Forest Dislocation Intersections in Stage I Deformation of Copper Single Crystals

Abstract

The obstacle profiles for the intersection of thermally penetrable forest dislocations have been measured in pure copper single crystals in easy glide in two batches of crystals that were pre-strained to two different levels of resolved shear stress of 0.3 and 0.6 MPa, having two different densities of forest dislocations. Almost identical relations were found from the two experiments for the dependence of the activation area on the obstacle cutting force, indicating that the activation area did not scale with the mean obstacle spacing in the plane as was expected. This departure from expected behavior is attributed to a break-down of thermal activation considerations based on fully relaxed dislocation configurations when the mean obstacle spacings in the plane become very large.