Thermomechanical treatment method for improving stress corrosion resistance of 7xxx series aluminum alloy

Abstract

The invention provides a thermomechanical treatment method for improving stress corrosion resistance of a 7xxx-series aluminum alloy. The 7xxx-series aluminum alloy is subjected to solid solution-water quenching and then sequentially subjected to precooling deformation and three-stage artificial aging heat treatment. According to the thermomechanical treatment method, pre-cooling deformation is adopted firstly, a large number of dislocations are formed in alloy grains and at the grain boundary, different-degree precipitation of an intragranular precipitated phase and a grain boundary precipitated phase can be promoted, and then it is guaranteed that coarsening of the intragranular precipitated phase is not obvious by shortening the subsequent overaging time; the grain boundary precipitated phase is obviously coarsened and distributed with high discretization, and the effect of blocking an anode dissolution channel is achieved; besides, dislocation generated by pre-cooling deformation provides a channel for diffusion of intragranular Cu atoms to a grain boundary, the content of Cu atoms in a grain boundary precipitated phase is promoted to be greatly increased, the electrode potential is increased accordingly, and the effect of increasing the anode dissolution barrier is achieved. Through the synergistic effect of the two effects, the 7xxx series aluminum alloy has high strength and good corrosion resistance at the same time.

Description

technical field [0001] The invention relates to the technical field of aluminum alloys, in particular to a deformation heat treatment method for 7xxx series aluminum alloys. Background technique [0002] 7xxx series ultra-high-strength aluminum alloys have the advantages of low density, high strength, and easy processing. They are important structural materials for aircraft, rockets, rail transit, and weaponry, and play an extremely important role in economic and social development and national defense modernization. At present, this kind of aluminum alloy material is developing in the direction of high comprehensive performance, which requires not only ultra-high strength, but also good toughness and corrosion resistance. However, the aging precipitates of 7xxx series ultra-high strength aluminum alloys with high Zn content or low Cu content are easy to enrich at the grain boundary and the electrode potential is low, so that the characteristics of corrosion and fracture alo...

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Problems solved by technology

However, the above heat treatment method, while improving the corrosion resistance, will be accompanied by a certain strength loss, which still has certain limitations in solving the contradiction between the alloy strength and corrosion resistance, and the corrosion resistance still restricts the 7xxx series. Bottlenecks in the development and application of super-strength aluminum alloys

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