Load relaxation studies of AgCl

Room-temperature load relaxation experiments were performed on single crystals of nominally pure, UV-illuminated, γ-irradiated, and Cd²⁺-doped single crystals of AgCl. The resulting log σ-log ε{lunate} curves, all of which are concave downward, were analyzed in terms of Hart's two branch rheological model. The constant hardness log σ-log ε{lunate} curves obtained at several prestrain levels on nominally pure crystals can be translated into a single master curve demonstrating that the plastic deformation behavior of nominally pure AgCl at room temperature can be described by a mechanical equation of state. The log σ-log ε{lunate} curves for UV-illuminated and Cd²⁺-doped crystals deviate at low strain rates from those for nominally pure crystals suggesting that dislocation-precipitate and dislocation-point defect interactions are important at low strain rates in the UV-illuminated and Cd²⁺-doped samples. At a given stress level, the log σ-log ε{lunate} curves of the γ-irradiated crystals are more steeply curved than those of the nominally pure crystals and can be superimposed onto the curves for the nominally pure crystal by translation to higher stress and strain rate levels. These observations indicate that the high-temperature branch in Hart's model contributes more to the flow stress in the γ-irradiated samples than it does in the nominally pure crystals. In addition, the deformation behavior of crystals deformed along the [100] and [111] axes were studied in order to compare flow on the {110}〈110〉 and {001}〈11̄0〉 slip systems. The log σ-log ε{lunate} curves for the [100] crystal are more steeply concave downward than those for the [111] crystals, indicating that the high-temperature mechanism in Hart's model is more important for flow on {110}〈110〉 than on {001}〈110〉.