Effect of Oxygen on the Microstructure and Mechanical Properties of Ti_1.5ZrNbMoV Refractory High-Entropy Alloy

Alloying is a crucial and effective strategy for developing high-entropy alloys (HEAs) with enhanced mechanical properties. In this study, a series of (Ti_1.5ZrNbMoV)_{100 − x}O_x refractory HEAs (x = 0, 0.5, 1.0, 1.5, 2.0, and 3.0) were prepared using a vacuum arc melting method. Within the given range of O content, the single body-centered cubic (BCC) solid solution structure of the base alloy remained unchanged. However, the morphology of the dendrites displayed noticeable alterations with increase in oxygen content. The study revealed a positive correlation between the oxygen content and the hardness and yield strength of the alloys. This trend was attributed to the presence of oxygen atoms in the solid solution of the BCC matrix, which contributed to the alloy’s enhanced strength. The alloy containing 0.5 at.% oxygen exhibited the highest ductility among all the studied compositions. The improved ductility could be attributed to the relatively large fraction of the dendrites with smoother and blunt boundaries. These features effectively reduced stress concentration and increased the complexity of the facture surface, thereby enhancing the ductility of the alloy. These findings provide valuable insights for tailoring the properties of high-entropy alloys by carefully controlling their oxygen content.