Ductile spall in copper of different structure

The spall signals and post mortem metallography of crystals of Cu+0.1{\%}Si solid solution and copper with sub-micron silica inclusions were studied in planar impact experiments at two different load durations. The samples contained large (4-5 mm in diameter) grains with [100] axes parallel to the sample normal. Fractography of the spall surfaces correlate with the free surface velocity histories. The main fracture surface of the Cu+0.1{\%}Si grains consists of dimples $\sim $5 $\mu $m to 50 $\mu $m diameter. The fracture surfaces of copper with silica inclusions are covered by a net of dimples of 1 $\mu $m to 5 $\mu $m size some of which contain Si particles. In both cases the grain boundaries crossing the fracture surface are partially open and covered by a fine net of tensile dimples of $\sim $5$\mu $m. The free surface velocity histories demonstrate prolonged spall fracture process for Cu+0.1{\%}Si samples and faster fracture at lower fracture stress for copper with brittle inclusions.