Investigation of void linkage in magnesium using SEM and micro computed X-ray tomography

Ductile fracture in metallic materials occurs by the nucleation, growth, and linkage of microvoids within the bulk of the material. As a result, two dimensional techniques must be complimented with three dimensional techniques in order to completely characterize the fracture process. In the present study, tensile testing coupled with: scanning electron microscope (SEM) imaging, electron backscattered diffraction (EBSD) patterning, and micro computed x-ray tomography (XCT), have been used to analyze void linkage in magnesium, which exhibits poor formability at room temperature. SEM imaging and EBSD patterning have been used to characterize the mechanisms responsible for void linkage and to determine the effects of void fraction and void orientation on the failure strain. Micro XCT has been used to examine the evolution of internal voids. It has been established that void fraction and void orientation have a weak influence on the failure strain due to the premature linkage of voids. EBSD analysis has shown that this premature void linkage is associated with the failure of twin and grain boundaries. The results suggest that (in contrast with more ductile fcc metals) the local microstructure has a significant impact on void linkage.