First-principles calculation for displacive phase transition of atomic-scale precipitates in aluminum alloys

Abstract In the precipitation of β ″ phase in Al-Mg-Si and Guinier-Preston-Bagaryatsky (GPB) zone in Al-Cu-Mg alloys, columns of atoms shifting phenomenon was reported as an important step for the displacive phase transition. We build an atomic crystal model and use first-principles calculation to simulate the displacive phase transitions in the aluminum alloys. We show that the model could be successfully applied in explaining experimental results of the phase transitions of early-stage precipitation in both Al-Mg-Si and Al-Cu-Mg alloys. Then we use the model to predict the promising ternary aluminum alloys that may have similar displacive phase transitions at early-stage of aging. The first-principles method and the database of displacive phase transition identified here enrich the theory of phase transitions in atomic-scale materials and help design novel aluminum alloys with early-stage aging hardening.