Chemical and Biological Engineering, Materials Science and Engineering, Physics and Astronomy, Ames Laboratory
Journal or Book Title
High-temperature disordered multi-component alloys, including high-entropy alloys, experience either segregation or partially-ordered phases to reach low-temperature phases. For Ti0.25CrFeNiAlx (0≤x≤1), experiments suggest a partially-ordered B2 phase, whereas CALculation of PHAse Diagrams (CALPHAD) predicts a region of L21+B2 coexistence. We employ first-principles KKR-CPA to assess stability of phases with arbitrary order and a KKR-CPA linear-response theory to predict atomic short-range order (SRO) in the disorder phase that reveals the competing long-range ordered (LRO) phases in a given Bravais lattice. The favorable SRO provides a specific concentration-waves (site occupation probabilities and partially-ordered unit cells) and estimated energy gains that can then be assess directly by KKR-CPA formation enthalpies. Our results are in good agreement with experiments and CALPHAD in Al-poor regions (x≤0.75) and with CALPHAD in Al-rich region (1≥x>0.75). Our first-principles KKR-CPA and SRO-based concentration-wave analysis is shown to be a powerful and fast method to assess competing LRO phases in complex solid-solution alloys, and our results suggests more careful experiments in Al-rich region are needed.
Singh, Prashant; Smirnov, Andrei V.; Alam, Aftab; and Johnson, Duane D., "First-principles concentration-wave approach to predict incipient order in high-entropy alloys: case of Ti0.25 CrFeNiAlx" (2019). Materials Science and Engineering Publications. 353.