Effect of oxygen addition and annealing time on microstructure and mechanical properties of Ti-34Nb alloy

The effect of oxygen addition and annealing time on microstructure and mechanical properties of Ti-34Nb and Ti-34Nb-0.2O alloys was investigated.The addition of O suppresses the martensitic transformation.The phase composition changes from singleα''phase toα''+βphases with oxygen addition.The addition of oxygen increases strength significantly at as-received,cold-rolled,and annealed alloys through solid solution strengthening.The accumulation of abundance of defects and grain refinement introduced by cold rolling have a significant strengthening effect but also damage plasticity.The addition of oxygen increasesα/βtransformation temperature and promotes the precipitation ofαphase during annealing in Ti-34Nb-0.2O alloy.αprecipitates can inhibit grain growth during annealing.The strength decreases with annealing time increased due to the increase in grain size in Ti-34Nb alloy,while the strength increases in Ti-34Nb-0.2O alloy mainly due to the precipitation ofαphase.The cold rolling followed by annealing and addition of oxygen can improve the properties of alloys.