Internal Friction Studies in Nickel Crystals from 77° to 298°K

Publisher Website
Google Scholar
Abstract
The deformation‐induced damping spectrum has been studied in nickel single crystals from 77° to 290°K. There is a strong correlation between the peaks observed and the stages of deformation. Peak X (Bordoni) rises linearly with resolved shear stress in Stages I and II, the slope in Stage I being probably higher than in Stage II, and then falls in Stage III. The orientation dependence in Stages I and II is consistent with the hypothesis that dislocations in the primary glide system are responsible for it. This linear rise is shown to follow, with the aid of well‐known relations, from Paré's version of Seeger's double‐kink theory, which predicts that the damping should be proportional to ρl, where ρ is the dislocation density and l the average loop length. Other theories (Brailsford, Seeger) give other powers of l (l2, l0 respectively). The fall of Peak X in Stage III, and its behavior on annealing, are shown to be consistent with pinning (or unpinning) by point defects. Peak Y, which we no longer believe to be the Niblett‐Wilks Peak, is associated almost entirely with Stage III, and has an orientation dependence for which there is no immediate explanation.