The Yielding of Copper Single Crystals at Different Stages of Work-hardening

Abstract

The yield parameter of Hocks' statistical work-hardening theory was measured in monotonic deformation of copper single crystals at room temperature. Three different orientations and two different shear strain rates were used in the tests. The yield parameter was measured at different stages of work-hardening. A slight dependence of yield parameter on crystal orientation was found. The form of yield parameter at stage I work-hardening was found to differ strongly from the form of the parameter at later stages of work-hardening. The forms of yield parameter curves at stages II and III were quite similar. The penetration probability function of dislocations was determined on the basis of received results. The function was found to depend strongly on crystal orientation and the stage of work-hardening. A slight influence of strain rate on penetration probability function was revealed. The influence of crystal orientation, stage of work-hardening (dislocation structure) and strain rate on yielding behavior of copper single crystals is discussed. A comparison between monotonic and cyclic deformation of copper single crystals is made on the basis of recent and previously measured results. The similarities between the two modes of deformation are discussed in the terms of Rocks' statistical theory.