Comparison of beginning and ending microstructures in metal shaped charges as a means to explore mechanisms for plastic deformation at high rates

Optical metallography and transmission electron microscopy (TEM) observations were made of a variety of forged or sputtered copper, molybdenum, and tantalum shaped charge components. The beginning shaped charge liner grain sizes and sub-structures were compared with those observed in residual (ending), recovered and corresponding jet fragments and slugs. The wide range of microstructures and evolutionary features of observed microstructures can be characterized by low-energy dislocation structure (LEDS) principles which are altered because the shaped charge deformation corresponds to hot working, and dynamic recovery and recrystallization play a prominent role. There is a prominent relationship between the starting liner grain size, Do, and the ratio Do/Ds, where Ds is the ending (slug or jet), steady-state grain size. As a consequence of this relationship, it appears that the volumetric stored energy, which depends upon the grain size and dislocation density (or degree of deformation), is the critical issue in controlling shaped charge jet stability.