Vz Bengus

Anelastic deformation processes in metallic glasses and activation energy spectrum model

Abstract The isothermal kinetics of anelastic deformation below the glass transition temperature (so-called ‘stress induced ordering’ or ‘creep recovery’ deformation) was investigated in Ni-Si-B metallic glass. The relaxation time spectrum model and two recently developed methods for its calculation from the isothermal experimental data sets seem to be powerful tool for the study of anelastic deformation processes in disordered systems. Reliability of the used calculation methods (the first is based on the Fourier transformation technique and the second on the non-linear regression) is expressed in the fact that both provide qualitatively the same result (without prior assumptions concerning the form or nature of the spectrum): creep recovery relaxation spectrum consists of three relatively separated peaks with the well defined characteristic relaxation times. The influence of (i) loading time, (ii) the structural relaxation and (iii) unloading temperature on the spectrum is demonstrated and discussed. Using the assumption that different peaks in creep recovery spectra represent different type of elementary deformation processes (or different type of deformation defects) detected during the creep recovery, discussion concerning the eventual deformation defects will be actualized.

Direct spectrum analysis of anelastic deformation response during structural relaxation of amorphous metals

Direct relaxation time spectrum analysis method has been successfully used to observe and to study changes in the kinetics of isothermal anelastic deformation response of soft magnetic metallic glass Fe/sub 40/Ni/sub 40/B/sub 20/ during structural relaxation. Computed relaxation time spectra contain three or four quite well separated peaks. >

Mechanical properties of amorphous alloys ribbons prepared by rapid quenching of the melt after different thermal treatments before quenching

The mechanical properties of amorphous alloy are greatly influenced by the thermal treatment of its melt before rapid quenching. The strength and the fracture toughness of some amorphous alloys obtained after melt beating above the melt critical temperature T-CR are essentially higher than those obtained from melts that were not heated above T-CR. This difference is considered to be caused by changes in the melt atomic structure under heating above T-CR

Low temperature mechanical properties of metallic glasses - Connection with structure

Available data on plasticity and strength of metallic glasses below the room temperature (down to 0.5 K) are considered and explained on the basis of the polycluster model of amorphous solids especially with taking into consideration possible atomic structure of clusters and defects of intercluster boundaries.

FAILURE CRACK ORIENTATION AT DUCTILE SHEAR FRACTURE OF FE80-XNIXB20 METALLIC-GLASS RIBBONS

AbstractOrientation of failure cracks of oblique mode at ductile shear fracture are measured for Fe80−xNixB20 (x=10, 20, 30, 40, 50, 60) metallic glass ribbons (MGR) uniaxially extended with strain rate

STATISTICAL INVESTIGATIONS OF FRACTURE DEMONSTRATIONS ON NI-SI-B METALLIC-GLASS RIBBONS FAILED IN TENSION AT 4.2 TO 300-K

\dot \varepsilon

Fracture toughness of amorphous Fe40Ni40B20 ribbons: strain rate dependence

from 3.3×10−6 to 1.25×10−3 s−1 at temperatures 300, 77 and 4.2 K. An angle between the failure crack and tension axis is found to depend non-monotonously on nickel concentrationx and strain rate