THE IRREVERSIBILITY OF DISLOCATION-WALL FORMATION IN PERSISTENT SLIP BANDS

By cyclic deformation of copper single crystals with an amplitude of r esolved plastic shear strain gamma(pl) almost-equal-to gamma(M) almost -equal-to 1.2 x 10(-4) at 300 K, a saturated hard matrix structure was established. Then a certain volume fraction of the matrix was transfo rmed into persistent slip bands (PSBs) by increasing gamma(pl). After this step the cyclic deformation was continued with an amplitude gamma (pl) less-than-or-equal-to gamma(M) up to cumulative plastic strains o f more than 40 in order to test whether it is possible to retransform the characteristic ladder-like dislocation arrangement of PSBs into a matrix-like structure. Transmission electron microscopy revealed that such a retransformation did not occur.