Divacancy-driven diffusion in L12 Al3RE compounds and Al/Al3RE interfaces

The diffusion behavior of rare-earth (RE) elements is critical to the nucleation and growth kinetics of L1 2 Al 3 RE precipitates in high-strength aluminum alloys, yet direct experimental measurement within the extremely narrow homogeneous range is still challenging. In this work, atomic diffusion of L1 2 Al 3 RE with 15 RE elements is investigated using first-principles calculations combined with transition-state theory. Compared with classical mono-vacancy models, divacancy mechanism provides a reliable description in Al 3 RE diffusion at higher temperature. Diffusion in the L1 2 phase is found to be drastically slower than that in FCC Al matrix, with differences scaling up to 30 orders of magnitude. In Al 3 RE, Al atoms move faster than RE atoms, indicating that mass transport is primarily carried by Al atomic flow. Incorporating these diffusivities into a Matano–Boltzmann framework depicts the Al/Al 3 RE interface migration which is in good agreement with experiments. Among them, Yb- and Ce-containing systems exhibit sluggish diffusion and interface migration. This work offers new insights into the nucleation and growth of Al 3 RE precipitates, and provides quantitative guidance for the development of Sc-free or Sc-lean, RE-strengthened aluminum alloys.