An unstable constituent in quenched steel, formed without diffusion and only during cooling below a certain temperature known as the Ms (or Ar) temperature. The structure is charac?terized by its acicular appearance on the surface of a polished and etched specimen. Martensite is the hardest of the transfor?mation products of austenite. Tetragonality of the crystal structure is observed when the carbon content is greater than about 0.05%.
The metastable iron-carbon solid solution phase with an acicular, or needle like, microstructure produced by a diffusionless transformation associated with the quenching of austenite.
A hard, brittle, constituent of carbon steel. It is formed when the steel is cooled rapidly by quenching.