Synergistic development of ultra-high strength 7055 aluminum alloy by hot working processing

With the current increasing demand for energy-saving materials, the development of Al-based lightweight and ultra-high-strength aerospace alloys has been a sought-after goal. Here, we independently design the melting of 7055 aluminum alloy with the main alloy composition of Al-8.1Zn-2.05Mg-2.4Cu-0.12Zr (wt%), modification of the alloy is implemented through the addition of trace grain refiners. The ultra-high strength 7055 alloy with excellent performance was developed by the multi-process coupled modulation of indirect isothermal extrusion-room temperature cold rolling combined with artificial aging treatment process, with the comprehensive characterization and testing of its microstructure and mechanical properties. The analysis indicated that the mechanical properties of the alloy after reverse isothermal extrusion and room temperature cold rolling combined with artificial aging showed an obvious preferential orientation. The percentage of low-angle grain boundaries of 7055 aluminum alloy increased after the addition of grain refiners, which is related to the increase of deformed and sub-grained grains. The maximum tensile strength (UTS) and yield strength (YS) peaked (UTS: 771 MPa, YS: 750 MPa) to reach an impressive combined elongation at break of 6.3 %. The alloy strengthening is primarily based on the distribution of nano-precipitation strengthening phases MgZn2 and Al3Zr dispersions, as on the weaving enhancement and pinning effect on grain boundaries and dislocations. With the addition of grain refiners, the alloy fracture mode exhibits a mixed fracture pattern of intergranular fracture, dimples and shear fracture.