Behavior of the bordoni peak in zone-refined Cu during annealing at high temperatures

Abstract

The Bordoni peak is thrown as a relaxation peak which appears at around 50K (for measuring frequency f {approximately} 1Hz) in various cold worked metals with the fcc structure. Seeger has proposed that this relaxation is associated with a kink pair formation (KPF) on dislocations. Since all the characteristics of the Bordoni peak so far observed experimentally are consistent with the KPF model, this model was widely accepted as the origin of the Bordoni peak. However, the flow stress at low temperatures expected from the temperature of the Bordoni peak is about two orders of magnitude larger than that observed in the macroscopic deformation experiments. If the Bordoni peak is attributed to the KPF model, the authors have to postulate the presence of preferential deformation sites on dislocations (deformation short-circuits) to explain the very low flow stresses in fcc metals. Possible candidates for such sites might be sites at bent corners of extended dislocations, and lubrication sites. They have, however, no definite model at present. In the present work, the behavior of the Bordoni peak in zone-refined Cu was studied during annealing after cold work. In contrast to the results on the ordinary pure Cu, the Bordoni peak was foundmore » to grow during annealing even after 800 C. The results will be shown to be in excellent agreement with the KPF model.« less