (P(αed+Cmed)
αI(α’+CmIII)+(P(αed(α’ed+CmIII)+Cmed)
35
36. At composition C
L γ
At composition D
L
L+γI γII+CmII P(αed+Cmed)+CmII
P(αed (α’ed+CmIII)+Cmed)+CmII
L+γI γI+LB γI’(γII+CmII)+LB’ (γ’eu(γII+CmII)+Cmeu)
(P(αed+Cmed)+CmII)+ LB’ (P(αed+Cmed)+CmII+Cmeu)
(P(αed(α’ed+CmIII)+Cmed) +CmII)+ LB’
((P(αed(α’ed+CmIII)+Cmed)+CmII)+Cmeu)
36
37. At composition E
L
At composition F
L Fe3C
L+CmI LB(γeu+Cmeu+CmI
LB’ (γeu(γII+CmII)+Cmeu)+CmI
LB’ (P(αed+Cmed)+CmII)+Cmeu)+CmI
LB’ ((P(αed(α’ed+CmIII)+Cmed) +CmII)+ Cmeu)+CmI
37
38. Limitations of equilibrium phase diagram
Fe-Fe3C equilibrium/metastable phase diagram
Stability of the phases under equilibrium condition only.
It does not give any information about other metastable phases.
i.e. bainite, martensite
It does not indicate the possibilities of suppression of
proeutectoid phase separation.
No information about kinetics
No information about size
No information on properties.
38