L. V. Spivak

Effect of hydrogen on the properties of amorphous alloys finemet type:: PEN-X effect

Abstract Elastic properties of the amorphous metallic alloys based on iron and cobalt were found to decrease after hydro-genation, and to recover upon subsequent storage at 295 K. The possible causes for this unusual behaviour are discussed on the basis of measurements of electrical resistance and magnetic susceptibility, as well as X-ray diffraction data. 1999 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.

The Barkhausen effect in a hydrogen-saturated Fe-B-Si-Ni amorphous alloy

Is is established that saturation of a Fe78B12Si9Ni1 amorphous alloy ribbon with hydrogen leads to a several-fold increase in the emf observed under the Barkhausen effect conditions. The magnitude of the observed effect is related to the hydrogen content in the alloy.

The effect of hydrogen on the shear modulus of polycrystalline aluminum

Electrolytic hydrogen saturation of polycrystalline aluminum leads to a significant (up to about 30%) decrease in the shear moduli G of samples. This change in G is accompanied neither by the loss of plasticity (no hydrogen-induced brittleness) nor by a change in the electric resistance (in contrast to that observed during the hydrogenation of typical hydride-forming metals and alloys, including those in the amorphous state).

Interaction of Hydrogen with Amorphous Alloys in Open Thermodynamic Systems

In the present study, we report the hydrogenation of amorphous or nanocrystalline iron, cobalt and titanium-nickel based alloys. Hydrogenation of these materials leads to a multiple acceleration of the creep deformation at room temperature. After hydrogenation, an almost full reduction of the shear resistance was observed on the iron-based alloys. The physical and mechanical characteristics of the alloys return to the initial values after a complete evacuation of hydrogen from the samples.

The effect of hydrogen on crystallization of a Ti50Ni25Cu25 amorphous alloy

Two effects not reported previously for the interaction of hydrogen with amorphous metal alloys were observed in a Ti50Ni25Cu25 alloy: (i) hydrogen-induced increase in the crystallization temperature and (ii) suppression of the reverse martensitic transition B19→B2 in the alloy samples hydrogenated upon crystallization.

The effect of hydrogen on the shear modulus of quasibinary alloys of the TiNi-TiCu system

Hydrogen saturation of amorphous quasibinary alloys of the TiNi-TiCu system is accompanied by a catastrophic decrease in their shear moduli. The effect is not related to the formation of new phases or structural components during hydrogenation.

The Barkhausen effect and percolation threshold in amorphous metal-dielectric nanocomposites

A new percolation situation has been found in metal-dielectric nanocomposites containing ferromagnetic components. For a certain concentration of metal atoms, the vectors of spontaneous magnetization of individual nanoparticles exhibit a correlated behavior. As a result, a structure containing a very large number of ferromagnetic nanoparticles shows magnetization reversal in a macroscopic nanocomposite volume in a single giant Barkhausen jump.

Anomalous thermal effects in crystallization of hydrogenated amorphous alloys of the TiNi-TiCu system

Several anomalous effects not reported previously for the interaction of hydrogen with amorphous alloys of the TiNi-TiCu system have been observed, including (i) the passage from one-to multistage mechanism of the transition from the amorphous to crystalline state in hydrogenated alloys, (ii) a manifold increase in the thermal effect of glass transition in hydrogen-saturated compositions, and (iii) the appearance of an endothermal peak in the differential scanning calorimetry curves of hydrogenated alloys, which is related to the decomposition of finely dispersed hydride phases.

The domain structure and barkhausen effect in Fe78B12Si9Ni1 amorphous alloy

There is no correlation between dimensions of the domain structure elements in an Fe78B12Si9Ni1 amorphous alloy ribbon and the Barkhausen effect characteristics in this alloy in various states: initial, hydrogenated, and annealed. Traditional notions of the Barkhausen effect, the nature of which is related to the domain size and the domain wall mobility, are inapplicable to disordered systems such as magnetically soft amorphous metal alloys.

On the nature of low-temperature anomalies of the anelastic properties of metallic glasses

In Memory of A. M. Roshchupkin The low-temperature (30<T<300 K) internal friction and elastic modulus of the metallic glass (MG) Ni60Nb40 subjected to preliminary cold working by rolling, high-temperature uniform straining, or electrolytic hydrogenation is investigated. It is established that cold rolling, which induces localized plastic flow, or hydrogenation radically alters the temperature dependences of the internal friction and elastic modulus: hysteresis appears in the background damping and intense relaxational peaks arise in the internal friction, accompanied by a defect of the elastic modulus. A uniform strain does not affect the low-temperature anelastic behavior of MGs. Microplastic deformation is observed to accompany the hydrogenation of weakly loaded samples. It is asserted that localized microplastic deformation also occurs on hydrogenation with no load. Plastic flow accompanying both rolling and hydrogenation occurs by the formation and motion of dislocationlike defects, which in the presence of an external load of alternating sign give rise to the observed anelastic anomalies. It is concluded that the low-temperature internal-friction peaks, described in the literature, in the “as-quenched,” cold-deformed, or hydrogenated MGs are all of a dislocation nature.