Comparison of jetting-related microstructures associated with hypervelocity impact crater formation in copper targets and copper shaped charges

Shaped charge jet and slug formation is characterized prominently by dynamic recrystallization which may occur in deformation-recrystallization cycles, providing a mechanism for extreme plastic flow in jetting. There was no evidence for melting or melt-related phenomena. Hypervelocity impact crater development is also dominated by dynamic recrystallization in a narrow flow zone where target material is jetted into the crater rim. The crater rim can particulate by velocity gradients along the jetting rim just like the shaped charge jet. Like the shaped charge, there was no significant melt phenomenon associated with the cratering process, and extreme plastic, high-strain-rate flow occurs in the solid state. Microbands are created in a zone removed from the crater wall in copper targets in response to hypervelocity impact which, like deformation twins, are coincident with the trace of primary 111 planes. Their density and extent increase with both impact velocity and grain size. Neither microbands nor deformation twins are observed in recovered shaped charge slug and jet fragments.