Hot Deformation Behavior of Al-Zn-Mg-Cu Alloy during Compression Tests

Dynamic recrystallization (DRX) plays an important role in microstructure evolution during hot deformation. In this paper, the hot deformation behavior and DRX mechanism of 7075 aluminum alloy were investigated by hot compression tests at a temperature of 250-450 degrees C and strain rate of 0.01-10 s(-1). The experimental results show that the DRX is the main softening mechanism of the AA7075, and the relationships among temperature, strain rate and Z parameter were established. Besides that, the recrystallization fraction and grain size increase with the rising of temperature (250-450 degrees C) due to the accelerating of the grain boundary migration and movement. As the values of Z parameters increase, three typical softening mechanisms occur, ranging from discontinuous dynamic recrystallization (DDRX) to continuous dynamic recrystallization (CDRX). The characteristic of DDRX is mainly grain boundary (GB) bulging relying on GB migration. With regard to the situation of CDRX, the transformation of low angle grain boundary to high angle grain boundary due to the rearrangement of dislocation could be observed based on the electron backscatter diffraction analysis. The mechanism of CDRX and DDRX existed simultaneously in condition of moderate Z parameter.