Effect of alloy empirical design parameters and process methods on refractory high-entropy alloys (RHEA) microstructure and mechanical properties: a review

High-entropy alloys (HEAs) possess unique strengthening mechanisms, and a vast design possibility, distinguishing them from conventional alloys. Refractory high-entropy alloys (RHEAs), a subclass of HEA, offer better high-temperature structural stability, making them ideal replacement for traditional high-temperature alloys. This review systematically evaluates the critical role of empirical alloy design parameters and processing methods in influencing the microstructure and mechanical properties of RHEAs. Key parameters, including enthalpy of mixing (ΔH_mix), atomic size difference (δ), valence electron concentration (VEC), Pauling electronegativity, and melting point are analyzed for their impact on phase formation and mechanical performance. Furthermore, the effects of various processing techniques, such as arc melting, powder metallurgy, and magnetron sputtering, are explored for their ability to optimize the microstructure and mechanical response. The review highlights the interplay between these factors, offering pathways for improving yield strength, ductility, and high-temperature softening resistance. These insights provide a foundational understanding of the factors governing the performance of RHEAs for high-temperature applications and outline pathways for future research and development.