Dislocation Behavior in Pure Niobium at Low Temperatures

Foils of niobium single crystals with [110] (001) orientation were deformed in tension at — 100 °C inside a 500 kV electron microscope, and the behavior of individual dislocations was studied by means of a VTR system. Screw dislocation mobility was determined by the density of superjogs caused by cross slip or cutting. Probabilities of dislocation multiplication, cutting, and debris formation during 0.1% plastic strain were measured for three mean velocities of screw dislocations. The frictional stress for ideally straight edge dislocations in niobium was estimated to be 10% of flow stress, which was significantly larger than that in iron.