Study of Shape and Microstructure Changes of Ta Linear for Building an Explosively Formed Penetrator

An explosively formed penetrator (EFP) is a kind of kinetic energy warhead that contains a metal linear structure. After exploding, the linear structure in the EFP is deformed and hits the target as a form of aero-stable long-rod penetrator. To achieve high penetration performance, Ta is commonly used as the linear material due to its high density and formability. In this study, we investigated changes in the shape and microstructure of the Ta linear after explosion, especially for two cases; flying just before impact, and after impact. The computational simulation revealed that the disc shaped linear structure was elongated in the flying direction after the explosion, which was consistent with the results of the experiment. As the microstructure of the Ta linear could be changed during flight and after penetrating the target, samples of each stage were prepared. Microstructure analysis showed that severe deformation and dynamic recrystallization occurred repeatedly during flight after explosion, which seemed due to the increased temperature that results from the friction between the linear and air. After penetrating the target, the shape of the Ta linear was severely changed and grain size was drastically increased. At the moment when the EFP hit the target, the sharp increase in temperature would exert a critical impact on grain growth. Key words: explosively formed penetrator, linear, tantalum, microstructure