The influence of electron concentration and mixing enthalpy on the lattice parameter of single-phase solid solutions of high-entropy alloys based on both bcc or fcc phases

The analysis of single-phase high-entropy alloys (HEA) based on both bcc or fcc phases shows that the lattice parameter depends on the electron concentration, mixing enthalpy, and distortion. Single-phase HEAs based on the bcc lattice are formed in the electron concentration range from 4.12 to 7.2 el/at. Single-phase HEAs based on the fcc lattice appear when the electron concentration is ≥ 8 el/at. When the electron concentration increases, the change in the lattice parameter for HEAs with bcc or fcc phases is oppo­site. For single-phase HEAs with an bcc phase, an increase in the lattice parameter values decrease, while with a fcc phase it increases. The shift of the mixing enthalpy towards negative values leads to a decrease in the lattice parameter, while an increase in distortion leads to its increase. It is found that in most cases, the determined lattice parameter of single-phase HEAs based on both bcc and fcc phases is greater than that calculated accor­ding to the mixture rule. At the same time, for single-phase HEAs in which a negative value of the mixing enthalpy and a pair with a negative enthalpy of mixing lower than –35 kJ/mol is observed, the determined lattice parameter is smaller than the calculated one. One of the features of single-phase HEAs is the dependence of the elastic modulus on the lattice para­meter based on bcc and fcc phases.