Influence of aging treatment on hardening response and intergranular corrosion of 7A20 aluminum alloy

doi:10.13251/j.issn.0254-6051.2021.07.033

Abstract

Abstract: Influence of natural aging(NA) on artificial aging hardening behavior of the 7A20 aluminum alloy was investigated. The Vickers hardness and mechanical properties were tested. The microstructure evolution was characterized by means of OM, SEM and TEM. The results indicate that the specimens after solution treatment have obvious natural aging effect during the natural placed process. The softening effect is observed during the artificial aging treatment after NA for 3 days(NA3) and 8 days(NA8) and the micro-hardness decreases 25.3% and 22.7% respectively after 2 h AA treatment. The grain size has no obvious difference after different heat treatments, while the inner grain structure has obvious difference. PFZ zone with about 20 nm width exists at grain boundaries of all the specimens after heat treatment. The fraction of the rod-like precipitation phase in crystals of the specimens of NA3+160 ℃×40 h and NA8+160 ℃×40 h is increased. The specimen under artificial aging directly after solution treatment has the best resistance to intergranular corrosion, its corrosion depth is 80-120 μm, while the specimens of NA3+160 ℃×40 h and NA8+160 ℃×40 h have the intergranular corrosion depth of 100-140 μm and 120-160 μm, respectively, and have obviously peeled off phenomenon.

Key words: 7A20 aluminum alloy, natural aging, microstructure evolution, intergrannular corrosion

CLC Number:

TG156.92

Wang Shan, Wang Shuhui, Liu Wenwen, Teng Dunbo, Zhang Riqiang, Wang Xuqiang, Xiang Kangning. Influence of aging treatment on hardening response and intergranular corrosion of 7A20 aluminum alloy[J]. Heat Treatment of Metals, 2021, 46(7): 173-177.

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