On dislocation loss in thin film electron microscopy of polycrystalline copper

Experiments are described in which flow stress, electrical resistivity and dislocation density were measured as functions of tensile plastic strain in 99·996% polycrystalline copper extended up to 10%. Dislocation density was measured by the technique of thin film electron microscopy. An apparent anomaly in the results involving dislocation density measurements is interpreted as being due to dislocation loss during thinning. This appears to have increased rapidly with dislocation density above a critical dislocation density.