Composition optimization and mechanical properties of Al-Zn-Mg-Si-Mn crossover alloys by orthogonal design

The development of crossover Al alloy is of significance to meet the demand for the ease recycling of Al scraps meanwhile for the improved combined properties. The composition optimization of Al-Zn-Mg-Si-Mn crossover alloys was investigated by orthogonal design based on 5056, 6082 and 7003 Al alloys. The microstructure, the precipitation behavior and the mechanical properties were studied by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), hardness test, conductivity test and mechanical test. The range analysis results showed that both Zn and Mg element dominate the ultimate tensile strength (UTS) whereas both Mg and Si element dominate the elongation (EL) for as-extruded and as-aged Al alloys. The optimized alloy composition is Al-0.3Si-5Mg-8Zn-1Mn (wt. %), which exhibits high UTS and good EL of as-extruded and as-aged Al alloys.