In previous work, the grain boundary diffusivity of nickel in Ni3Al had been studied. The typical concentration profile obtained there was characterized by a steep initial part, followed by a concentration tail that was used for the assessment of grain boundary diffusion characteristics. The steep part of the profile close to the surface was usually attributed to volume diffusion from the free surface. However, in the given case, the diffusant was dragged deeper into the sample than could be explained by volume diffusion only. Mishin et al. (1995) had proposed a theory that explained such a dragging-in of diffusant by the movement of a certain fraction (between 0 and 1) of grain boundaries. The aim of the present work was to re-evaluate previously obtained diffusion profiles in order to extract information on grain boundary movement in pure and boron-doped Ni3Al. It was found that, for identically treated alloys, the addition of boron lowered the mean velocity of grain boundary motion but, at the same time, increased the fraction of moving grain boundaries. The activation energies for grain boundary diffusion in the transverse and parallel directions were equal to within experimental error.

Movement of Grain Boundaries in Pure and Boron-Doped Ni3Al Polycrystals. Cermak, J., Stloukal, I.: Scripta Materialia, 1997, 37[1], 17-22