Oxidation resistance properties of refractory high-entropy alloys with varied AlxCrTiMo content

The quaternary light refractory high-entropy alloys of AlxCrTiMo were fabricated by spark plasma sintering method. Investigation of the oxidation kinetics behavior of the alloys with different Al content at 1000 °C shows varying degrees of weight gain, and the curve of the sample with low Al concentration expresses distinctly different variation tendency. Formation process of oxide layers was analyzed and microstructure and cross sections of distribution of elements were examined by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). TiO2 and Al2O3 phases were observed on the oxide film after exposure to air at 1000 °C for 1 h and 7 h time intervals. These experiments show that the Al-content in the alloy can promote the formation of Al2O3, and the equilibrium of the volatilization rate of the refractory elements as well as the formation rate of the oxidation protective layer determines the weight gain of the AlxCrTiMo.