Contribution of Twins to the Strengthening of Commercial Purity Titanium after Equal-Channel Angular Pressing
Room temperature equal-channel angular pressing (ECAP) was employed on commercial purity titanium in the present work. Mechanical twining was observed in ~90% grains while the grains were not significantly refined (~10 μm) after ECAP. TEM observations showed that the twins observed under OM are usually composed of a serial of parallel twin bands with a width of ~1 μm. Microhardness and tensile tests showed that such a coarse-grained microstructure combined with a high fraction of mechanical twins has a microhardness of ~ 240 Hv, yield strength of ~ 730 MPa, tensile strength of ~ 740 MPa and elongation to failure of ~ 16%. This yield strength is much higher than 620-640 MPa, the yield strength of ultrafine-grained titanium by 8~12 passes of ECAP at 450 oC with a grain size of 200-300 nm, and is close to ~ 790 MPa, the yield strength of commercial Ti-6Al-4V alloys.
Jing Tao Wang, Roberto B. Figueiredo and Terence G. Langdon
Y. Zhang et al., "Contribution of Twins to the Strengthening of Commercial Purity Titanium after Equal-Channel Angular Pressing", Materials Science Forum, Vols. 667-669, pp. 719-724, 2011