Abstract
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.
Highlights
The first generation of 7xxx super-hard aluminum alloy was investigated in 1930, and developers are looking at fifth generation aluminum alloy materials
According to the addition of elements, alloys are mainly classified into two categories: Al-Zn-Mg alloy has exhibited better weldability and general corrosion resistance, and high strength can be obtained when heat treatment is appropriate; the other is developed on the basis of Al-Zn-Mg alloy by adding Cu, which has high specific strength, low density, yield strength close to tensile strength, and exhibits better corrosion resistance and high toughness
Fine grain strengthening; inhibits recrystallization nucleation and growth; Improve anti SCC ability Improved maximum tensile strength and fracture toughness, performance of low cycle fatigue, quenching sensitivity Reduced the number of strengthening phases Improved the strength, toughness, aging effect and corrosion resistance of the alloy Promoted the formation of GP region and transition phase; delayed the over-aging of the alloy Improved the hardenability; retention of subcrystalline structure Refined grain, improved casting properties Improved the toughness; hardenability; dimples appear Grain refinement; recrystallization inhibition Improved anti SCC ability Improved the hardness, tensile strength, elongation Hindered dislocation; grain boundary movement Reduced plasticity and fracture toughness Reduced plasticity and fracture toughness
Summary
The first generation of 7xxx super-hard aluminum alloy was investigated in 1930, and developers are looking at fifth generation aluminum alloy materials. According to the addition of elements, alloys are mainly classified into two categories: Al-Zn-Mg alloy has exhibited better weldability and general corrosion resistance, and high strength can be obtained when heat treatment is appropriate; the other is developed on the basis of Al-Zn-Mg alloy by adding Cu, which has high specific strength, low density, yield strength close to tensile strength, and exhibits better corrosion resistance and high toughness It is the highest strength series of aluminum alloy and is easy to machine, and is applied widely in large aircraft manufacturing and aerospace, and internationally recognized as the main aviation material [6,7,8]. The new principle of process-microstructure-performance correlation is used to continuously improve the microstructure-performance characterization method of aluminum alloy, based on the composition-process-microstructure-performance relationship of 7xxx series aluminum alloy, which shows good prospects for the future development direction of aluminum alloy
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