Microstructure and selected mechanical properties of aged Ti-15Zr-based alloys for biomedical applications

In this study, Ti-15Zr-xMo (5, 10, 15, and 20 wt%) alloys were submitted to solution and aging treatments and their effects evaluated in terms of phase composition and selected mechanical properties (Vickers microhardness and Young's modulus) for use as biomedical implants. The solution treatment was performed at 1123 K for 2 h, while aging treatments were carried out at 698 K for 4, 8, and 12 h, followed by water quenching. Phase composition and microstructure were dependent of the heat treatments, with Ti-15Zr-5Mo (alpha + beta type) and Ti-15Zr-10Mo (metastable beta type) alloys exhibiting intense alpha phase precipitation. The alpha-phase precipitates were related to alpha '' -> alpha and beta -> alpha phase decompositions. The Ti-15Zr-10Mo alloy exhibited an intermediary isothermal omega-phase precipitation after aging for 4 h. Vickers microhardness and Young's modulus values changed gradually with the amount of alpha phase. Aged Ti-15Zr-15Mo and Ti-15Zr-20Mo alloys presented better combinations of hardness and Young's modulus than CP-Ti and Ti-64 ELI for biomedical applications.