In-situ SEM and EBSD investigation of the deformation behavior of extruded Mg-6Al-1Zn-1.1Sc alloy

The present study subjects the extruded Mg-6Al-1Zn-1.1Sc (wt%) alloy to reveal the deformation during in-situ tensile testing at room temperature by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results demonstrate that the parallel slip traces are increasingly observed on the surfaces of grains with increasing strains owing to the movement of dislocations inside the grains toward the sample surface, while microcracks are frequently observed at grain boundaries. The slip trace analysis indicate that many basal slips are activated during the deformation. The twinning behaviors of the extruded alloy during tensile testing are dominated by extension twinning. The orientation of grains is demonstrated to have a profound effect on their deformation, where grains with orientations deviating greatest from <0001>//TD exhibit the highest dislocation density after deformation. This can be attributed to the fact that these oriented grains are prone to activate basal slip due to the large Schmid factor (SF). Similarly, the deformation of grains is also found to be highly dependent on their size, where the dislocation density of coarser grains increases more significantly than that of finer grains during deformation because coarser grains have greater space available for accommodating dislocations than finer grains.