Improving oxidation resistance of TaMoZrTiAl refractory high entropy alloys via Nb and Si alloying

Here, we investigate the interplay effects of Si and Nb alloying on the oxidation behaviors of the refractory high entropy alloys (RHEAs) at 1000 ℃. The alloying of Nb and Si promotes the formation of dendritic microstructures, suppresses the transition from parabolic to linear oxidation kinetics and significantly improves the oxidation resistance. Severe cracking of oxide scales is also reduced via Nb and Si alloying. According to the scanning transmission electron microscopy analysis, ZrO₂ and TiO₂ are initially formed during oxidation, and oxidation proceeds with the inward diffusion of oxygen, preferentially through the interdendritic region and BCC grain boundaries.