Effect of Nonisothermal Creep Aging on Mechanical Properties and Corrosion Resistance of Al-Zn-Mg-Cu Alloy

The effects of the heating rate and peak temperature on the springback, mechanical properties, and corrosion resistance of Al-Zn-Mg-Cu alloy were investigated. The precipitation behavior and aging strengthening mechanism of the alloy were analyzed by transmission electron microscope. Results show that with decreasing the heating rate and increasing the peak temperature, the springback of the alloy is decreased; the size of intragranular precipitates is increased; the volume fraction of intragranular precipitates is firstly increased and then decreased; the grain boundary precipitates become discontinuous and the precipitate-free zone is expanded. After nonisothermal creep aging (NICA) treatment (20 °C/h, 180 °C), the main precipitates of alloy are compact η' phase, the grain boundary precipitates are discontinuous, and the free zone width is approximately 44.2 nm. The mechanical properties and corrosion resistance of the alloy treated by NICA (20 °C/h, 180 °C) are better than those of the alloy treated by common isothermal creep aging (120 °C, 24 h), and the aging time is shortened by 67%. Copyright © 2023, Northwest Institute for Nonferrous Metal Research. Published by Science Press. All rights reserved.