Annealing of deformation substructure in fatigued silver single crystals

Abstract

The annealing behavior of dislocation substructures and point-defect clusters produced by fatigue deformation was studied in single crystals of silver. Crystals fatigued to saturation in alternate tension and compression at a constant plastic strain amplitude of ±0.02 were annealed at different temperatures, and the resulting microstructural changes were studied by transmission electron microscopy. High-temperature annealing (> 500°C) of the dislocation cell structure results in almost complete annihilation of the dislocation cell walls with no indication of polygonization and recrystallization. Annealing at intermediate temperatures results in a partially annealed structure consisting of dislocation tangles formed by primary and secondary dislocations, several of which are held up at Lomer Cottrell barriers and point-defect clusters. A large number of dislocation dipoles and loops comprising the dislocation cell walls in fatigued specimens anneal out in the temperature range 300–500°C. Upon annealing, the point defects produced during fatigue deformation acquire various configurations which include Frank loops, stacking fault tetrahedra, and prismatic loops.