Aspects of dynamic recrystallization in shaped charge and explosively formed projectile devices

Abstract

Under a shock wave, a shaped charge (SC) liner or an explosively formed projectile (EFP) device transforms into a jet and a slug. At various laboratories, it was found that the transformation was closely related to extensive plastic flow occurring at high strain rates. Along with the shape trans-formation, there is evidence of changes in hardness, strength, grain configuration, microstructure, and resultant texture in the slug when compared to the starting liner. This article examines the effect of material parameters on jet and slug formation. Based on microstructure (metallography and trans-mission electron microscopy) and texture data, an analysis is made of the recovery and recrystalli-zation processes which are believed to be closely associated with the deformation. Grain rotations and shifts in texture are described from the starting liners to the recovered slugs. While fully re-crystallized grains are found in a “soft” recovered copper EFP slug, only partial recrystallization is achieved in a tantalum counterpart. The difference in extent of recrystallization of copper and tan-talum EFP slugs is analyzed. An attempt is made to explain the difference in terms of the deformation structures between the two types of metal. Experimental evidence tends to support a grain rotation concept for recrystallization phenomena.