On the damage and fracture of commercially pure magnesium using x-ray microtomography

The nucleation, growth and linkage of microvoids are examined in commercially pure magnesium using x-ray computed microtomography (XCT). Tensile testing was performed inside the chamber of an XCT system with each test stopped at various levels of deformation to acquire scans. The nucleation of flat penny-shaped voids is observed relatively early during plastic deformation due to failure at twin and grain boundaries. Once nucleated the voids exhibit rapid growth along preferential directions related to the crystallographic texture of the material as well as the sample geometry. The final fracture occurs by a macroscopic shearing process. Furthermore, the fracture surface reveals two main characteristics: a faceted surface associated with twinning and irregular features related to the failure of grain boundaries. The data exhibit both a quantitative and qualitative difference in the damage development process in magnesium as compared with FCC metals such as aluminum and copper.