L. Novák

Influence of the melt overheating and the cooling rate on the magnetic properties of Fe83.4B16.6 amorphous alloys

Abstract The correlation between some technological parameters and magnetic properties of amorphous rapid quenched Fe 83,4 B 16,6 ribbons has been investigated. The results show an important role of the cooling rate and the melt overheating on the coercive force, magnetization and microstructure as well as on the amorphous-crystalline transformation of the alloys.

Effect of processing conditions on physical properties of transition metal-metalloid metallic glasses

The influence of processing conditions on the physical properties of transition metal-metalloid based metallic glasses was studied. It was shown that if the melt superheat and cooling rate are changed, the quenched-in stresses and the local environment of the constituent atoms are modified causing remarkable changes in several magnetic, mechanical and chemical properties. In addition, the relaxation characteristics and thermal behaviour were also drastically changed by the processing.

Crystallization of Fe-RE-B quasi-binary glassy alloys

Abstract A small percentage of rare-earth additives in iron-boron amorphous alloys has a big stabilization effect on the amorphous state. Simultaneous magnetization and electrical resistivity measurements were made to determine the crystallization temperatures. The crystalline products after various isothermal heat treatments were identified by X-ray phase analysis in order to clarify the sequence of the appearance of the products.

Magnetic and stress annealing of Fe80T3B17 amorphous alloys

Abstract The influence of transition metal additives to eutectic Fe-B on the magnetic and stress induced anisotropy was investigated. The results are compared with the same properties of binary Fe-B amorphous alloys and treated by taking into account the chemical and physical properties of the transition metal in question.

Magnetic properties of Fe-B amorphous alloys containing rare earth additives

Abstract The influence of a few per cent rare earth additives to iron-boron amorphous alloy was investigated. Compared with binary Fe-B, changes in Curie temperature, magnetization, coercive force and amorphous-crystalline transition were observed. The role of the atomic size effect and the chemical properties of rare earth in these changes are discussed.

Correlation between magnetic properties and density of Fe-T-B (T=W, Cr)glassy alloys

Abstract The influence of tungsten and chromium on the density, mean magnetic moment, exchange constant and Curie temperature was studied in Fe-T-B metallic glasses. In Fe-W-B the change in magnetic properties can be correlated with density, especially with molar volume. This correlation is supported by positron annihilation investigations which show the existence of extended ( N v ≈ 5–10) vacancy agglomerations. In Fe-Cr-B the magnetic properties vary systematically with Cr concentration in spite of the fact that the density remains constant. These results together show that the correlation between density and magnetic properties is not unambiguous.

Influence of heating on magnetic properties of Fe60Ni20B20 amorphous alloys

Abstract The coercive force and the initial magnetic permeability of amorphous Fe60Ni20B20 ribbons heated at temperatures too low to cause any crystallization have been investigated. The observed variations of magnetic quantities are discussed in the relationship to the changes of the internal stresses and to the topological reorganization of the amorphous structure.

Magnetic anisotropy of Fe−B metallic glasses introduced by casting in magnetic field

Fe-B metallic glass ribbons were prepared by melt-spinning in longitudinal and transversal magnetic field, and without an applied magnetic field. The effect of the magnetic field applied during casting was investigated by comparing several parameters such as magnetization, coercive force, magnetic anisotropy, Curie and crystallization temperature, and the domain structure of the ribbons.

Surface magnetic properties of Fe-Cr-B metallic glasses influenced by different heat treatments

Direct investigations of surface magnetic properties were performed on Fe-Cr-B metallic glasses after various heat treatments. Alloying some at.% Cr to the Fe-B increases the temperature difference between the Curie and the crystallization temperature so one can carry out heat treatments over Tc. The surface hysteresis loop was investigated by magneto-optical hysteresigraph and magnetic domain observations were made.

Rapid annealing of metallic glasses under tension

Abstract Pulse heat treatment using 0.4 s current pulses was applied to Fe 80 B 14 Si 6 amorphous ribbons above its Curie temperature in order to avoid magnetically induced anisotropy. After relaxation the pulse heat treatment was continued while applying 128 MPa mechanical stress to obtain induced anisotropy. The results of pulse annealing were monitored by coercive force and effective anisotropy measurements carried out between the pulses at room temperature. It is shown that pulse annealing enables a magnetically soft relaxed state to be achieved and if mechanical stress is applied during the process, induced anisotropy can be developed.