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Journal of the Korean Physical Society, Vol. 77, No. 2, July 2020, pp. 116∼121
Effects of Nb Addition and Heat Treatment on the Crystallization Behavior,
Thermal Stability and Soft Magnetic Properties of FeSiBPCuC Alloys
Chenfeng Fa n , Yuanzheng Yan g ,∗Jia Xu,TingLuo and GuoTai Wang
Faculty of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, China
(Received 27 February 2019; accepted 1 July 2019)
In this paper, the effect of the replacement of Fe by Nb on the glass forming ability (GFA),
the thermal stability and the crystallization behavior of Fe84.5−xSi0.5B10.5P3.5Cu0.7C0.3Nbx(x=
0, 1, 2) alloys were investigated. The results show that the addition of Nb increases the GFA.
Increasing Nb content can enhance the first onset crystallization temperature (Tx1), the second
onset crystallization temperature (Tx2)andΔTx(ΔTx=Tx2−Tx1), which broadens the range
of annealing temperatures. The coercivity (Hc) of ribbons decreases with increasing Nb content
after annealing at a low heating rate and reach as a minimum of 24.5 A/m when the Nb content
is 2 at.%. The process of annealing at a high heating rate distinctly decreases Hc, and all samples
present excellent soft magnetic properties. The nanocrystalline alloy exhibits the lowest Hcof 6.4
A/m after annealing at 460 ◦C for 5 min.
Keywords: Fe-based amorphous/nanocrystalline alloys, Crystallization behaviors, Soft magnetic properties
DOI: 10.3938/jkps.77.116
I. INTRODUCTION
Fe-based amorphous/nanocrystalline alloys have at-
tracted considerable interests due to their excellent soft
magnetic properties with low coercivity (Hc), low core
loss (P), high effective permeability (μe) and high sat-
uration flux density (Bs) [1, 2]. The nanocrystalline
structure is obtained by elaborate annealing from amor-
phous alloys, and the α-Fegrainsdistributeintheamor-
phous matrix homogeneously with random magnetic
anisotropy, which results in a low Hc[3,4]. The origin
of the considerably high Bsis the strong inter-granular
exchange magnetism of the α-Fe grains. However, the
Bsis still lower than that of Si-steel. The conventional
method to cover this shortage is to increase the Fe con-
tent [5, 6]. High Fe-content alloys like FeSiBPCu [7, 8]
and FeSiBPCuC [9, 10] have been developed one after
another. However, the Hcof high Fe-content alloys in-
creases rapidly during annealing at a low heating rate
due to the rapid crystallization of α-Fe on pre-existing
nuclei [11].
Two main methods restrict Hcfrom increasing. Ad-
justing ingredients is the more effective way. The addi-
tion of early transition metals such as Mo [12], Nb [13]
and Zr [14] is well known to inhibit the growth of α-Fe
grains to decrease Hcduring the process of annealing,
and the addition of element Nb may be considered as
the most effective [15]. Another is the process of anneal-
ing. Hcis reported to be reduced by relaxation of inner
∗E-mail: yangyzgdut@163.com
stress and the decrease in magnetic anisotropy caused by
adjusting heat treatments [16]. The Hcof FeSiBPCuC
alloys is decrease slightly by heat treatment at a higher
heating rate [17]. Annealing at a high heating rate in
vacuum is manifested the most effective way to reduce
Hcin high-Fe FeSiBPCu alloys [18]. However, this is
hard to do in ordinary circumstance or is uncontrollable
in industrial production.
In this work, the transition metal Nb is combined with
a simplified process of annealing to reduce Hc,andthis
technique is expected to achieve large-scale production in
ordinary circumstances. The influences of the addition
of Nb on the glass formation ability (GFA), the crystal-
lization behavior and the magnetic properties in the FeS-
iBPCuC alloys are discussed. The different influences of
diverse heating rates of annealing on the magnetic prop-
erties of FeSiBPCuC alloys were investigated.
II. EXPERIMENTAL PROCEDURES
Alloy ingots with the nominal compositions of
Fe84.5−xSi0.5B10.5P3.5Cu0.7C0.3Nbx(x=0,1,2)were
prepared by using high-purity arc-melting equipment.
All raw materials had industrial purity Fe (99.9 wt.%),
Si (99.99 wt.%), Cu (99.9 wt.%), C (99.9 wt.%), Nb (99.9
wt.%), pre-alloyed Fe-B ingots (17.5 wt.%B), pre-alloyed
Fe-P ingots (24.8 wt.%P). The protective high-purity Ar
gas was charged and discharged three times to ensure
the atmosphere purity before melting the alloys. All the
ingots were inverted and remelted four times to ensure
pISSN:0374-4884/eISSN:1976-8524 -116- c
2020 The Korean Physical Society
Effects of Nb Addition and Heat Treatment on the Crystallization Behavior··· – Chenfeng Fan et al. -117-
Fig. 1. XRD patterns of melt-spun Fe84.5−xSi0.5B10.5P3.5
Cu0.7C0.3Nbx(x= 0, 1, 2) alloy ribbons.
Fig. 2. Differential scanning calorimeter (DSC) curves of
Fe84.5−xSi0.5B10.5P3.5Cu0.7C0.3Nbx(x=0,1,2)melt-spun
ribbons.
homogeneity. Ribbons were prepared by using a single
Cu-roller at a speed of 50 m/s under an Ar atmosphere.
The ribbons had widths of around 1.5 mm and thick-
nesses of 25 ±2μm.
The structure of the ribbons was identified by us-
ing D/Max-ULtima IV X-Ray diffraction (XRD) with
Cu-Kα(λ= 0.15418 nm) radiation. The thermal pa-
rameters, such as the onset temperature (Tx)andthe
peak temperature (Tp) of crystallization, were investi-
gated by using a Q600 TA Instruments differential scan-
ning calorimeter (DSC) at a heating rate of 20 K/min
under a high-purity nitrogen atmosphere with a gas flow
100 ml/min. The coercivity (Hc) was measured by us-
ing a DC B-H loop tracer under a field of 210 A/m, and
the saturation magnetization (Ms) was measured by us-
ing a vibrating sample magnetometer (VSM) under a
maximum applied field of 12500 Oe. The density of the
samples, as measured by using a Archimedes method was
about 7.4 g/cm3.
For the ordinary annealing process (OA), the ribbons
were heated in a tubular furnace under a nitrogen at-
mosphere at a constant heating rate of 20 K/min from
room temperature to various temperatures (350–520 ◦C)
for 10 min and were cooled to room temperature in the
atmosphere. The anneal process at a high heating rate
(HA) were a simplified version of the OA process, but
relatively high heating rate. Ribbons were annealed at a
precise temperature for several mins in tubular furnace
and were cooled to room temperature at atmosphere.
III. RESULTS AND DISCUSSION
The XRD patterns of as-quenched Fe84.5−xSi0.5B10.5
P3.5Cu0.7C0.3Nbx(x= 0, 1, 2) alloy ribbons are shown
in Fig. 1. The XRD patterns are taken from the free
surface of the ribbons as-quenched. The patterns of rib-
bons have a typical diffuse scatter peak around 2θ=45
◦
without any appreciable crystalline peaks being observed
with the addition of Nb, indicating that the ribbons have
an amorphous structure. The only crystalline diffraction
peak was found around 2θ=65
◦in the sample with-
out the addition of Nb, and corresponded to the α-Fe
(200) plane. This illustrates that Nb-free ribbon is par-
tially crystallization on the amorphous matrix and that
the addition of Nb increases the glass forming ability
(GFA). This may be due to the strong bonding between
Nb and Fe atoms which results in the formation of FeNb
clusters and then enhances the formation of short-range-
order clusters with the addition of Nb [19]. Furthermore,
the negative mixing enthalpy of Nb-B (−54 kJ/mol) and
Nb-P (−69.5 kJ/mol) are larger than that of Fe-B (−26
kJ/mol) and Fe-P (−39.5 kJ/mol), which decreases the
mixing enthalpy of the alloy system with the addition of
Nb and increases the glass forming ability. Clearly, the
substitution of Nb for Fe increases the amorphous form-
ing ability of Fe84.5−xSi0.5B10.5P3.5Cu0.7C0.3Nbxalloys.
The DSC curves for the Fe84.5−xSi0.5B10.5P3.5Cu0.7
C0.3Nbx(x= 0, 1, 2) melt-spun ribbons are shown in
Fig. 2. All DSC curves display two separate exothermic
peaks, which indicates that the crystallization process
consists of two stages. The first onset temperature (Tx1)
of crystallization corresponds to the precipitation of the
α-Fe phase in the amorphous matrix [20]. The value of
Tx1increases slightly the Nb addition, which means the
precipitation of the α-Fe phase occurs at a higher tem-
perature, leading to better thermal stability. A higher
Tx1also corresponds to a stronger GFA of alloys [21].
On the one hand, the nucleation and growth of grains
depend on the diffusion of atoms, and Nb as a large-
radius atom hinders the diffusion of atoms during the
precipitation of the α-Fe phase. On the other hand, the
-118- Journal of the Korean Physical Society, Vol. 77, No. 2, July 2020
Table 1. Characteristic temperatures of Fe84.5−xSi0.5B10.5
P3.5Cu0.7C0.3Nbx(x= 0, 1, 2) melt-spun ribbons.
x(at.%) Tx1Tp1Tx2Tp2ΔTxΔTp
(◦C) (◦C) (◦C) (◦C) (◦C) (◦C)
X= 0 414.2 428.6 533.9 542.2 119.7 113.6
X= 1.0 424.1 438.9 557.7 565.7 133.6 126.8
X= 2.0 426.3 442.5 587.6 594.3 161.3 151.8
addition of Nb increases the entropy of the alloy sys-
tem, which may be beneficial to forming an amorphous
alloy. The second onset temperature (Tx2) corresponds
to the forming of FeB/FeP compounds [22] clearly in-
creases with the addition of Nb. Elements with larger
negative entropies are well known to tend to combine,
and B/P prefers to combining with Nb instead of Fe in
the residual amorphous matrix because of the large mix-
ing enthalpies between Nb-P and Nb-B [23]. Moreover,
Nb plays the role of a energy barrier to further inhibit
the precipitation of α-Fe [16]. The value of ΔTxincreases
from 119.7 ◦C to 161.3 ◦C due to the significant increase
in the value of Tx2caused by the addition of Nb, a large
ΔTxis beneficial to the process of annealing because the
broad temperature range contributes to the formation of
a stable nano-structure. The characteristic temperatures
are shown in Table 1.
Figure 3(a) shows the Hcof Fe84.5−xSi0.5B10.5P3.5
Cu0.7C0.3Nbx(x=0,1,2)ribbonsasafunctionofan-
nealing temperature (Ta), For value of Taup to 350 ◦C,
the Hcof the ribbons decreases with increasing anneal-
ing temperature which may be due to the structural re-
laxation of amorphous ribbons. For value of Tafrom
350 ◦C to 400 ◦C, the value of Hcincreases sharply,
which may be attributed to the precipitation of α-Fe,
which increases the magnetic anisotropy. Compared to
Nb-free (x= 0) alloy, the value of Hcfor the ribbons (x=
1,2) increases sharply because of the higher Tx1or better
thermal stability, which can be manifested in the DCS
curves (Fig. 2) and in the XRD patterns after anneal-
ing (Fig. 4 XRD patterns of alloy annealed at 400 ◦C).
With the further increases in the value of Ta,thevalue
of Hcdecreases gradually because of the formation of
nanocrystalline grains.Worth noteing is that the value
of Hcfor the ribbons decreases with the addition of Nb
after annealing. The minimum Hcabout 24.5 A/m for
the x= 2.0 sample is lower than that for Nb-free sample
(Hc∼30.4 A/m) annealed at 460 ◦C. This indicates that
the decrease in the value of Hcis not obvious with the
addition of Nb in high-Fe alloys [24]. However, the an-
nealing temperature range is extended with the addition
of Nb. Figure 3(b) shows the saturation magnetization
(Ms)ofFe
84.5−xSi0.5B10.5P3.5Cu0.7C0.3Nbx(x=0,1,
2) ribbons after annealing at 460 ◦C for 10 min. The
Msis well known to be related to the Fe mass percent-
age. The value of Msdecreases from 179.66 emu/g (1.65
T) to 175.61 emu/g (1.63 T) because of a decrease in
Fig. 3. (a) Hcof ribbons after annealing at different tem-
peratures and (b) Msof ribbons after annealing at 460 ◦C
for 10 min.
the Fe mass percentage with the replacement Fe by Nb.
However, the value of Bsis higher than that of Finemet
alloys.
TheXRDpatternsofFe
84.5Si0.5B10.5P3.5Cu0.7C0.3
ribbons after annealing at various temperatures for 10
min are shown in Fig. 4(a). All XRD patterns can be
seen to consist of three typical α-Fe diffraction peaks
for value of Taup to 400 ◦C. The change in the in-
tensities of the diffraction peaks with increasing tem-
perature are due to the more precipitation of α-Fe.
A slight diffraction peak of Fe(B,P) can be seen at
520 ◦C, which is due to deterioration of the soft mag-
netic properties. Figure 4(b) shows the XRD patterns of
Fe84.5Si0.5B10.5P3.5Cu0.7C0.3Nb2ribbons after annealing
at various temperatures for 10 min. The ribbons start
to crystallization at 400 ◦C while the intensity is weaken
than that of Nb-free, Nb plays a role as an energy barriers
which inhibits crystallization from the amorphous phase,
and pre-existing nuclei are present in the Nb-free rib-
bons because of the partial amorphous alloy as-quenched.
Worth noting is no diffraction peak associated with the
Effects of Nb Addition and Heat Treatment on the Crystallization Behavior··· – Chenfeng Fan et al. -119-
Fig. 4. XRD patterns of Fe84.5Si0.5B10.5P3.5Cu0.7C0.3Nbx
(x= 0, 2) ribbons after annealing at various temperatures
for 10 min, (a) x=0and(b)x=2.
precipitation of Fe(B,P) was observed at 520 ◦C due to
theincreaseinthevalueofΔTxcaused by the addition
of Nb.
In order to decrease Hcfurther, we investigated the
effect of the HA process on Fe84.5−xSi0.5B10.5P3.5Cu0.7
C0.3Nbx(x= 0, 1, 2) ribbons. The Hcfor ribbons an-
nealed by using different annealing processes (OA and
HA) at 460 ◦C for 10 min is shown in Fig. 5(a) as a
function of the Nb content. The value of Hcfor ribbons
annealed by using the HA process for 10 min are slightly
lower than those for the ribbons annealed by using the
OA process. The unconspicuous decreasing of Hcmay
be caused by the growth of α-Fe during the 10-min HA
process. Therefore, the ribbons were annealed by using
the HA process for less time, and the results are shown
in Fig. 5(b). The value of Hcdecreases rapidly when
the annealing time is short, even lower than that of the
as-quenched ribbon. That may be due to the increasing
nucleation of α-Fe at the high heating rate. The insuffi-
cient diffusion of atoms results a fine α-Fe grain, which
decreases the magnetic anisotropy during annealing for
a short time. However, that the decrease in the value of
0
1
2
22
23
24
25
26
27
28
29
30
31
Hc
(
A
/
m
)
x
(
Nb
)
OA
HA
460Ș for 10 min
(a)
012345678910
4
6
8
10
12
14
16
18
20
22
24
460Ș
H
c
(A/m)
Time (min)
(b)
30 40 50 60 70 80 90
j
j
3 min
j
j
j
5 min
Intensity (a.u.)
2θ (deg.)
10 min
j
ワα-Fe
(c)
Fig. 5. (a) Hcof Fe84.5−xSi0.5B10.5P3.5Cu0.7C0.3Nbx(x
= 0, 1, 2) melt-spun ribbons annealed by using the OA and
HA processes at 460 ◦C for 10 min. (b) Hcdependence on
annealing time for the HA process at 460 ◦C. (c) XRD pat-
terns of Fe84 Si0.5B10.5P3.5Cu0.7C0.3Nb2ribbons annealed at
460 ◦C by using the HA process for time from 3 min to 10
min.
Hcmay be caused by structural relaxation of the inner-
stress and the formation of nanocrystals cannot be ex-
clude. The phase structure of ribbons was identified by
using XRD, and the results are shown in Fig. 5(c), which
-120- Journal of the Korean Physical Society, Vol. 77, No. 2, July 2020
30 40 50 60 70 80 90
j
j
j
j
j
500Ș
460Ș
440Ș
Intensity (a.u.)
2θ (deg.)
420Ș
j
ワα-Fe
(a)
24 28 380 400 420 440 460 480 500
5
10
15
H
c
(A/m)
Temperature (Ș)
aq
(b)
24 28 380 400 420 440 460 480 500
140
145
150
155
160
165
Magnetization ,M
s
(emu/g)
Temperature (Ș)
(c)
aq
Fig. 6. (a) XRD patterns of Fe82.5Si0.5B10.5P3.5Cu0.7C0.3
Nb2ribbons annealed at temperatures from 420–500 ◦Cby
using the HA process for 5 min. (b) Hcand (c) Msof
Fe82.5Si0.5B10.5P3.5Cu0.7C0.3Nb2ribbons after HA anneal-
ing.
shows that the ribbons are completely amorphous when
annealed for 3 min and that crystallization is initiated
at an annealing time of 5 min.
TheXRDpatternsofFe
82.5Si0.5B10.5P3.5Cu0.7C0.3
Nb2ribbons annealed by using the HA process for 5 min
at temperatures from 420 ◦C to 500 ◦Careshownin
Fig. 6(a). The figures show the present of a completely
amorphous structure for the HA process at 420 ◦Cand
the initiation of crystallization at 440 ◦C. For the HA
process at 500 ◦C the three typical diffraction peaks of
α-Fe can be seen. The Hcdependence on annealing tem-
perature is shown in Fig. 6(b). The Hcexhibits an as-
cending tendency with increasing annealing temperature
at 420 ◦C and above. The ribbons exhibit the lowest Hc
of 5.3 A/m at 420 ◦C for the amorphous alloys and the
lowest Hcof 6.4 A/m at 460 ◦C for the nanocrystalline
ribbons while the Msis 157.7 emu/g (1.46 T). The op-
timum annealing temperature range for nanocrystalline
formation is 440–460 ◦C. The rise in Hcwith increasing
annealing temperature in the optimal range may caused
by more precipitation of the α-Fe phase, which increases
the magnetic anisotropy. The value of Msfor the rib-
bons annealed by using the HA process for 5 min are
shown in Fig. 6(c) as a function of the annealing tem-
perature. The Msis mainly affected by the crystalline
volume fraction of the α-Fe phase [25,26]. The value of
Msincreases with increasing annealing temperature due
to more α-Fe precipitation in higher temperatures.
IV. CONCLUSIONS
The effect of Nb addition on the glass formation ability
(GFA), thermal stability, crystalline behavior, and mag-
netic properties of Fe84.5−xSi0.5B10.5P3.5Cu0.7C0.3Nbx
(x= 0, 1, 2) ribbons after different annealing process
were investigated.The results can be summarized as fol-
lows:
(1) In Fe84.5−xSi0.5B10.5P3.5Cu0.7C0.3Nbx(x=0,1,
2) alloys, the addition of Nb increases both the GFA and
the thermal stability, including the first onset temper-
ature (Tx1) and the second onset temperature (Tx2)of
crystallization, a well ΔTx(Tx2−Tx1) at temperatures
from 119.7 ◦C to 161.3 ◦C.
(2) The addition of Nb is beneficial to decreases the
Hcof ribbons. Ribbons annealed at temperature in the
range 460–480 ◦C by using the ordinary annealing pro-
cess (OA) exhibiteda lower Hc, and the addition of Nb
decreased Hcto 24.5 A/m, while Mswas 175.6 emu/g
(1.63 T).
(3) The Hcof ribbons was distinctly decreased by an-
nealing at high heating rate (HA), and all samples pre-
sented the excellent soft magnetic properties. The rib-
bon exhibited the lowest Hc∼6.4 A/m after having been
annealed at 460 ◦C for 5 min, while the Mswas 157.7
emu/g (1.46 T).
ACKNOWLEDGMENTS
This work is supported by the National Science Foun-
dation of China (No. 50971046).
Effects of Nb Addition and Heat Treatment on the Crystallization Behavior··· – Chenfeng Fan et al. -121-
REFERENCES
[1] T. Gheiratmand and H. R. M. Hosseini, J. Magn. Magn.
Mater. 408, 177 (2016).
[2] Y.Y.Sunet al., J. Alloys Compd. 509, 6603 (2011).
[3] G. Herzer, J. Magn. Magn. Mater. 294, 99 (2005).
[4] A.D.Wanget al., Thin Solid Films 519, 8283 (2011).
[5] F.L.Konget al., J. Alloys Compd. 615, 163 (2014).
[6] A. Urata et al.,J.Appl.Phys.113, 6044 (2013).
[7] P. Sharma et al.,Scr.Mater.95, 3 (2015).
[8] A.D.Wanget al., J. Alloys Compd. 656, 729 (2016).
[9] T. Takahashi et al.,AIPAdv.7, 056111 (2017).
[10] J. Xu et al., Mater. Res. Bull. 97, 452 (2018).
[11] K. Suzuki et al., Appl. Phys. Lett. 110 (2017).
[12] C. F. Conde et al., J. Alloys Compd. 509, 1994 (2011).
[13] W. Lefebvre et al., J. Magn. Magn. Mater. 301, 343
(2006).
[14] L. H. Kong et al., J. Magn. Magn. Mater. 323, 2165
(2011).
[15] Y. Yoshizawa, Mater. Sci. Forum 307, 51 (1999).
[16] S. Kim et al., Curr. Appl. Phys. 17, 548 (2017).
[17] J. Xu et al.,J.Non-Cryst.Solids499, 420 (2018).
[18] A. Makino, IEEE T. Magn. 48, 1331 (2012).
[19] X. L. Li et al., J. Alloys Compd. 694, 643 (2017).
[20] F. L. Kong et al.,J.Appl.Phys.109, 219 (2011).
[21] B-S. Dong et al., Prog. Nat. Sci.: Mater. Int. 21, 164
(2011).
[22] H. R. Lashgari et al.,Mat.Sci.Eng.A626,480 (2015).
[23] W. Lin et al., J. Alloys Compd. 735, 1195 (2018).
[24] Y. Wang et al.,J.Appl.Phys.120, 99 (2016).
[25] A. Urata et al., J. Alloys Compd. 509, S431 (2011).
[26] E. Lopatin et al.,ActaMater.96, 10 (2015).
