Interfacial diffusion in a nanostructured Cu produced by means of dynamic plastic deformation

A nanostructured pure Cu sample consisting of nano-scale twin bundles and nano-sized grains was produced by means of dynamic plastic deformation (DPD) at cryogenic temperature. The apparent activation energy for recrystallization of the nanostructured Cu was determined, being ∼57 kJ mol−1. Interfacial diffusion of Zn in the nanostructure was investigated using secondary ion mass spectrometry within the temperature range 358-463 K, in which the volume diffusion is negligible. The measured penetration profiles showed two distinct sections with different slopes, owing to the direct and independent diffusion fluxes along twin boundaries (TB) and grain boundaries (GB). The determined GB diffusivity is ∼2 orders of magnitude higher than the TB diffusivity. Relative to the diffusivities and free energies of GB and incoherent TB in coarse-grained Cu, both values in the DPD Cu sample are slightly higher at temperatures <373 K, and approach comparable values at higher temperatures.