Improving mechanical properties and corrosion resistance of Al-Zn-Mg-Cu alloy through natural aging coupled pre-stretching

doi:10.13251/j.issn.0254-6051.2024.04.017

Abstract

Abstract: Effect of natural aging time coupled with 3% pre-stretching on the aging precipitation microstructure, mechanical properties and corrosion resistance of Al-Zn-Mg-Cu alloy was studied by using transmission electron microscope (TEM), scanning electron microscope (SEM), tensile testing, exfoliation corrosion and intergranular corrosion. The results show that natural aging for 4 days coupled with 3% pre-stretching can regulate the aging precipitation behavior near grain boundaries during subsequent aging processes, significantly reducing the width of the precipitation free zone near grain boundaries. The reason is that the precipitation free zone containing amount of solution atoms is formed after natural aging for 4 days, followed by the subsequent 3% pre-stretching to induce a large number of dislocations in precipitation free zone, promoting the subsequent aging process to precipitate phase nucleation and reducing the width of the precipitation free zone. The elongation of the Al-Zn-Mg-Cu alloy is significantly improved due to the narrow precipitation free zones near grain boundaries can avoid the accumulation of dislocations, suppress pore growth and crack propagation. Meanwhile, the exposed area of the corroded anode is reduced during the anodic dissolution process, which can reduce the corrosion rate and increase the resistance of exfoliation corrosion and intergranular corrosion. The tensile strength, elongation, and maximum intergranular corrosion depth obtained by coupling natural aging for 4 days process with 3% pre-stretching are 562 MPa, 17.23% and 191.4 μm, respectively.

Key words: thermo-mechanical treatment, Al-Zn-Mg-Cu alloy, precipitation free zone, tensile properties, corrosion resistance

CLC Number:

TG146

Dong Taili, Li Fang, Chen Geng, Zhang Chen, Guo Zilong, Chen Kanghua, Chen Songyi. Improving mechanical properties and corrosion resistance of Al-Zn-Mg-Cu alloy through natural aging coupled pre-stretching[J]. Heat Treatment of Metals, 2024, 49(4): 104-110.

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