Investigations of mechanical properties and deformation behaviors of the Cr modified Ti–Au shape memory alloys

Abstract

In view of the population aging issues, the functional materials, Ti–Au–Cr shape memory alloys (SMAs), have been explored in this study for the crucial biomaterial applications. This ternary system was chosen for solving the hypersensitivity problem in the conventional SMAs containing Ni and also for its high X–ray contrast, which is an essential requirement in medical applications. Physical metallurgy methods were utilized for the specimen preparation and the fundamental properties and functional performances were also evaluated. Cold–workability was greatly improved with the Cr addition. The parent β–phase was stabilized by 4.5 at.% Cr alloying concentration, while the discrimination of the α′–martensite phase and the α′′–martensite phase at low Cr addition concentrations was clarified. Lattice parameters and the deformation strains were further calculated based on the results of the X–ray diffraction analysis. Most of the specimens possessed shape recovery upon heating, while the Ti–4.0Au–5.5Cr alloy showed an almost perfect shape recovery rate of 96.7%. Pseudoelastic behavior was observed in most of the alloys. The austenite transformation temperatures were determined by the step–by–step heating processes.