Synchrotron Tomographic Characterization of Damage Evolution During Aluminum Alloy Solidification

Fast synchrotron X-ray microtomography was used to directly observe damage accumulation in a semi-solid Al-15 wt pct Cu alloy with a solid fraction of similar to 0.75 during isothermal tensile deformation. The evolution of damage was quantified in terms of size distribution of internal and surface-connected damage, strain mapping, and volume change to provide an insight into hot tear formation. A combination of existing void growth, void nucleation, and void coalescence all contribute to the final failure, although each dominates during different stages of deformation. Specifically, internal voids are shown to grow and coalesce from the region of high triaxiality at the center of the gage length outward and prove to be the contributing factor to final failure caused by insufficient liquid feeding. (C) The Minerals, Metals & Materials Society and ASM International 2012