Interpretation of microflow measurements in niobium crystals

Abstract

The application of the microstrain technique to b.c.c. metal deformation is discussed and an interpretation of microflow data given with reference to experiments on pure Nb single crystals deformed in tension. Microflow in prestrained crystals is explained in terms of a transition from edge dislocation motion to screw dislocation motion at the macroflow stress. Interstitial effects are found to be particularly significant during microflow and are probably important in determining the low temperature flow stress in even the highest purity b.c.c. metals. A further low temperature contribution comes from a directional component of the internal stress field which depends on the distribution of dislocations rather than on their density.