Effect of Al on the Isothermal Oxidation Behavior of a Ti70Zr20Ta10 Shape Memory Alloy at 900 °C

Ti70Zr20Ta10 alloy is a β-titanium based shape memory alloy with a high martensitic transformation temperature and large recoverable strain. It is thought to be to develop into a new generation of high-performance high-temperature shape memory alloy materials. By partially replacing the Ta element in the Ti70Zr20Ta10 alloy with Al, Ti-Zr-Ta-Al alloys with different Al contents were prepared. In this study, isothermal oxidation tests at 900 °C were conducted on Ti-Zr-Ta-Al alloys with different Al contents to investigate the effect of Al content on the high-temperature oxidation behavior of the Ti70Zr20Ta10 alloy. The results show that the isothermal oxidation kinetics curves of Ti70Zr20Ta10−xAlx (x = 0, 0.5, 1, 3 at.%) at 900 °C all follow a parabolic law. The oxide films formed on the alloy surface are mainly composed of TiO2, Ta2O5 and (Ti,Zr)O2. However, the surface of the oxide films is relatively rough. The films are not dense and there are pores and cracks, leading to spallation during the oxidation process. After the addition of Al, the high-temperature oxidation resistance of the Ti-Zr-Ta alloy is improved. When the Al content is 1 at.%, Ti70Zr20Ta9Al1 exhibits the best high-temperature oxidation resistance.