CHEN S S, DUAN J Y, XU Z C, et al．Effect of multi-stage solution treatment on the microstructure and overall properties of 7075 aluminium alloy [J]. Journal of Henan Polytechnic University (Natural Science)，doi:10.16186/j.cnki.1673-9787.2024060060.

doi:10.16186/j.cnki.1673-9787.2024060060

Received：2024-06-29

Revised：2024-11-02

Online：2025-10-27

Effect of multi-stage solution treatment on the microstructure and overall properties of 7075 aluminium alloy (Online)

CHEN Shuisheng¹, DUAN Jiuyi¹, XU Zhichao², ZHANG Nannan¹, ZHOU Yang¹

(1. School of Mechanical and Power Engineering, Henan Polytechnic University, Jiaozuo 454000, Henan, China; 2. School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, Henan, China)

Abstract: Objectives Poor room-temperature formability is the main challenge for 7075 aluminium alloy in its wide application in lightweight body structures, the solid solution process is vital to enhance the room temperature forming properties of 7075 aluminium alloy. To understand the effects of multi-stage solid solution process on the microstructure, mechanical properties and corrosion resistance of 7075 aluminium alloy during solid solution forming. Methods The microstructure analysis, tensile testing, and electrochemical experiment were employed to investigate the microstructure and mechanical properties of 7075 aluminum alloy in different states, as well as the corrosion resistance properties after T6 aging. Results The results show that: (1) the second phase particles of 7075 aluminum alloy rolled sheet are mainly composed of η (MgZn2), S (Al2CuMg), CuAl2 and Mg2Si. (2) After 475 ℃×4 h + 485 ℃×4 h + 495 ℃×2 h of three-stage solid solution process, η (MgZn2) and S (Al2CuMg) phase in the solid solution state of 7075 aluminum alloy is nearly completely dissolved.(3) The multi-stage solid solution process makes more solute atoms in the alloy to be dissolved into the aluminium matrix, resulting in more homogeneous composition and more recrystallization, and after which the tensile strength and elongation at break of the alloy in the solid solution state increase by 11.9% and 22.2% respectively compared to those after the single-stage solid solution process. (4) After T6 aging, recrystallization softening and precipitation strengthening occur, the tensile strength and hardness of the alloy treated by three-stage solid solution process decreased by 2.5% and 0.8%, respectively, comparing with those of the single-stage solid solution process. (5) With the dissolution of S(Al2CuMg) particles, the charge transfer property of the aged alloy and the self-corrosion current density decreases, which can effectively improve the corrosion resistance of the aged alloy. Conclusions Proper three-stage solid solution process can effectively improve the solubility of the second phase particles of solid solution 7075 aluminium alloy, which significantly improves the room temperature forming performance of 7075 aluminium alloy and the corrosion resistance of the alloy in T6 state under the premise of ensuring the mechanical properties of the alloy after aging.

Key words: solid solution state; microstructure evolution; room temperature forming; mechanical properties; corrosion resistance