Enhanced oxidation resistance of TiAlNbCr processed by isothermal forging

Abstract

Poor ductility at room temperature and oxidation resistance at high temperature have hindered the wide usages of TiAl-based alloys, especially in advanced aero-engines. Room temperature ductility of TiAl-based alloys can be improved by grain refinement through the isothermal forging (ISF) method, whereas their oxidation behavior is unknown. In the present study, we investigate the oxidation behavior of TiAlNbCr -casting and -2nd-ISF alloys through the experiment of oxidation weight gain. Structure and phase characteristics before and after oxidation are examined through scanning electron microscopy, transmission electron microscopy and an electron probe microanalyzer. The results indicate that TiAlNbCr-2nd-ISF has higher oxidation resistance than that of TiAlNbCr-casting. The smaller grain size and more uniform structure of TiAlNbCr-2nd-ISF lead to the formation of smaller TiO2 particles on the alloy surface after oxidation, which is beneficial in hindering further diffusion of oxygen.