S. B. Kustov

Influence of impurity content on the acoustoplastic effect, internal friction, and Young's modulus defect during deformation of Cu-Ni single crystals

Abstract Oscillatory stress amplitude dependences of the acoustoplastic effect, absorption of ultrasonic vibrations (frequency of about 100 kHz) causing this effect, and Youngs modulus defect were simulataneously measured 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 Youngs modulus defect diminish 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 amplitude. Data on the kinetics of the acoustoplastic effect revealed ‘instant’ (time-independent) and ‘relaxational’ (time-dependent) components. Both components show a similar dependence on Ni concentration, thus indicating their common origin. It is concluded that, while the amplitude—dependent internal fri...

STRAIN AMPLITUDE-DEPENDENT ANELASTICITY IN CU-NI SOLID SOLUTION DUE TO THERMALLY ACTIVATED AND ATHERMAL DISLOCATION-POINT OBSTACLE INTERACTIONS

Experimental investigations of the internal friction and the Young’s modulus defect in single crystals of Cu-(1.3–7.6) at. % Ni have been performed for 7–300 K over a wide range of oscillatory strain amplitudes. Extensive data have been obtained at a frequency of vibrations around 100 kHz and compared with the results obtained for the same crystals at a frequency of ∼1 kHz. The strain amplitude dependence of the anelastic strain amplitude and the average friction stress acting on a dislocation due to solute atoms are also analyzed. Several stages in the strain amplitude dependence of the internal friction and the Young’s modulus defect are revealed for all of the alloy compositions, at different temperatures and in different frequency ranges. For the 100 kHz frequency, low temperatures and low strain amplitudes (∼10−7–10−5), the amplitude-dependent internal friction and the Young’s modulus defect are essentially temperature independent, and are ascribed to a purely hysteretic internal friction component. ...

Effect of temperature on the amplitude dependences of the acoustoplastic effect and internal friction during deformation of crystals

Abstract Oscillatory strain amplitude dependences of the acoustoplastic effect and absorption of ultrasonic vibrations (frequency of about 100 kHz) causing this effect were measured in a wide temperature range in situ during quasistatic deformation of NaCl and Al single crystals. An increase in efficiency of the ultrasonic effect on the plastic deformation process has been found with an increase in temperature. The data obtained provide evidence for the distinction in basic mechanisms of the acoustoplastic effect and amplitude-dependent internal friction. The absorbtion of ultrasound is largely due to dislocation-point-defect interactions under reversible movement of mobile dislocations. Mechanical activation of irreversible movement of the same mobile dislocations through long-range internal stress fields of other dislocations and dislocation pileups is suggested as the basic mechanism of the acoustoplastic effect. Mechanisms are discussed determining the temperature dependences of the acoustoplastic eff...

Acoustic study of martensitic-phase aging in copper-based shape memory alloys

An acoustic technique was applied to study aging of the β1′ martensitic phase in a number of copper-based shape memory alloys (Cu-Zn-Al, Cu-Al-Ni, Cu-Al-Be) characterized by various degrees of martensitic-phase stabilization. The nonlinear anelasticity of the martensitic phase was studied in wide ranges of temperature (7–300 K) and vibrational strain amplitude (2 × 10−7 −2 × 10−4) at vibrational-loading frequencies of ∼100 kHz. It was shown that aging effects of the martensitic phase can have homogeneous and heterogeneous components. The homogeneous component is associated with a change in the degree of atomic order in the crystal volume. The basic heterogeneous mechanisms of martensitic-phase aging are associated with the formation of atmospheres of point defects and local changes (which are greater than those in the crystal volume) in the degree of atomic order in the vicinity of partial dislocations and the boundaries between martensite variants. It is concluded that various stabilization properties of the alloys at hand result not only from the different diffusion properties of quenching point defects but also from the different influence of these defects on the degree of atomic order and the different features of their interaction with partial dislocations and intervariant boundaries.

Temperature Dependence of the Internal Friction of Polycrystalline Indium

The temperature dependences of the internal friction and the elastic modulus of polycrystalline indium have been investigated in the temperature range 7–320 K at oscillatory loading frequencies of approximately 100 kHz. The effect of temperature on the amplitude dependence and the effect of high-amplitude loading at 7 K on the temperature and amplitude dependences of the internal friction of indium have been analyzed. It has been demonstrated that the thermocycling leads to microplastic deformation of indium due to the anisotropy of thermal expansion and the appearance of a “recrystallization” maximum in the spectrum of the amplitude-dependent internal friction. The conclusion has been drawn that the bulk diffusion of vacancies and impurities begins at temperatures of approximately 90 K and that, at lower temperatures, the diffusion occurs in the vicinity of dislocations. It has been revealed that the high-temperature internal friction background becomes noticeable after the dissolution of Cottrell atmospheres.

Amplitude dependence of the internal friction and Young’s modulus defect of polycrystalline indium

The dependences of the internal friction and the Young’s modulus defect of polycrystalline indium on the oscillatory strain amplitude have been studied over a wide range of temperatures (7–320 K) and oscillatory strain amplitudes (10−7−3.5 × 10−4) at oscillatory loading frequencies of about 100 kHz. It has been revealed that the amplitude dependences of the internal friction and the Young’s modulus defect include stages associated with the interaction of dislocations with point defects and the interdislocation interaction. The temperature range characterized by the formation of point-defect atmospheres (the Cottrell atmospheres) near dislocations in indium has been determined.