  This study advances our understanding of how chemical binding and solute
distribution impact grain boundary segregation behavior and subsequent
annealing texture modification in lean Mg-X-Zn alloys (X = RE or Ca). Notably,
differences in Ca and Gd solute behavior at grain boundaries were revealed,
where Ca exhibited stronger binding to vacancy sites than Gd, resulting in
elevated Ca segregation and an RD-TD-type texture. The introduction of Zn
showed significant synergistic effects on solute clustering, with Gd-Zn pairs
forming more favorably than Ca-Zn pairs, leading to a strong synergy between Zn
and Gd. This promoted their co-segregation and high concentration at the grain
boundary, generating a unique TD-spread texture. In contrast, weaker binding in
Ca-Zn pairs did not affect Ca segregation but influenced Zn segregation, which
underscores the importance of solute binding behavior in alloy design concepts.
Additionally, the combined atomicscale experiments and ab initio predictions
provide strong evidence that selective texture development in Mg alloys is tied
to heterogeneous solute-boundary interactions, where the sensitivity of the
binding energy to volumetric strain affects solute segregation at grain
boundaries, resulting in varying grain boundary mobilities and specific texture
component growth. It also emphasizes that solute behavior in clustering and
segregation is influenced not only by atomic size but also by chemical binding
strength with vacancies or co-added Zn.
