Martensitic transformation

Summary

A martensitic transformation is a solid-to-solid phase change in which the crystal lattice changes its shape by a coordinated shift of atoms, without diffusion. A high-symmetry phase, the austenite, changes into a low-symmetry phase, the martensite, which exists in several symmetry-related variants. The variants form fine twinned microstructures that fit together with the austenite, and these patterns are studied as energy-minimizing sequences in nonlinear elasticity. The transformation is behind the hardening of steel by quenching and behind the shape-memory effect of alloys such as nickel-titanium.