I. Janotova

Evolution of Structure and Magnetic Properties of Rapidly Quenched Fe–B-Based Systems With Addition of Cu

Rapidly quenched Fe85B15 and Fe64Co21B15 with addition of 1 at.% Cu have been prepared by planar flow casting. Selected magnetic properties were measured in as-cast state and after annealing targeted to produce fine-grain structure of body-centered cubic (bcc)-Fe in amorphous matrix. The transformation process has been followed by electrical resistivity and magnetization measurements. The evolution of structure has been compared with alloys without the Cu addition. Suitable processing conditions are analyzed in order to obtain the control of size and content of crystalline phase. The results are discussed with respect to the possible enhancement of properties related to the microstructure and leading to potential application for power electronics or alternatively to convenient tailoring of magnetic characteristics using thermal treatment in external magnetic fields.

Evolution of Complex Phases in Al-Fe-Si Systems

Phase transformations and composition of Al-Fe-Si, Al-Co-Si and Al-Ni-Si based rapidly quenched ribbons have been investigated. Different Al-Si based alloys with varying Si content and additions of third metallic element, namely Al80Si20, Al60Si40, Al75Fe5Si20, Al70Fe10Si20, Al75Co5Si20, Al70Co10Si20, Al75Ni5Si20, Al70Ni10Si20 were analyzed. Variation of phase composition with elemental composition was observed. Evolution of phases was determined by resistometry, differential scanning calorimetry (DSC). In situ X-ray diffraction (XRD) and transmission electron microscope (TEM) records were observed during isothermal and isochronal annealing.

Crystallization in Rapidly Quenched Fe-B-Si System with Additions of C and Cu

Glass formability and phase transformations in rapidly quenched ferromagnetic nano-structured (Fe85B15-xSix)98-yC2Cuy (where x=0; 5 and y=0; 1) systems were investigated. The consecutive crystallization stages of bcc-Fe and borides were determined by resistometry, differential scanning calorimetry and by thermogravimetry, where the values of important transformation parameters were estimated and mutually correlated with the results from the structure analysis by TEM and XRD. Morphology of the nano-sized Fe grains in amorphous matrix and their transformation to borides matrix was observed by TEM in dependence on the chemical composition and thermal treatment. The effects of systematic alloying on the transformation process and on the resulting structure have been correlated with selected magnetic properties of the samples after suitable annealing.

Structure of Rapidly Quenched Fe-Co-Sn-B Systems with Varying Fe/Co Ratio

Abstract We present a study of ferromagnetic systems based on Fe-Co-Sn-B in nanocrystalline state. Interesting magnetic properties potentially are given by the homogeneous and ultrafine structure of bcc Fe grains in amorphous structure. The effect of alloying by Sn improves the properties of resulting structure constituted be crystalline grains in amorphous matrix. The structure transformation from amorphous state was investigated by selected techniques of thermal analysis and the resulting phase and morphology of crystalline products were analyzed.

The Comparison of Rapidly Quenched Co-Sn-B and Fe-Sn-B Alloys

The ferromagnetic systems based on Fe-Sn-B, Co-Sn-B and Fe-Co-Sn-B were studied in nanocrystalline state due to their interesting magnetic properties that are caused by the homogeneous and ultrafine structure. The alloying of Co-B and/or Fe-B by Sn 3.5 and/or 5 at. % improves the properties of resulting structure composed of the ferromagnetic grains in the amorphous matrix as proved by the XRD and TEM methods. The structure transformation from amorphous to (nano)crystalline state was investigated by DSC and TGA methods and the resulting phase and morphology of crystalline products were analyzed.

Selected Trends in New Rapidly Quenched Soft Magnetic Materials

Classical rapidly quenched nanocrystalline soft magnetic materials such as FINEMET, NANOPERM and HITPERM are seconded by new intensely investigated systems where special attention is put on materials with high saturation magnetization while preserving low coercivity. Diverse systems based on Fe-B with additions of Co, Cu, C, P and other elements were developed and tested. Successful compositional and processing design have lead to a new class of soft magnetic materials fulfilling these requirements based on Fe-Co-B, where the role of nanocrystal-forming element, namely nanograin size control, is taken up by Sn. Selected results will be presented on the case of rapidly quenched amorphous Fe-Sn-B alloy and its nanocrystallization by thermal treatment.

Influence of Ga addition on structure, thermal and magnetic properties of CoFeBSiNb metallic glasses

Rapidly quenched Co-Fe-B-Si-Nb-(Ga) ribbons were investigated. We have concentrated on the influence of small addition of gallium (2 at.%) into base composition Co₄₇Fe_20.9B_21.2Si_4.6Nb_6.3 on structure, thermal and magnetic properties in as-cast state and upon transition to nanocrystalline state. Structure of the samples was examined by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution electron microscopy (HREM). Thermal stability associated with glass transition temperature (T_g), crystallization temperature (T_x) and supercooled liquid region (ΔT_x=T_x-T_g) were examined by differential scanning calorimetry (DSC). The Curie temperature of the investigated ribbons was determined by magnetic thermogravimetry analysis (TGA).