Modulus and Damping of Copper after Plastic Deformation at 4.2°K

Abstract

An investigation of the Bordoni dislocation relaxation peaks in copper has been carried out under experimental conditions which permit plastic deformation of specimens at 4.2\ifmmode^\circ\else\textdegree\fi{}K, with measurement of their Young's modulus and internal friction upon subsequent warmup. Isochronal annealing at progressively higher temperatures in the interval from 100\ifmmode^\circ\else\textdegree\fi{} to 360\ifmmode^\circ\else\textdegree\fi{}K, taking data from 4.2\ifmmode^\circ\else\textdegree\fi{}K after each anneal, shows (a) a pronounced reduction in height of both the major peak at 62\ifmmode^\circ\else\textdegree\fi{}K and the minor peak at 28\ifmmode^\circ\else\textdegree\fi{}K for annealing temperatures to 200\ifmmode^\circ\else\textdegree\fi{}K, (b) a slow regrowth and shift to higher temperature of the major peak with annealing above 200\ifmmode^\circ\else\textdegree\fi{}K, accompanied by continued diminution of the minor peak, and (c) a monotonic increase, through the full range of annealing temperatures, of the Young's modulus as measured at 4.2\ifmmode^\circ\else\textdegree\fi{}K. A qualitative discussion of these results indicates that the interaction between point defects and dislocations is an essential feature of the dislocation relaxation process.