Diffusion mechanisms near tilt grain boundaries of orientations [100] and [111] were studied by the method of molecular dynamics in the dependence on a disorientation angle. The interactions between different pairs of atoms in the alloy were presented by the model potentials constructed on the basis of tight-binding potentials. The calculated crystal block limited by rigid and periodical boundary conditions amounted to atoms. In the experiments, the crystal was impulsively heated during 100-300 ps at different temperatures. As the result, three basic mechanisms of grain boundary diffusion were distinguished: atomic migration along the nucleus of grain boundary dislocation, cyclic mechanism of atomic migration near the nuclei, the formation of the chains of atomic moving from one dislocation nucleus to the other nucleus. The mechanisms began to act successively with the growth of temperature. It depended on disorientation angles of the boundaries. Then, a grain boundary slipping and intergrain slipping with dislocations emission, the formation of fault defects were added to the above mentioned mechanisms at the presence of uniaxial deformation. At relatively low temperatures, diffusion took place only over sublattices of Ni atoms without disturbing the superstructure order. The disturbance of the superstructure order took place at more elevated temperatures.

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