Development of extruded Mg-6Er-3Y-1.5Zn-0.4Mn (wt.%) alloy with high strength at elevated temperature

Abstract

Abstract A new Mg-6Er-3Y-1.5Zn-0.4\u2009Mn (wt.%) alloy with high strength at high temperature was designed and extruded at 350\u2009°C. The as-extruded alloy exhibits ultimate tensile strength of 301\u2009MPa, yield strength (along ED) of 274\u2009MPa and thermal conductivity of 73\u2009W/m⋅K at 300\u2009°C. Such outstanding high-temperature strength is mainly attributed to the formation of nano-spaced solute-segregated basal plane stacking faults (SFs) with a large aspect ratio throughout the entire Mg matrix, fine dynamically recrystallized (DRXed) grains of 1-2\u2009μm and strongly textured un-DRXed grains with numerous sub-structures. Microstructural examination unveils that long period stacking ordered (LPSO) phases are formed in Mg matrix of the as-cast alloy when rational design of alloy composition was employed, i.e. (Er\u2009+\u2009Y): Zn\u2009=\u20093: 1 and Er: Y\u2009=\u20091: 1 (at.%). It is worth mentioning that it is the first report regarding the formation of nano-spaced basal plane SFs throughout both DRXed and un-DRXed grains in as-extruded alloy with well-designed compositions and processing parameters. The results provide new opportunities to the development of deformed Mg alloys with satisfactory mechanical performance for high-temperature services.