Lattice and Grain Boundary Self-Diffusion in Nickel

Lattice and grain boundary self-diffusion coefficients of radioactive nickel 63 into high purity nickel have been measured over the temperature range 650°–475°C. The lattice diffusion coefficients, measured by radioactive counting of the surface, are given by DL=1.9 exp(−66 800/RT) cm2sec−1in agreement with previous measurements at higher temperatures. The grain boundary diffusion coefficients, determined from activity-penetration data, are similarly given by DB=0.07 exp(−27 400/RT) cm2sec−1and found to be independent of grain diameter in the range of about 0.03 to 0.07 mm.