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Vol.60, No.1, 83 ~ 94, 2022
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| Title |
| Effect of Dissolution of η′ Precipitates on Mechanical Properties of A7075-T6 Alloy |
| 김영위 Young-we Kim , 조용희 Yong-hee Jo , 이윤수 Yun-soo Lee , 김형욱 Hyoung-wook Kim , 이제인 Je-in Lee |
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| Abstract |
| The effects of dissolution of the η′ phase by solution treatment on the mechanical properties of A7075-T6 alloy were investigated. Immediately after solution treatment of the T6 sheet at 450 ℃ or higher, elongation significantly increased and dissolution of the η′ phase occurred. η′ is the main hardening phase. After natural-aging, GPI, which is coherent with the aluminum matrix, was formed and strength increased. When bake hardening after natural-aging was performed, the yield strength slightly increased due to partial dissolution of the GPI and re-precipitation of the η′ phase. In contrast, after solution treatment at 400 ℃, there was less elongation increase due to the precipitation of the coarse η phase at grain boundaries and low dissolution of the η′ phase. In addition, when bake hardening after natural-aging was performed, the yield strength decreased due to insufficient GPI, which is the nucleation site of the η′ phase. To promote re-precipitation of the η′ phase, the solution treatment temperature was set to a level that would increase solubility. As a result, the yield strength was significantly increased through re-precipitation of a large number of fine and uniform η′ phase. In addition, to increase the effect of dissolution, a pre-aging treatment was introduced and the bake hardenability can be improved after dissolution.
(Received August 6, 2021; Accepted October 1, 2021) |
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| Key Words |
| Al-Zn-Mg-Cu, 7075, dissolution, precipitation, mechanical properties |
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