What is "martensite"

n. 1 (context metallurgy English) A solid solution of carbon in iron; the chief constituent of steel 2 (context physics chemistry English) Any crystal structure formed by a martensitic transition

n. a solid solution of carbon in alpha-iron that is formed when steel is cooled so rapidly that the change from austenite to pearlite is suppressed; responsible for the hardness of quenched steel

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. When viewed in cross section, the lenticular (lens-shaped) crystal grains are sometimes incorrectly described as acicular (needle-shaped).