Martensite refers to specific microstructures created through a diffusionless transformation, maintaining a defined crystallographic relation between the original and new phases. This transformation produces a needle-like pattern in the microstructure of both ferrous and nonferrous alloys. The characteristics of martensite can vary depending on the placement of solute atoms within its lattice: when these atoms are in interstitial positions, like carbon in iron, the resulting structure is hard and highly strained. Conversely, when solute atoms are in substitutional positions, such as nickel in iron, the martensite is softer and more ductile. The proportion of the high-temperature phase that changes into martensite during cooling largely depends on the minimum temperature reached, with a distinct onset temperature (Ms) and a finishing temperature (Mf) where the transformation is nearly complete.
