Effect of Mg-Controlled Solidification Pathways on Microstructure and Properties of As-Cast Al-1Y-xMg Alloys

<title>Abstract</title> <p> Understanding the relationships among solidification processing, microstructure, and properties is central to the design of advanced aluminum alloys. In this work, as-cast Al-1Y-xMg (x = 0–8 wt.%) alloys were prepared via conventional casting to investigate how Mg content controls solidification pathways and, consequently, the resulting microstructure and associated mechanical and thermal properties. With increasing Mg content, the solidification pathway evolves from isolated Y-rich phases to sequential precipitation of τ-Al _x MgY and β-Al ₃ Mg ₂ , ultimately forming a continuous τ + β eutectic network at high Mg levels. The alloy with 6 wt.% Mg achieves a peak tensile strength of 158.0 MPa—approximately 95% higher than the Mg-free alloy—while retaining 11.0% uniform elongation, demonstrating a favorable strength-ductility balance. Concurrently, the eutectic network topology governs fracture behavior, transitioning from ductile dimple to quasi-cleavage, and mediates dynamic strain aging via Portevin-Le Chatelier serrations. Physically, electrical and thermal conductivities are continuously tunable within 28.2–51.8% IACS and 148–218 W·m ^− 1 ·K ^− 1 , respectively. The dominant electron scattering mechanism shifts from solute-controlled scattering at low Mg contents to interface-controlled scattering at high Mg contents, directly correlating with the evolving eutectic network. This study establishes quantitative processing-microstructure-property relationships in Al-Mg-Y alloys, offering guidance for tailoring cast aluminum alloys for combined structural and thermal management applications. </p>