Crystallographic orderings in the AlTiVNb and AlTiCrMo refractory high-entropy superalloys: first-principles theory and atomistic simulations
Date:
Contributed talk at the 2025 IOP CMQM Conference.
Abstract
Refractory high-entropy superalloys (RSAs) are metallic alloys containing aluminium and at least three further early transition metal elements. Although in general high-entropy alloys are expected to form single-phase solid solutions in which all lattice sites have uniform probabilities of being occupied by different elements, the addition of Al as an alloying element is understood to promote the formation of crystallographically ordered structures. Here, we combine ab initio electronic structure calculations, a concentration wave analysis, and atomistic simulations to examine the phase stability of two prototypical RSAs: AlTiVNb and AlTiCrMo [1]. In alignment with experimental observations, we predict B2 crystallographic orderings emerging at high temperatures in both alloys, as well as eventual decomposition into multiple competing phases with decreasing temperature. We interpret these findings in terms of the alloys’ underlying electronic structure, with hybridisation between the sp states of Al and the d states of the transition metals understood to play an important role. We then examine the impact of these crystallographic orderings on the alloys’ residual resistivity. Counterintuitively, for both alloys, we find that the emergence of (partial) long-range crystallographic order results in an increase in residual resistivity. We understand this increase as originating in a reduction in the electronic density of states at the Fermi level induced by the ordering, as well as qualitative changes to the nature of the alloys’ smeared-out Fermi surfaces.
References
[1] C. D. Woodgate, H. J. Naguszewski, D. Redka, J. Minar, D. Quigley, J. B. Staunton, arXiv:2503.13235.