Dislocation dynamics and thermally activated deformation in polycrystalline silver chloride

Abstract

The deformation of polycrystalline silver chloride containing approximately 500 p.p.m. impurities has been investigated over the temperature range 77°K to 400°K. At temperatures below 296°K the results show only fair qualitative agreement with Fleischer and Frank theories for interaction between dislocations and tetragonal defects, providing no basis for discrimination between the theories. It is shown that the power-law representation of deformation is not applicable unless entropy effects are invoked. The thermal component of the flow stress and the activation volume are independent of strain and hence the dislocation debris often resulting from deformation of ionic solids is not controlling the deformation. At temperatures above 296°K jerky flow is observed and this is attributed to dynamic strain ageing.