Precipitation of Al3Zr Dispersoids under Various Homogenization and Its Effect on Recrystallization in 2198 Al-Cu-Li Alloy

Herein, the precipitation of Al3Zr during one- and two-step homogenization processes is studied by the transmission electron microscopy method, and its effect on recrystallization is investigated by the electron backscattering diffraction technique after the same hot compression and solution treatment, respectively. The results show that when the temperature reaches 430 & DEG;C, just some small Al3Zr dispersoids are visible in samples that undergo one-step treatment. As the first-step homogenization temperature increases from 365 to 430 & DEG;C, Al3Zr radius increases from 9.4 to 19.1 nm while the number density decreases rapidly from 1201 to 183 & mu;m(-3). In addition, the average radius of Al3Zr increases to 22.1 nm while the number density decreases to 76 & mu;m(-3) when the sample is homogenized at 500 & DEG;C/24 h. After a double-step homogenization with decreased first-step temperature, lower recrystallization fraction is obtained. Therefore, the optimal homogenization treatment is determined to be 365 & DEG;C/16 h + 500 & DEG;C/24 h, after which the most desirable Al3Zr distribution and the smallest recrystallization fraction are obtained during thermomechanical process. This result can provide a more appropriate parameter for homogenization treatment in order to achieve a more dispersed distribution, which will result in stronger pinning force during the thermomechanical process.