A new way to cast high-alloyed Al–Zn–Mg–Cu–Zr for super-high strength and toughness

Low-frequency electromagnetic casting (LFEC) was introduced to semi-continuously cast three new high-alloyed Al–Zn–Mg–Cu–Zr alloys. Compared with conventional direct chilling casting (DC), the effects of low-frequency electromagnetic field on surface quality, as-cast microstructures, the contents of solute elements within grains and mechanical properties were investigated. The results show that microstructures of LFEC are fine, uniform, equiaxed, rosette-shaped, and the average sizes at the center of the ingots are 20–50 μm; the surface of the ingots of LFEC has no cold shut and less exudations. The contents of solute elements within grains and as-cast mechanical properties of LFEC are greatly increased: local relative concentration of Zn, Mg and Cu are 75–65, 72–66 and 45–40%, respectively. The as-cast ultimate tensile strength is 330–350 MPa and elongation is 0.8–1.2%. The ultimate tensile strength of the final products of two alloys is bigger than 760 MPa, and their elongation is bigger than 8%.