Improvement in the mechanical properties of as-rapidly solidified Al-Zn-Mg-Cu alloys with Zr addition before and after aging

High cooling rate can increase the concentration of solute atoms in the solidification structure to produce a supersaturated solid solution. As-rapidly solidified Al-Zn-Mg-Cu alloys with different Zr mass fractions were prepared. The microstructure and tensile properties of as-cast and aged alloys showed that the increase of Zr element did not significantly refine the grain size. But it obviously improved the mechanical properties of alloys before and after aging. The addition of Zr in the as-cast alloys improved the mechanical properties of the alloy by solution strengthening. In the aged alloys, the mechanical properties were enhanced mainly by the precipitation of L12-Al3Zr, which has a coherent relationship with the Al matrix and refined the size of θʹ-Al2Cu. With superfluous Zr content, the coarsening of L12-Al3Zr precipitations harmed the mechanical properties.