Influence of texture on dislocation creep and grain boundary sliding in fine-grained cadmium

Abstract

The creep behavior of cadmium was studied over the temperature range 0°-260° C (0.46–0.9 T m ) and was found to depend on grain size and texture. Whereas the creep behavior of cast cadmium of moderate grain size (150 μm) is comparable to the creep of most pure polycrystalline metals, unusual creep behavior was observed for a fine-grained (9 μm), textured, powder metallurgy cadmium. The following characteristics were noted for the fine grained textured material. At high stresses and low temperatures, marked change of texture with creep deformation are observed, and the stress exponents and activation energies obtained are consistent with control of deformation by a short circuit diffusion dislocation mechanism. At low stresses and high temperatures, all observations imply that deformation occurred by grain boundary sliding accommodated by slip in the vicinity of the grain boundary. A stress exponent of two, an activation energy equal to that for grain boundary diffusion and no strain hardening characterize plastic flow in this region; furthermore, it was noted that the ease of grain boundary sliding was influenced by texture, an observation which suggests that crystallographic factors contribute to grain boundary sliding.