A new high-pressure die casting Mg-Gd-Sm-Al alloy with high strength-ductility synergy

A high-pressure die casting (HPDC) Mg-5Gd-1.5Sm-0.7Al alloy was newly developed and exhibits outstanding strength-ductility synergy, with the yield strength and the tensile elongation to fracture being approximately 200 MPa and 8.5%, respectively. This alloy has two types of a-Mg grains: coarse a1Mg ((46 +/- 18) mm) and fine a2-Mg ((9.2 +/- 2.3) mm) grains, and various Al-GS (GS = Gd and Sm) particles located at grain boundaries while clear solute-atom segregation near grain boundaries with limited or free intermetallic particles. Characterizations using Cs-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) indicate the crystal structures of Al-GS phases. After aging, dense b' precipitates and chain-shaped b"-like structures precipitated near grain boundaries while a high density of ultrafine b"-(Mg,Al)3Sm precipitates and Al-GS clusters formed in grain center. Relatively fine grains, Al-GS primary particles, solute-atom segregation near grain boundaries, and/or multiple precipitates contribute to the high strength of the studied alloy, while the multi-scale a-Mg grains, variety of intermetallic particles but discontinuous skeleton, and the multi-typed precipitated lead to its satisfactory ductility. (c) 2024 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.