Microstructure and mechanical properties of Al-7.9Zn-2.7Mg-2.0Cu (wt%) alloy strip fabricated by twin roll casting and hot rolling

Abstract

High Zn content Al-7.9Zn-2.7Mg-2.0Cu (wt. %) aluminum alloy strip with 5.5 mm thickness was successfully fabricated by twin roll casting (TRC). Fine grain size, second phase and second dendrite arm spacing (SDAS) were obtained in the cast strip due to the high cooling rate during TRC process. Short-time annealing treatment of 480 ºC-1 h could effectively reduce the second phases, and the elongation of the strip was improved. The TRC alloy sheet with 2.0 mm thickness was fabricated by the annealing treatment (480 ºC-1 h) and hot rolling. The yield strength, tensile strength and elongation along the rolling direction of the TRC sheet after solution treatment, pre-aging and natural aging were 398 MPa, 590 MPa and 15.74%, respectively. After bake-hardening, the yield strength, tensile strength and elongation along the rolling direction were 550 MPa, 605 MPa and 10.07%, respectively.