The hardness, conductivity and room temperature tensile test were used to study the properties of the new aluminum alloy aged at 110-140 ℃ for different time.The microstructure of the alloy was observed by transmission microscope (TEM).The results show that the optimum aging process of the new aluminum alloy is aging at 110 ℃ for 24 h.Tensile strength, yield strength and elongation are 808, 785 MPa, 6.9%, respectively.Aging temperature is the main factor affecting the type, density and size of precipitates.When aged at 110 ℃, the main precipitations are GPⅠ zones, GPⅡ zones and metastable η' phase. After aging at 110 ℃ for a long time (up to 96 h), GPⅠ zones and GPⅡ zones still exist stably.Compared with aging at 110 ℃, the precipitation process accelerates at 140 ℃.After aging at 140 ℃ for 4 h, no GP zone is observed, and the main precipitate phase is η'.After aging at 140 ℃ for 24 h, the main precipitates are η' phase and η phase.
CHEN G H , LI G A , CHEN J Z , et al. Effect of rolling microstructure characteristics on fracture toughness of 7B50-T7751 aluminum alloy thick plate[J]. Light Alloy Fabrication Technology, 2018, 46 (6): 29- 33.
ZHANG X F , LU Z , ZHAO Z , et al. Microstructure evolution of as-extruded 7A85 aluminum alloy during high temperature deformation[J]. Journal of Hunan University (Natural Sciences), 2017, 44 (6): 7- 11.
Technical data: rod and bar alloy 7068[Z/OL].[2021-03-18].http://www.kaiseraluminum.com/customer-portal/product-information/#collapse-3.
YANG S J , XING Q Y , YU H J , et al. Heat-treatment process of a new high zinc Al-Zn-Mg-Cu alloy[J]. Journal of Materials Engineering, 2016, 44 (12): 41- 47.
LIAO F , FAN S T , DENG Y L , et al. First-principle calculations of mechanical properties of Al2Cu, Al2CuMg and MgZn2 intermetallic in high strength aluminum alloys[J]. Journal of Aeronautical Materials, 2016, 36 (6): 1- 8.
YUAN D L , CHEN S Y , ZHOU L , et al. Microstructures in as-cast and as-homogenized Al-Zn-Mg-Cu alloys with high zinc ultra-high strength[J]. The Chinese Journal of Nonferrous Metals, 2018, 28 (12): 2393- 2403.