Material Enhancement through Cryogenic ECAP

Warhead liner performance is greatly affected by three liner material properties, namely, strength, ductility and circumferential symmetry. Extensive work done in the area of on-axis upset forging of round bar stock to form liner plates has demonstrated symmetry of texture which is necessary for uniform geometry during explosive formation. Additional development has focused on severe plastic deformation, using the technique of equal channel angular pressing (ECAP) of the starting bar stock, to condition the material prior to upset forging and to eliminate microstructure variations from multiple material vendors. Recent work in the rolling of copper plate at cryogenic temperatures, followed by a rapid anneal, has been found to create a duplex grain structure that produces high levels of strength and ductility simultaneously. The extension of the cryogenic temperature environment to ECAP processing, offers the possibility of warhead liners with an unprecedented combination of ductility and strength, which would provide enhancements in penetrator length and penetration depth respectively. In addition, the use of upset forging following cryogenic ECAP will generate the texture symmetry needed for uniform geometry during explosive forming. Such characteristics would offer the warhead designer the best possible material performance for a variety of applications.