Effect of high-pressure torsion processing on microstructure and mechanical properties of a novel biomedical β-type Ti-29Nb-13Ta-4.6Zr after cold rolling

Abstract

High mechanical biocompatibility, which implies excellent mechanical properties such as great strength and hardness with keeping low Young's modulus in a new biomedical β–type titanium alloy, Ti–29Nb–13Ta–4.6Zr (TNTZ), can be achieved by microstructural control. Strengthening of TNTZ by grain refinement and increasing dislocation density is expected to provide high mechanical strength with keeping low Young's modulus because they maintain the original β phase. In this case, high–pressure torsion (HPT) processing is one of the effective ways to obtain these properties simultaneously in this alloy. This study systematically investigated the effect of HPT processing on the microstructure and the mechanical properties of TNTZ. The microstructure of TNTZ, which was subjected to HPT processing after cold rolling, exhibits a single β phase composed of grains with diameter of less than a few hundred nanometres and high–angle boundaries. The grains have non–uniform subgrains with high angle misorientation and high dislocation density due to severe plastic deformation. The tensile strength of the specimen after HPT processing increases significantly compared with the specimen processed by cold rolling.