Martensitiska

Martensitiska is an adjective used to describe materials or phases associated with martensite, the hard and typically brittle phase that forms in many iron-carbon alloys when austenite is rapidly cooled. The martensite transformation is diffusionless and involves a coordinated distortion of the crystal lattice, producing a body-centered tetragonal structure in iron with a high carbon content trapped in solution.

The transformation begins when the steel is cooled through the martensite start temperature (Ms) and finishes near the martensite finish temperature (Mf). The exact temperatures depend on carbon content and alloying elements. Because it is diffusionless, martensite forms very quickly, locking in high hardness and residual stress. In steels, the resulting microstructure can appear as plate or lath martensite, and is commonly rendered slightly tougher by tempering, which reduces brittleness through carbide precipitation and lattice relaxation.

Properties of martensitic steels include high hardness, high strength, and good wear resistance, but relatively low ductility and impact resistance if left untempered. Tempering improves toughness at the cost of some hardness. Martensitic microstructures are typical in quenched and tempered tool steels, high-carbon steels, and many stainless steels, where a combination of hardness and strength is desired.

In addition to steels, diffusionless martensitic transformations occur in other alloy systems, including certain shape memory alloys such as nickel-titanium (NiTi), where a martensitic transformation underlies functional properties.