Microstructure evolution and corrosion behaviour of a high Mo containing α + β titanium alloy for biomedical applications.

In the present work, effect of heat treatment on microstructure and corrosion behaviour of a high Mo containing α + β titanium alloy (Ti-6Al-1 V-4Mo-0.1Si) has been investigated. Heat treatment results in the formation of wide variety of microstructure depending on the heating temperature (below or above the β transus) and cooling conditions. Martensite was observed after oil quenching (OQ), Widmanstatten α (α WS) + β after air cooling (AC) and lamellar α (α L) + β after furnace cooling (FC). The corrosion behaviour of the heat-treated specimens were studied in simulated body fluid (SBF) at 37 °C using open circuit potential-time (OCP), electrochemical impedance spectroscopy (EIS) and potentio-dynamic polarization tests. X-ray photoelectron spectroscopy (XPS) was used to investigate the chemical nature of the corroded surfaces. The study revealed that, in general, OQed samples had increased corrosion resistance than the ACed and FCed samples. XPS confirmed the presence of TiO 2 and Al 2 O 3 on the corroded sample. The alloy's improved corrosion resistance was attributed to stable inert TiO 2 film. Samples heat treated at 950 °C were found to have better corrosion resistance in general. • Martensite, Widmanstannen α, Basketweaven α structure were formed after heat treatments. • All samples exhibited self-passivation behavior in simulated body fluid solution. • XPS analysis confirmed the presence of TiO 2 and Al 2 O 3 layer. • The oxide film consisted of two layers i.e., outer porous layer and inner barrier layer. • Heat treatment in α + β region showed optimum corrosion properties. [ABSTRACT FROM AUTHOR]