Recovery Mechanisms in a Compressed Ni-Ti Superelastic Alloy

The stress-strain curve under compression showed the absence of the Stress-Induced-Martensite (SIM) plateau and 42% of remaining austenitic phase (B2). identified by the Electron Backscattered Diffraction (EBSD) technique on a Scanning Electronic Microscope (SEM). Annealing at 150 ºC increased the volume fraction of austenite to 70%.

Annealing at 200 ºC reduced the volume fraction of austenite to 33% and increased the classical Vickers hardness and the dynamic elastoplastic hardness. This increase suggests the presence of a phase with higher indentation resistance, which can be the R phase reported in the literature. Annealing at 250 ºC decreased the classical Vickers hardness and the dynamic elastoplastic hardness, probably due to recovery.