  Mg alloys are promising lightweight structural materials due to their low
density and excellent mechanical properties. However, their limited formability
and ductility necessitate improvements in these properties, specifically
through texture modification via grain boundary segregation. While significant
efforts have been made, the segregation behavior in Mg polycrystals,
particularly with basal texture, remains largely unexplored. In this study, we
performed atomistic simulations to investigate grain boundary segregation in
dilute and concentrated solid solution Mg-Al alloys. We computed the
segregation energy spectrum of basal-textured Mg polycrystals, highlighting the
contribution from specific grain boundary sites, such as junctions, and
identified a newly discovered bimodal distribution which is distinct compared
to the conventional skew-normal distribution found in randomly-oriented
polycrystals. Using a hybrid molecular dynamics/Monte Carlo approach, we
simulated segregation behavior at finite temperatures, identifying grain
boundary structural transitions, particularly the varied fraction and
morphology of topologically close-packed grain boundary phases when changing
thermodynamic variables. The outcomes of this study offer crucial insights into
basal-textured grain boundary segregation and phase formation, which can be
extended to other relevant Mg alloys containing topologically close-packed
intermetallics.
