Mukul Kumar¹, Roger W Minich¹; ¹Lawrence Livermore National Laboratory

The scaling of mechanical properties with a microstructural length scale such as grain size is well known. However, the role of grain boundary crystallography is only recently starting to emerge. In this paper, we shall report on the scaling recently observed in the case of dynamic failure or spall under shock deformation conditions for different microstructures in high purity copper. The spall strength is observed to increase as the length scales coarsen, which is counter to the Hall-Petch relationship, eventually leveling off for single crystals. It is also observed that the spall strength decreases with increasing yield strength. These apparent contradictions will be explored in the context of nucleation site density and grain boundary character distribution in the context of the scaling laws that emerge from this data. This work was performed under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.