Peculiarities of self-diffusion in fine-grained nickel

In the present work, detailed aspects of the properties of the boundaries of fine grains are revealed by comparing them with grain boundaries in an ordinary polycrystal. The investigation was done on commercially pure nickel (NP-2, 99.5% Ni), treated to produce a fine grain by rapid electrical heating of cold-deformed (e=50%) wire specimens to 675°C and rapid quenching. A polycrystal with grain size 100-150 μm was obtained from the original fine-grained nickel by annealing for 10 hr at 1100°C. A diffusion experiment was used for investigation of grain boundaries, so that the state of the interfaces and the diffusion permeability of the boundaries, one of its specific properties, could be determined. For quantitative comparison of the character of diffusion of 63 Ni on grain boundaries and verification of stability of the grain structure during diffusion annealing, high-resolution (∼0.3 μm) autoradiography was used