Effects of grain boundary structure and distribution on the spall response of copper

Abstract

Plate impact experiments have been carried out to examine the influence of grain boundary characteristics, i.e density and structure, on the spall response of Cu samples with grain sizes of 30-, 60-, 100- and 200-μm. The peak compressive stress is ∼1.50 GPa for all experiments, low enough to cause an early stage of incipient spall damage. A clear effect of the grain size is observed in the free surface velocity behavior after the pull-back minima, when re-acceleration occurs. The post-impact metallographic analyses show that for the materials with intermediate grain sizes (60 μm), the damage behavior is dominated by the growth of isolated voids and plastic dissipation. Whereas in the 30- and 200-μm samples, void coalescence is observed to dominate the damage behavior. Electron backscatter diffraction (EBSD) observations show that special boundaries corresponding to Σ3-type (∼ 60° <111> misorientation) are more resistant to void formation. © 2012 American Institute of Physics.