Relation of the köster effect to low-temperature internal friction peaks in deformed copper

Abstract

A study is made to determine the relationship between the Köster effect, i.e. the modulus defect due to dislocations which is present in a freshly deformed sample and which subsequently anneals out, and the various low temperature relaxation peaks which have been observed. It is shown that the Köster modulus defect at room temperature is made up of several parts. The largest fraction corresponds to dislocation motion which contributes to the high-temperature side of the Bordoni peak and also to the subsidiary Niblett-Wilks peak. About 40% of the Köster modulus defect is still present at 5°K. The significance of the present results to the interpretation of the Bordoni relaxation is discussed. In particular, it is shown that these results are consistent with a mechanism for which the relaxation time depends on a power of the dislocation loop length. © 1965.