AN INVESTIGATION OF GRAIN-BOUNDARY PLANE CRYSTALLOGRAPHY IN POLYCRYSTALLINE NICKEL

An investigation has been carried out to measure and categorize the gr ain-boundary plane indices of boundaries in pure nickel. Coincidence s ite lattices (excluding Sigma = 3s) were found to be either asymmetric al tilt boundaries with high indices, or have irrational boundary plan es. For the Sigma = 3s, almost half were asymmetrical tilt boundaries displaced from the 111/111 symmetrical tilt boundary on the 110 zone. Such boundaries have low energies compared to other Sigma = 3s. The 21 1/211 incoherent twin was not observed, which was explained on the bas is of its higher energy compared to other boundaries on the 110 zone. The results are compared and contrasted with previous data, where boun daries abutted the specimen surface during annealing, which is not the case for the present data. Comments are made with respect to the rela tionship between macroscopic and atomic-level boundary geometry and im plications of the results for grain-boundary properties.