A novel Al-Mg-Zn(-Cu) crossover alloy with ultra-high strength

Improving the strength continues to be the key to the development of high-performance Al-Mg-Zn(-Cu) crossover alloys. Here, a novel ultra-high strength Al-5.64 Mg-5.43Zn-0.51Cu (wt.%) crossover alloy was designed by utilizing CALPHAD (Calculation of Phase Diagram) assisted design. The yield strength, tensile strength and elongation are 570.7 ± 2.7 MPa, 628.0 ± 9.6 MPa and 9.5 ± 0.2 %, respectively. Compared with reported Al-Mg-Zn based crossover alloys and typical ultra-high strength 7075-T6 alloy, the developed alloy demonstrates the highest yield strength (70.7 MPa higher than the second) with an acceptable elongation. This is because, the high-solute supersaturation of Mg, Zn and Cu elements promotes the precipitation of the high-density T-type phases (Mg32(Al,Zn,Cu)49), thus hindering dislocation movement and increasing the strength of the alloy. The developed ultra-high strength novel Al-Mg-Zn(-Cu) crossover alloy is expected to provide a desirable material option for the lightweight design of transportation industries.