Abstract: Effect of pre-aging at 120-180 ℃ for 5 min before baking at 180 ℃ for 30 min on the bake hardening response of AA7075 high-strength aluminum alloy was studied using high-resolution transmission electron microscopy, microhardness tester, and tensile testing machine. The results indicate that when the pre-strain before pre-aging is 3%-30%, an increase in the pre-strain will also promote a more significant bake hardening effect. When the pre-strain is 5%, with the increase of pre-aging temperature (120-180 ℃), the η′ strengthening phase amount of the AA7075 alloy gradually increases, and the strength and hardness increase from 405 MPa and 142 HV5 to 478 MPa and 160 HV5, respectively. At the same time, when pre-aged at 180 ℃ for 5 min, there is a certain amount of η′ phase and a small amount of η phase in the matrix. Adding pre-aging process before baking enables to promote the formation of GP zone significantly, and the bake hardening response is the best.

Key words: AA7075 aluminum alloy, bake hardening response, microstructure, tensile property