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The Structure and Magnetocaloric Effect of MnCoGe Alloy Modified by Nb

100%

Kutynia K. , Gębara P. , Przybył A.

Archives of Metallurgy and Materials

2022

tom Vol. 67, iss. 3

879--883

The aim of this work was to investigate the effect of partial substitution of Mn by Nb on structure and thermomagnetic properties in the (Mn, Nb)-Co-Ge alloy. The master alloys were prepared by arc-melting in an arc furnace with high purity of constituent elements under a low pressure of Ar. The prepared specimens were studied in as-cast state. The X-ray was performed by BRUKER D8 Advance diffractrometer with Cu Kα radiation. The analysis of the XRD pattern revealed coexistence of two orthorhombic phases with different lattice constants. The analysis of the temperature dependence of magnetizaton confirmed the XRD results and showed that produced material manifested two magnetic phase transitions corresponding to detected phases. The values of the Curie temperature were 275 and 325 K. The values of magnetic entropy change ∆SM equaled 3.30 and 2.13 J/(kg K), respectively for recognized phases. Biphase structure of produced material allowed to reach relatively high refigeration capacity 307 J/(kg). Moreover, the analysis of field dependences of magnetic entropy change (∆SM = CBn) allowed to construct temperature dependence of exponent n. The analysis of elaborated n vs. T curve confirmed biphasic structure of produced material.

Modelling hysteresis loops of non-oriented electrical steel

88%

Chwastek K. , Koprivica B. , Rosić M. , Gozdur R. , Gębara P.

Przegląd Elektrotechniczny

2023

tom R. 99, nr 11

221--223

Non-oriented electrical steels constitute the most important segment of the market of soft magnetic materials. In the paper the usefulness of the model based on hyperbolic tangent nonlinear transformation for the description of quasi-static hysteresis loops for this type of material is verified.

Blachy elektrotechniczne o ziarnach niezorientowanych stanowią najważniejszy segment rynku materiałów magnetycznie miękkich. W pracy zweryfikowano użyteczność modelu opartego na nieliniowej transformacji tangens hiperboliczny do opisu quasi-statycznych pętli histerezy dla tego typu materiału.

Influence of annealing conditions on changes of the structure and selected properties of Al88Y7Fe5 and Al88Y6Fe6 alloys

75%

Babilas R. , Spilka M. , Łoński W. , Radoń A. , Kądziołka-Gaweł M. , Gębara P.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2023

tom Vol. 71, nr 2

art. no. e144614

Al-Y-Fe amorphous and nanocrystalline alloys are characterized by a unique collection of diverse properties that are influenced by various factors, including heat treatment. In this paper, the effect of heat treatment on the structural changes and selected properties of Al-Y-Fe metallic glasses in the as-spun state is investigated. The structure of the Al88Y7Fe5 and Al88Y6Fe6 alloys was examined by X-ray diffraction (XRD) and Mössbauer spectroscopy (MS). The corrosion resistance of the samples was characterized using polarization tests in a 3.5% NaCl solution at 25 °C. The effect of sodium chloride on the surface was studied with scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The magnetic properties of Al-based alloys were explored using a vibrating sample magnetometer (VSM). It was revealed that the tested alloys show better properties after annealing than in the as-spun state. The annealing of the Al88Y7Fe5 and Al88Y6Fe6 alloys in the temperature range of 200 to 300 °C improved the magnetic properties and corrosion resistance of these materials. After 3,600 s, the better EOCP values were recorded for the Al88Y6Fe6 and Al88Y7Fe5 alloys after annealing at 300 °C and 200 °C, adequately. On the basis of the polarization tests, it was concluded that the electrochemical properties are better for Al88Y6Fe6 alloys after annealing at 300 °C.