Effect of Re addition on microstructure, properties, and performance of AlMo0.5NbTa0.5TiZr refractory high entropy alloy

The AlMo0.5NbTa0.5TiZr refractory high-entropy alloy (RHEA) is one of the prominent systems that has recently attracted significant attention mainly due to its significant high-temperature strength. In this study, the effect of Rhenium (Re) addition on microstructure, chemical composition, mechanical properties, corrosion behavior, and high-temperature oxidation characteristics of this alloy has been investigated. Addition of Re triggered the formation of a new Zr-rich intermetallic compound with hexagonal close-packed (HCP) structure and changed the orthogonal configuration of the nano-scaled basket-weave structure into a wavy pattern by affecting the diffusion rate during the spinodal decomposition process. While the hardness of the alloy in the homogenized state increased by 13% after Re addition, a slight decrease was observed in respect of toughness mainly due to the formation of the new HCP intermetallic phase. The Re-added alloy showed a reduced corrosion resistance, whereas an improved lower corrosion rate was recorded after Re addition. The high-temperature oxidation rate was shown to have been decreased slightly by Re addition because of relatively improved adhesion between the oxide layers and the substrate.