Superplasticity in the Ti–6Al–7Nb alloy processed by high-pressure torsion

Abstract

The Ti–6Al–7Nb alloy is considered a promising material for biomedical applications as it is free of V, which is replaced with Nb for better biocompatibility. This Ti alloy was processed by high-pressure torsion (HPT) at room temperature to refine the grain size to ~100nm. The Vickers microhardness was increased from 325 HV at the initial as-annealed state to 385 HV after the HPT processing. The HPT-processed samples were deformed under tension at 1073K (~0.58Tm, Tm is the melting point) with an initial strain rate in the range of 10–4 to 10–2s–1. The HPT-processed sample through 5 revolutions exhibited an excellent superplastic elongation of 930% at an initial strain rate of 2×10−3s−1. To conclude, HPT processing is effective in achieving superplasticity of the Ti–6Al–7Nb alloy.