Tension–Compression Asymmetry of Commercially Pure Titanium: Strain Rate Sensitivity and Microstructure Evolution

Abstract

The behavior of hot-rolled commercially pure titanium under tension and compression was investigated at different strain rates, specifically from 1 × 10−5 s−1 to 5 × 10−3 s−1, at room temperature. Strong tension–compression asymmetry in yielding and strain hardening and its sensitivity to the strain rate were observed. With the increase of strain rate, the asymmetry in yielding and strain hardening increased because of the different strain rate sensitivity during tension and compression. Electron backscattered diffraction analysis was conducted to capture the relation between the microstructure evolutions (including twinning and texture evolution) and the macrostructure responses. The results showed that the microstructure texture had changed and a new component produced during compression was perpendicular to the rolling direction, which was associated with the formation of $$ \left\{ {10\bar{1}2} \right\} $$ extension twins. The fraction of twins activated during compression was much higher than that produced during tension. Specifically, the $$ \left\{ {10\bar{1}2} \right\} $$ twinning accommodated for the compressive deformation and played a major role in compressive strain hardening, whereas the dislocation mediated the plasticity under tension. The dominant twinning activity following the Basinski hardening mechanism, and the texture evolution affected by the dislocation slip and deformation twinning were responsible for the tension–compression asymmetry in the commercially pure titanium.