Superelastic properties of porous TiNi shape memory alloys prepared by hot isostatic pressing

The reactive sintering of Ni and Ti powders was successfully performed by hot isostatic pressing (HIP) and conventional sintering (CS). It was found that porous TiNi shape memory alloys (SMAs) manufactured by HIP show a homogeneous pore distribution with spherical pores, while the pores have irregular shape in the samples prepared by CS. The superelastic and fracture behaviors of porous TiNi SMAs, fabricated by HIP and CS, were investigated after they were aged at 450 °C for 30 min. It was found that the superelastic properties of porous TiNi SMAs prepared by HIP are superior to those fabricated by CS. The porous alloys fabricated by HIP exhibit almost complete superelasticity at room temperature, a flat yield plateau and small strain hysteresis with maximum recoverable strain of 4%. The present results suggest that the pore characteristics play a key role in mechanical properties and superelasticity of porous TiNi SMAs.