Role of omega phase evolution in plastic deformation of twinning-induced plasticity β Ti-12V-2Fe-1Al alloy

The evolution of the omega phase and its role in plastic deformation in a twinning-induced plasticity beta Ti-12 V-2Fe-1Al alloy aged at 373-573 K have been studied in this work. The results show that isothermal omega forms at about 398 K and above, and the growth of isothermal omega is accompanied by a rejection of solute atoms from omega into beta. The composition partitioning increases internal elastic strain energy and hydrostatic pressure resulting from the coherency of isothermal omega phase in beta. Moreover, the isothermal omega phase becomes hard and even undeformable due to composition partitioning based on first-principles calculations. It is suggested that the internal elastic strain stabilizes the beta phase, which suppresses {332} deformation twinning and leads to dislocation glide and stress-induced omega phase transformation in the alloy aged at low temperature. And the embrittlement of the alloy aged at high temperature is thought to arise from undeformability of isothermal omega phase. (c) 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).