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 ∼5 μm to 50 μm diameter. The fracture surfaces of copper with silica inclusions are covered by a net of dimples of 1 μm to 5 μm 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 ∼5μm. 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.