9 Questions
What are the factors that influence diffusion in self-diffusion?
Temperature
What is the maximum solid solubility of carbon in ferrite?
0.022%
Pearlite is a type of microstructure in the heat treatment of ferrous alloys.
True
Aging is also known as __________ hardening.
age
Match the alloy heat treatment with its description:
Solution treatment = Heating to solid-solution phase and rapid cooling Precipitation hardening = Time and temperature-dependent process Maraging = Derived from martensite age hardening
What is self-diffusion?
The process whereby atoms of one metal diffuse to the same metal
Define hardenability of ferrous alloys.
Hardenability is the capability of an alloy to be hardened by heat treatment. It measures the depth of hardness that can be obtained by heating and subsequent quenching.
Match the following microstructures with their respective descriptions:
Pearlite = A mixture of ferrite and cementite phases with a lamellar structure Spheroidite = A microstructure resulting from a specific heat treatment process that changes the shape of cementite Bainite = A microstructure that forms at temperatures between pearlite and martensite transformation ranges Martensite = A microstructure that is the hardest and most brittle phase resulting from rapid quenching
What is the purpose of annealing in metalworking?
The purpose of annealing in metalworking is to restore a cold-worked or heat-treated metal or alloy to its original properties, increase ductility, reduce hardness and strength, modify the microstructure, relieve residual stresses, improve machinability, and enhance dimensional stability.
Study Notes
Self-Diffusion
- Self-diffusion is the process of atoms of one metal diffusing to the same metal
- Factors that influence diffusion are the diffusing species and temperature
Metal Alloys
- Alloys are composed of two or more chemical elements, at least one of which is a metal
- Most metals used in engineering applications are some form of alloy
Alloying
- Alloying consists of two basic forms: solid solution and inter-metallic compounds
The Iron-Carbon System
- Ferrite: a solid solution of body-centered cubic iron with a maximum solid solubility of 0.022% carbon at 727°C (1341°F)
- Ferrite is relatively soft and ductile, and is magnetic from room temperature to 768°C
- Austenite: has a solid solubility of up to 2.11% carbon at 1148°C
- Cementite: 100% iron carbide (Fe3C) with a carbon content of 6.67%, a hard and brittle inter-metallic compound
Heat Treatment of Ferrous Alloys (Microstructure)
- Pearlite
- Spheroidite
- Bainite
- Martensite
- Retained austenite
- Tempered martensite
Hardenability of Ferrous Alloys
- Hardenability is the capability of an alloy to be hardened by heat treatment
- It is a measure of the depth of hardness that can be obtained by heating and subsequent quenching
- The fluid used for quenching the heated alloy also affects hardenability
Heat Treatment of Non-Ferrous Alloys and Stainless Steel
- Solution treatment: heating the alloy to within the solid-solution phase and then cooling rapidly
- Precipitation hardening:
- Aging: a time and temperature dependent process, also known as age hardening
- Maraging: a precipitation-hardening treatment for a special group of high strength iron-base alloys, derived from martensite age hardening
Annealing
- Annealing is the restoration of a cold-worked or heat-treated metal or alloy to its original properties
- It increases ductility, reduces hardness and strength, or modifies the microstructure
- Annealing also relieves residual stresses in a manufactured part for improved machinability and dimensional stability
The Annealing Process
- Heating the workpiece to a specific range of temperature
- Holding it at that temperature for a period of time
- Cooling it slowly
Classifications of Annealing
- Process annealing: restoring ductility, part or all of which may have been exhausted by work hardening during cold working
- Stress-relief annealing: reducing or eliminating residual stresses
Self-Diffusion
- Self-diffusion is the process of atoms of one metal diffusing to the same metal
- Factors that influence diffusion are the diffusing species and temperature
Metal Alloys
- Alloys are composed of two or more chemical elements, at least one of which is a metal
- Most metals used in engineering applications are some form of alloy
Alloying
- Alloying consists of two basic forms: solid solution and inter-metallic compounds
The Iron-Carbon System
- Ferrite: a solid solution of body-centered cubic iron with a maximum solid solubility of 0.022% carbon at 727°C (1341°F)
- Ferrite is relatively soft and ductile, and is magnetic from room temperature to 768°C
- Austenite: has a solid solubility of up to 2.11% carbon at 1148°C
- Cementite: 100% iron carbide (Fe3C) with a carbon content of 6.67%, a hard and brittle inter-metallic compound
Heat Treatment of Ferrous Alloys (Microstructure)
- Pearlite
- Spheroidite
- Bainite
- Martensite
- Retained austenite
- Tempered martensite
Hardenability of Ferrous Alloys
- Hardenability is the capability of an alloy to be hardened by heat treatment
- It is a measure of the depth of hardness that can be obtained by heating and subsequent quenching
- The fluid used for quenching the heated alloy also affects hardenability
Heat Treatment of Non-Ferrous Alloys and Stainless Steel
- Solution treatment: heating the alloy to within the solid-solution phase and then cooling rapidly
- Precipitation hardening:
- Aging: a time and temperature dependent process, also known as age hardening
- Maraging: a precipitation-hardening treatment for a special group of high strength iron-base alloys, derived from martensite age hardening
Annealing
- Annealing is the restoration of a cold-worked or heat-treated metal or alloy to its original properties
- It increases ductility, reduces hardness and strength, or modifies the microstructure
- Annealing also relieves residual stresses in a manufactured part for improved machinability and dimensional stability
The Annealing Process
- Heating the workpiece to a specific range of temperature
- Holding it at that temperature for a period of time
- Cooling it slowly
Classifications of Annealing
- Process annealing: restoring ductility, part or all of which may have been exhausted by work hardening during cold working
- Stress-relief annealing: reducing or eliminating residual stresses
Understanding the properties of metal alloys, focusing on ferrous alloys and their heat treatments. Learn about self-diffusion and its influencing factors.
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