Evolution of deformation mechanisms of Ti-22.4Nb-0.73Ta-2Zr-1.34O alloy during straining

The plastic deformation behavior of Ti-22.4Nb-0.73Ta-2Zr-1.34O alloy was investigated by compression testing at room temperature. The multi-peak stress oscillations of the true stress-strain curve, characterized by a stress plateau, initial strain-hardening, followed by strain-softening and a second strain-hardening stages, is observed in a titanium alloy for the first time. The experimental results show that the above four-stage plastic deformation behavior is caused by a change in the dominant deformation mechanisms. At the stress plateau stage, the alloy deforms via multiple plastic deformation mechanisms. The initial strain hardening is caused mainly by tangling of dislocations. Subsequent strain softening is due to the formation of kink bands. The second strain hardening corresponds to the formation of shear bands. The above results suggest that the dominant deformation mechanisms of Ti-Nb-Ta-Zr-O alloys are related not only to the stability of the beta phase, but also to the extent of plastic deformation. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.