Microstructural properties of (Fe, Co)SiBCuNb nanocrystalline alloys

Abstract

Fe73.5-xCoxSi13.5B9Cu1Nb3 (x = 13.5 and 60 at.%) nanocrystalline alloys were studied by means of x-ray diffraction, 57Fe Mössbauer spectrometry and thermomagnetic measurements. For the first time, the compositions of both the Fe, Co, Si nanocrystalline and the residual amorphous phases were determined on the basis of combined structural and magnetic hyperfine data. The Co content of the nanocrystalline phase was found to be the same as the Co content of the as-cast alloy. The hyperfine magnetic field distribution of the intergranular phase shows the emergence of a bimodal behaviour, consistent with a two-cluster-like model. Such behaviour is attributed to the presence of iron-rich and iron-poor zones located in the bulk of the intergranular region and at the periphery of the crystalline grains, respectively.

On the effects of partial substitution of Co for Fe in FINEMET and Nb-containing HITPERM alloys

“…However, at temperatures above the Curie temperature of the residual amorphous phase, the outstanding magnetic properties are lost and their applicability cannot be extended over ∼600 K. Partial substitution of Co for Fe in HITPERM alloys improves their applicability at high temperatures due to the higher saturation magnetization and Curie temperature of the crystalline and amorphous phases [8,9]. Co-containing FINEMET alloys have also been studied [10][11][12][13][14][15].…”

“…Although several studies have been devoted to Nb-containing HITPERM [19,[21][22][23][24][25][26][27][28][29] and Co-FINEMET alloys [10][11][12][13][14][15] separately, a detailed comparative study showing the common mechanisms of the nanocrystallization phenomenon of the α-Fe, Co(Si) phase is missing. In this work, this study is performed in terms of their microstructure and magnetic properties.…”

A simple method for determining the lattice parameter and chemical composition in ternary bcc-Fe rich nanocrystals

“…6 between the lattice parameter values of the alloys Fe 67 Co 33 and Fe 67 Si 33 using an average experimental data for the alloy Fe 67 Co 8 Si 25 obtained from [31,38]. According to these results, the published values for the nanocrystals compositions Fe 67 Co 17 Si 16 [5] and Fe 68.5 Co 13.5 Si 18 [6] obtained with different approaches (probably linear ones), with a = 5.670 Å and 5.668 Å respectively, will need a Si content of about 20% to remain within the chart performed with parabolic relationships. These aspects will be addressed in a future work.…”

“…Some of them provide the chemical composition of the nanograins using different approaches (sometimes not entirely clear). For example Borrego et al [2] and Zorkovská et al [3] in bcc Fe-Si-Al nanocrystals, Blázquez et al in bcc Fe-Co-Ge nanocrystals [4], Gómez-Polo et al [5], Borrego et al [6] and Zbroszczyk et al [7] in bcc Fe-Co-Si nanocrystals. In some other works, having the necessary data to determine the chemical composition, it is not reported due perhaps to the lack of a tool for this purpose (for example, [8] in bcc Fe-Si-Al and [9] in bcc Fe-Si-Ge nanocrystals).…”

Nanocrystals and amorphous matrix phase studies of Finemet-like alloys containing Ge

“…The fitting procedure of Mössbauer spectra in this kind of materials is a matter of continuous discussion regarding the number of subspectra corresponding to the crystalline sites (from 4 to 7) and the function for fitting the area corresponding to the amorphous phase. The amorphous phase has a large distribution of hyperfine parameters and usually is observed as bimodal: it is not clear whether this is due to the presence of two distinct iron concentration regions [16] or to some effect of the electric quadrupole interaction at low magnetic hyperfine fields [17]. The distribution can be fitted with Gaussian or discrete distributions, or large sextets with Lorenzian, Gaussian or pseudo-Voigt line shapes.…”