The interplay between solute atoms and vacancy clusters in magnesium alloys

P Yi and TT Sasaki and SE Prameela and TP Weihs and ML Falk, ACTA MATERIALIA, 249, 118805 (2023).

DOI: 10.1016/j.actamat.2023.118805

Atomic-scale calculations indicate that both stress effects and chemical binding contribute to the redistribution of solute in the presence of vacancy clusters in magnesium alloys, leading to solute segregation driven by thermodynamics. As the size of the vacancy cluster increases, chemical binding becomes more important relative to stress. These solute-vacancy interactions also impact the diffusivity of vacancies and vacancy clusters in a solid solution. Simulations show that solute atoms accelerate mono-vacancy diffusion but decelerate the diffusion of vacancy clusters. As a result, solute atoms facilitate clustering and stabilize the resulting vacancy clusters, increasing their potential to promote solute segregation and to serve as heterogeneous nucleation sites during precipitation. Experimental observation of solute segregation in simultaneously deformed and aged Mg-Al alloys provides support for this mechanism.

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