INFLUENCE OF IMPURITY CONTENT ON THE ACOUSTOPLASTIC EFFECT, INTERNAL-FRICTION, AND YOUNGS MODULUS DEFECT DURING DEFORMATION OF CU-NI SINGLE-CRYSTALS

Oscillatory stress amplitude dependences of the acoustoplastic effect, absorption of ultrasonic vibrations (frequency of about 100 kHz) caus ing this effect, and Young's modulus defect were simultaneously measur ed in situ during quasistatic deformation of Cu-1.3-7.6 at.% Ni single crystals. The time dependences of the magnitude of the acoustoplastic effect at constant oscillatory stress amplitudes were also obtained. The amplitude-dependent internal friction and Young's modulus defect d iminish drastically with increasing Ni content. The dependence of the magnitude of the acoustoplastic effect on the Ni concentration is much less pronounced and is reversed with increase in oscillatory stress a mplitude. Data on the kinetics of the acoustoplastic effect revealed ' instant' (time-independent) and 'relaxational' (time-dependent) compon ents. Both components show a similar dependence on Ni concentration, t hus indicating their common origin. It is concluded that, while the am plitude-dependent internal friction is largely due to dislocation-poin t-defect interactions, the acoustoplastic effect originates mainly fro m dislocation-dislocation interactions.