Martensitic transformation and superelasticity of Ti-Nb-Pt alloys

Abstract

Shape memory properties and martensitic transformation of Ti-Nb-Pt alloys were investigated in order to develop Ni-free biomedical superelastic alloys. The effect of Pt addition on the transformation strain was investigated by measuring the lattice constants of the parent and martensite phases of Ti-Nb-Pt alloys. The Ti-Nb-Pt alloys were fabricated by arc melting. The ingots were cold-rolled up to 99% reduction in thickness. The cold-rolled specimens were heat treated at 873 K for 0.6 ks. The shape memory effect and/or superelastic behavior were observed in the Ti-Nb-Pt alloys. The martensitic transformation temperature decreases by about 160 K with a 1 at% increase of Pt in the Ti-Nb-Pt alloys. The addition of Pt as a substitute of Nb was effective to increase the transformation strain when compared with compositions which reveal similar transformation temperatures. An aging treatment at 573 K was effective for increasing the stress for inducing the martensitic transformation and the critical stress for plastic deformation, resulting in good superelasticity. © 2007 The Japan Institute of Metals.