High pressure torsion induced lowering of Young's modulus in high strength TNZT alloy for bio-implant applications

Abstract

An exceptional combination of low Young's modulus (E similar to 68 GPa) and high flow strength (sigma(f) similar to 1 GPa) was achieved for a consolidated beta-Ti-based metastable Ti-35Nb-7Zr-5Ta (TNZT) alloy subjected to room temperature high-pressure torsion (HPT). The mechanical properties of the alloy were studied by quasistatic nanoindentation tests at different strain rates, where a reduction in Young's modulus E similar to 73 GPa (N-HPT(10)) and E similar to 68 GPa (N-HPT(40)) is observed together with an increase in plastic deformability (or HPT rotations). The microstructure evolution with increasing shear strain has been investigated. The stabilized bcc beta-Ti phase with homogeneous nanostructure distribution was observed leading to a low Young's modulus. Severe straining causes a uniform hardness distribution without any noticeable change in the strength of the material. This study may be useful for developing excellent removable implant materials.