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Recovery, recrystallization and diffusion in cold-rolled Ni
Recovery and recrystallization processes in cold-rolled Ni are investigated. While recrystallization and grain growth at temperatures above 700 K lead to a significant (three-fold) decrease in micro-hardness, recovery at 600 K is shown to cause a measurable micro-hardness increase. This increase in micro-hardness is confirmed by atomic force microscopy observations of Vickers indents, and it is correlated with the vacancy-annihilation peak of the calorimetric signal. Diffusion of impurity–vacancy complexes to the dislocation cores and the resulting pinning of dislocations are surmised to contribute to the measured micro-hardness increase. Self-diffusion along interfaces in cold-rolled and partially recrystallized Ni samples is measured employing the radiotracer serial sectioning technique. Diffusion rates similar to those of general high-angle grain boundaries in well-annealed coarse-grained Ni polycrystals are observed. The results imply that the diffusion rate along the stationary recrystallization front, i.e. the interfaces separating the recrystallized and the as-deformed regions of the material, is similar to that along a general high-angle grain boundary.