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Melting of the master alloys in

the form of ingots (series Iseries I)

Structure: crystalline

Compositions: Finemet-type

Fe73.5Si13.5B9Nb3Mo0Cu1 (Mo0)

Fe73.5Si13.5B9Nb1.5Mo1.5Cu1 (Mo1.5)Fe73.5Si13.5B9Nb1Mo2Cu1 (Mo2)

Lab. de Slidos Amorfos, Facultad de Ingeniera, INTECIN, Universidad de Buenos Aires-CONICETBuenos Aires, Argentina

*jsilveyra@fi.uba.ar

Table I. Obtained hyperfine parameters.

Samples preparation

ASSUMPTIONS FOR MSSBAUER FITTING

2 hyperfine field distributions of Fe sites corresponding tothe amorphous phase Gaussian distributions

1 sextet corresponding to the small crystalline -Fe(Si)phase The relative intensities between lines 2 and 3 (A23) wereset equal for all subspectra in the fitting. The relative intensities between lines 1 and 3 (A13) wereset equal to that of the callibration. Zero quadrupolar splitting was assumed for the cubic -Fe site and the amorphous distributions.

Fe atom in A siteFe atom in D siteSi atom in D site

Fig. 5: Unit cell of the DO3 structurefor Fe3Si.

The precursor amorphous samples of Finemet alloys, Fe73.5Si13.5Nb3-xMoxB9Cu1, (series I) have been analyzed by means of Mssbauer

spectroscopy as well as as-quenched ribbons with a composition equivalent to that of the remaining amorphous matrix of the

nanocrystalline alloys (series II). XRD showed an amorphous structure for both series, but MS revealed the presence of a small fraction of crystalline -Fe in Mo1.5_am-rem

and Mo2_am-rem (Bhf = 33T).

Am1: Fe, Si and B atoms as close neighbours of Fe sites.

Am2: Fe, Nb/Mo and B atoms as close neighbours of Fe sites.

Series I: Bhf-Am1 ~ 23 T - Bhf-Am2 ~ 18 T. No structural difference was found among the set of samples of series I; thus, the exchange of

Nb by Mo did not significantly affect the electronic neighbourhoods of the Fe atoms.

Series II: Bhf-Am1 ~ 20 T - Bhf-Am2 ~ 15 T.

The hyperfine fields of series II were smaller than those of series I due to the smaller Fe content in the alloys.

The mean Bhf was ~17 T in agreement with the one found for the actual remaining amorphous phase of the nanocrystalline alloys in [2].

Am1 was smaller in series II than in series I, whereas Am2 was higher because most of the Si atoms diffused to the grains during the

nanocrystallization of the samples of series I, while Nb, Mo and B atoms remained in the amorphous matrix.

XII Latin American Conference on the applications of the Mssbauer Effect. November 7th-12th, 2010, Lima, Peru

Results

References[1] Y. Yoshizawa, S. Oguma, and K. Yamauchi,J. Appl. Phys. 64 (1988) 6044[2] J.M. Silveyra , V.J. Cremaschi, D.Janikovi, P. vec and B. Arcondo, J. Magn.Magn. Mater. 323 (2011) 290

Josefina M. Silveyra*, Bibiana Arcondo

Mssbauer study of the remaining amorphous phase

in Finemet alloys

Fe3-xSixnanograins

Remaining

amorphous

phase with high

B and Nb/Mo

content

Fig. 1: Induction Furnace

Re-melting and rapid-

quenching of the amorphous

precursor alloys in the

form of ribbons with the

planar flow casting technique

Structure: amorphous

Fig. 2: Amorphous ribbons

Controlled heat treatment

Structure: nanocrystallineFig. 4: Nanocrystalline structure ofthe Finemet-type alloys

Melting of the alloys in the form of coin-

ingots (series IIseries II)

Structure: crystalline

Compositions: remaining amorphous-type

Fe64.8Si6.2B20.1Nb6.7Mo0Cu2.2 (Mo0_rem-am)

Fe63.4Si4B22.6Nb3.7Mo3.7Cu2.5 (Mo1.5_rem-am)Fe61.8Si2B22.5Nb2.8Mo5.6Cu2.8 (Mo2_rem-am)

Fig. 3: Planar flow casting

Re-melting and

rapid-quenching of

the amorphous

remaining alloys in

the form of ribbons

with the planar flowcasting technique

Structure: amorphous

1 2 3 4 5

Estimation of the

chemical

compositions of

the phases: Ref [2]

Fig. 6: Electric arc furnace

AcknowledgmentsA special thanks to RNDr. Duan Janikovi ofthe Institute of Physics of the Slovak Academy ofSciences (Bratislava, Slovakia) for his help in thepreparation of the samples and to Ing. PeterSvec, DrSc. for his help in the measurement ofthe XRD.

Fig.7: X-ray diffractograms of the top side of the samples (i.e. sidewhich was in contact with air during the casting of the ribbon)

Series Mo Subspectrum IS (mm/s) Bhf (T) Area (%) A23

Am1 0.15 23.0 66

Am2 0.06 18 34

Am1 0.15 23.1 66

Am2 0.07 18 35

Am1 0.14 23.5 63

Am2 0.08 18 37

Am1 0.15 20.5 36

Am2 0.10 15 64

Am1 0.17 20.7 24Am2 0.14 15 75

Cryst 0.00 33.0 2

Am1 0.2 19 25

Am2 0.10 13 71

Cryst 0.00 33.0 4

I

II

2.4

2.5

2.4

2.5

2.8

0

1.5

2

0

2.6

1.5

2

AbstractAmorphous ribbons with the composition of Finemet-type alloys were

fabricated with the planar flow casting technique. A set of alloys with the

composition equivalent to that of the remaining amorphous phase of

nanocrystalline Finemet-type alloys were also casted. Both series of alloyswere studied by Mssbauer spectroscopy, which was able to detect a small

fraction of crystalline -Fe in some of the alloys. Variations were found in

the spectra due to differences in the chemical compositions of the alloys.

IntroductionOne of the softest magnetic materials is the nanocrystalline alloy known as Finemet [1]. In a previous

work, the structural and the magnetic correlation of a series of Finemet alloys in which Nb had been

replaced by Mo (Fe73.5Si13.5B9Nb3-xMoxCu1) was studied by means of X-ray diffraction (XRD) and

Mssbauer spectroscopy (MS) [2]. The fractions (in at%, wt% and vol%) and the chemical composition ofthe crystalline and amorphous phases of the alloys were calculated.

In this work, the series of alloys casted with composition equivalent to that of the remaining amorphous

phase of the nanocrystalline alloys are studied by MS and compared with the original amorphous sample.

Fig.8: Mssbauer subspectra fittings