The interaction between a dislocation and an impurity in Mg2+-doped (0.035mol% in the melt) samples was investigated at 77 to 178K, using 2 models. One was the Fleischer model, and the other was a Fleischer model which took account of the Friedel relationship. The dependence of strain-rate sensitivity, due to impurities, upon temperature was better fitted by the Fleischer model than by the Fleischer-Friedel model. The activation enthalpy, ΔH, for the Fleischer model appeared to be nearly proportional to the temperature, in comparison with the Fleischer-Friedel model. The Friedel relationship between effective stress and average dislocation segment-length was exact for most weak obstacles to dislocation motion. However, the results implied that the Friedel relationship was unsuitable for treating the interaction between a dislocation and an impurity. The value of ΔH(Tc), for the Fleischer model, was found to be 0.61eV. This value corresponded to the activation enthalpy required by a dislocation at 0K in order to overcome the strain field around the impurity. The Gibbs free energy for dislocation motion was determined to be between 0.42 and 0.48eV.

Interaction between a Dislocation and an Impurity in KCl:Mg2+ Single Crystals. Y.Kohzuki, T.Ohgaku: Journal of Materials Science, 2003, 38[6], 1301-6