Effect of high-pressure torsion on the microstructure and wear behavior of NiTi alloy

Abstract

The wear property of NiTi is one of the most important properties of this alloy. In the current study, the effect of high-pressure torsion (HPT) process on the wear properties of an austenitic NiTi shape memory alloy is investigated. Full density NiTi samples with a composition of Ti-56 wt% Ni are fabricated using hot isostatic pressing (HIP), followed by the HPT process at room temperature, with an applied pressure of 6 GPa for 10 turns. The microstructural analysis reveals that the HIP-processed samples with a B2-NiTi phase evolve into significant grain refinement after HPT process and an interwoven B2-B19′ nanocrystalline/amorphous structure formed, leading to increased hardness in these samples. The results of the wear tests using a ball-on-disc configuration at room temperature demonstrate that the wear performance of the samples is improved after the HPT process. This is due to greater hardness and better pseudo-elasticity in the HPT-processed samples.