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Martensite, named after the German metallurgist Adolf Martens (1850–1914), most commonly refers to a very hard form of steel crystalline structure, but it can also refer to any crystal structure that is formed by diffusionless transformation. It includes a class of hard minerals occurring as lath- or plate-shaped crystal grains.
This structure is called martensite and is desired when maximum hardness is essential.
In the ordinary practice of hardening steels, the quenching is not so drastic, and the transformation of austenite back to ferrite and cementite is more or less completely effected, giving rise to certain transitory forms which are known as "martensite," "troostite," "sorbite," and finally, pearlite.
The engineers are running programs that show how adding tiny amounts of alloys to ferrite and martensite—crystalline structures of iron—during the steelmaking process changes the steel's strength, as well as its ability to be shaped into different parts.
When cooled rapidly, however, as in the tempering of steel, martensite remains a homogeneous solid solution, or hard steel.
When cooled slowly below 670 degrees, martensite yields a heterogeneous mixture of pearlite and ferrite (or cementite, if the original mixture contained between 0.8 per cent. and two per cent. of carbon).
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