Influence of fabrication methods on the microstructures and hardness of Ti-Ni, Ti-Nb and Ti-Ta for biomedical applications

Abstract

Ti-based alloys namely, Ti-Ni, has been used as biomedical material due to its superior properties. However, it has been reported recently that nickel is toxic to the human body and thus alternative nickel-free alloys has been rigorously studied. The best candidate materials are Ti-Nb and Ti-Ta which are known to be biocompatible. These alloys maybe produced either via casting or through powder metallurgy route. Both production and fabrication methods produced dense and porous materials respectively which have different applications in biomedical field. This paper describes the influence of production and fabrication methods on the microstructures and hardness of nickel-free Ti-alloys, namely, Ti-Nb and Ti-Ta alloys with Ti-Ni as a reference alloy. The alloys were produced by three different methods: casting in vacuum induction furnace, compaction of powders followed by microwave sintering and compaction of powders followed by spark plasma sintering. The presence of porosity was analysed on the as cast and sintered samples by Archimedes drainage method while microstructures analysis was done using standard materials characterisation techniques such as optical and electron microscopy as well as X-ray diffractometry. Hardness test was also conducted by Vickers hardness test. It was found that the alloys with different production and fabrication methods give slight variation in the microstructures in terms of grain size and structures, porosity intensities and pore size. As-cast Ti alloys have the lowest amount of porosity and highest hardness values while Ti alloys fabricated by microwave sintering have the highest porosity content with lowest hardness values.