Valence Electron Structures and Mechanical and Thermal Properties of Single-Phase Refractory High-Entropy Alloys

Valence electron structures (VESs) and mechanical and thermal properties of single-phase refractory high-entropy alloys (RHEAs) have been investigated with the empirical electron theory (EET) of solids and molecules. The calculated bond lengths agree well with the experimental ones. The physical properties of RHEAs, which include the hardness, yield strength, melting point, and cohesive energy, are strongly related to their VESs. It shows that the hardness and yield strength of RHEAs are enhanced with increasing linear density of covalence electron pair ρL along the direction of the strongest bond and the covalence electron number per atom nc/atom. The melting points of RHEAs increase with increasing covalence electron pair nA and the average of the covalence electron number nc/atom. The cohesive energies for RHEAs significantly depend upon the average of the covalence electron number per atom. It is suggested that the mechanical and thermal properties of RHEAs are modulated by their covalence electrons.