plaatmartensiet

Plaatmartensiet, or plate martensite, is a morphological form of martensite observed in iron–carbon alloys. It arises during the diffusionless, shear-dominated transformation of austenite when steel is cooled rapidly enough to cross the martensite start temperature. The resulting structure is a mosaic of relatively flat, plate-like subunits that can align into larger packets within the prior austenite grains.

In microstructure, plate martensite consists of broad, plate-shaped features that are often organized into packets and blocks. This contrasts with lath martensite, which forms as finer, slender laths. The appearance and scale of plate martensite are influenced by factors such as carbon content, prior austenite grain size, and cooling rate. Higher-carbon steels and certain quench conditions tend to promote plate-like morphologies, while very rapid cooling or refined austenite grains can favor finer, lath-like martensite.

Mechanical properties of plate martensite reflect its high hardness and strength due to the supersaturated carbon in a body-centered tetragonal iron lattice. However, the plates and their boundaries can act as sites for crack initiation and reduced toughness. Heat treatment, such as tempering, is commonly used to decrease brittleness and improve ductility while retaining part of the strength gained from martensitic transformation.

Plaatmartensiet is a key consideration in steel heat-treatment design, affecting tuning of hardness, strength, and toughness. Its occurrence and morphology are determined by alloy composition, heat-treatment schedule, and the microstructural history of the prior austenite.