High-Energy Diffraction Microscopy Characterization of Spall Damage

Abstract

The emerging characterization technique of high-energy diffraction microscopy (HEDM) was used to investigate ductile dynamic damage evolution in a Cu polycrystal. Experimental efforts were undertaken with the goal of elucidating correlations between microstructural features with preferred damage nucleation sites and the progression of damage at the localization stage. HEDM was used to microstructurally map the initial volume of a 1.2 mm-diameter Cu sample. HEDM in the near-field mode collects diffraction information from high-energy synchrotron radiation to non-destructively probe microstructure and orientation in three dimensions in volumes approaching the bulk scale. The Cu sample was subsequently planar shock-loaded in a plate-on-plate geometry and soft-recovered, using an assembly specially developed for sub-size samples. The ex situ shocked sample was then re-characterized by HEDM, providing data on the location of incipient spall voids with respect to the local microstructural neighborhood. In addition, diffraction quality and misorientation gradient data provide qualitative measures of the spatial distribution of stored work and indicate regions of plastic localization. This provides the potential for unprecedented insight as to the relative preference of spall nucleation sites and correlations between microstructure, damage, and plastic flow.