On the widths of the hysteresis of mechanically and thermally induced martensitic transformations in Ni–Ti-based shape memory alloys

Abstract

Abstract It is well known that a good crystallographic compatibility between austenite and martensite in Ni–Ti-based shape memory alloys results in narrow thermal hystereses (e.g. Ball and James, Arch. Ration. Mech. Anal., 1987). The present work suggests that a good crystallographic fit is moreover associated with a small mechanical hysteresis width, observed during a forward and reverse stress-induced transformation. Furthermore, shape memory alloys with a good crystallographic fit show smaller transformation strains. The results obtained in the present study suggest that these correlations are generic and apply to binary Ni–Ti (with varying Ni contents) and quaternary Ni–Ti–Cu–X (X = Cr, Fe, V) alloys. For binary Ni–Ti, it was observed that Ni-rich compositions (good lattice fit) show a lower accummulation of irreversible strains during pseudoelastic cycling.