Fatigue deformation of silver single crystals

The defect microstructure at saturation of silver single crystals subjected to constant plastic strain amplitude, γ_p, fatigue tests in the range γ_p = ±0.0025 to ±0.025 was studied by transmission electron microscopy. The rate of fatigue hardening and the saturation stress increase with increasing plastic strain amplitude. The dislocation microstructure at saturation changes from an open band structure at small plastic strain amplitudes to a closed cell structure at large plastic strain amplitude. The defect microstructure at saturation can be characterized by the density and distribution of point defect clusters and the dislocation wall spacing along the primary Burgers vector direction. The saturation stress is inversely proportional to the dislocation wall spacing along the primary Burgers vector direction and to the spacing of the point defect clusters on the primary slip plane. There is no significant difference between the fatigue hardening, the cyclic stress-strain curve and the dislocation microstructure at saturation of silver and copper single crystals.