ON THE NATURE OF THE INFLUENCE OF AN ELECTRIC-CURRENT ON THE MAGNETICALLY STIMULATED MICROPLASTICITY OF AL SINGLE-CRYSTALS

A large increase in dislocation mobility in AI single crystals in a st atic magnetic field in the absence of mechanical loading of the sample s is observed when a dc electric current of low density (10(5)-10(6) A /m(2)) is additionally passed through the samples. Apparently, the rol e of the current reduces to depinning of dislocations from strong pinn ing centers on the surface of the crystal as a result of surface elect romigration of defects. This interpretation is supported by the fact t hat in samples whose surface is insulated by a layer of lacquer the pa ssage of a current through the volume of the crystal does not change t he ordinary dislocation mobility level in a magnetic field. It is hypo thesized that surface electromigration of defects, which frees disloca tions and unblocks dislocation sources, also plays a key role in the p hysical mechanism of the long-ago discovered macroplastification of me tals upon the passage of an electric current through them. (C) 1998 Am erican Institute of Physics. [S0021-3640(98)01410-8].