Mechanical properties and shape memory behavior of ti-nb alloys

Mechanical properties and shape memory behavior of Ti-(20-29)at%Nb alloys were investigated in order to develop Ni-free biomedical shape memory alloys. The Ti-Nb alloys were fabricated by arc melting method. The ingots were cold-rolled with a reduction up to 95% in thickness and then solution treated at 1173 K for 1.8 ks. The martensitic transformation temperature decreased by 43 K per 1 at% increase of Nb content. The shape memory effect and superelastic behavior were observed at room temperature in the Ti-(22-25)at%Nb alloys and Ti-(25.5-27)at%Nb alloys, respectively. A small enthalpy of the martensitic transformation and a large difference between Ms and Mf were observed in the Ti-Nb alloys compared to Ti-Ni shape memory alloys. The maximum recovered strain of 3% was obtained at room temperature in solution treated Ti-(25-27)at%Nb alloys. The heat treatment at 573 K for 3.6 ks stabilized superelastic behavior of Ti-Nb alloys by increasing the critical stress for slip.