Developing a high-performance Mg-5.7Gd-1.9Ag wrought alloy via hot rolling and aging

Abstract

Abstract Developing wrought Mg alloys with excellent mechanical properties and their profiles act a pivotal part in extending Mg alloys' applications. Here, an Mg-5.7Gd-1.9Ag wt. % alloy sheet with high strength-ductility synergy was developed by hot rolling combined with aging. The microstructure, tensile mechanical properties, and strain hardening behavior of this alloy under different conditions were systematically investigated. The tensile results demonstrated that the strength and ductility were synchronously and significantly enhanced via hot rolling, and a further improvement in strength was obtained via subsequent aging. Microstructure results indicated that the hot rolling processing introduced fine grains, β phase precipitates, a few twins, moderate dislocations density, weak and spread basal texture, which guaranteed the synchronous improvement in strength and ductility. After peak aging, high-density γ'' nanoplates and few β′ nanoplates within α-Mg grains were found, as well as many nanoscale β phase particles segregated at grain boundaries. This multiphase precipitate microstructure was responsible for the strong aging response. Moreover, a suppressed stage II of strain hardening was observed in the rolled and aged alloy, while it was visible in the as-cast alloy. The suppressed stage II of strain hardening was mainly stemmed from the weak basal texture and fine grains.