Mechanisms for Synergistically Enhanced Mechanical Properties and Corrosion Resistance in Mg−Al−Sn Alloys
Twin-roll casting (TRC) Mg−3Al−1Sn−0.5Ca−0.2Mn (ATXM) alloys exhibit limited deformation resistance and inadequate corrosion performance, constraining their commercial deployment. This study integrates rare earth (RE) microalloying (Sm, Ce, or Y at 0.1 wt.%) with rolling to address the strength–plasticity–corrosion trilemma. Rolling reduces grain size from ~50 μm to below 5 μm and transforms Al8Mn5 secondary phases into Al8Mn4RE, modifying phase composition, dimension, and spatial arrangement. The rolled ATXM-0.1Y alloy achieves a yield strength of 238 MPa, tensile strength of 305 MPa, and elongation of 23%, coupled with a corrosion rate of approximately 1.7 mm/a—an ~80% reduction relative to TRC ATXM. Sm and Ce additions yield strengths of 238 and 232 MPa, elongations of 18% and 17%, and corrosion rates of 3.4 and 2.9 mm/a, respectively. Strengthening mechanisms are attributed to fine-grain and Orowan strengthening, while corrosion mitigation arises from reduced individual galvanic corrosion and enhanced protective corrosion product film quality. The work establishes a screening protocol for RE elements and processing parameters to synergistically improve mechanical and corrosion properties, facilitating commercial adoption of Mg alloys.