Gaining understanding of the effect of alloy composition on the properties of Ti–Cu–Mn–Al alloys

Abstract

High performance cheaper Ti alloys can be developed based on the addition of several alloying elements, amongst which are Cu, Mn and Al. Studies are available in literature about binary and some ternary alloys based on the addition of these elements; however, no quaternary Ti–Cu–Mn–Al alloys were developed. Therefore, in this study quaternary Ti–Cu–Mn–Al alloys were manufactured via powder metallurgy to gain a better understanding of the effect of the alloy composition and the achievable mechanical performance. It is found that the selected quaternary Ti–Cu–Mn–Al alloys are characterised by a lamellar structure, which is progressively refined as the amount of alloying elements increases, and precipitation of the Ti2Cu intermetallic occurs if the Cu content is high enough. The amount of residual porosity increases and changes morphology as more thermal energy is invested in the diffusion of the alloying elements. In terms of mechanical behaviour, the quaternary Ti–Cu–Mn–Al alloys undergo both elastic and plastic deformation upon tensile loading. Strength and hardness linearly increase and the ductility monotonically decreases, which is the result of the compromise between the amount of residual porosity and the several strengthening mechanisms brought about by the actual total amount of alloying elements added.