Electron Microscope Observation of Dislocation Motion in Iron at Low Temperatures

Abstract

Iron foil crystals are extended on a deformation stage in an electron microscope over a temperature range between 23 and -100°C. At 23°C screw dislocations bow but between pinning points, while at -100°C they are straightened except the sharp curve in the vicinity of pinning points. The radius of curvature of dislocations around the drag point decreases with decreasing temperature. These results imply that the Peierls stress for edge dislocations is very small compared with that for screw dislocations. Local stress is estimated from the radius of curvature, showing the same temperature dependance as macroscopic yield stress.