Load-biased shape-memory and superelastic properties of a precipitation strengthened high-temperature Ni50.3Ti29.7Hf20 alloy

A slightly Ni-rich NiTi–20Hf (at.%) alloy was aged for 3 h at 550 °C to form a homogeneous distribution of 10–20 nm precipitates. To determine the effect of such structures on the martensite–austenite transformation, preliminary load-biased shape-memory and superelastic properties were measured. The alloy exhibited reasonably high transformation temperatures, near-perfect dimensional stability and a work output as high as 18.7 J cm−3 during load-biased thermal cycling. Isothermal stress cycling of the austenite between 180 and 220 °C resulted in near-perfect superelastic behavior up to 3% applied strain.