NANOMETER GRAIN-BOUNDARY SLIDING IN CU [011] SYMMETRICAL TILT BOUNDARIES, MISORIENTATION DEPENDENCE AND ANISOTROPY

Sliding on [011] symmetric tilt boundaries in Cu has been studied between 323 and 584 K, using an electron microscope technique and bicrystals of an aged Cu-1.05% Fe-0.45%Co alloy. The b.c.c. Fe-Co particles formed by aging on boundaries suppress the sliding so that it amounts to less than 1 nm. The sliding has been detected by observing a change in the direction of Moire fringes formed by the matrix {111} and the particle {110}. Finely dispersed f.c.c. Fe-Co particles in grains abutting boundaries completely prevent crystal dislocations playing any role in boundary sliding. The sliding increases with increasing temperature and saturates to a value determined by the size and distribution of the boundary particles and the applied shear stress. A boundary with a higher energy can slide at a lower temperature, as low as 350 K. A curve showing the ease of sliding against the misorientation angle is similar, with cusps, to the energy vs misorientation angle curve. The sliding parallel to the tilting axis, [011], occurs at lower temperatures than that in the direction normal to the tilting axis.