Parallel Dislocations in Cobalt Whiskers

Abstract

A study of 30 cobalt whiskers obtained by hydrogen reduction of the halide is herein reported. The whiskers were grown in the face-centered cubic phase but were cooled through the phase transformation to the hexagonal phase before being examined. The majority of the whiskers had a [10·0] axis; however, whiskers with [00·1], [11·1], and [1̄1·1] axes were also observed. These hexagonal axes are related to simple growth directions in the face-centered cubic system. An axial strain caused perhaps by a screw dislocation restricts the atom movement in this phase transformation to the close-packed planes perpendicular to the whisker axis. Single and multicrystal whiskers were obtained. Aligned edge dislocations parallel to the whisker axis gave rise to multicrystal filaments. Heating the multicrystals resulted in the disappearance of the symmetric small angle grain boundaries through the movement of the edge dislocations toward the central core of the whisker.