Microstructural evolution associated with hypervelocity impact crater formation in metallic targets

摘要

This investigation is a detailed analysis of the residual microstructure associated with hypervelocity (>5 km/s) impact crater formation in three different metallic targets. Light and transmission electron microscopy techniques have revealed significant differences in the type of microstructures among an OFHC copper target, an 1100 aluminum alloy target and a 6061-T6 aluminum alloy target. The residual microstructure of the impact crater in copper is characterized by a recrystallized region adjacent to the crater wall followed by an extensive region of microband clusters, and a zone of dislocation cells which incrase in size as the deformation decrases. In addition, the microstructure below the impact crater in the 1100 aluminum target is characterized by a recrystallized region and a zone of sub-grains or cells which also incrase in size as the distance from the crater wall increases. In contrast, the microstructure of the 6061-T6 aluminum alloy target, containing precipitates, exhibits variations in dislocation density along the impact axis below the crater wall with no apparent recrystallization.