Papers by Author: V.A. Khonik

Abstract: By means of the vibrating reed technique, measurements of internal friction have been performed in the temperature range of 120 K < T < Tg (= glass temperature) on two amorphous alloys, each produced as ribbon and bulk material. The different contents of free volume result in an only slight shift of the onset of irreversible structural relaxation to lower temperatures (i.e., lower activation energies) for the ribbons, while considerably different amounts of structural relaxation occur. After correcting for the thermoelastic effect, the reversible structural relaxation, i.e., an approximately exponential increase of damping with rising temperature, is well described by KWW kinetics (β ≈ 0.3). For the Zr-based alloy only, a clear relaxation peak occurs in the range from 270 K to 320 K (for the first flexural vibration mode between 100 Hz and 400 Hz) induced by hydrogenation. In addition, the effect of plastic deformation on the damping behavior by cold rolling of the bulk materials has been examined.

Abstract: The effect of uniaxial compression on the ultrasound velocities in bulk glassy Zr52.5Ti5Cu17.9Ni14.6Al10 and Pd40Cu30Ni10P20 has been studied and the third-order elastic moduli of these glasses have been determined.

Abstract: The paper presents the results of detailed measurements of the isothermal tensile stress relaxation in Pd40Cu30Ni10P20 bulk and ribbon samples, which differ by ∼ 104 times in their production quenching rates. The relaxation law is derived. It is shown that the relaxation kinetics is not much affected by the quenching rate.

Abstract: Irreversible structural relaxation of bulk amorphous Zr52.5Ti5Cu17.9Ni14.6Al10 was studied by means of logarithmic decrement and shear modulus measurements using an inverse torsion pendulum in the frequency range from 5 Hz to 40 Hz. Irreversible contributions to the decrement and shear modulus and their frequency, temperature, and time dependences were investigated. The activation energy spectrum of irreversible structural relaxation has been reconstructed. It has been shown that irreversible structural relaxation can be regenerated by a special heat treatment. The results obtained are discussed within the framework of a phenomenological model, which implies existence of two-well relaxation centers in the glass structure.