A comparison of warm and combined warm and low temperature processing routes for the equal-channel angular pressing of pure titanium.

Two different processing routes were used to investigate the microstructure and strength of commercial purity (CP) titanium of grade 4 processed by equal-channel angular pressing (ECAP). In the combined temperature (CT) route the specimens were pressed at 723 K in the first pass and at 373 K in the second pass but in the warm temperature (WT) route the specimens were pressed through two passes at 723 K. Both routes led to an inhomogeneous microstructure with average grain sizes of ~1.5 and ~1.7 um after the CT and WT routes, respectively. Both routes gave improved strengthening and higher hardness but the CT route with a lower temperature step gave the highest ultimate tensile strength of ~790 MPa. The inclusion of a lower temperature processing step may be important for optimizing the strength of CP Ti for use in medical implants