Morphology, microstructure, and mechanical properties of TiZrTa0.7NbMo refractory high-entropy alloy spherical powder prepared by ultrasonic atomization

Abstract

Refractory high-entropy alloys (RHEAs) have potential for high-temperature applications, such as aerospace and gas turbines, owing to their excellent mechanical properties at high-temperature. However, it is difficult to prepare high-quality spherical RHEA powders by conventional atomization techniques because of their high melting point and poor melt wettability. Therefore, the present study applies a novel technology, namely ultrasonic atomization, to prepare TiZrTa_0.7NbMo RHEA powder. The 2D morphology, 3D structural characteristics (i.e., sphericity and porosity), microstructure, and mechanical properties of the prepared RHEA powder are systematically studied. Scanning electron microscopy and micro-computed tomography indicate that the RHEA powder obtained following ultrasonic atomization have a narrow particle size distribution, high sphericity, low porosity, smooth surfaces, and no satellite balls. X-ray diffraction results show that the powder mainly comprises BCC1 and BCC2 phases. The microstructure of the powder is mainly dendritic, with fine dendrite spacing, and slight composition segregation is observed. Moreover, a small proportion of single-crystal powder particles are identified. The nano-hardness of the powder (average = 5.96 GPa; maximum = 6.18 GPa) is higher than that of the as-cast RHEAs of the same composition. Overall, this work demonstrates that high-quality RHEA spherical powder can be prepared via ultrasonic atomization, which is expected to be applied in additive manufacturing, powder metallurgy, and related fields in the future.