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

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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°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° to 360°K, taking data from 4.2°K after each anneal, shows (a) a pronounced reduction in height of both the major peak at 62°K and the minor peak at 28°K for annealing temperatures to 200°K, (b) a slow regrowth and shift to higher temperature of the major peak with annealing above 200°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°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.