Influence of the casting in magnetic field and of annealing history on the elasticity moduli in the Fe79Cr6.6B14.4 metallic glass

Journal of Magnetism and Magnetic Materials 112 (1992) 317-319 North-Holland

Influence of the casting in magnetic field and of annealing history on the elasticity moduli in the Fe79Cr6.6Bi4.4 metallic glass Z b i g n i e w Kaczkowski a, l~va Kisdi-Kosz6 b and Ladislav Potock~ ~ a Polish Academy of Sciences Institute of Physics, AI. Lo:nikdw 32/46, PL-02-668 Warsaw, Poland b Hungarian Academy of Sciences Central Research insti?ate for Physics, P.O. Box 49, H-1525 Budapest, Hungao, c Faculty of Science, P.J. Safdrik Unit,ersity, Nam. Febrt,..~roc#ho Vitazstca 9, CS-04154 Ko#ice, Czechoslocakia

In the Fe79Cr6.6Bl.l. 4 metallic glass ribbons, prepared in longitudinal or transversal magnetic fields, the dependences of the elasticity moduli at constant field H and at constant induction B were obtained for the as-cast state and after annealing at the temperature range from 80 to 360°C.

1. Introduction and experimental part The aim of the investigations was to find a optimum treatment of the Fe79Cr6.6B14.4metallic glass ribbons produced in magnetic field for the providing of the magnetomechanical couplin~ coefficient (k) higher than 0.2 and of the good AE effect. Fe79Cr6.6B14.4 metallic glass ribbons were prepared by the melt spinning technicue it a longitudinal (ML) or transverse (MT) ~aagrt,-tic field of 13-15 kA/m, produced by an "lp~ropriate ferromagnetic yoke [1-3]. The magnetic field was applied either to the melt puddle from which the ribbon was formed (ML, MT) or 3,9 mm away from it (MLS, MTS), where the melt was solidified and left the cooling wheel [1,3]. T i e composition was determined by the atomic absorption method. From these ribbons the 59-60 mm long and about 4 mm wide strips were ,'ut. Their thickness was equal to 27.5 (MTS), 28.0 (MT), 31.8 (ML) and 32.3 Ixm (MLS) [3]. These samples lldU

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temperature there are two annealings: for 2 and 4 h [3]. The elasticity moduli at constant magnetic field (E H) and at constant magnetic induction (E B) were calculated from the resonant and antiresonant frequencies [4]. These strip-shape samples were working as the half-wavelength resonators after applying the ac magnetic field of 1-3 A / m amplitude (with the frequency range covering the resonance and the antiresonance, i.e. from about 36 to 42 kHz), superposed on the magi.etic bias field produced inside the measure-

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Sciences Institute of Physics, AI. Lotnik6w 32/46, PL-02-668 Warsaw, Poland. Tel.: +48-2-435212; telefax. +48-2-430926; telex: 812468.

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Correspondence to: Prof. Z. Kaczkowski, Polish Academy of

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0304-8853/92/$05.00 © 1992 - Elsevier Science Publishers B.V. All rights reserved

Z. Kaczkowski et aL / Elasticity moduli in F e - C r - B metaNc glass

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ment solenoid and changed up to the technical saturation or just belox~ this saturation. The dependences of the E moduli on the bias magnetic field for as-cast state and after annealing at the temperatures from 80 to 360°C are presented in figs. 1-4.

2. Discussion; final remarks and conclusions The b E effect is connected with the magnetostriction and the magnetomechanical coupling, e.g. refs. [4,5]. Maximum values of the magne-

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Fig. 2. Moduli of elasticity vs. magnetic bias field H for as-cast samples and after annealing them for 2 h at the temperatures of 280, 300 and 350°C.

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Fig. "~. Moduli of elasticity vs. magnetic bias field H for as-cast samples and after annealing them at the temperature of 360°C for 2 and 4 h.

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Fig. 4. Moduli of elasticity at the demagnetization state E o ( = EHO = EBtl), at the magnetic saturation E, ( = Eus = EBs) and minimum values of E n (Enmi,) vs, annealing temperature T.

tomechanical coupling coefficient k for three samples cut from the same ribbon ML quenched in longitudinal field were equal to 0.11 up to 0.17 and for 3 samples from the other ribbon quenched in transversal field (MT) from 0.12 to 0.18. The values of the k coefficient for the next two groups of 3 samples MTS and MLS were changing from 0.14 to 0.20 and from 0.11 to 0.19, respectively. For further investigations the samples with following kin, x were chosen: ML - 0.I1, MT - 0.12, MLS - 0.I9, MTS - 0.17. The annealing at temperatures below Curie point (127°C) and up to 150°C which partially removes internal stresses introduced during production and partly destroyed the perpendicular arrangement of part of the magnetic domains and the magnetomechanical coupling and the A E effect in the MT sample does not increase and k and E were stable in a wide range of the bias field (fig. 1). It confirmed Squire's theory for field-annealed amorphous ribbons [6]. Annealing above the Curie temperature removes internal stresses but destroys the partially ordered magnetic structure induced during the casting (f~gs. 2 and 3). The A E effect then increases. Annealing at temperatures of 270°C and higher increases the coefficient k over 0.15 and shifts the maximum values towards the bias fields, even lower than those for the ML sample [2,3]. It means that above the Curie temperature the previous magnetic structures were destroyed and the differences in the thickness have now

Z. Kaczkowski et ai. / Elasticity moduli in Fe-Cr-B metallic glass

some greater influences. The samples annealed at 360°C were partly crystallized and the magnetomechanical coupling and the A E effect dropped (figs. 3 and 4). Annealing at t e m p e r a t u r e s of 300 and 350°C increased the maximum values of k up to 0.20-0.23 [3] and the A E effect was the greatest (figs. 2 and 4). After annealing at temperatures of 360°C for 2 and 4 h the k m coefficient dropped to 0-0.05 (ML), 0.005-0.12 (MT), 0-0.05 (MLS) and 0.06-0.1 (MTS) and the maxima of k occurred at a higher than previous bias field [3], the values of the E moduli increased and the A E effect decreased (figs. 3 and 4). In the metallic glasses where crystalline anisotropies do not occur, the relatively low induced anisotropies have even higher influence on magnetic properties than in the crystalline magnetic materials. The heat treatment in a parallel or transverse magnetic field or u n d e r a mechanical stress are used to improve magnetic parameters [6]. A serious disadvantage of heat treatment is often the loss of their ductility. The casting of the metallic glass in magnetic field is a useful alternative for an improvement of magnetic properties without the worsening of the mechanical characteristics, e.g. refs. [1,7,8]. T h e iron rich F e - C r - B metallic

319

glasses are good piezomagnetic materials after the heat treatment above the Curie temperature and below the beginning of crystallization. Casting in the magnetic field, ~enerally improving the magnetic properties, also somewhat increases the magnetomechanical coupling, but in the discussed alloy with a very low Curie point, the annealing between 300 and 350°C was necessary for increasing about two times the A E effect.

References

[1] L. Potoclo), 1~, Kisdi-Kosz6,A. Lovas, L. Pogfiny, E. Kr6n, J. Kovfic, L. Novfik and P. Kolhlr, J. de Phys. 49 (198~,) C8-1315. [2] Z. Kaczkowski,t~. Kisdi-Kosz6and L. Potock~, Mater. Sci. Eng. A 133 (1991) 220. [3] Z. Kaczkowski, I~. Kisdi-Kosz6 and L. Potock~, J. Magn. Magn. Mater. 101 (1991) 25. [4] Z. Kaczkowski,Arch!wum Elektrotech. 11 (1962) 35. [5] Z. Kaczkowski,in: Applied Electromagnetics in Materials, ed. K. Miya (Pergamon Press, Oxford, 1988) p. 325. [6] P.T. Squire, J. Magn. Magn. Mater. 87 (1990) 299. [7] H.Y. Yu, D.R. Huang, P.C. Yao and S.E. Hsu, Mater. Res. Sci. 58 (1986) 19. [8] L. Potocky, J. Kov~ic, L. Novfik, A. Lovas, L. Pogfiny and I~. Kisdi-Kosz6, Phys. Scr. 40 (1989) 536.