Electron microscopy was used to investigate the sliding of [001] symmetrical tilt boundaries at temperatures below 573K. The sliding was detected by measuring changes in the direction of moiré fringes of a-Fe-Co particles on the boundaries of aged Cu-Fe-Co bi-crystals. The magnitude of the sliding was less than 1nm. The pre-exponential factor and activation energy (for grain-boundary viscosity), as a function of misorientation angle were similar to the boundary energy dependence upon misorientation. A higher-energy boundary slid more easily, with a lower viscosity, and was described by a higher pre-exponential factor and a lower activation energy. The misorientation-dependence of Bi diffusivity along the same boundaries was also examined. A close correlation was found between the viscosity and the boundary diffusivity: the higher the boundary diffusivity, the lower was the boundary viscosity. It was suggested that the sliding process was controlled by boundary diffusion.

Nanometer-Scale Sliding and Inherent Viscosity of [001] Symmetric Tilt Boundaries in Cu with Boundary Particles R.Monzen, N.Takada: Materials Transactions, 1997, 38[11], 978-82