Comparison of residual microstructures associated with impact craters in fcc stainless steel and bcc iron targets: the microtwin versus microband issue

Abstract Deformation microtwins characteristic of Neumann bands dominate the residual microstructures beyond a dynamic recrystallization and highly deformed regime below the crater wall of impact craters in polycrystalline bcc iron targets impacted by 3.2 mm diameter iron projectiles at velocities ranging from 0.5 to 3.8 km s −1 . Corresponding impact craters in polycrystalline fcc 304L stainless steel targets impacted by 3.2 mm diameter stainless steel projectiles at velocities ranging from 0.5 to 3.9 km s −1 were observed to have a more limited dynamic recrystallization zone at the crater wall followed by a highly deformed transition into a region of mostly microtwins, but with some intermixing of grains containing microbands.