Mechanical properties of Ti–(∼49 at%) Ni shape memory alloy, part II: Effect of ageing treatment

Abstract

The present investigation aims to study the effect of ageing treatment on the mechanical properties and shape memory characteristics of the Ti-rich Ti–Ni alloy. The ageing treatment of the homogenized and deformed Ti-rich alloys results in the formation of Ti2Ni precipitate phase. The coarser precipitates occasionally provide the nucleation sites for the martensite plates. In the case of the deformed samples, the austenites to martensite and reverse transformations have been constrained due to the presence of deformation strain as evidenced from the corresponding XRD pattern. In the case of the aged samples, the martensitic transformation evolved through the one-stage (B2→B19′) and two-stage transformation routes via the formation of R phase. The most favorable shape recovery is achieved at the peak aged condition of the samples owing to the formation of optimum particle size conducive to delaying the onset of plastic straining.