EFFECT OF TEMPERATURE ON THE AMPLITUDE DEPENDENCES OF THE ACOUSTOPLASTIC EFFECT AND INTERNAL-FRICTION DURING DEFORMATION OF CRYSTALS

Oscillatory strain amplitude dependences of the acoustoplastic effect and absorption of ultrasonic vibrations (frequency of about 100 kHz) c ausing this effect were measured in a wide temperature range in situ d uring quasistatic deformation of NaCl and Al single crystals. An incre ase in efficiency of the ultrasonic effect on the plastic deformation process has been found with an increase in temperature. The data obtai ned provide evidence for the distinction in basic mechanisms of the ac oustoplastic effect and amplitude-dependent internal friction. The abs orbtion of ultrasound is largely due to dislocation-point-defect inter actions under reversible movement of mobile dislocations. Mechanical a ctivation of irreversible movement of the same mobile dislocations thr ough long-range internal stress fields of other dislocations and dislo cation pile-ups is suggested as the basic mechanism of the acoustoplas tic effect. Mechanisms are discussed determining the temperature depen dences of the acoustoplastic effect, amplitude-dependent internal fric tion and type of amplitude hysteresis of the internal friction.