ACOUSTOPLASTIC EFFECT AND INTERNAL-FRICTION OF ALUMINUM SINGLE-CRYSTALS IN VARIOUS DEFORMATION STAGES

The dependences of the acoustoplastic effect and the internal friction on the oscillatory strain amplitude are measured in various deformati on stages of low-purity aluminum single crystals. It is discovered tha t the acoustoplastic effect is observed not only in the macroscopic pl astic region of the stress-strain diagram, but also for microplastic d eformation in the ''elastic'' loading and unloading stages. The sign o f the effect reverses during unloading. An increase in the strain rate leads to enhancement of the acoustoplastic effect and the absorption of the energy of ultrasonic vibrations causing this effect with a freq uency of about 100 kHz. It is concluded that the acoustoplastic effect observed during both macro-and microplastic deformation is caused by the irreversible high-speed motion of dislocations through the long-ra nge stress field of the other dislocations after breaking through the Cottrell atmospheres. (C) 1997 American Institute of Physics.