martensítica

Martensítica refers to a specific crystal structure and phase transformation that occurs in certain steels and other alloys. It is named after the German metallurgist Adolf Martens. The transformation involves a diffusionless process where the parent phase, typically austenite, rearranges its atomic structure upon rapid cooling. This rapid cooling, known as quenching, prevents the diffusion of atoms which would otherwise lead to the formation of softer phases like ferrite and pearlite. Instead, the austenite transforms into a body-centered tetragonal (BCT) structure called martensite.

The key characteristic of martensite is its hardness and brittleness. This is due to the strained crystal lattice, where carbon atoms are trapped in interstitial positions within the iron matrix, causing significant distortion. The degree of hardness depends on the carbon content of the steel; higher carbon content generally leads to harder martensite. While desirable for applications requiring high wear resistance and strength, the brittleness of martensite often necessitates further heat treatments, such as tempering, to reduce internal stresses and improve toughness. Tempering involves reheating the martensitic steel to a lower temperature for a period, allowing some carbon diffusion and the formation of fine carbide precipitates, thus increasing ductility while retaining a significant portion of the hardness. The formation and properties of martensite are fundamental concepts in the heat treatment of steels for various industrial applications.