Effects of Initial Grain Size of Al-Zn-Mg-Cu Alloy on the Recrystallization Behavior and Recrystallization Mechanism in Isothermal Compression

Fine-grained (average gain size 3.8 mu m) and coarse-grained (average gain size 24.9 mu m) Al-Zn-Mg-Cu alloys were subjected to isothermal compression at 10(-3) s(-1) and temperature ranges from 300 degrees C to 450 degrees C. The grain structures after isothermal compression were observed by electron backscatter diffraction (EBSD). The results show that the continuous dynamic recrystallization (CDRX) mechanism dominated to form sub-grains in grain interiors during isothermal compression of coarse-grained materials, and sub-grains were gradually developed in grain interiors as the effective strain increased. Discontinuous dynamic recrystallization (DDRX) was the main recrystallization mechanism during isothermal compression of fine-grained materials, in which finer recrystallized grains were formed at grain boundaries. The temperature of isothermal compression had little influence on the recrystallization when the growth of recrystallized grains was slight, and sub-grains were hardly developed in fine-grain interiors.