It was found that deformation micro-twins, which were characteristic of Neumann bands, dominated the residual microstructures beyond dynamically recrystallized and highly deformed regions below the crater walls of impact craters in polycrystalline body-centered cubic Fe targets which had been impacted with 3.2mm-diameter Fe projectiles at velocities ranging from 0.5 to 3.8km/s. The corresponding impact craters in polycrystalline face-centered cubic 304L stainless steel targets, impacted with 3.2mm-diameter stainless steel projectiles at velocities ranging from 0.5 to 3.9km/s, were observed to exhibit a more limited dynamic recrystallization zone at the crater walls; followed by a highly deformed transition into a region of mainly micro-twins, but with some intermixing of grains which contained micro-bands.

Comparison of Residual Microstructures Associated with Impact Craters in FCC Stainless Steel and BCC Iron Targets - the Micro-Twin Versus Microband Issue. L.E.Murr, E.A.Trillo, A.A.Bujanda, N.E.Martinez: Acta Materialia, 2002, 50[1], 121-31

Figure 3

Diffusivity of 51Cr in Fe-50Cr-8W and Fe-50wt%Cr