Influence of Fe addition in CP titanium on phase transformation, microstructure and mechanical properties during high pressure torsion

Abstract

In the present study, commercially pure (CP) titanium with four different Fe additions varying from 0.04 to 1.0 wt% were specifically deformed by high pressure torsion (HPT) process at room temperature. Significant influence of Fe content on the phase transformation, microstructure evolution, and mechanical properties were observed based on systematic evaluations. This study provided the first experimental evidence to support the previously reported theoretical calculation which predicted that the onset pressure of α→ω phase transformation in pure titanium decreased with increasing Fe addition. It has been found that ω phase only formed in CP titanium when it had Fe content higher than 0.25 wt% if the HPT process was conducted under 4.0 GPa. By comparison, ω phase was observed for all four Fe additions if the CP titanium was deformed under pressure of ≥6.0 GPa, with its volume fraction increasing significantly before 1 HPT rotation and then saturating after 10 rotations. Besides, the results also indicate that the Fe addition is very effective in enhancing the grain refinement and improving the mechanical properties of CP titanium by HPT deformation.