Effect of atomic order on a martensitic transformation

Abstract A simple model is proposed to account for the influence of the β-phase atomic order on the martensitic transformation undergone by shape-memory alloys. The dependence of the elastic constants of the high-temperature phase on atomic order is calculated within the harmonic approximation, giving rise to a coupling between order and strain in the free energy of the alloy. This coupling term is quadratic in both order parameters and leads to a quadratic dependence of the transition temperature on atomic order.