The Instability of the Work Hardened State. I. Slip in Extraneously Deformed Crystals

Copper single crystals were strained in tension after being extraneously deformed either by twisting or spark damaging. In both cases a transient region of low hardening was observed after extraneous deformation. Slip line studies showed that this low hardening region was associated with slip band formation and inhomogeneous deformation along the gauge length. The dislocation distributions in strained crystals were studied by an etch pit technique. It was found that slip band formation is accompanied by dislocation multiplication on the main glide plane but not on other planes. It is proposed that dislocation distributions are in general unstable to slip on a single system unless they have been formed by slip on that system.