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Öğe The effect of furnace annealing and surface crystallization on the anisotropy, ?E and magnetoimpedance effects in Fe71Cr7Si9B13 amorphous wires(Iop Publishing Ltd, 2004) Bayri, N; Kolat, VS; Atalay, FE; Atalay, SThe dependence of the magnetization loops, coercivity, anisotropy constant, DeltaE and magnetoimpedance (MI) effects in positively magnetostrictive Fe71Cr7Si9B13 amorphous wires on annealing conditions were studied. Samples were annealed at temperatures of 440degreesC and 460degreesC for durations between 0.3 and 300 min. The results indicate that progressive annealing first leads to relief of internal stresses and annealing of wires at 460degreesC for 60 min produces the minimum coercivity of about 1 A m(-1). Further annealing increases the coercivity and anisotropy, due to partial crystallization at the surface. It was found that the anisotropy changes its direction to the circumferential direction with the surface crystallization. The maximum change in Young's modulus was measured to be about 75% in a partly surface crystalline sample. It was observed that the magnitude of the MI effect of the stress relieved sample could exceed 200% at 1 MHz.Öğe Giant stress-impedance effect in Fe71Cr7Si9B13 amorphous wires(Elsevier Science Sa, 2004) Bayri, N; Atalay, SThe giant stress-impedance (SI) effect in as-received and furnace annealed Fe71Cr7Si9B13 amorphous wires is studied. Samples were annealed at temperature of 460degreesC for times between 0.3 and 300 min to remove internal stresses. The results show that the magnetoimpedance and SI effect change sharply with annealing and a maximum stress-impedance ratio of 255% is observed in the wire annealed for 10 min under an applied tensile stress of 250 MPa. (C) 2004 Elsevier B.V. All rights reserved.Öğe Hydrogen effect on the field dependence of Young's modulus of FeCuNbSiB alloy(Elsevier Science Sa, 2002) Kolat, VS; Bayri, N; Atalay, SThe magnitude of the magnetic field dependence of Young's modulus of FeCuNbSiB alloys was found to decrease after hydrogenation but to nearly recover after 2-3 h. A large variation in the magnetic and the magnetoelastic properties of as-received sample was observed after hydrogenation. DeltaE and M-H results of samples annealed at 450degreesC showed that annealing could reduce hydrogen permeation into the sample. Practically no variation in the magnetic and magnetoelastic properties of samples annealed at 550degreesC were observed before and after hydrogenation. (C) 2002 Elsevier Science B.V. All rights reserved.Öğe The influence of chromium content on the properties of Fe74-xCrxCu1Nb3Si13B9 alloys(Wiley-V C H Verlag Gmbh, 2002) Bayri, N; Adigüzel, HI; Atalay, S; Sovak, PIn this study, we have investigated the effect of Cr substitution on the structural, magnetic and magnetoelastic properties of Fe74-xCrxCu1Nb3Si13B9 (x = 2, 4, 8, 11, 14) alloys. The samples were annealed between 450 and 600 degreesC for 1 It under argon atmosphere to induce various nanocrystalline fractions. The change in microstructure upon annealing were examined by the X-ray spectrum data. A large influence of Cr content on the formation of alpha-FeSi phase was observed. The magnetic field dependence of the Young's modulus (DeltaE effect) was measured using the vibration reed method. The DeltaE results are interpreted partly in terms of the stress relief and the reduced magnetostriction in nanocrystalline samples.Öğe Low field magnetoimpedance in FeSiB and CoSiB amorphous wires(Elsevier Science Bv, 2004) Atalay, S; Bayri, NThe low magnetic field, H, dependence of real part of impedance, R, of as-received FeSiB and CoSiB wires have been investigated. The measurements were performed at various frequencies for various wire lengths. The wires with length longer than 7cm show sharp peaks in the R-H curves. The combination of R-H data with M-H data indicates the existence of interaction between motion of the domain wall in the inner core and the magnetic moments in the outer shell. (C) 2003 Elsevier B.V. All rights reserved.Öğe Non-destructive Crack detection using GMI sensor(Wiley-V C H Verlag Gmbh, 2004) Goktepe, M; Ege, Y; Bayri, N; Atalay, SIn this study, the variation of the magnetic flux distribution in a magnetised ferromagnetic material which has inhomogeneity as a crack is studied using giant magnetoimpedance, GMI, sensor. The sensor was moved by a specially designed moving system. The amorphous (Co0.94Fe0.06)(72.5)Si2.5B15 wire was used as a GMI sensor and 1 MHz with 5 mA ac current applied to the GMI sensor. A large decrease in the output voltage of the sensor circuit was observed when the sensor was moved on the top of the crack, after the further movement of the sensor the output voltage came back to the nearly previous value. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Öğe Torsional stress impedance effect in Fe71Cr7Si9B13 amorphous wire(Wiley-V C H Verlag Gmbh, 2004) Atalay, FE; Bayri, N; Bahadir, AR; Atalay, SThe magnetoimpedance effect has been measured in as-received and current annealed Fe71Cr7Si9B13 amorphous wires under torsional stress varied up to 1.2 rad/cm. It was found that the torsional stress dependence of impedance of as-received amorphous wire has a non-monotonous shape with first an increase of the impedance and then a decrease. On the other hand, the impedance of current annealed wire directly starts to decrease with increasing torsional stress. The current annealing of wire results in a large variation in the magnitude of torsional stress impedance effect, (DeltaZ/Z)xi(%), up to 150%. Also, a simple mathematical model based on the magnetic moment rotation to explain torsional stress versus impedance data was developed and the results were partly discussed on the basis of this model.
