The possibility of monitoring the dynamic behaviour of grain boundaries during high-temperature annealing, via post mortem atomic force microscopic studies of the surface topography, was demonstrated. Jerky motion of the grain boundaries in Ni-rich material was observed during annealing at 1400C. This type of motion resulted in a characteristic morphology of ghost lines in the area which had been swept by migrating grain boundaries. Atomic force microscopic measurements of the grain boundary groove topography at the original grain boundary position showed that the root of the groove was blunted. This proved that the grain boundary left its original position. The Mullins coefficient, which depended upon the surface energy and surface diffusivity, was deduced from the distance between the groove root and the maximum of the hump. The topography of the ghost-line region was measured, by using atomic force microscopy, and it was found to have a periodic character in which the amplitude decreased in going from the final to the original grain boundary position. It was shown that the logarithm of the amplitude of the maxima decreased linearly with ghost-line number. The time between 2 successive grain-boundary jumps was estimated to be 3.5s. It was concluded that the grain boundary migrated for only a small fraction of the total annealing time.

Jerky Motion of Grain Boundaries in NiAl - an Atomic Force Microscopy Study. E.Rabkin, V.Semenov, T.Izyumova: Scripta Materialia, 2000, 42[4], 359-65