Phase structure and crystallization of the bulk glassy FeCoZrWB alloys
|Katarzyna Pawlik 1, Jozef Bednarcik 2, Piotr Pawlik 1, Jerzy J. Wysłocki 1, Waldemar Kaszuwara 3, Bartosz Michalski 3|
1. Institute of Physics, Częstochowa University of Technology, Al. Armii Krajowej 19, Częstochowa 42-200, Poland
It was shown in previous studies , that Fe61Co10+xZr5W4−xB20 alloys (where x = 0, 2, 3 at.%) reveal good glass forming abilities, which allow to process bulk glassy samples in a form of rods up to 2 mm diameter, for the x=1 alloy, by suction-casting technique. Furthermore, the suction-casting process, led to produce thin wall tubes of even larger outer diameters up to 4 mm. Magnetic measurements had shown good soft magnetic properties of the investigated alloys. The low fraction of crystalline phase present in the rod samples was impossible to detect by conventional XRD equipment, therefore the synchrotron radiation is due to its advantages, more preferred technique of studying the glass forming abilities. In the present work, the high-energy X-ray diffraction (XRD) measurements performed using monochromatic synchrotron radiation of 112 keV (λ=0.110696 Ǻ) at undulator beamline PETRA 2 of synchrotron facility DESY/HASYLAB (Hamburg, Germany), were utilized to compare a phase constitution of melt-spun ribbon and suction-cast rods and tubes. The analysis of diffraction patterns revealed fully glassy structure for ribbon samples of all compositions investigated. In case of the bulk samples, some traces of crystallinity were detected for the rod samples, due to lower cooling rates applied for processing bulk glassy alloys. The most evident traces of crystalline phase were observed for the 1mm dia. rods of the x=2 alloy. The X-ray diffraction analysis shown existence of B6Fe23 metastable phase embedded within an amorphous matrix. Similar studies of the thin walled tube samples revealed their fully amorphous nature for all compositions investigated.
The Mössbauer spectroscopy was used to determine hyperfine parameters characteristic for the amorphous phase in rod, tube and ribbon samples. The hyperfine field Bhf distributions calculated from the Mössbauer spectra indicated non-equivalent surroundings of Fe atoms in the amorphous phase. Furthermore, dissimilar Bhf distributions were observed for samples produced by various rapid solidification techniques.
It was shown that admixture of W into the alloy composition, play important role in the glass forming ability. In the present investigations, the differential scanning calorimetry (DSC) allow to determine the thermal stability parameters of the samples, as well as crystallization processes during continuous heating. For all alloy compositions the activation energy and the crystal growth process parameters were determined using modified Matusita equation .
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 K. Matusita, T. Komatsu, R. Yokota, J. Mater. Sci., 19 (1984) 291-296.
Presentation: Oral at E-MRS Fall Meeting 2009, Symposium H, by Jerzy J. Wysłocki
See On-line Journal of E-MRS Fall Meeting 2009
Submitted: 2009-05-25 13:32 Revised: 2009-06-07 00:48
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