High-temperature oxidation behavior of a cast Ti-47.5Al-2.5V-1.0Cr-0.2Zr alloy

The oxidation behavior of the Ti-47.5Al-2.5V-1.0Cr-0.2Zr alloy at 900 °C was investigated at different oxidation times (5,20,60 and 100 h).The results show that the total weight gain of the alloy after 100 h at 900 °C oxidation is 9.1 g·m-2,and the oxidation rate decreases with oxidation time.The oxides on the alloy surface are mainly TiO2and Al2O3.At the beginning of oxidation (5 h),the oxide film is relatively complete,thin,and the interface between the oxide layer and the matrix is virtually flat.At the end of oxidation (100 h),the thickness of the oxide film is expanded,cracking and spalling occur,and the spalling form is intra-film spalling.At the same time,oxygen is mainly distributed in the oxide film and the oxygen content in the alloy substrate is reduced,confirming that the TiAl alloy has a certain oxidation stability at 900 °C.From the outer surface of the oxide layer to the matrix,the TiO2content increases and the Al2O3content decreases.Oxidation proceeds to completion in this system via the dissolution and diffusion of O atom.