Surface studies of superplasticity in Al–Zn–Mg–Cu alloy via in-situ tensile test.

The grain boundary sliding and its accommodation mechanism during superplastic deformation have been identified by surface observations with focused ion beam in an Al–Zn–Mg–Cu alloy. The high-temperature in-situ tensile test is carried out in the scanning electron microscope under the region Ⅱ superplastic conditions. The experiment results indicate that the grain boundary sliding is the dominant superplastic deformation mechanism accommodated by diffusion creep and a little dislocation activity. The grain rotation also plays an essential role in superplastic deformation. There are no striated zones found in a vacuum environment, just cracks. A grain boundary sliding model is proposed based on the surface features. [ABSTRACT FROM AUTHOR]