An unusual topography of the grain boundary thermal grooves in Ni-rich samples was observed after annealing at 1400C. One of the surfaces which formed the grain-boundary groove exhibited no curvature that was measurable in the atomic force microscope; thus indicating its singular nature. The theory of grain-boundary grooving at singular surfaces was developed in the small-slope approximation, assuming a negligible diffusivity on the surfaces. The calculated groove-shapes were in good agreement with experimental data, and differed appreciably from the shapes which were predicted by the classic Mullins grooving-theory for isotropic surfaces.

Grain Boundary Grooving at Singular Surfaces. E.Rabkin, L.Klinger, V.Semenov: Acta Materialia, 2000, 48[7], 1533-40