Grain refinement and precipitation are conventionally employed to enhance the mechanical properties of magnesium alloys. However, there remains a challenge in obtaining a fine grain structure together with a high-density precipitates, particularly in rare-earth containing magnesium alloys. In this study, a strong and ductile Mg-RE (WE43) alloy featuring a fine twin structure and dense nano-precipitates was fabricated via a processing combining multi-directional compression with multi-intermediate aging. The mechanical characterization demonstrated that the fabricated WE43 alloy exhibits an exceptional work-hardening capacity and enhanced ultimate tensile strength, albeit with some compromise in yield strength. Microstructural investigations reveal that the multi-directional compression promotes extensive grain refinement through the formation of nanostructured deformation twins, while the multi-intermediate aging inhibits twin expansion via solutes and precipitates pinning along twin boundaries. Further transmission electron microscopy analysis revealed the formation of high-density nano-precipitates within the matrix. The fine twins and dense precipitation structure strongly promote dislocation multiplication and accumulation, by interaction among dislocations, twin boundaries and nano-precipitates, leading to the significantly improved work-hardening capability and ultimate strength. The current study presents a new approach for the fabrication of rare-earth containing magnesium alloys with high ductility and ultimate strength.

Atomistic simulations were adopted to study the solute segregation effect on dislocation transmutation across the {1012} twin boundaries in magnesium. For pure magnesium, the dislocation-twin reaction resulted in the formation of sessile dislocations accompanied by the fast migration of the twin boundary, and no 〈c + a〉 dislocation occurred. With Al segregation, instead, two basal dislocations transmuted into one prismatic 〈c + a〉 dislocation in the twin. Twin migration was significantly impeded, and the resultant twin disconnections stayed localized and had a higher step character than in pure Mg. To reveal the mechanism of the effect of solute segregation, the Peierls barriers of twin disconnections were calculated, and the dynamic evolutions of twin disconnection dipoles were simulated. The results suggested that Al segregation softened the Peierls barrier of twin disconnections but imposed a high pinning force on twin disconnections, thus attenuating their mobility. Moreover, given the same Al segregation, the twin disconnection dipole with a higher step showed greater stability, which explained the presence of localized twin disconnections with a higher step in the cases with Al segregation than in pure magnesium. The solute segregation induced low mobility of twin disconnections contributed to the occurrence of 〈c + a〉 dislocations.