Notably, 7xxx series aluminum alloy has become the most popular nonferrous alloy, extensively used in industry, construction and transportation trades, due to its high comprehensive properties such as high static strength, high strength, heat resistance, high toughness, damage resistance, low density, low quenching sensitivity and rich resource. The biggest challenge for aluminum alloy today is to greatly improve the corrosion resistance of the alloy, while maintaining its strength. The preparation method of 7xxx series aluminum alloy requires controlling time lapses in the process of heating, holding and cooling, and there are many species precipitates in the crystal, but the precipitated strengthening phase is a single type of equilibrium η′ phase. Therefore, more attention should be paid to how to increase the volume fraction of η′ precipitates and modify the comprehensive performance of the material and focus more on the microstructure of the precipitates. This article reviews the progress of 7xxx series aluminum alloy materials in micro-alloying, aging precipitation sequence, the strengthening-toughening mechanism and the preparation method. The effect of adding trace elements to the microstructure and properties of 7xxx series aluminum alloy and the problems existing in aging precipitation characteristics and the reinforcement mechanism are discussed. The future development direction of 7xxx series aluminum alloy is predicted by developing a method for the process-microstructure-property correlation of materials to explore the characteristic microstructure, micro-alloying, controlling alloy microstructure and optimizing heat-treatment technology.
The intermetallic phase evolution during the homogenization of an Al–Zn–Mg–Cu–Zr alloy with Nd addition is investigated. Large amounts of the eutectic interdendritic acicular‐state η (MgZn2) phase, primary phase T (AlZnMgCu), Al8Cu4Nd, and Al7Cu2Fe exist at the grain boundaries of the as‐cast Al–Zn–Mg–Cu–Zr–Nd alloy. The homogenized intermetallic phase evolves as follows: the η phase dissolves into the α (Al) matrix, most of the T phase is dissolved in 16 h, and the remaining part of the T phase is transformed into the S phase (Al2CuMg) after 24 h. The stable Al8Cu4Nd phase in the alloy captures Cu atoms and inhibits the further generation of the S phase during homogenization. The addition of Nd decreases the fraction of the S phase, and only Al7Cu2Fe, Al8Cu4Nd, and Al2CuMg remain after homogenization for 24 h. Homogenization kinetics analysis suggests that the Al–Zn–Mg–Cu–Zr–Nd alloy is suitably homogenized at 470 °C 24 h−1.
Since the first generation of 7xxx superhard aluminum alloy was investigated in 1930, hitherto the fifth generation aluminum alloy materials with high comprehensive properties such as high static strength, high strength, heat resistance, high toughness, damage resistance, low density and low quenching sensitivity have been improved and developed. This paper reviews the progress of 7xxx aluminum alloy materials in composition, microstructure, properties, preparation methods, heat treatment strengthening and applications from 2014 to 2021. The effect of adding trace elements on microstructure and properties of 7xxx series alloy and the problems existing in aging precipitation characteristics and reinforcement mechanism are discussed. The future development direction of 7xxx superhard aluminum alloy is prospected by optimizing heat treatment technological, adding appropriate trace elements to alloy and controlling alloy microstructure.
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