Self-Diffusion in Silver during Plastic Deformation in Torsion

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Abstract
Self‐diffusion of Ag110 in silver polycrystals subjected to simultaneous torsion was studied near 700° and 800°C using the sectioning technique. Strains ⩽ 0.50 and strain rates ⩽ 13.8×10−5 sec−1 were employed. Specimen structures before and after deformation were also examined. The effects of straining on diffusion were relatively small in all cases. At 800°C the diffusivity was increased by no more than ∼50%. At 700°C the increase was no more than ∼100%. A substantial part of this observed enhancement was undoubtedly only apparent and due to difficulties associated with surface roughness. The results agreed generally with our previous work involving deformation in extension and compression but were in marked disagreement with recent results of Lee and Maddin and Forestieri and Girifalco [C. H. Lee and R. Maddin, Trans. AIME 215, 397 (1959); A. F. Forestieri and L. A. Girifalco, J. Phys. Chem. Solids 10, 99 (1959)], who have reported enhancements larger by one to two orders of magnitude. No simple explanation for these differences was found. Estimates of dislocation short‐circuiting and the generation of extra point defects indicated that only small enhancements should be expected in agreement with the present results.