Ultrafast diffusion and internal porosity in ultrafine-grained copper-lead alloy prepared by equal channel angular pressing

Room-temperature diffusion of Ni-63 radiotracer in ultrafine-grained Cu-1 wt.%Pb alloy prepared by equal channel angular pressing reveals the existence of ultrafast transport paths. Some of these paths remain in the material even after complete recrystallization. Using the focused ion beam technique, numerous cracks/pores are revealed. Long-range tracer penetration over tens of micrometers proves that this internal porosity is interconnected by highly diffusive paths. This network of porosity comprises non-equilibrium interfaces, micropores and microcracks. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.