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Bainite is a plate-like microstructure that forms in steels at temperatures of 125–550 °C (depending on alloy content). [1] First described by E. S. Davenport and Edgar Bain, [2] [3] it is one of the products that may form when austenite (the face-centered cubic crystal structure of iron) is cooled past a temperature where it is no longer thermodynamically stable with respect to ferrite ...
TTT diagram of isothermal transformations of a hypoeutectoid carbon steel; showing the main components obtained when cooling the steel and its relation with the Fe-C phase diagram of carbon steels. Austenite is slightly undercooled when quenched below Eutectoid temperature. When given more time, stable microconstituents can form: ferrite and ...
Metallography allows the metallurgist to study the microstructure of metals. A micrograph of bronze revealing a cast dendritic structure Al-Si microstructure. Microstructure is the very small scale structure of a material, defined as the structure of a prepared surface of material as revealed by an optical microscope above 25× magnification. [1]
These measurements may be made using manual procedures with the aid of templates overlaying the microstructure, or with automated image analyzers. In all cases, adequate sampling must be made to obtain a proper statistical basis for the measurement. Efforts to eliminate bias are required. An image of the microstructures of ductile cast iron
In carbon steel, for example, Widmanstätten structures form during tempering if the steel is held within a range around 500 °F (260 °C) for long periods of time. These structures form as a needle or plate-like growths of cementite within the crystal boundaries of the martensite.
300 series stainless steels are the larger subgroup. The most common austenitic stainless steel and most common of all stainless steel is Type 304, also known as 18/8 or A2. Type 304 is extensively used in such items as cookware, cutlery, and kitchen equipment. Type 316, also known as A4, is the next most common austenitic stainless steel.
Mild steel (carbon steel with up to about 0.2 wt% C) consists mostly of α-Fe and increasing amounts of cementite (Fe 3 C, an iron carbide). The mixture adopts a lamellar structure called pearlite . Since bainite and pearlite each contain α-Fe as a component, any iron-carbon alloy will contain some amount of α-Fe if it is allowed to reach ...
Eutectoid steel can in principle be transformed completely into pearlite; hypoeutectoid steels can also be completely pearlitic if transformed at a temperature below the normal eutectoid. [6] [7] Pearlite can be hard and strong but is not particularly tough. It can be wear-resistant because of a strong lamellar network of ferrite and cementite.