Microstructure evolution in cooling process of Al-Zn-Mg-Cu alloy and kinetics description
(1. Engineering Training Center, Harbin University of Science and Technology, Harbin 150080, China;
2. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China)
2. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China)
Abstract: The microstructure evolution of Al-Zn-Mg-Cu alloy was studied by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) during different rate cooling processes. Based on the DSC results, the kinetics analysis was carried out. The results indicate that the precipitation of η phase is the predominant transformation for the alloy during the cooling process after the solution treatment. And the η phase nucleates on dispersoids and at grain boundaries. The amount of η phase decreases with increasing cooling rate, and reduces by 75% as the cooling rate increases from 5 to 50 °C/min. The kinetics of the precipitation of η phase can be described by the Kamamoto transformation model when the cooling rate is a constant.
Key words: Al-Zn-Mg-Cu alloy; microstructure evolution; precipitation; kinetics model