General Introduction
Austenite (γ-iron) is an important phase of iron and its alloys, and is an important component in the process of forming steel. Austenite generally has a body-centered cubic crystal structure, and its crystal lattice is composed of iron atoms, which can change with temperature and composition. Austenite is generally produced by heating the iron alloy above A1 point, which is a temperature-composition transform point, and is the first phase to form when heated above the critical point in the iron-carbon phase diagram. The process of austenitizing steel converts the structure of the steel from ferrite to austenite or a combination of both. The transformation of austenite to other iron-carbon alloys such as pearlite, martensite and bainite is necessary to obtain the desired properties in certain applications.
Austenite, also known as gamma iron, is a metallic material with a body-centered cubic crystal structure due to its iron atoms. It is a nonmagnetic material that can be formed from iron and its alloys, such as steel. The structure of the austenite is relatively inert and does not easily react with other materials.
Definition
Simply put, austenite is the solid-state phase of iron and its alloys between the temperature of 723°C (1,333°F) and the melting point of iron. It is also known as gamma iron, high temperature ferrite, or non-magnetic iron. Austenites crystal structure is composed of iron atoms that change with temperature and composition, and is generally produced by heating the iron alloy above A1 point.
Formation
Austenite can be formed in two ways. When an iron alloy is heated to a temperature above the A1 point, it undergoes a transformation called austenitizing and the structure changes from ferrite to austenite. The other way is by cooling the molten iron alloy. This cooling process is called quenching and it forms a structure called martensite, which is composed of austenite and some other elements, such as carbon or nitrogen.
Properties
The properties of austenite are determined by the temperature and composition of the iron alloy, and can vary from highly ductile and soft to hard and brittle. Austenite is a relatively inert material that does not easily react with other materials, making it suitable for various applications. It is also nonmagnetic, making it the ideal material for applications that require nonmagnetic properties.
Applications
Austenite is commonly used in the production of steel and its alloys. It is used to form different types of steel, such as carbon steel, stainless steel, and tool steel. Austenite can also be used to form other specialized alloys such as maraging steels and nitrogen steels. Austenite is also used to form the hardening structures in certain types of cast iron, such as manganese-alloyed and chromium-alloyed cast irons.
Conclusion
Austenite is a body-centered cubic crystalline form of iron and its alloys that can be formed by heating the alloy above A1 point and by cooling the molten alloy. The properties of austenite vary with temperature and composition and it is a relatively inert material that is nonmagnetic and suitable for various applications. Austenite is commonly used in the production of steel and its alloys, as well as other specialized alloys such as maraging steels and nitrogen steels.
