Electrical resistivity of fatigued copper crystals

Measurements made during fatigue at very low temperatures show that electrical resitivity saturates with the flow stress. The net crystal defect content therefore reaches an equilibrium value. Isochronal anneal of the fatigued crystals showed no reduction of resistivity below 80 K, and <4% reduction at 100 K. The fundamental fatigue mechanism operating at low temperature is thus unlikely to involve point defect recovery processes. The resistivity then decreases with increasing anneal temperature; at 300 K ≈40% remains. There is no correlation between resistivity anneal data and PSB profile shapes. Dislocation density in PSB walls, calculated from resistivity, exceeds that for which description in dislocation terms is valid; the material is dislocation-saturated. Such PSB wall material should behave as a perfect sink for dislocations, providing a natural explanation for fatigue saturation.