Effect of Short-Range Ordering in High-Entropy Alloys

The description of the short-range ordering (SRO) for binary systems was expanded to multi-component systems in the framework of the CALPHAD method. The present formulation estimates the effect of SRO in high entropy alloys (HEAs) based on the Gibbs energy functions from the CALPHAD-type thermodynamic assessments. It was applied to the BCC- and FCC-based HEAs and their subsystems. The excess Gibbs energy and excess entropy due to SRO in the FCC solutions were higher than those in the BCC solutions because of the difference in their coordination numbers. In the present calculation, the total contribution of the SRO to the Gibbs energy was approximately -1 kJ mol(-1) and -0.2 kJ mol(-1) in the BCC- and FCC-based HEAs at 1000 K, respectively. The variations in the excess Gibbs energy and excess entropy due to SRO in lower-order systems can disappear in the HEAs because of the mixing of multiple elements, as formally suggested in the previous work for the excess Gibbs energy in Cantor alloy.