Designing order–disorder transformation in high-entropy ferritic steels

Order-disorder transformations hold an essential place in chemically complex high-entropy ferritic-steels (HEFSs) due to their critical technological application. The chemical inhomogeneity arising from mixing of multi-principal elements of varying chemistry can drive property altering changes at the atomic scale, in particular short-range order. Using density-functional theory based linear-response theory, we predict the effect of compositional tuning on the order-disorder transformation in ferritic steels -focusing on Cr-Ni-Al-Ti-Fe HEFSs. We show that Ti content in Cr-Ni-Al-Ti-Fe solid solutions can be tuned to modify short-range order that changes the order-disorder path from BCC-B2 (Ti atomic-fraction = 0) to BCC-B2-L21 (Ti atomic-faction $>$ 0) consistent with existing experiments. Our study suggests that tuning degree of SRO through compositional variation can be used as an effective means to optimize phase selection in technologically useful alloys.