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 single α″ phase to α″ + β phases 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 increases α/β transformation temperature and promotes the precipitation of α phase during annealing in Ti–34Nb–0.2O alloy. α precipitates 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 of α phase. The cold rolling followed by annealing and addition of oxygen can improve the properties of alloys.