Nanocrystalline refractory metals for extreme condition applications

For the last decade, there has been research aimed at engineering plastic instability into the deformation behavior of body centered cubic (b.c.c.) metals. At dynamic strain rates, the adiabatic shear band deformation mode has been shown to improve the performance of kinetic energy penetrator materials. However, for some b.c.c. metals the transition to localized plastic deformation dominates at all strain rates. This limits the traditional engineering properties (e.g., ductility and toughness) and feasibility of incorporation into a long rod penetrator system. Recently, we demonstrated that nanocrystalline tantalum shows significant promise as it deforms via adiabatic shear bands in dynamic compression but shows significant tensile elongation in quasi-static deformation.