Precipitation hardening and microstructure evolution of the Ti-7Nb-10Mo alloy during aging

A biomedical beta titanium alloy (Ti-7Nb-10Mo) was designed and prepared by vacuum arc self-consumable melting. The ingot was forged and rolled to plates, followed by quenching and aging. Age-hardening behavior, microstructure evolution and its influence on mechanical properties of the alloy during aging were investigated, using X-ray diffraction, transmission electron microscopy, tensile and hardness measurements. The electrochemical behavior of the alloy was investigated in Ringer's solution. The microstructure of solution-treated (ST) alloy consists of the supersaturated solid solution beta phase and the omega(ath) formed during athermal process. The ST alloy exhibits Young's modulus of 80 GPa, tensile strength of 774 MPa and elongation of 20%. The precipitation sequences during isothermal aging at different temperatures were determined as beta + omega(ath) -> beta + omega(iso) (144 h) at T-aging = 350-400 degrees C, beta + omega(ath) -> beta + omega(iso) + alpha -> beta + alpha at T-aging = 500 degrees C, and beta + omega(ath) -> beta + alpha at T-aging = 600-650 degrees C, where omega(iso) forms during isothermal process. The mechanical properties of the alloy can be tailored easily through controlling the phase transition during aging. Comparing with the conventional Ti-6Al-4 V alloy, the Ti-7Nb-10Mo alloy is more resistant to corrosion in Ringer's solution. Results show that the Ti-7Nb-10Mo alloy is promising for biomedical applications. (C) 2016 Elsevier B.V. All rights reserved.