Deformation twins in oriented, columnar-grained tungsten rod ballistic penetrators

Deformation twins coincident with traces of {211} planes in sections cut from [001], [011], and [111] columnar-grained tungsten rod ballistic penetrators in rolled homogeneous armor targets have been identified by transmission electron microscopy and selected-area electron diffraction. These twins have been shown to coincide with Neumann bands observed by optical metallography. In addition, the twin density appears to increase at the head of the projectile and twins are observed to coincide with flow features which are characterized by dynamic recovery and recrystallization which provide the flow mechanism. Since deformation twins appear to play a prominent role in columnar and single-crystal tungsten rod flow, and twinning is limited by grain size, sintered or polycrystalline tungsten or tungsten alloy penetrators cannot be expected to perform like single crystal penetrators and penetrator strategies may need to focus on inducing twinning or in developing superplastic behavior.