Spall fracture of coarse- and ultrafine-grained FCC metals under nanosecond high-current relativistic beam irradiation

Experimental data are presented on the fracture mechanism and plastic deformation and thickness of the spalled layer obtained on irradiation of targets made from coarse- and fine-grained fcc metals (copper and aluminum) by a nanosecond high-current relativistic beam. The general and special features inherent in the modification of the microstructure of the spalled layer and near the surface of the spall fracture are discussed for the coarse- and fine-grained materials of the targets. Possible reasons for the varying extent to which the characteristics of the spall fracture of the copper and aluminum targets are affected by the grain size are suggested.