Diffusion phenomena in nano-crystalline Cu produced by severe plastic deformation

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Since their invention in early eighties, nano-crystalline materials attract growing interest in view of their beneficial properties that rely on an increased amount of grain boundaries. Among different production routes, the Equal-Channel Angular Pressing (ECAP) is an attractive method to prepare bulk ultra-fine-grained materials. It is argued that non-equilibrium grain boundaries are created by the ECAP procedure. However, the kinetic properties of such materials are almost not investigated. How fast is the diffusion along grain boundaries in comparison to their conventional coarse-grained counterparts indeed? What is the relation between the structure and the kinetic properties? These and similar problems will be solved in the proposed project. The key point of the project will be a careful and extensive radio tracer investigation of grain boundary diffusion of Cu, Ag, and Ni tracers in nano-crystalline Cu and Cu-Zr alloys produced by the ECAP. The experiments will be complemented by analytical high-resolution transmission electron microscopy. As the goal, reliable experimental data should be derived on the kinetic and thermodynamic properties of internal interfaces in ECAP materials.