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The 500°C isothermal section of the phase diagram of the ternary HoFeNb system
ELSEVIER
Journal of Alloys and Compounds 248 (1997) 206-208
The 500 “C isothermal section of the phase diagram of the ternary Ho-FeNb system Zhuang, W e n Qin, Huiying Zhou
Yinghong Insriture
of Marerids
Science.
Gwngxi
University,
Nanning.
Guangxi
53MMd.
People 5 Reprrhlic
of Chino
Received 31 May 1996: revised 3 July 1996
The 500°C isothermal section of the Ho-Fe-Nb system was investigated by X-ray powder diffraction, differential thermal microanalysis and electron-probe microanalysis techniques. It consists of 10 single-phase regions. I8 two-phase regions and 9 three-phase regions. At 500°C the maximum solubilities of Nb in Ho,Fe,, and Ho in Fe,Nb and FeNb are about 2.0, 2.0 and 3.0 at.% respectively. In !he Fe-Nb binary system, the composition ranges of the phases B(Fe,Nb) and y(FeNb) were determined as 32.0 to 41.Oat.s Nb and 48.0 to 53.0 at.% Nb respectively. The other compounds, including the tettagonal compound HoFe, ,Nb, have no observable homogeneity
Keywordr:
Ternary systems: Ho-Fe-Nb: Phase diagrams
1. Introduction
2. ExperImentaI
Since the discovery of NdsFe,,B as a permanent magnetic material, it was considered possible that new permanent magnetic .materials could bc found by investigating intermetallic compounds in the R&Fe-M systems (RE = rare earth metal, M = transition metal). Phase diagrams can provide important information about the existence of compounds; they are the basis of developing new materials. So far, the phase diagram of the Ho-Fe-Nb ternary system has not been reported. The Ho-Fe binary system can be found in Ref. [I]. It consists of four compounds at SOO’C (HoFe,. HoFe,, Ho,Fe,,, HosFe,,). The phase diagram of the Fe-Hb binary system has been reported in Refs. [2-71. Recently, Sikanth and Pettic [7] showed that the phases B(Fe,Hb) and y(FeHb) exist. The corresponding composition ranges arc 32.0 to 37.0at.% Nb and 48.0 to 52.0at.% Nb at room temperature. The Ho-Nb phase diagram is unknown, but the RE-M (RE= Dy. Ho; M = MO, V, Ti, Y) phase diagrams reported in Refs. [8,9] suggest that no binary compounds exist in the Ho-h& system. In the present study, this has been confirmed. 0925.8388/97/117.00 P/I
SO925-8388(96)02493-O
8
1997 Elseviet
Sciincc
S.A.
All rights
reserved
details
The starting materials used for the alloys were of high purity (Fe 99.9%. Ho 99.9%. Nb 99.9%). Alloy buttons (147) were prepared by induction melting the appropriate metals in alumina crucibles or by arc melting in pure argon. The weight losses after melting were insignificant (less than 0.7%). The homogenization temperature of the alloys was chosen on the baais of the binary phase diagrams of the Ho-Fe and Fe-Nb systems and the solidus
of some representativeternary alloys determinedby diffemtial themal microanalysis. All tbe alloys were homogenized at $00 “C for 30 days in vacuum and cooled at the rate of 10 “C h- ’ to 500 “C, kept at 500 “C for 5 days and then quenched in ice water. Samples for X-ray diffraction analysis were pow&red and anwaled at 500 “C for 5 days in small evacuated glass tubes, and subsequently quenched in liquid nitrogen. The X-ray analysis was
performedusing a Rigaku 3015 X-ray diffractometerwith Co Ku radiationwith iron filters. Tbe phasediagramwas mainly determined by X-ray diffraction analysis. The phases in some alloys were determined by electron-probe microanalysis in order to determine the maximal solubility of the single phase.
Y. Zhumg er ui. I Journal of Alloys and Compounds 248 (1997) .?M-208
3. Results 3.1.
Isothermal
section
(500
“C)
By comparing and analysing the X-ray diffraction patterns of 147 samples and identifying the phases present in each sample, the 500 “C isothermal section of the phase diagram of the Ho-Fe-Nb system was determined; it is shown in Fig. I. This section consists of: 10 single-phase regions a(Fe). tiHo), 6(Nb), dHo,Fe,,). q(Ho,Fe&, B(HoFe,h m(HoFe,), P(Fe,Nb), $FeNb). @(HoFe,,Nb): 18 two-phase regions a+p, f3+y, y+8, S+T, a+&, e+q, q+e, e+m P+T* a+JL, p+e,q+p, p+p, fs+q. e+p, sr+f3, p+r,r+y; 9 three-phase regions a+p+p, a+e+ p, p.+sz+q, pL+l)+p, p+l)+e, e+p+n, n+p+7, s+ p+y, y+7+e. 3.2.
Pitme
analysis
From the analysis of the X-ray diffraction patterns of the samples, we have confirmed the existence of six binary compounds Ho,Fe,,, Ho,Fers, HoFe,, HoFez, Fe,Nb, FeNb and one ternary compound HoFe;,Nb. The X-ray diffraction data of Ho,Fez,, HoFe,, HoFez, FezNb and
Fig. 1. The isothermal three-phase q$m.
207
FeNb were in exceltent agreemm with theii pm&r diffraction files (ASTM). Tltere are no powder diffmctkn files (ASTM) for Ho&, and HoFe,,Nb: the indexing results of the HoFe,,Nb and Ho&,, compounds wete checked by the De Wolff s figure of merit criterion M,, = Qz,,1(2~4,) [lo]. We found M=31 for r&e HoFe,,Nb compound and M = 23 for the Ho,Fe,, compound. The HoFe, ,Nb compound was indexed successfully on the basis of a tetragonal kttii with LI =O.SSlO and c = OASOOnm. The diffmctkn data for this compound are shown in Table 1. The systematic extinction is in agteement with that of space gnntp 14/tnmm. The difkacthm data for the compound Ho,Fe,, confirm that this compound is hexagonal with space group P6,/mmm, o= 0.8426 and c = 0.5288 MI, as reported in Ref. [l I]. The single-phase ranges in the isodkmml section at 500 T were determhud by X-ray diffra&m and by electron-probe microanalysis. We found that the singkphase regions of Ho+,, extend paralkl to the Fe-Nb boundary line. The maximum sohrbilities of Nb in Ho@ ,, and Ho in Fe+ and FeNb at 500°C are about 2.0. 2.0 and 3.0 at.% respectively. With increasing Nb content, the diffraction lines of the B and p. phases in the Fe-Nb system moved distinctly to tower angks. so the two phases
of Ihe Ho-Fe-Nb
l . singk-phase qion;
0.
Y. zhumg
e, a,. I Joemat
of Alloys
Table I Ddfmction data of the fi phase Number
114,
28
sin’ I?,.,.
sin’ .9..,,
hkl
1
6 22 IO 38 14 3 loo 48
24.1 34.9 38.9 43.0 43.7 47.4 50.0 50.7 53.0 68.5 13.2 73.8
0.0457 O.O%Q 0.1109 0.1343 0. I385 0.1622 0.1786 0. I833 0.1991 0.3168 0.3955 0.3605
0.0458 0.0901 0.1106 0.1344 0.1393 0.1614 0. I787 0. I835 0.1992 0.3163 0.3557 0.3w6
101 211 310 301 002 II2 321 202 330 402 521 422
2 3 4 5 6 7 8
6 8 8
10
II 12
should have broad composition ranges. The composition ranges of the p and y phases were determined as 32.0 to 41.0 at.% Nb and 48.0 to 53.0 at.% Nb respectively. The X-my diffraction paxems for the alloys near the compositions of the (I, 7. 6, q, 8, 71 and p phases showed that the diffraction lines did not shift and the diffraction patterns of the second phases could easily be detected. Therefore, these phases do not have significant homogeneity ranges at 500 “C.
4.
Lliscussion
De Mooij and Buschow [12] indicated that ternary compounds based on the tetragonal ThMn,, type structure were formed when rare earth elements (Y, Gd) are combined with iron and elements M (M = Si, Ti, V, Cr. MO. W). Moreover, some authors think that REFe,M, compounds may exist in ternary RE-Fe-M systems (RE = rare earth metal, M = transition metal) [13]. We prepared
and Conlpounds
248 (1997)
206-208
several samples near the composition HoFe,Nb,, but the diffraction pattern of HoFe,Nb, obviously consists of the pattern of the phase p(HoFe,,Nh) together with the patterns of the phases P(Fe,Nb) and q(Ho,Fe,,). Furthermore, metallographic examination of these samples showed that the HoFe,Nb, sample obviously belongs to the three-phase region. Therefore, the HoFe,Nb, compound does not exist in the ternary Ho-Fe-Nb system at 500 “C.
Acknowledgments This work was Science Foundation of China.
by the National Natural
References [I] C.J. Smithells. Meruls Reference Book. Butterworth. London, 5th edn.. 1976, p. 603. [21 S.A. Pogodin. N.F. Blagov and M.B. Reifmao, Merallurgio. 8 ( 1937) 3. I31 H.J. Cioldrhmidt. Memllurgia. 43 (1951) 157. I41 R. Gender and R. Hrmison, J. Iron Steel Insr.. I40 (1939) 29. I51 E. Paul and L.J. Swartzendmber. Bull. A//q Phase Diogr.. 713) ( 1986) 248. I61 J.M.Z. Barano. S. Gama. C.A. Rib&o and G. Effenkrg. 2. Mctalkd.. 84 (1993) 160. 171 S. Srlkanlh and A. PeIric, Z. Merallkd.. 85 (1994) 164. 181 R.P. Elliott. Consrirurion of Binwy Alloys. First Suppl.. McGrawHill, New York, I%5 191 EA. Shunk. Consfiwion of Binary A!ioys, Second Soppl., McGrawHill, New York. l%9. [IO] P.M. De Wolff. b H.P.KluS and L.E. Alexander (eds.), X-ruy
,
Diffraction
Procedures
for
Polycryscallinr
and
Amorphous
a/s. Wiley, New York. 2nd edn.. 1974. p. B468. II II X. Fang et al.. J. Alloys Camp.. I% (1993) LIS. [I21 D.B. De M&j and K.H. Busebow, 1. Less-Common ( 1988) 207.
1131 J. Tim er al., Sci.
China,
Ser. A. (1992)
505.
Mar.+
Met..
136
Journal of Alloys and Compounds 248 (1997) 206-208
The 500 “C isothermal section of the phase diagram of the ternary Ho-FeNb system Zhuang, W e n Qin, Huiying Zhou
Yinghong Insriture
of Marerids
Science.
Gwngxi
University,
Nanning.
Guangxi
53MMd.
People 5 Reprrhlic
of Chino
Received 31 May 1996: revised 3 July 1996
The 500°C isothermal section of the Ho-Fe-Nb system was investigated by X-ray powder diffraction, differential thermal microanalysis and electron-probe microanalysis techniques. It consists of 10 single-phase regions. I8 two-phase regions and 9 three-phase regions. At 500°C the maximum solubilities of Nb in Ho,Fe,, and Ho in Fe,Nb and FeNb are about 2.0, 2.0 and 3.0 at.% respectively. In !he Fe-Nb binary system, the composition ranges of the phases B(Fe,Nb) and y(FeNb) were determined as 32.0 to 41.Oat.s Nb and 48.0 to 53.0 at.% Nb respectively. The other compounds, including the tettagonal compound HoFe, ,Nb, have no observable homogeneity
Keywordr:
Ternary systems: Ho-Fe-Nb: Phase diagrams
1. Introduction
2. ExperImentaI
Since the discovery of NdsFe,,B as a permanent magnetic material, it was considered possible that new permanent magnetic .materials could bc found by investigating intermetallic compounds in the R&Fe-M systems (RE = rare earth metal, M = transition metal). Phase diagrams can provide important information about the existence of compounds; they are the basis of developing new materials. So far, the phase diagram of the Ho-Fe-Nb ternary system has not been reported. The Ho-Fe binary system can be found in Ref. [I]. It consists of four compounds at SOO’C (HoFe,. HoFe,, Ho,Fe,,, HosFe,,). The phase diagram of the Fe-Hb binary system has been reported in Refs. [2-71. Recently, Sikanth and Pettic [7] showed that the phases B(Fe,Hb) and y(FeHb) exist. The corresponding composition ranges arc 32.0 to 37.0at.% Nb and 48.0 to 52.0at.% Nb at room temperature. The Ho-Nb phase diagram is unknown, but the RE-M (RE= Dy. Ho; M = MO, V, Ti, Y) phase diagrams reported in Refs. [8,9] suggest that no binary compounds exist in the Ho-h& system. In the present study, this has been confirmed. 0925.8388/97/117.00 P/I
SO925-8388(96)02493-O
8
1997 Elseviet
Sciincc
S.A.
All rights
reserved
details
The starting materials used for the alloys were of high purity (Fe 99.9%. Ho 99.9%. Nb 99.9%). Alloy buttons (147) were prepared by induction melting the appropriate metals in alumina crucibles or by arc melting in pure argon. The weight losses after melting were insignificant (less than 0.7%). The homogenization temperature of the alloys was chosen on the baais of the binary phase diagrams of the Ho-Fe and Fe-Nb systems and the solidus
of some representativeternary alloys determinedby diffemtial themal microanalysis. All tbe alloys were homogenized at $00 “C for 30 days in vacuum and cooled at the rate of 10 “C h- ’ to 500 “C, kept at 500 “C for 5 days and then quenched in ice water. Samples for X-ray diffraction analysis were pow&red and anwaled at 500 “C for 5 days in small evacuated glass tubes, and subsequently quenched in liquid nitrogen. The X-ray analysis was
performedusing a Rigaku 3015 X-ray diffractometerwith Co Ku radiationwith iron filters. Tbe phasediagramwas mainly determined by X-ray diffraction analysis. The phases in some alloys were determined by electron-probe microanalysis in order to determine the maximal solubility of the single phase.
Y. Zhumg er ui. I Journal of Alloys and Compounds 248 (1997) .?M-208
3. Results 3.1.
Isothermal
section
(500
“C)
By comparing and analysing the X-ray diffraction patterns of 147 samples and identifying the phases present in each sample, the 500 “C isothermal section of the phase diagram of the Ho-Fe-Nb system was determined; it is shown in Fig. I. This section consists of: 10 single-phase regions a(Fe). tiHo), 6(Nb), dHo,Fe,,). q(Ho,Fe&, B(HoFe,h m(HoFe,), P(Fe,Nb), $FeNb). @(HoFe,,Nb): 18 two-phase regions a+p, f3+y, y+8, S+T, a+&, e+q, q+e, e+m P+T* a+JL, p+e,q+p, p+p, fs+q. e+p, sr+f3, p+r,r+y; 9 three-phase regions a+p+p, a+e+ p, p.+sz+q, pL+l)+p, p+l)+e, e+p+n, n+p+7, s+ p+y, y+7+e. 3.2.
Pitme
analysis
From the analysis of the X-ray diffraction patterns of the samples, we have confirmed the existence of six binary compounds Ho,Fe,,, Ho,Fers, HoFe,, HoFez, Fe,Nb, FeNb and one ternary compound HoFe;,Nb. The X-ray diffraction data of Ho,Fez,, HoFe,, HoFez, FezNb and
Fig. 1. The isothermal three-phase q$m.
207
FeNb were in exceltent agreemm with theii pm&r diffraction files (ASTM). Tltere are no powder diffmctkn files (ASTM) for Ho&, and HoFe,,Nb: the indexing results of the HoFe,,Nb and Ho&,, compounds wete checked by the De Wolff s figure of merit criterion M,, = Qz,,1(2~4,) [lo]. We found M=31 for r&e HoFe,,Nb compound and M = 23 for the Ho,Fe,, compound. The HoFe, ,Nb compound was indexed successfully on the basis of a tetragonal kttii with LI =O.SSlO and c = OASOOnm. The diffmctkn data for this compound are shown in Table 1. The systematic extinction is in agteement with that of space gnntp 14/tnmm. The difkacthm data for the compound Ho,Fe,, confirm that this compound is hexagonal with space group P6,/mmm, o= 0.8426 and c = 0.5288 MI, as reported in Ref. [l I]. The single-phase ranges in the isodkmml section at 500 T were determhud by X-ray diffra&m and by electron-probe microanalysis. We found that the singkphase regions of Ho+,, extend paralkl to the Fe-Nb boundary line. The maximum sohrbilities of Nb in Ho@ ,, and Ho in Fe+ and FeNb at 500°C are about 2.0. 2.0 and 3.0 at.% respectively. With increasing Nb content, the diffraction lines of the B and p. phases in the Fe-Nb system moved distinctly to tower angks. so the two phases
of Ihe Ho-Fe-Nb
l . singk-phase qion;
0.
Y. zhumg
e, a,. I Joemat
of Alloys
Table I Ddfmction data of the fi phase Number
114,
28
sin’ I?,.,.
sin’ .9..,,
hkl
1
6 22 IO 38 14 3 loo 48
24.1 34.9 38.9 43.0 43.7 47.4 50.0 50.7 53.0 68.5 13.2 73.8
0.0457 O.O%Q 0.1109 0.1343 0. I385 0.1622 0.1786 0. I833 0.1991 0.3168 0.3955 0.3605
0.0458 0.0901 0.1106 0.1344 0.1393 0.1614 0. I787 0. I835 0.1992 0.3163 0.3557 0.3w6
101 211 310 301 002 II2 321 202 330 402 521 422
2 3 4 5 6 7 8
6 8 8
10
II 12
should have broad composition ranges. The composition ranges of the p and y phases were determined as 32.0 to 41.0 at.% Nb and 48.0 to 53.0 at.% Nb respectively. The X-my diffraction paxems for the alloys near the compositions of the (I, 7. 6, q, 8, 71 and p phases showed that the diffraction lines did not shift and the diffraction patterns of the second phases could easily be detected. Therefore, these phases do not have significant homogeneity ranges at 500 “C.
4.
Lliscussion
De Mooij and Buschow [12] indicated that ternary compounds based on the tetragonal ThMn,, type structure were formed when rare earth elements (Y, Gd) are combined with iron and elements M (M = Si, Ti, V, Cr. MO. W). Moreover, some authors think that REFe,M, compounds may exist in ternary RE-Fe-M systems (RE = rare earth metal, M = transition metal) [13]. We prepared
and Conlpounds
248 (1997)
206-208
several samples near the composition HoFe,Nb,, but the diffraction pattern of HoFe,Nb, obviously consists of the pattern of the phase p(HoFe,,Nh) together with the patterns of the phases P(Fe,Nb) and q(Ho,Fe,,). Furthermore, metallographic examination of these samples showed that the HoFe,Nb, sample obviously belongs to the three-phase region. Therefore, the HoFe,Nb, compound does not exist in the ternary Ho-Fe-Nb system at 500 “C.
Acknowledgments This work was Science Foundation of China.
by the National Natural
References [I] C.J. Smithells. Meruls Reference Book. Butterworth. London, 5th edn.. 1976, p. 603. [21 S.A. Pogodin. N.F. Blagov and M.B. Reifmao, Merallurgio. 8 ( 1937) 3. I31 H.J. Cioldrhmidt. Memllurgia. 43 (1951) 157. I41 R. Gender and R. Hrmison, J. Iron Steel Insr.. I40 (1939) 29. I51 E. Paul and L.J. Swartzendmber. Bull. A//q Phase Diogr.. 713) ( 1986) 248. I61 J.M.Z. Barano. S. Gama. C.A. Rib&o and G. Effenkrg. 2. Mctalkd.. 84 (1993) 160. 171 S. Srlkanlh and A. PeIric, Z. Merallkd.. 85 (1994) 164. 181 R.P. Elliott. Consrirurion of Binwy Alloys. First Suppl.. McGrawHill, New York, I%5 191 EA. Shunk. Consfiwion of Binary A!ioys, Second Soppl., McGrawHill, New York. l%9. [IO] P.M. De Wolff. b H.P.KluS and L.E. Alexander (eds.), X-ruy
,
Diffraction
Procedures
for
Polycryscallinr
and
Amorphous
a/s. Wiley, New York. 2nd edn.. 1974. p. B468. II II X. Fang et al.. J. Alloys Camp.. I% (1993) LIS. [I21 D.B. De M&j and K.H. Busebow, 1. Less-Common ( 1988) 207.
1131 J. Tim er al., Sci.
China,
Ser. A. (1992)
505.
Mar.+
Met..
136