Martensitic transformation temperature in the Co–Ni–Al ferromagnetic shape memory system

Abstract

A mathematical expression relating the martensitic start transformation temperature with the composition of the 𝛽–phase for the Co-Ni-Al ferromagnetic shape memory alloy system is presented. The formula was obtained by fitting to selected published experimental data of transforming single 𝛽–phase alloys. The application to alloys that present a two-phase 𝛽+𝛾 structure is also discussed, obtaining in general good agreement. The validity of the equation is extended to different experimental conditions where the equilibrium 𝛽–phase fraction would not be achieved.