Effect of Different Annealing Temperatures on the Phase Analysis, Microstructures and Corrosion Resistance of Binary Ti-Cu Alloys

One of the key challenges confronting the use of implant materials is degradation, which occurs when the biomaterial interacts with the human body physiological fluids. This degradation is referred to as corrosion; hence, corrosion resistance is one of the vital properties the implant material should possess. Among the few biocompatible and most promising implant materials for long-term use is titanium (Ti) and its alloys, which have been extensively applied in various fields due to their excellent mechanical properties, and promising corrosion resistance. Alloying Ti with small amounts of copper (Cu) does not only increase the strength and corrosion resistance but also exhibits antibacterial properties which are beneficial to implants transplants. In this study, two Ti-Cu alloys containing 5 and 10 weight percent (wt.%) compositions of Cu were produced using an arc-melting process under a controlled inert atmosphere. The cast ingots were annealed at 900 ℃ and 1050 ℃ for 2h followed by furnace cooling. Samples were cut into thin plates of about 3mm thickness and undergone phase, microstructural and electrochemical analyses. Characterisation using XRD and SEM-EDX techniques revealed strong presence of the α-Ti(Cu) phase forming below the eutectoid point and hypereutectoid intermetallic Ti₂Cu phase. The size and volume fraction of intermetallic phase was found to increase with both Cu content and increase in the annealing temperature. In summary, this study demonstrates a correlation between phase, morphology and corrosion resistance. Particularly, the XRD, SEM-EDX and the corrosion tests showed that, as the Cu content and annealing temperature increased in the binary Ti-Cu alloys, the amount and size of intermetallic phase(s) increased, corresponding with significantly improved corrosion resistance performance. Current results validate our recent theoretically formulated mechanism that links the alloy oxidation state to corrosion resistance, an indication that both the α-Ti and intermetallic phases contribute towards the improved corrosion resistance.