Influence of retrogression temperature and time on microstructure, mechanical properties and corrosion behaviors of cryogenically-deformed 7A85 aluminum alloy
(1. Research Institute of Light Alloy, Central South University, Changsha 410083, China;
2. State Key Laboratory of High Performance Complex Manufacturing, Changsha 410083, China;
3. Capital Aerospace Machinery Corporation Limited, Beijing 100076, China;
4. School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China)
2. State Key Laboratory of High Performance Complex Manufacturing, Changsha 410083, China;
3. Capital Aerospace Machinery Corporation Limited, Beijing 100076, China;
4. School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China)
Abstract: To balance the strength, plasticity, and corrosion resistance of the alloy, the microstructure and comprehensive properties of cryogenically-deformed 7A85 aluminum alloy at various retrogression temperatures and time were investigated. The results showed that under the retrogression and re-aging (RRA) of lower retrogression temperature and time and T6 (120 °C, 24 h) tempers, the alloy had higher strength but poorer corrosion resistance. For RRA, increasing the retrogression temperature and time within a certain range reduced the strength but significantly improved the electrical conductivity and corrosion resistance of the alloy. However, excessively increasing the retrogression temperature and time led to a reduction in corrosion resistance. At the same retrogression temperature, the elongation of the alloy first decreased and then increased with the extension of retrogression time. The optimal temper matched to the three-dimensional cryogenically deformed 7A85 aluminum alloy was RRA180-0.5 ((120 °C, 24 h) + (180 °C, 0.5 h) + (120 °C, 24 h)).
Key words: cryogenically-deformed 7A85 aluminum alloy; retrogression temperature; retrogression time; strength; corrosion resistance; optimal temper