Thermodynamic evaluation of the phase stability in mechanically alloyed AlCuxNiCoTi high-entropy alloys

This study investigates the phase stability of AlCuxNiCoTi high-entropy alloys with varying amounts of copper. The regular solution and Kohler’s models are used to thermodynamically evaluate the alloys and determine a symmetrical enthalpy across their compositions. The study calculates the Gibbs energy of mixing for a quinary alloy system using the extended Miedema theory and considering the change in enthalpy of mixing of the solid-solution and amorphous phases of 10 binary alloys. By comparing the experimental and predicted results, this study suggests that thermodynamic properties can help predict stable phases in multicomponent alloys comprising equiatomic and near-equiatomic elements. Furthermore, the structural instability of the solid-solution state resulting from differences in valence electron concentrations of the constituent elements in binary mixtures is discussed, highlighting the influence of alloying elements on the phase stability of multicomponent alloys.