Processing and properties of powder metallurgy Ti-Cu-Nb alloys

Abstract

Binary Ti-Cu and Ti-Nb alloys have been extensively studied for biomedical applications, but the potential of ternary Ti-Cu-Nb alloys, where the combined benefits of adding Cu and Nb on the performance of biomedical Ti alloys is harvested, has not been fully exploited. Therefore, this study aims to investigate the processing and properties of Ti-Cu-Nb alloys obtained via powder metallurgy. Independently of their actual chemistry, the studied Ti-Cu-Nb alloys are characterised by a lamellar microstructure, which is refined by the incremental addition of Cu+Nb, and a eutectoid substructure is formed for sufficiently high contents of Cu. The balance between slightly higher residual porosity and the microstructural changes, including the stabilisation of a greater amount of β phase, a lamellar structure with refined features, and the precipitation of the Ti2Cu intermetallic phase, leads to a monotonic linear increment of the resistance to plastic deformation. However, the ductility initially increases for small additions of Cu+Nb and subsequently decreases due to the change in failure mode induced by the progressively higher impact of the residual pores. The studied Ti-Cu-Nb alloys share the same strengthening mechanism and have better strength/ductility pairs with respect to binary Ti-Cu and Ti-Nb alloys and better elongation compared to cast Ti-Cu-Nb alloys.