Developing texture in nanocrystalline permanent magnet alloys is of significant importance. Directional annealing is shown to produce texture in the permanent magnet alloy (Sm12Co88)99Nb1. Melt spinning produced isotropic grain structures of the hard magnetic metastable SmCo7 phase, with grain sizes of ∼300 nm. Conventional annealing of melt-spun (Sm12Co88)99Nb1 alloy produced Sm2Co17 phase with random crystallographic orientation. Directional annealing of melt-spun (Sm12Co88)99Nb1 alloy, with appropriate combinations of annealing temperature and translational velocity, produced Sm2Co17 phase with (0 0 0 6) in-plane texture, as determined by x-ray diffraction analysis and magnetic measurements. The magnetization results show out-of-plane remanence higher than the in-plane remanence resulting in the degree of ‘magnetic’ texture in the order of 25–40%. Coercivity values above 2 kOe were maintained. The texture development via directional annealing while minimizing exposure to elevated temperatures provides a new route to anisotropic high-energy permanent magnets

Jayaraman, Tanjore V.

Rogge, P.

Shield, Jeffrey E.

English

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2010 
Directional annealing-induced texture in melt-spun 
(Sm12Co88)99Nb1 alloy 
Tanjore V. Jayaraman 
University of Nebraska-Lincoln, tjayaraman2@unl.edu 
P. Rogge 
University of Nebraska-Lincoln 
Jeffrey E. Shield 
University of Nebraska-Lincoln, jshield@unl.edu 
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Jayaraman, Tanjore V.; Rogge, P.; and Shield, Jeffrey E., "Directional annealing-induced texture in melt-
spun (Sm12Co88)99Nb1 alloy" (2010). Mechanical & Materials Engineering Faculty Publications. 43. 
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IOP PUBLISHING JOURNAL OF PHYSICS D: APPLIED PHYSICS
J. Phys. D: Appl. Phys. 43 (2010) 272004 (5pp) doi:10.1088/0022-3727/43/27/272004
FAST TRACK COMMUNICATION
Directional annealing-induced texture in
melt-spun (Sm12Co88)99Nb1 alloy
T V Jayaraman1,2, P Rogge1 and J E Shield1,2
1 Department of Mechanical Engineering, University of Nebraska, Lincoln, NE 68588, USA
2 Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588, USA
E-mail: tjayaraman2@unl.edu
Received 30 April 2010, in final form 4 May 2010
Published 23 June 2010
Online at stacks.iop.org/JPhysD/43/272004
Abstract
Developing texture in nanocrystalline permanent magnet alloys is of significant importance.
Directional annealing is shown to produce texture in the permanent magnet alloy
(Sm12Co88)99Nb1. Melt spinning produced isotropic grain structures of the hard magnetic
metastable SmCo7 phase, with grain sizes of ∼300 nm. Conventional annealing of melt-spun
(Sm12Co88)99Nb1 alloy produced Sm2Co17 phase with random crystallographic orientation.
Directional annealing of melt-spun (Sm12Co88)99Nb1 alloy, with appropriate combinations of
annealing temperature and translational velocity, produced Sm2Co17 phase with (0 0 0 6)
in-plane texture, as determined by x-ray diffraction analysis and magnetic measurements. The
magnetization results show out-of-plane remanence higher than the in-plane remanence
resulting in the degree of ‘magnetic’ texture in the order of 25–40%. Coercivity values above
2 kOe were maintained. The texture development via directional annealing while minimizing
exposure to elevated temperatures provides a new route to anisotropic high-energy permanent
magnets.
(Some figures in this article are in colour only in the electronic version)
1. Introduction
Sm–Co based magnets have drawn attention since the 1970s for
their highly attractive properties, namely high-energy density
(15–30 MG Oe), reliable coercive force, best high temperature
performance and relatively good corrosion and oxidation
resistance. These properties have made these alloys an ideal
material in applications such as generators, high speed motors,
turbo-machinery, travelling wave tube and applications over a
range of temperatures (cryogenic to 180 ◦C) [1]. Currently
nanocomposite Sm–Co based permanent magnets continue to
attract interest because of the need for stronger permanent
magnets, and the exchange-spring permanent magnets offer
the best opportunity to increase the energy products [2]. Rapid
solidification of binary Sm–Co alloys results in relatively
coarse grain structures [3–5]. However, ternary alloying
additions has produced the desired nanoscale two phase
structures in rapidly solidified Sm–Co alloys [6–10]. Texture
development while maintaining nanocrystalline grain sizes is
challenging with existing processing routes since prolonged
exposure to elevated temperatures causes grain growth and
subsequent loss of the nanostructure. Texture development
using controlled, directional heat transfer has produced
texture during both primary crystallization from amorphous
precursors and recrystallization of heavily deformed metals
and alloys [11–15]. When applied to rapidly solidified
permanent magnet alloys, it is expected that the controlled
grain growth can produce texture for both bulk and bonded
magnet applications.
In the past researchers have reported texture development
in nanocrystalline Sm–Co based alloys in a variety of
ways including unidirectional solidification, deformation and
magnetic field-assisted methods [16, 17]. In this paper
we report the observance of (0 0 0 6) in-plane texture upon
directional annealing of rapidly solidified (Sm12Co88)99Nb1
alloy. The effect of directional annealing temperature and
0022-3727/10/272004+05$30.00 1 © 2010 IOP Publishing Ltd Printed in the UK & the USA
J. Phys. D: Appl. Phys. 43 (2010) 272004 Fast Track Communication
Figure 1. Schematic of the experimental set-up for directional
annealing. Sample is translated (arrow) past the heat shield and into
the furnace.
translational velocity on the development of the texture and its
effect on the magnetic properties of this alloy were determined.
2. Experimental procedures
2.1. Alloy preparation, melt spinning and conventional
annealing
Alloy ingots of (Sm12Co88)99Nb1 were prepared from high-
purity (>99.95%) elemental constituents (Sm, Co and Nb)
by arc-melting in UHP argon atmosphere. An extra 5 wt%
Sm was added to account for the vaporization loss of Sm
during the melting process. The arc-melted ingots were rapidly
solidified by melt spinning at a tangential wheel velocity of
40 m s−1. The melt spinning was performed under high-
purity argon environment at a chamber pressure of 1 atm.
Conventional annealing of melt-spun (Sm12Co88)99Nb1 alloy
involved isothermal heat treatment of the ribbon (sealed in a
glass tube under UHP Ar) at 850 ◦C for 10 min.
2.2. Directional annealing
The directional annealing was performed on the melt-spun
ribbons in a specially designed furnace having a motorized
actuator to translate the ribbon (sealed in a glass tube) into the
furnace [15]. The dimensions of the melt-spun ribbons were
7 mm×2.5 mm×0.05 mm. The schematic of the experimental
set-up for directional annealing is shown in figure 1. Two
halogen lamps (500 W/500 W or a 500 W/1000 W depending
on the temperature of the directional annealing process)
were enclosed in a furnace made of ceramic bricks. A
small opening created in the furnace houses a ceramic plate
(MgO). This plate (thickness 1.5 mm) which also acts as a
heat shield has a small slit cut to allow the sample to be
translated into the furnace. The maximum temperature of
the furnace (Tmax) was controlled by adjusting the voltage of
the lamps using a variac. Tmax was measured using a K-type
(chromel–alumel) thermocouple located directly between the
two halogen lamps. The maximum furnace temperature that
could be obtained was 1200 ◦C. A motorized actuator was
used to translate the ribbon (sealed in a glass tube) into the
furnace. The maximum translation distance of the actuator
was 12 mm and it was capable of generating a translational
velocity ranging from 6 to 1530 mm h−1. The temperature
gradient in the furnace was dependent on Tmax, when all
other parameters of the furnace (namely the heat shield
material/thickness and ceramic brick material/thickness) were
kept constant. With the heat shield and the ceramic
brick materials mentioned above, a temperature gradient
of 82 ◦C mm−1 was achieved for a Tmax of 1000 ◦C. The
as-solidified melt-spun ribbons were directionally annealed at
various annealing temperatures (600–1100 ◦C) and translation
velocities (5–35 mm h−1) combination.
2.3. X-ray and magnetic characterization
The melt-spun, conventionally annealed and directionally
annealed melt-spun ribbons were analysed by a Rigaku
MultiFlex x-ray diffractometer with θ–θ geometry using
Cu Kα radiation. The magnetic property measurements
were performed using Quantum Design Magnetic Property
Measurement System (MPMS-XL) magnetometer. The
magnetization curves were obtained at room temperature
(300 K) with a maximum field of 7 T. They were performed on
the ribbon samples both in-plane (parallel and perpendicular
to the long axis of the ribbon) and out-of-plane (perpendicular
to the plane of the ribbon). The magnetization curves were
corrected for self-demagnetizing fields that arise due to the
shape of the ribbon and the direction of the applied field.
3. Results and discussions
3.1. X-ray and magnetization results for melt-spun and
conventionally annealed ribbons
The x-ray diffraction pattern, magnetization curves and
microstructure for the melt-spun (Sm12Co88)99Nb1 have
been previously reported [10, 18]. Sm12Co88 modified
with 1 at% Nb obtained by rapid solidification using
melt spinning resulted in an isotropic structure with a
grain size of approximately 300 nm having remanence
∼6 kG and coercivity ∼8 kOe [10]. While the melt-spun
(Sm12Co88)99Nb1 alloy formed the metastable TbCu7-type
SmCo7 structure [18], conventional annealing of melt-spun
(Sm12Co88)99Nb1 alloy ribbon resulted in the formation of the
rhombohedral Th2Zn17-type Sm2Co17 structure [19]. Figure 2
shows the x-ray diffraction spectra and the magnetization
curves for conventionally annealed ribbon. While the crystal
structure of Sm2Co17 is rhombohedral, the hexagonal indexing
scheme [20] has been used here since it more readily identifies
the c-axis texture. The x-ray diffraction peak intensities
indicate an isotropic structure. Similarly, the magnetization
curves, figure 2(b), show the presence of an isotropic structure
in the conventionally annealed ribbon having remanence
∼5 kG and coercivity ∼4.5 kOe.
3.2. X-ray diffraction results for directionally annealed
ribbon
Directional annealing was performed on melt-spun
(Sm12Co88)99Nb1 alloy ribbons at various annealing tempera-
tures (600–1200 ◦C) and translational velocities (5–35 mm h−1)
2
J. Phys. D: Appl. Phys. 43 (2010) 272004 Fast Track Communication
Figure 2. (a) X-ray diffraction spectra of melt-spun and conventionally annealed melt-spun (Sm12Co88)99Nb1 ribbons. (b) Magnetization
curves for conventionally annealed melt-spun (Sm12Co88)99Nb1 alloy ribbon: out-of-plane perpendicular to the ribbon [A], in-plane parallel
and perpendicular to the long axis of the ribbon, [B] and [C], respectively.
Figure 3. X-ray diffraction spectra of directionally annealed melt-spun (Sm12Co88)99Nb1 alloy ribbons.
combinations. Figure 3 shows the x-ray diffraction spec-
tra of the directionally annealed (Sm12Co88)99Nb1 alloy at
annealing temperatures 750, 850 and 950 ◦C. Similar to con-
ventionally annealed ribbon, the original TbCu7-type struc-
ture in as-solidified melt-spun ribbons has transformed to
Sm2Co17 for directionally annealed ribbons. The development
of (0 0 0 6) in-plane texture was observed at translational veloc-
ities 10 mm h−1, 12 mm h−1 and 26 mm h−1, for temperatures
750 ◦C, 850 ◦C and 950 ◦C, respectively. It can be observed
that with an increase in directional annealing temperature, tex-
ture development occurred at higher translational velocity. The
enhanced (0 0 0 6) diffraction peak is observed in directionally
annealed ribbons and not in melt-spun and conventionally ann-
ealed melt-spun ribbons. The basal planes lie preferentially in
the ribbon plane so that the [0 0 0 1] easy magnetization direc-
tion points out-of-plane. It may be noted that the directional
annealing was performed at each temperature over a range
of translational velocities; however, the texture was observed
at only certain combinations of annealing temperature and
translation velocity, indicating distinct processing windows in
which texture development occurs. For a directional anneal-
ing temperature 850 ◦C a translational velocity of 12 mm h−1
leads to development of (0 0 0 6) in-plane texture. However,
at lower and higher translational velocities, 10 mm h−1 and
16 mm h−1, respectively, one can observe the tendency for the
(0 0 0 6) in-plane texture formation. At lower translational vel-
ocity (10 mm h−1) the exposure time at the directional anneal-
ing temperature (850 ◦C) is higher than that for a translational
velocity 12 mm h−1, leading to isotropic grain growth after ini-
tial texture development and subsequent loss of the texture. At
higher translational velocity (16 mm h−1) the exposure time at
the directional annealing temperature (850 ◦C) is less, leading
to incomplete texture formation.
The development of texture indicates that there is
mobility advantage of the energetically favoured boundaries
as compared to the normal grain growth in the processing
window where texture is observed [21]. Mobility advantage
depends on the hot zone velocity, temperature gradient and
activation energy [22, 23]. In this study the temperature
gradient along the ribbon and the translational velocity of
the ribbon dictate the mobility advantage for the texture and
the temperature gradient along the sample during directional
annealing is solely dependent on the directional annealing
temperature. The temperature gradients observed were
64 ◦C mm−1, 73 ◦C mm−1 and 81 ◦C, for a Tmax of 750 ◦C,
850 ◦C and 950 ◦C, respectively. The ability to vary
thermal gradient for a particular temperature can increase the
3
J. Phys. D: Appl. Phys. 43 (2010) 272004 Fast Track Communication
Figure 4. Magnetization curves for directionally annealed melt-spun (Sm12Co88)99 Nb1 alloy ribbons: (a) 750 ◦C at 10 mm h−1, (b) 850 ◦C
at 12 mm h−1 and (c) 950 ◦C at 26 mm h−1. [A] out-of-plane perpendicular to the ribbon, [B] in-plane parallel to the long axis of the ribbon
and [C] in-plane perpendicular to the long axis.
processing window and have better control over the texture
development.
3.3. Magnetization results for the directionally annealed
ribbon
Figure 4 shows the magnetization curves for directionally
annealed melt-spun (Sm12Co88)99Nb1 ribbons. The magnetic
measurements were performed on the same ribbons on which
the x-ray diffraction spectra were obtained. It can be
observed that the magnetization curves for the directionally
annealed ribbons that showed texture in x-ray diffraction
spectra show out-of-plane remanence higher than the in-plane
remanence: 5.5 kG and 4.0 kG (750 ◦C/10 mm h−1), 5.0 kG
and 4.0 kG (850 ◦C/12 mm h−1) and 4.5 kG and 3.5 kG
(950 ◦C/26 mm h−1), respectively. The degree of ‘magnetic’
texture can be approximated by the ratio of difference between
out-of-plane and in-plane remanence to the in-plane remanence
[16], which in this case are in the order of 25–40% for the
directionally annealed ribbons. However, there is appreciable
decrease in coercivity of directionally annealed ribbons
(∼2–3 kOe) as compared with conventionally annealed ribbon
(4 kOe). This may be due to grain growth in the directionally
annealed samples which results in a lower coercivity. The
fact that directional annealing at higher temperatures results
in the lowest coercivities supports this hypothesis. Further
optimization of the experimental set-up to limit the grain
growth is underway.
4. Conclusions
Directional annealing of rapidly solidified (Sm12Co88)99Nb1
alloy ribbons resulted in the development of the (0 0 0 6)
in-plane texture, as shown by both x-ray diffraction and
magnetometry. The development of texture was sensitive to
annealing temperature and translational velocity, including
10 mm h−1, 12 mm h−1 and 26 mm h−1, for temperatures
750 ◦C, 850 ◦C and 950 ◦C, respectively. The magnetization
results show out-of-plane remanence higher than the in-plane
remanence. The degree of ‘magnetic’ texture ranged between
25–40% for the directionally annealed ribbons, depending
on processing conditions. No texture was observed in melt-
spun and conventionally annealed (isothermal heat treatment
at 850 ◦C for 10 min) ribbons. This study shows a feasible
process for developing texture in nanocrystalline permanent
magnet alloys by directional annealing.
Acknowledgments
The authors gratefully acknowledge the research support from
the Department of Defense Office of Naval Research under
grant no N00014-09-1-0620.
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5


Directional annealing-induced texture in melt-spun (Sm\u3csub\u3e12\u3c/sub\u3eCo\u3csub\u3e88\u3c/sub\u3e)\u3csub\u3e99\u3c/sub\u3eNb\u3csub\u3e1\u3c/sub\u3e alloy

Je présente ici quelques photos issues de mon terrain qui s’est déroulé du 1er au 15 aout dans les Alpes italiennes. Dans une optique comparative, je présente ici mes deux terrains de recherche. D’une part, la participation des habitants de la Vallée d’Aoste aux pèlerinages régionaux de haute montagne. Ces pèlerinages et ce qui s’y déroule seront ensuite comparés aux pratiques observées lors des pèlerinages provenant de la même région, mais à destination de Medjugorje, en Bosnie Herzégovine. ..

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Directional annealing-induced texture in melt-spun (Sm\u3csub\u3e12\u3c/sub\u3eCo\u3csub\u3e88\u3c/sub\u3e)\u3csub\u3e99\u3c/sub\u3eNb\u3csub\u3e1\u3c/sub\u3e alloy

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