Superplastic Tensile Deformation Behavior and Microstructural Evolution of Al-Zn-Mg-Cu Alloy

The microstructural evolution of the Al-Zn-Mg-Cu alloy during the superplastic deformation process has been studied by high temperature tensile experiment. The superplastic deformation behaviors are investigated under different temperatures of 470 degrees C, 485 degrees C, 500 degrees C, 515 degrees C and 530 degrees C, and different strain rates of 3 x 10(-4) s(-1), 1 x 10(-3) s(-1), 3 x 10(-2) s(-1) and 1 x 10(-2) s(-1). The microstructure observation shows that uniform and equiaxed grains can be obtained by dynamic recrystallization in the initial stage of superplastic deformation. Once the recrystallization process has been finished, the variations of the fraction of high angle boundary, the grain aspect ratio and the Schmid factor are negligible during the superplastic deformation, which shows that the grain boundary sliding and grain rotation are the main deformation mechanisms. The maximum texture intensity decreases compared with the initial microstructure, indicating that grain boundary sliding and grain rotation can weaken the texture, however, the texture intensity increases in the final stage of superplastic deformation, which may be resulted from the stress concentration.