Martenzitát

Martenzitát is a Hungarian term referring to martensite, a hard, brittle microstructural phase of steel. It is formed by the rapid cooling (quenching) of austenite. Austenite is a high-temperature phase of steel that is stable above a certain temperature. When steel is heated into the austenite range and then cooled quickly, the carbon atoms do not have enough time to diffuse out and form carbides. Instead, they become trapped within the iron lattice, distorting it into a body-centered tetragonal structure. This highly supersaturated solid solution of carbon in iron is known as martensite.

The formation of martensite is a diffusionless transformation, meaning it occurs almost instantaneously as the temperature drops below the martensite start (Ms) temperature. The degree of hardness and brittleness of martensite depends on the carbon content of the steel. Higher carbon content leads to a higher Ms temperature and a harder, more brittle martensite.

Martensite is typically undesirable in its as-quenched state due to its brittleness. Therefore, steel that has been quenched to form martensite is usually tempered. Tempering involves reheating the steel to a lower temperature for a specific period, which allows for some carbon diffusion and the formation of fine carbide precipitates. This process reduces brittleness and increases toughness while retaining a significant portion of the hardness. The resulting tempered martensite is a desirable microstructure for many applications requiring a combination of hardness and strength. The term martenzitát specifically highlights this phase in the context of Hungarian metallurgical terminology.