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Effect of Ta addition on a heat-trated Ti-6Al-4V alloy

Abstract:

The development of the Ti-6Al-4V alloy has widened its range of potential applications, with biomaterial medical implants standing out due to their excellent mechanical properties, high corrosion resistance and good biocompatibility. The present study follows the microstructural changes and variations in Vickers hardness (VH) in a Ti-6Al-4V alloy with varying contents of Ta (4.8, 7.2 and 15.8 %). The aforementioned alloys were obtained by refusion in an electric arc furnace and were subject to a subsequent heat treatment at 850°C for one hour, and then cooled by air. The microstructural characterization was performed via Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Analysis (EDS) and X-Ray Diffraction (XRD). Additions of Ta coupled with the application of the heat treatment fostered changes in the α+β two-phase microstructure typical of these alloys, controlling both the growth of the acicular α phase (regarding size, thickness and orientation) at the expense of the β phase and the respective amounts of the present phases. An initial increase in alloy hardness as function of Ta content was observed, followed by a decrease in hardness as a result of both the smaller size and thickness of the acicular α phase (hcp) and the simultaneous increase in the proportion of the of the β phase (bcc).