Titanium alloys developed on the basis of the addition of cheap strong eutectoid β-stabilisers

Abstract

Historically, titanium alloys have been developed disregarding the addition of eutectoid β-stabilisers as they generally lead to the formation of brittle intermetallic phases upon solidification of the alloy. However, such phenomenon can be prevented using powder metallurgy. Thus, this study considered the concurrent addition of cheap strong eutectoid β-stabilisers, namely Mn and Fe, for the development of new ternary Ti–Mn–Fe alloys, reducing the intrinsic cost of Ti alloys. It is found that the progressive addition of Mn and Fe in equal concentration enhances the densification of Ti during sintering, leading to lower amount of residual porosity, the transformation of the microstructure from purely lamellar to metastable, and the associated refinement of the microstructural features (grains and lamellae), as well as the stabilisation of a greater amount of β phase, and the formation of the metastable α″ phase. Such microstructural changes result in the strengthening (higher yield and ultimate tensile strength and hardness) and embrittlement of the alloy by changing the fundamental strain hardening mechanism of the ternary Ti–Mn–Fe alloys.