latmartensiet

Latmartensiet, also known as lath martensite, is a microstructural form of martensite found in iron-carbon alloys such as steel. It arises during the rapid cooling of austenite (quenching) when the diffusionless transformation converts the face-centered cubic structure of austenite into a body-centered tetragonal martensitic phase. The resulting microstructure is composed of slender, elongated laths of martensite that extend within prior austenite grains. These laths commonly form in packets and are separated by boundaries, creating a characteristic lamellar appearance under microscopy.

Lath martensite is one of the two main morphologies observed in quenched martensite, the other being plate martensite. Lath martensite tends to form in steels with lower to medium carbon content and under cooling conditions that favor rapid, but not excessively fast, transformation. Plate martensite, by contrast, is more typical in higher-carbon steels or under cooling histories that promote coarser austenite grains. The differing morphologies influence mechanical properties: lath martensite generally offers a favorable balance of hardness and toughness when tempered, although its properties are highly dependent on lath size, density, and packet structure.

Characterization often relies on transmission electron microscopy or electron backscatter diffraction to reveal the lath arrangement and habit planes. In heat treatment practice, the martensitic microstructure, including lath density and packet size, is a key factor governing the strength and ductility of quenched steel, and tempering further modifies the lath martensite into tempered martensite.