(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China) (2. National Key Laboratary for Powder Metallurgy, Central South University, Changsha 410083, China)
The thermal stabilities of nano-precipitates are critical in determining the service temperature of metallic alloys. Taking the Al-RE (rare earth) alloys as an exemplary case, we performed intensive first-principles calculations on solute segregation, coherent strains, and formation energies of L12-phase nano-precipitate interfaces. Based on the classic nucleation theory, the first-principles energetics results were further employed to evaluate the precipitation thermodynamics and relative stabilities of various possible structures of L12 nano-phases, including binary L12-Al3X (X=Sc/Zr/Er) and various complex structured ternary L12-Al3(ErxZr1-x) and L12-Al3(ScxZr1-x), under a certain aging temperature with an equi-atomic ratio of RE solutes. Finally, all the results were combined to establish the thermal stability advantage of core-shelled L12 nano-phases in Al alloys, which can provide the fundamental understanding of diverse experimental observations in the literatures.