Thermo-mechanical processing and phase analysis of titanium alloys with copper additions

Abstract

In dentistry and orthopaedics, to replace and mend broken bones, any replacement material needs to have: low density, high strength, good biocompatibility and must be able to integrate closely with the bone. Titanium-based alloys have these properties, although currently used alloys contain toxic elements, and commercially pure Ti does not have sufficient strength. Within ten years, 7% of dental implants have complete failure, mainly from bacterial infection. Therefore α + β type Ti-alloys were developed by adding b stabilisers, with similar phase proportions to Ti-6Al-4V without the toxic elements, with Cu additions for antibacterial properties and Ru for corrosion resistance. Deformation behaviour of Ti-6Al-4V and Ti-Ta-Nb Zr alloys were also studied using a Gleeble thermomechanical simulator. The compositions of the new alloys were derived using Thermo-Calc. Ti-8Nb-4Zr alloys had bimodal microstructures and the addition of Cu formed the Ti2Cu phase. The Ti-6Ta-1.5Zr and Ti-6Ta-1.5Zr-0.2Ru alloys with no Cu had coarse α lamellae, whereas the alloys with Cu had parallel α plates. The Gleeble results showed that higher flow stresses were obtained at higher strain rates and lower temperatures, agreeing with literature. At 850 °C, the Ti-6Al-4V alloy had higher flow stresses than Ti-10.1Ta-1.7Nb-1.6Zr. The Ti-6Al-4V and Ti-10.1Ta-1.7Nb-1.6Zr alloys had steady-state flow stresses at 950 °C, and continuous flow softening at 850 °C for both strain rates.