Effect of omega phase on deformation behavior of Ti–7.5Mo–xFe alloys

In an earlier study, it was found that Ti–7.5Mo–1Fe and Ti–7.5Mo–2Fe alloys exhibited markedly different mechanical properties. While Ti–7.5Mo–2Fe alloy exhibited excellent mechanical properties, Ti–7.5Mo–1Fe alloy showed an extremely brittle behavior. The present study is a continual research on these two particular alloys with a focus on the effect of ω phase on the deformation behavior of the alloys. The results indicate that 2Fe alloy exhibited a ductile type fracture surface covered with normal deformation dimples. The fracture surface of 1Fe alloy exhibited a terrace-like morphology with numerous sub-micron-sized dimples. Throughout the entire plastically deformed region of 1Fe alloy, {1 1 2}〈1 1 1〉 type twins were observed, but few twins formed in 2Fe alloy. It is suggested that the numerous, larger-sized ω particles in 1Fe alloy have effectively restricted the slip of dislocations that largely limited plastic deformation capability of the alloy. The less and smaller ω particles could not do the same to 2Fe that led to the observed ductile behavior.