Grain boundary migration and recrystallization in Ni induced by C diffusion

Abstract

When Ni specimens annealed at 1200°C for 24 h are heat-treated at 900, 1000, and 1100°C in a carburizing atmosphere, some of the grain boundaries migrate and new grains form at the specimen edges and corners. Some of the migrating grain boundaries reverse their directions. The specimen heat treated in vacuum do not show any change of the grain boundary structure. The diffusion of C is thus shown to induce the grain boundary migration and recrystallization in Ni at three temperatures. The observed grain boundary migration behaviour does not appear to be consistent with the diffusional coherency strain theory because of the high lattice diffusivity of C. The new grains appear to nucleate because of the lattice parameter change induced by the diffusion of both substitutional and interstitial solute atoms.