Microstructural Aspects of Grain Boundary Bulge in a Dynamically Recrystallized Mg-Al-Zn Alloy

Microstructural features of grain boundary bulging have been studied in a dynamically recrystallized (DRXed) Mg-Al-Zn alloy. Unidirectional compression was used to deform the specimens to different strains at 473 K (200 A degrees C). Microstructural characterization of the deformed specimens was performed by using both scanning electron microscopy and transmission electron microscopy (TEM). From the present results, it is suggested that in AZ31 Mg alloy, the DRXed grain is developed from grain boundary bulging. After a grain boundary segment starts to bulge, a bridging dislocation wall forms and anchors the bulged grain boundary. During further deformation, the misorientation of this bridging wall gradually increases, then transforms into a grain boundary, and a DRXed grain forms. Electron backscattered diffraction was used to study the orientation relationship between bulges/DRXed grains and the parent grains, and no special orientation relationship was found between them.