Microstructure and Mechanical Property Tailoring in Asymmetrically Shear-Extruded Mg-2.0Al-0.8Sn-0.5Ca Alloys via Zn Addition

This study systematically examines the influence of Zn addition (≤0.6 wt.%) on the microstructure and mechanical properties of Mg-2Al-0.8Sn-0.5Ca (wt.%) alloys. Minor Zn alloying marginally increases secondary phase fraction in as-cast alloys, with complete Zn dissolution achieved after solution treatment and asymmetric severe shear extrusion. Extruded alloys exhibit non-monotonic strength evolution with Zn content, peaking at 0.2 wt.% Zn (yield strength ≈ 235.1 MPa, ultimate tensile strength ≈ 289.2 MPa), while elongation reaches 16.1%. This strength enhancement originates from synergistic grain boundary, solid-solution, and dislocation strengthening mechanisms. These results demonstrate Zn’s critical role in optimizing the strength-ductility balance of rare-earth-free magnesium alloys.