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Ultra-high strength aluminum alloy has achieved extensive application in the nuclear，aerospace，and aviation industries because of its high specific strength and low density. The fifth generation of ultra-high strength aluminum alloy has been produced，and in comparison to the fourth generation’s 600 MPa level，its ultimate strength has been consistently redefined and increased from 650-700 MPa to 750 MPa or even 800 MPa. This paper reviews the history of the research on aluminum alloys with ultra-high strengths and introduces the current state of development both domestically and internationally. The key issues and recent research development are further explored，including computer simulation，thermal deformation，heat treatment，homogenization，melting，and casting，as well as composition design. Finally，combined with the development needs of future equipment and domestic technology status，it is pointed out that in-depth study of basic theory to solve the problem of comprehensive performance matching，the promotion and application of special materials in specific application scenarios are the development trend and important direction of ultra-high strength aluminum alloy.

Long-term thermal stability plays an important role in practical applications of Al-Zn-Mg-Cu alloys. In the present work, thermal stability of the T7452-treated 7085 Al alloy was assessed at temperatures of 100, 125, 150 and 175 °C for 100, 500 and 1000 h, through hardness, electrical conductivity and tensile tests after thermal exposure. The nanoscale precipitates under different thermal exposure conditions were also qualitatively studied by transmission electron microscopy (TEM). The results show that thermal stability of the alloy is more sensitive to thermal exposure temperature than to exposure time. The hardness increases first and then decreases with the increase of exposure temperature while it decreases gradually as exposure time prolongs. However, the variation of electrical conductivity is opposite. The tensile strength, yield strength and hardness after 100 °C/100 h thermal exposure increased by 2.4%, 6.7% and 9.2% than those of the alloy without thermal exposure, respectively. The precipitate sequence during thermal exposure is coincident with that of aging. In addition, as thermal exposure deepens, the average radius of precipitates increases while the volume fraction decreases. Meanwhile, the grain boundary precipitates coarsen and transform from continuous to discrete. The influence of precipitates on properties of the alloy is discussed quantitatively. • Thermal stability of 7085 alloy was conducted under different temperatures for different durations. • Correlations between hardness and electrical conductivity of the 7085 alloy during thermal exposure were investigated. • Thermal exposure temperature played more significant effect on strength and electrical conductivity than the exposure time. • The average precipitate size increased while the volume fraction decreased as thermal exposure deepened. • The increments of yield strength before and after thermal exposure were calculated. [ABSTRACT FROM AUTHOR]

As a new generation of Al-Zn-Mg-Cu alloy, 7085 aluminum alloy is a promising structural material in the field of aerospace industry. However, research on its thermal stability is still lacking. In the present work, thermal exposure was carried out on the T7452-treated 7085 aluminum alloy under different temperatures (100 °C, 125 °C, 150 °C and 175 °C) for 500 h. Variations of tensile properties and hardness were exhibited. The microstructure, nano-scale precipitates and fracture characteristics of the alloy were investigated using optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that with the increase of exposure temperature, the strength and hardness increase first and then decrease while the elongation and the reduction of area increase continuously as compared to those of the non-thermal exposed alloy. The transformation from η′ phase to η phase during thermal exposure occurs continuously during thermal exposure. In addition, as the exposure temperature increases, the average dimensions of precipitates and the average spacing of neighbor precipitates become larger. The influence of precipitates on mechanical properties of the alloy is discussed. [ABSTRACT FROM AUTHOR]