An investigation of the Dy-Fe-Cr phase diagram: Phase equilibria at 773 K

Article abstract of DOI:10.1016/j.jallcom.2008.08.033

Phase equilibria in the Dy-Fe-Cr system were investigated by X-ray powder diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM) techniques and the isothermal section at 773 K was obtained. It consists of 8 single-phase

Full text of DOI:10.1016/j.jallcom.2008.08.033

Journal of Alloys and Compounds 475 (2009) 286–288
Contents lists available at ScienceDirect
Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jallcom
An investigation of the Dy–Fe–Cr phase diagram: Phase equilibria at 773 K
Qingrong Yao∗, Hailong Wang, Zhanwei Liu, Huaiying Zhou, Shunkan Pan
Department of Information Material and Engineering, Guilin University of Electronic, Guangxi 541004, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 18 June 2008
Received in revised form 4 August 2008
Accepted 8 August 2008
Available online 14 November 2008
Phase equilibria in the Dy–Fe–Cr system were investigated by X-ray powder diffraction (XRD), differential
thermal analysis (DTA), scanning electron microscopy (SEM) techniques and the isothermal section at
773 K was obtained. It consists of 8 single-phase regions, 14 two-phase regions and 7 three-phase regions.
The existence of the compound DyFe12−xCrx (1.6 ≤ x ≤ 3.0, space group I4/mmm) with ThMn12 -type struc-
ture was confirmed. The maximum solid solubility of Cr in Fe, Dy2Fe17 , Dy6Fe23, DyFe3 and DyFe2 is about
15, 13, 6, 5 and 16 at.%, respectively.
Keywords:
Rare earth alloys and compounds
Crystal structure
© 2008 Published by Elsevier B.V.
Phase diagrams
X-ray diffraction
1. Introduction
(space group I4/mmm) and the compound Dy3 (Fe, Cr)29 crystal-
lizes with Nd3 (Fe, Ti)29-type structure (space group A2/m). Like
The properties of ternary rare earth iron-rich compounds of the
type RFe12−xMx and RFe29−xMx (R = Y, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm
and Lu, with M = Si, Ti, V, Cr, Mo and W) have been studied inten-
sively [1–6].Those studies have been stimulated for a great deal
by the possibility of using some of these materials for high perfor-
mance permanent magnet applications. Moreover, phase diagrams
can provide important information for developing new materials.
So, it is essential to have a detailed knowledge of the phase dia-
gram of RE–Fe–M systems. In this work, we studied the isothermal
section of Dy–Fe–Cr ternary system phase diagram at 773 K.
A detail description of the binary Dy–Fe, Fe–Cr and Dy–Cr phase
diagrams has been reported in our previous work [7], together with
the available crystallographic data and stability temperature range
of all the intermediate phases [8]. There are four compounds in the
Dy–Fe system, namely Dy2Fe17 (Th2Ni17 -type structure), Dy6Fe23
(Th6Mn23-type structure), DyFe3 (NbBe3-type structure) and DyFe2
(MgCu2-type structure). The lowest liquidus temperature in the
Dy–Fe system is 1163 K. There is one compound FeCr in the Fe–Cr
binary system at 800–1147 K. No intermetallic phase was found in
the Dy–Cr binary system.
the Th2Ni17 -type (2:17), the ThMn12-type (1:12) and Nd3(Fe, Ti)29-
type (3:29) structure can be derived from the CaCu5-type structure
by replacement of a fraction of the R sites in the CaCu5 structure by
pairs of Fe atoms (dumb-bells).
2. Experimental
One hundred and forty alloy samples were produced from the constituent
element by arc melting in the water-cooled copper crucible under pure argon atmo-
sphere. The purities of Dy, Fe and Cr were 99.9%, 99.99% and 99.9%, respectively.
Each alloy was prepared with a total weight of 3 g. Weight losses during arc melting
were less than 1% of the total mass. Then they were sealed in evacuated quartz tubes
for homogenization annealing. The heat treatment temperature was determined by
differential thermal analysis (DTA) results of some alloys and based on the previous
work of binary systems. The Fe-rich alloys and Cr-rich alloys were kept at 1173 K for
500 h, the other alloys were homogenized at 973 K for 500 h. Then the samples were
cooled at a rate of 10 K/h to 773 K and kept at 773 K for 150 h. At last, the samples
were quenched into ice–water mixture.
The alloys for X-ray diffraction (XRD) analysis were powdered and investigated
by XRD on a Rigaku D/Max 2500 PC X-ray diffractometer (Cu K␣, monochroma-
tor), using JADE5 software [11] to analyze the angles, ranging from 2Â = 20◦ to 80◦
at 40 kV, 250 mA. Some representative alloys were analyzed in an S-570 scanning
electron microscopy (SEM) or by DTA. From all these result, the phase relations in
the Dy–Fe–Cr system were determined.
No Dy–Fe–Cr ternary phase diagram has been reported in the lit-
erature yet. However, two ternary compounds Dy (Fe, Cr)12 and Dy3
(Fe, Cr)29 have been identified by Bara et al. and Courtois [9,10]. The
compound Dy (Fe, Cr)12 crystallizes with ThMn12-type structure
3. Results and discussion
3.1. Phase analysis
In the Dy–Fe–Cr ternary system, four binary compounds, namely
Dy2Fe17 , Dy6Fe23, DyFe3 and DyFe2 have been reported. For all
of them, excepting Dy2Fe17 crystallographic data are available on
∗
Corresponding author.
E-mail address: qingry96@guet.edu.cn (Q. Yao).
0925-8388/$ – see front matter © 2008 Published by Elsevier B.V.
doi:10.1016/j.jallcom.2008.08.033

Q. Yao et al. / Journal of Alloys and Compounds 475 (2009) 286–288
287
Fig. 1. The observed, calculated and difference XRD pattern of DyFe10 Cr2.
Fig. 3. Isothermal section of the Dy–Fe–Cr system at 773 K.
JCPDS PDF cards. With the crystallographic data of Dy2Fe17 taken
from Ref. [7], using the LAZY program [12], were able to obtain
the calculated XRD pattern of the compound Dy2Fe17 . The results
of XRD analysis our alloy samples are in good agreement with
the data on the respective JCPDS PDF cards or the calculated XRD
pattern of Dy2Fe17 . Thus the existence of these four binary com-
pounds was confirmed. The binary compound of FeCr (␦-phase)
was believed to exist in a narrow temperature at 800–1147 K.
In order to identify this phase, we prepared a series of alloy
samples near the FeCr region. The results of XRD of these alloy
samples shown that the X-ray diagram consists of the patterns
of Fe and Cr. So, the compound of the FeCr does not exist at
773 K.
Dy3Fe29−xCrx, we prepared some alloy samples with composition of
Dy3Fe29−xCrx (0.6 ≤ x ≤ 4.0). The results of XRD analysis of our alloy
samples show that the compound of Dy3(Fe, Cr)29 structure was
not observed at 773 K. But the alloys were sealed in evacuated sil-
ica tubes and annealed in a box furnace at 1273 K for 2 weeks, then
quenched into ice–water mixture. The XRD patterns of the com-
pound Dy3Fe29−xCrx (x = 1.0) is in agreement with the data on the
calculated XRD pattern of R3(Fe, M)29. When the compound was
cooled at a rate 10 K/h to 773 K, it was decomposed to the three
phase of the Dy2Fe17 + DyFe12−xCrx + Fe.
Bara et al. and Courtois [9,10] reported the existence of two
ternary compounds, namely DyFe12−xCrx and Dy3Fe29−xCrx. The
samples were prepared by arc-melting the high purity (99.9%) con-
stituents in argon atmosphere. They were subsequently annealed
in a sealed quartz tube for a period of 7 days at temperatures around
1273 K, and then quenched in water. We prepared the alloy sam-
ples with composition of 7.69 Dy, 69.23–80 Fe, 12.31–23.77 at.%
Cr. The XRD patterns of these samples are in agreement with
the data on the calculated XRD pattern of R(Fe, M)12. The anal-
ysis of the XRD was performed with FULLPROF program [13].
Fig. 1 showed the observed, calculated and difference XRD pat-
tern of DyFe12−xCrx (x = 2.0) single-phase. Due to the compound of
3.2. Solid solubility
The single-phase regions in the 773 K isothermal section were
determined by XRD. The results show that the maximum solu-
bility of Cr in Fe, Dy2Fe17 , Dy6Fe23, DyFe3 and DyFe2 is about 15,
13, 6, 5 and 16 at.%, respectively. By analysing and comparing the
patterns, we found the composition range of DyFe12−xCrx is from
12.31 Cr to 23.77 at.% Cr. The dependence of the lattice param-
eters of the DyFe12−xCrx compounds on the Cr (x) is shown in
Fig. 2.
Fig. 2. Dependence of the lattice parameters of the DyFe12−xCrx compounds on the
Cr (x).
Fig. 4. XRD pattern of alloy the Dy18 Fe74 Cr8 situated in the three-phase region no.
5.

288
Q. Yao et al. / Journal of Alloys and Compounds 475 (2009) 286–288
3.3. Isothermal section at 773 K
Acknowledgements
From the combination of XRD analysis, SEM and electron probe
microanalysis results of the alloy samples; the 773 K isothermal
sections of the phase diagram of the Dy–Fe–Cr ternary sys-
tem were determined. The details of the phase relations are
shown in Fig. 3. The isothermal section of the Dy–Fe–Cr ternary
system at 773 K consists of 8 single-phase regions, 14 two-
phase regions and 7 three-phase regions. The three-phase region
DyFe12−xCrx + DyFe3 + Dy6Fe23 is (no. 5) of particular interest. The
XRD pattern of the alloy Dy18 Fe74 Cr8 which falls in this region and
the corresponding three-phase equilibrium is illustrated by means
of Fig. 4.
The financial support from the National Natural Science Founda-
tion of China (No. 50631040) and the National Science Foundation
of Guangxi (Matching Items) is greatly acknowledged.
References
[1] D.B. de Mooij, K.H.J. Buschow, J. Less-Common Met. 136 (1988) 207.
[2] R. Verhoef, F.R. de Boer, Z. Zhi-dong, K.H.J. Buschow, J. Magn. Magn. Mat. 75
(1988) 319.
[3] W.G. Haije, J. Spijkerman, F.R. de Boer, K. Bakker, K.H.J. Buschow, J. Less-Common
Met. 163 (1990) 123.
[4] V.R. Shah, G. Markandeyulu, K.V.S. Rama Rao, M.Q. Huang, K. Sirisha, M.E.
McHenry, J. Magn. Magn. Mater. 190 (1998) 233.
[5] V.K. Pecharsky, K.A. Gschneidner Jr., J. Magn. Magn. Mater. 200 (1999) 44.
[6] O. Kalogirou, C. Sarafidis, M. Gjoka, G. Litsardakis, J. Magn. Magn. Mater. 247
(2002) 34.
4. Conclusion
[7] H. Okamoto, Binary Alloy Phase Diagrams, ASM International, Materials Park,
1990.
[8] P. Villars, A. Prince, H. Okamoto, Handb. Ternary Alloy Phase Diag. 763/764 (666)
(1995) 665–666.
[9] J.J. Bara, B.F. Bogacz, A.T. Pedziwiatr, J. Alloys Compds. 265 (1998) 70–76.
[10] D. Courtois, Solid State Commun. 98 (6) (1996) 565–570.
[11] Materials Data JADE Release 5, XRD pattern processing, Materials Data Inc.
(MDI), 1999.
[12] K. Yvon, W. Jeitschko, E. Parthe, J. Appl. Crystallogr. 10 (1977) 73.
[13] S. Hong, J.M.P. Coey, Y. Otani, P.P.F. Hurley, J. Phys. Condens. Matter 2 (1990)
6465.
1. The existence of the phases DyFe12−xCrx (1.6 ≤ x ≤ 3.0) was con-
firmed in Dy–Fe–Cr ternary system.
2. The maximum solubility of Cr in (Fe), Dy2Fe17 , Dy6Fe23, DyFe3
and DyFe2 is about 15, 13, 6, 5 and 16 at.%, respectively, while
that of Fe in (Cr) is about 13 at.%.
3. The 773 K isothermal section of the phase diagram of the
Dy–Fe–Cr ternary system consists of 8 single-phase regions, 14
two-phase regions and 7 three-phase regions.