Stress-induced phase transformations in Ni–Mn–Ga alloys: experiments and modelling

Ni–Mn–Ga ferromagnetic shape memory alloys (FSMA) appear to be very promising active materials because they exhibit giant and fast strains. In this paper, a study of the martensitic transformation is proposed. The pseudoelastic behaviour under pure compression of a Ni49.7Mn27.7Ga22.9 single crystal previously measured for five different external temperatures (more than Ms0) by Pons et al. [Proceedings of ICOMAT 02, J. Phys. IV, in press]—compression axes of the initial cubic austenitic phase are 〈0 0 1〉 and 〈1 1 0〉—is compared to a model for ferromagnetic shape memory alloy pseudoelastic behaviour. The identification of model parameters permits to fit well the experimental results. Moreover a prediction of initiation surface of phase transformation (austenite→martensite) is proposed for Ni–Mn–Ga polycrystals under biaxial mechanical loadings.