Effect of Al content on the thermal oxidation behaviour of AlHfMoNbTi high-entropy alloys analysed by in situ environmental TEM

摘要

The high-temperature oxidation behaviours of AlxHfMoNbTi-series refractory high-entropy alloys with an Al content ranging from 0 to 20 at.% (x=0-1) were tested at 700-1000 degrees C. An in situ oxidation experiment was performed at 25-900 degrees C using environmental transmission electron microscopy (ETEM) to reveal the oxidation mechanism. The addition of Al to the HfMoNbTi alloy effectively increased the alloy strength and hardness. The improvement in oxidation resistance by Al addition is attributed to the formation of mixed oxide structures instead of layered oxides. Mo-rich precipitates are preferentially oxidized, and their volatilization at the metal/ oxide interface accelerates alloy oxidation.