Al-induced self-forming oxide layer enhances high-temperature oxidation resistance of TiZrNb lightweight refractory multi-principal element alloy

Lightweight refractory multi-principal element alloys (MPEAs) based on the TiZrNb system have garnered significant attention for aerospace applications owing to their exceptional specific strength and high-temperature mechanical properties. However, their practical utility is hindered by poor oxidation resistance at elevated temperatures. This study investigates the effect of Al addition on the microstructural evolution and oxidation behavior of Al x (NbTiZr) 100- x ( x = 0, 4, 6, 8 at.%) MPEAs. The results demonstrate that the incorporation of Al promotes the formation of a protective Al 2 O 3 layer, which effectively inhibits oxygen diffusion into the alloy and significantly reduces the oxidation rate. This led to a 63% reduction in the oxidized weight gain of the alloy, decreasing from 179 mg/cm 2 to 66 mg/cm 2 after 50 hours of oxidation. Moreover, the addition of Al facilitates the formation of stable complex oxides, thereby further enhancing the oxidation resistance of the alloy. This study demonstrates that the addition of Al not only enhances oxidation resistance but also significantly increases the alloy's yield strength. These findings provide valuable insights for alloy design strategies aimed at simultaneously optimizing mechanical performance and high-temperature oxidation resistance.