Nanometer-Scale Sliding and Inherent Viscosity of [001] Symmetric Tilt Boundaries in Cu with Boundary Particles

Abstract

An electron microscope technique has been employed to investigate the boundary-dependent intrinsic capability of sliding of [001] symmetric tilt boundaries in Cu below 573 K. The sliding has been detected by measuring a change in the direction of moire fringes of α-Fe-Co particles on the boundaries in aged Cu-Fe-Co bicrystals. The magnitude of sliding is less than 1 nm. The pre-exponential factor η o and activation energy Q of grain-boundary viscosity against misorientation angle curves are similar to the boundary energy against misorientation curve. A higher-energy boundary slides more easily with a lower viscosity and is described by a larger value of η o and a smaller value of Q. The misorientation dependence of the diffusivity of Bi along the same boundaries of Cu has also been examined. A close correlation is found between the viscosity and the diffusivity of the boundary. The higher is the boundary diffusivity, the lower is the boundary viscosity. It is suggested that the sliding process is controlled by boundary diffusion.