Effects of oxygen addition on the microstructure, phase transformations, and oxidation resistance of TiAl alloys

Abstract

This study investigated the effects of oxygen addition on the microstructure, phase transformations, and oxidation resistance of TiAl alloys at 1023 K. The addition of oxygen stabilized the α (α2) phase at the expense of the γ phase and reduced the oxidation mass gains of the TiAl alloys by more than 20%. Oxide scales composed of external scattered Ti-rich oxide particles/Al-rich/Ti-rich mixed Ti/Al oxides, and internal affected zones with Al-rich precipitates were observed in all oxidized samples. The results showed that the microstructure and phase transformations of the alloys were altered by adding 1 at% oxygen. The addition of O accelerated the α → α2 chemical ordering reaction and partly suppressed the α → γ massive phase transformation. The oxidation resistance of the TiAl alloys in air at 1023 K was not significantly affected by the addition of oxygen.