Ni self-diffusion in alloyed Ni3Al

Volume, grain boundary and phase boundary Ni self-diffusion in Ni3Al-based alloys with Cr, Mo, Hf, Ta and with B has been studied over a wide temperature range (750-1100 degrees C). The sectioning technique followed by autoradiography has been used for determination of the concentration profiles. The diffusion data obtained prove that in the temperature range of 750-950 degrees C, intercrystalline boundaries make a dominant contribution to the overall diffusion flow. Grain boundary diffusion coefficients are 4-5 orders higher than the volume ones, the activation energy is 25-30% lower. Phase boundary diffusion coefficients are 3-4 orders higher than volume ones, the activation energy is 10%, lower. Increase of the aluminium content results in a decrease of diffusion permeability of both grain and phase boundaries. Copyright (C) 1996 Elsevier Science Limited