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NdCuSn system: identification of ternary phases and partial determination of the isothermal section at 400°C
this
system
nine
phases
are
reported:
Nd,Sn,
tm.p.
1660 “0,
Nd,Sn, (perhectic formation at 1558 “CL Nd, ,.%I,, (peritectic formation at 1396°C). NdSn (peritectic formation at 12.57 “C), Nd,Sn, (peritectic formation at 1140°C). NdSn2 (m.p. 1180°C). Nd,Sn, (peritectic formation at 114.5 “C). Nd,Sn, (peritectic formation at 1135 “C), and NdSn, (m.p. 1150 “C). In the part of the ternary isothermal section studied. only two compounds are involved: Nd,Sn, (hP6-Mn,Si, type) and Nd,Sn, (oP36-Ge,Sm, type).
3. Experimental
details
Neodymium Wlminal ptirity 99.9 mash%) and copper and tin (nominal purity 99.999 mass%) were u>ed as starting components. The alloys were prepared by sealing the appropriate amounts of the elements in small tantalum crucibles under an argon atmosphere The crucibles were induction-heated until completr fusion of the constituent elements. in a vacuum-tube furnace. and the alloys were homogenized by repeated shaking and quickly cooled to room temperature. The samples were then annealed at 4OO’C for two weeks and quenched in ice-water. X-ray diffraction (XRD) analysis, metallographic nnalysis and electron probe microanalysis (EPMA) were used to characterize the samples. X-ray examination was carried out on powder samples using a vertical diffractometer with Cu Ku radiation: the
NdCu,Sn Nd,Cu,,Sn,
auCI”re \,ruC1”re
addition
of a calibration standard (Si) to the sample was made to achieve higher accuracy in measurements of the d values. The observed diffraction intensities were compared with the calculated valws obtained using the program PI’LVERIX [IO]. The valws of the lattice parameters were refined using a least-squares routine.
The microstructure of the alloys was studied using standard
optical
and electronic
micrographic
methods
on
all the samples: the specimens were prepared by the conventional method and, if necessary. etched with dilute alcoholic HNO, sohuion to reveal the various phaspc. Semi-quantitative electron probe microanalysis of the phases was carried out using an energy-dispersive X-ray analyzer with the pure elements as standards.
4. Results No experimenta! investigation of the phase equilibria in the Nd-Cu-Sn ternary system has previously been reported in the literature. The data obtained in this work may be summarized in the following sections.
In the isothermal section at 4CQ”C the existence of the following phases has been confirmed: NdCuSn (hP6-Cain?
unhnown unbnown
NdCu..Sn,
cFI 12
u = 1215.2
,,=1213.81111
NdCuSn
NaZn,, hP6 Mll:
u =456.2
<’= 762.6
c = 761.4
fIrI
0=4s: 1131 (‘= w.? ol??
Gd,Ge,Sn,
h = 698.6
IPIO
(‘ = 4S3.8 L, = 443.2
CaBe,Ge,
< = 1026.9
L‘= 1026.4
Nd:Cu,Sn,
1122
‘I = 443.4
(I = 443.4 I ISI
SIll,CU,S!l,
c = 25.w.z
L’= 2510.8
Nd,CuSn,
hP3 AIB: oCl6 CeNiSi,
u = 437.8 <=-MO.1 a = 447.6 b= 1736 <=-MO.4
u = 447.0 I t 61 b = 1741 c = 439.8
Nd,Cu,Sn,
NdCu:Sn>
NdCu,, ,x $1.:Sn:
I, = 443.2 [ 141
a =447.0
1171
b = 1751.1 r=441.7
33.5
16.4
29.0
0.1
0.1
25.5
26.5
2.1
6.6
35.6
7.2
5.0
27.7
34.6
9
10
'"11
12
"13
14
15
32.6
32.1
29.5
29.6
332
27.6
0.1
7.6
52.0
62.0
246
64.1
6
27.2
14.6 61.3
20.6
23.7
14.7
49.2
6
7
"'5
50.9
50.4
4
15.5
Tahlr 2 Nd-Cu-Sn
33.1
36.6
25.9
27.6
45.0
21.3
25.2
37.3
37.2
19.6
32.9
0.6
T# hFSC&, VI
L
Q&n
ocao.
N&as
cFl12-
Qb%
oP36-
Q&nIl
6416.
QSn
oc%o-
t
hFSMn&ii,
hF+Caln, T, sbucl unknwnr~ hPgMn&i,
OP6-FOB
~453 c=766
r14m b= 697.5 (F455.4
F651.9 b=4777 c=432.5
~815.4 b=1614 eF614.0 a=1215
~549.6 b=477.2 c=432.9 a=1793
s921.6 -670.7
~921 c= 669.9
~457.1 cE759.6
c=667.0
56.1
33.6
20.1
20.4
33.7
21.0
7.4
51.7
34.3
0.4
20.5
61.7
44.3
329
364
39.4
33.6
36.0
26.7
0.4
1.0
6.0
0.4
35.6
'ta
T‘
oP36Ge&ims
r1
hFS-Caln,
-2-2
-es a tPlo_~
lPl0.
74
T, hFsc&l,
-2-z
WC-
N&I,
6112.
OP6-F*B
Oll2acu,
cF4-Q
o-4
a=4556 cc766.4
as443.1 A026
a=455.0 sY773.5
a=44o.u c=ln23
a=12157
!z;z;;
?? =436.4
a=919.1 c= 655.7
32.3
14.7
7.5
33.6
97.0
33.4
34.0
0.6
19.4
29.5
0.9
0.2
0.2
0.1
lirr two wcel\ and wter-quenched)
hWMn&i,
syran~:rewks obtainedI'ro~n selected alloys(annealedill Joi)T
Q
rz 0112-c&u,
skuu unknm
Nata
cF112-
oll2-cecu,
hP4-aLa
0112~cacuz
Oll2-c&J2
?? =437.7 b=701.3 c=746.5
: ‘i s 1
? v 2 5 u
9 1 x i g
5 .T < f 5
2,
> 5 5
2 c>
?z p =.
27.0
6.4
17.0
14.6
5.1
18.7
18.4
36.6
30.1
17
"'16
16
20
21
22
23
24
25
40.6 30.0
66.a
26.2
21 .o
0.0
21.1
20.4
16.0
27.6
33.4
50.4
461
41.3
389
38.2
37.1
37.0
31.4
a2.7
66.0
50.5
45.2
40.3
44.4
41.5
40.0
64.4
66.6
33.8
‘*’ For these alloy* microphotographr have ken rqxrrled
34.0
16
.
ocli WNiSi, t
,
,
1
16.446 b=l735 10440
a= 437.8 c=440.1
c=2530
Ala,
?? =443.4
-zw
Sm&u,Sq
IA027
(122.
I.=443
c=513.0
~421.2
c=1024
a= 441.6
c=1025
a==4416
c&514
tPlog
ck6@e* b hW-NiCs
lPIO-r
=A
SmzCur6nl 7,
Gd&9&u#b=669 rs c=4Y lm ?? =444.6
s14n6
c=762
r4 om
a=466
hFS.Cdn,
47.5
01
0.0
0.0
16.4
0.5
0.2
~.
20.6
27.8
463
25.7
255
255
44.0
25.5
45.;
26.7
37.2
384. aIoHO,,
OC8O-CU&l
c= 431.7
15.0
cc8o-Cu,Sn
0.0
6.6
0.0
Sm&u,SnB q oC80.curSn e4y;
a=1467 b=7w c=456
u22-
OC3O-CU,Sn
-7w r, hP4-Nti
~@@cus I tPIOsT
ol22-
48.0
260
28.7
256
13
t,
1122. sm,Cu,Sn~
oC80.Cu,Sn
tNG%
d=112-
oC80.Cua6n
.= 445.0 c=2516
.= 551.6 w777 c= 432.6
a=1168
.=652.4 b= 476.2 c= 432.6
E
type). NdCu,Sn, (tPIO-CaBe,Ge, type). NdCu,_,Sn,_, (oClh-CeNiSi, type). NdCu,Sn, (cFI IZ-NaZn,, type) and Nd,Cu,Sn, (tl22-Sm@t.,Sn, type). The existence, moreover, of four other ternary compounds has been observed: Nd,Cu,Sn, and Nd,CuSn,. which have been characterized as pertaining to the 0122~Gd,Cu,Ge, type and to the hP$AIB, type respectively. and two other phases with unknown structure corresponding to the NdCtt,Sn and Nd,Cu,,,Sn, stoichiometries (and probably isostructural with similar phases in the Ce-Cu-Sn and Pr-Cu-Sn systems). Crystal structure data of the ternary compounds are reported in Table I and compared with literature data. Among previously mentioned ternary compounds, NdCu,Sn,. NdCtt,Sn and Nd,Cu,,Sn, may be considered compounds’. NdCu$t, and stoichiometric ‘point Nd,Cu,Sn, are probably characterized by a solubility range whose extension is under study. (These phases actually show different compositions in different samples analyzed by EPMA.) A larger range of homogeneity should finally be attributed to the -Nd,CuSn,
Fig. 2. Electron micrograph of alloy I t 19.7 at.9 Nd. 9.0 at.5 Sn): large quantity of solid solution of NdCu, tgrey) plus ‘TV white) and NdCu, (black).
phase.
1.2. I.torhermal section A partial isothermal section at 400°C obtained in this work is reported in Fig. 1. This has been constructed mainly on the basis of analyses carried out in the three-phase regions in which the different phases have been identified and characterized by means of X-ray and EPMA analysis. The results concerning a number of selected alloys are reported in Table 2. in Fig. 2 Fig. 3 Fig. 4 Fig. 15 Fig. 6. selected scanning electron micrographs of alloys in typical three-phase fields are reported as examples. The following three-phase fields have been observed: Nd+NdCu+Nd,Sn, NdCu+NdCu,+Nd,Sn,. Nd,Sn,+ NdCuz+Nd,Sn,, Nd,Sn,+NdCtt2+NdCttSn, NdCua+ NdCuSn+NdCu,. NdCu,+NdCtt,+NdCttSn, NdCtt,+
Fig.
I. Nd-Cu-Sn
system: p&al
isothermal secdon at 400 “C
Fig. 3. Electron micrograph of alloy 5 (29.0 at.% Nd. 16.4 at.% Sn): white crystals of r, plus N&I,
tgrey) plus binary eutectic tNdCu,+NdCu,).
Fig. 4. Electron micmgrapb of alloy I I (35.8 al.% Nd. 27.2 at.% Sn): white crystals of TV plus NdCu, tgrey) plus Nd,Sn,.
and also the close analogy with other R-Cu-Sn systems when R is a light rare eatih. In particular. from a comparison with the Pr-Cu-Sn system. we may notice that the phases RCusSn, R,Cu, lSn,. RCu,Sn,. RCuSn. R,Cu,Sn,, RCu$n,. R2Cu,Sn,. RCu, ,Srr_, and R,CuSn, are f-d in both systems. The phases R,,Cu,,Sn2, and R,,Cu,,Sn,, reported for Pr have not been identified in the Nd system. Concerning the determination of tie-triangles, it is interesting to notice the difference between Pr and Nd. which can be attributed to the existence of the binary compound Pr,Sn absent in the Nd-Sn system.
Acknowledgments Fig. S. Electron micrograph of alloy
13 tS.Oat.%
Nd. %.5at.%
Snl:
ociculm crystals of T. plus E (black) and T..
We would like to thank the Ministero deR’Universit~ e della Ricerca Scientitica e Tecno!ogica (MURST. 40%) for the hrancial support afforded us.
References
121 R. Marwu P. Riam. D. Muzone. G. bnicchi and R. Fens. Illwnwnrllrc A. J ,l996) 131. 131 P Riani. R. Mxaua. D. Muzone. G. Zmicchi and R. Fens. Pmt. It Cwnrym~ INCU. Firrnrr 1% IS Frhru:~q 1995 p. 024. 141 G. Zanicchi. D. Muzone, P Rkmi. R. Mamzza and R. Fern i’mc. VI Mwr. on Swthrrur und Merhodolo~ics in inorganic Chemirt~. nrr.wusrl~~. IX-21 [S] R. Fig. 6. Electmn micrograph of alloy uciculnr cryads oft,
IX (5.4 at.9
G.
I)rwmtler
Zmiichi,
Nd. 37.Oat.5+ Snl.
Coa~pc~~dirrmof Ewlnarrd
NdCuSn+Nd,Cu,Sn,+Nd,Cu,,Sn,. NdCu,+NdCuSn, NdCu,Sn,+G+NdCu$t,. NdCu,Snz+Nd,Cu,Sn,+6. NdCu,Sn,+a+NdCu$t,, a+ b+NdCu,Sn,+a, NdCu,Snz+Nd,Cu,Sn, and a+Nd,Cu,Sn,+~. Other work 71s needed in the tields bounded by the phases Nd,Cu,Sn,, Nd,Cu,,Sn,, 6 and copper solid solution (Cu,,Sn,) and NdCu,. NdCuSn. Nd,Cu,,Sn, and NdCu,Sn respectively. In these regions, in fact, there are invariant temperatures
very close to 4OO“C. The thermal treatment generally adopted and previously described results therefore in .I number of samples not in equilibrium (four-phase alloys).
The
two-phase equilibria NdCuSn+NdCu,Sn and Nd,Cu ,,Sn, +copper solid solution (Cu,,Sn, ). however. seem to be ascertained. 5. General remarks The high number of phases obtained may be underlined
lws.
t!
pp. 93-w.
Riani
tCe.Pr.Sm.Ho.Tm.Yb.Lu)-copper-tin. F. Aldingcr et al. I&.). Trma~
plus E (black) and q.
probably transformations and/or
Fcmr.
and
R.
Maruza.
Yttrium
in G. Petzow. G. Effenbq. Allow - A Cmnprehensiw
Cnnsn’rndomd C41ta and Phaw
Dia-
,~rww. VCH. Weinheim. in press. 161 P.R. Subnmanian ad D.E. Laughlin. Bull. Al/o? Phase Diugr.. Y(3A) ,198X, 322. 171 T.B. MasaIski.
Binqv A//q! Phasr Di~9mmw. ASM. Metals Park.
OH. 2nd rdn.. lm. [Xl t?Villan and L.D. C&a-t. Pmrwn’.s Hundhwk of Cryndln~mphic Buu .fisr hnrmrudlic Phases. ASM. Metals Park. OH. 1991. 191 A. Sxxonr.
D. Mac&
and R. Ferm. J. Ath~~.xCmnp.. 2001(1993)
L9. [IO] K. Yvon. W. Jeitschko and E. RrlY.
1. Appl. Cq.s:dllogr..
IO
(1977) 73. [I II L.P. Komannskaya
[
and R.V. Skolozdra. D&l.
AN.
UkSSR. 88
(19x4) 37. 121 L.P. Komaruvskayp R.V. Skdozdra and I&! Filatova. Doll.
AN.
,198))
UkSSR. Al 82. I31 A.E. Dwight. Pmt. 12th Rwc Earth Raearch
[ [141 R.V. Skolozdm and L.P. Kamamvsl;aya.
Conf. (1976) 480.
Ukr. Fi:. Zhum.. 27 (1982)
I w.34. [IS]
L.P. Komamuskaya and R.V. Skolozdm. ix.
Akad. Nauk. SSSR
Met&. 3 ( 1992) 231. 116) L.P. Komamvskaya. S.A. Sadykov and R.V. Skotozdm. Ukr. Fi:. ZJwm. .7.7(8) (1988) 1249. 1171 M. Franc&. G. knnwini. B. Malaman and B. Rapes. Common Me!.. 160 ( 1990) 197.
1. Lew
system
nine
phases
are
reported:
Nd,Sn,
tm.p.
1660 “0,
Nd,Sn, (perhectic formation at 1558 “CL Nd, ,.%I,, (peritectic formation at 1396°C). NdSn (peritectic formation at 12.57 “C), Nd,Sn, (peritectic formation at 1140°C). NdSn2 (m.p. 1180°C). Nd,Sn, (peritectic formation at 114.5 “C). Nd,Sn, (peritectic formation at 1135 “C), and NdSn, (m.p. 1150 “C). In the part of the ternary isothermal section studied. only two compounds are involved: Nd,Sn, (hP6-Mn,Si, type) and Nd,Sn, (oP36-Ge,Sm, type).
3. Experimental
details
Neodymium Wlminal ptirity 99.9 mash%) and copper and tin (nominal purity 99.999 mass%) were u>ed as starting components. The alloys were prepared by sealing the appropriate amounts of the elements in small tantalum crucibles under an argon atmosphere The crucibles were induction-heated until completr fusion of the constituent elements. in a vacuum-tube furnace. and the alloys were homogenized by repeated shaking and quickly cooled to room temperature. The samples were then annealed at 4OO’C for two weeks and quenched in ice-water. X-ray diffraction (XRD) analysis, metallographic nnalysis and electron probe microanalysis (EPMA) were used to characterize the samples. X-ray examination was carried out on powder samples using a vertical diffractometer with Cu Ku radiation: the
NdCu,Sn Nd,Cu,,Sn,
auCI”re \,ruC1”re
addition
of a calibration standard (Si) to the sample was made to achieve higher accuracy in measurements of the d values. The observed diffraction intensities were compared with the calculated valws obtained using the program PI’LVERIX [IO]. The valws of the lattice parameters were refined using a least-squares routine.
The microstructure of the alloys was studied using standard
optical
and electronic
micrographic
methods
on
all the samples: the specimens were prepared by the conventional method and, if necessary. etched with dilute alcoholic HNO, sohuion to reveal the various phaspc. Semi-quantitative electron probe microanalysis of the phases was carried out using an energy-dispersive X-ray analyzer with the pure elements as standards.
4. Results No experimenta! investigation of the phase equilibria in the Nd-Cu-Sn ternary system has previously been reported in the literature. The data obtained in this work may be summarized in the following sections.
In the isothermal section at 4CQ”C the existence of the following phases has been confirmed: NdCuSn (hP6-Cain?
unhnown unbnown
NdCu..Sn,
cFI 12
u = 1215.2
,,=1213.81111
NdCuSn
NaZn,, hP6 Mll:
u =456.2
<’= 762.6
c = 761.4
fIrI
0=4s: 1131 (‘= w.? ol??
Gd,Ge,Sn,
h = 698.6
IPIO
(‘ = 4S3.8 L, = 443.2
CaBe,Ge,
< = 1026.9
L‘= 1026.4
Nd:Cu,Sn,
1122
‘I = 443.4
(I = 443.4 I ISI
SIll,CU,S!l,
c = 25.w.z
L’= 2510.8
Nd,CuSn,
hP3 AIB: oCl6 CeNiSi,
u = 437.8 <=-MO.1 a = 447.6 b= 1736 <=-MO.4
u = 447.0 I t 61 b = 1741 c = 439.8
Nd,Cu,Sn,
NdCu:Sn>
NdCu,, ,x $1.:Sn:
I, = 443.2 [ 141
a =447.0
1171
b = 1751.1 r=441.7
33.5
16.4
29.0
0.1
0.1
25.5
26.5
2.1
6.6
35.6
7.2
5.0
27.7
34.6
9
10
'"11
12
"13
14
15
32.6
32.1
29.5
29.6
332
27.6
0.1
7.6
52.0
62.0
246
64.1
6
27.2
14.6 61.3
20.6
23.7
14.7
49.2
6
7
"'5
50.9
50.4
4
15.5
Tahlr 2 Nd-Cu-Sn
33.1
36.6
25.9
27.6
45.0
21.3
25.2
37.3
37.2
19.6
32.9
0.6
T# hFSC&, VI
L
Q&n
ocao.
N&as
cFl12-
Qb%
oP36-
Q&nIl
6416.
QSn
oc%o-
t
hFSMn&ii,
hF+Caln, T, sbucl unknwnr~ hPgMn&i,
OP6-FOB
~453 c=766
r14m b= 697.5 (F455.4
F651.9 b=4777 c=432.5
~815.4 b=1614 eF614.0 a=1215
~549.6 b=477.2 c=432.9 a=1793
s921.6 -670.7
~921 c= 669.9
~457.1 cE759.6
c=667.0
56.1
33.6
20.1
20.4
33.7
21.0
7.4
51.7
34.3
0.4
20.5
61.7
44.3
329
364
39.4
33.6
36.0
26.7
0.4
1.0
6.0
0.4
35.6
'ta
T‘
oP36Ge&ims
r1
hFS-Caln,
-2-2
-es a tPlo_~
lPl0.
74
T, hFsc&l,
-2-z
WC-
N&I,
6112.
OP6-F*B
Oll2acu,
cF4-Q
o-4
a=4556 cc766.4
as443.1 A026
a=455.0 sY773.5
a=44o.u c=ln23
a=12157
!z;z;;
?? =436.4
a=919.1 c= 655.7
32.3
14.7
7.5
33.6
97.0
33.4
34.0
0.6
19.4
29.5
0.9
0.2
0.2
0.1
lirr two wcel\ and wter-quenched)
hWMn&i,
syran~:rewks obtainedI'ro~n selected alloys(annealedill Joi)T
Q
rz 0112-c&u,
skuu unknm
Nata
cF112-
oll2-cecu,
hP4-aLa
0112~cacuz
Oll2-c&J2
?? =437.7 b=701.3 c=746.5
: ‘i s 1
? v 2 5 u
9 1 x i g
5 .T < f 5
2,
> 5 5
2 c>
?z p =.
27.0
6.4
17.0
14.6
5.1
18.7
18.4
36.6
30.1
17
"'16
16
20
21
22
23
24
25
40.6 30.0
66.a
26.2
21 .o
0.0
21.1
20.4
16.0
27.6
33.4
50.4
461
41.3
389
38.2
37.1
37.0
31.4
a2.7
66.0
50.5
45.2
40.3
44.4
41.5
40.0
64.4
66.6
33.8
‘*’ For these alloy* microphotographr have ken rqxrrled
34.0
16
.
ocli WNiSi, t
,
,
1
16.446 b=l735 10440
a= 437.8 c=440.1
c=2530
Ala,
?? =443.4
-zw
Sm&u,Sq
IA027
(122.
I.=443
c=513.0
~421.2
c=1024
a= 441.6
c=1025
a==4416
c&514
tPlog
ck6@e* b hW-NiCs
lPIO-r
=A
SmzCur6nl 7,
Gd&9&u#b=669 rs c=4Y lm ?? =444.6
s14n6
c=762
r4 om
a=466
hFS.Cdn,
47.5
01
0.0
0.0
16.4
0.5
0.2
~.
20.6
27.8
463
25.7
255
255
44.0
25.5
45.;
26.7
37.2
384. aIoHO,,
OC8O-CU&l
c= 431.7
15.0
cc8o-Cu,Sn
0.0
6.6
0.0
Sm&u,SnB q oC80.curSn e4y;
a=1467 b=7w c=456
u22-
OC3O-CU,Sn
-7w r, hP4-Nti
~@@cus I tPIOsT
ol22-
48.0
260
28.7
256
13
t,
1122. sm,Cu,Sn~
oC80.Cu,Sn
tNG%
d=112-
oC80.Cua6n
.= 445.0 c=2516
.= 551.6 w777 c= 432.6
a=1168
.=652.4 b= 476.2 c= 432.6
E
type). NdCu,Sn, (tPIO-CaBe,Ge, type). NdCu,_,Sn,_, (oClh-CeNiSi, type). NdCu,Sn, (cFI IZ-NaZn,, type) and Nd,Cu,Sn, (tl22-Sm@t.,Sn, type). The existence, moreover, of four other ternary compounds has been observed: Nd,Cu,Sn, and Nd,CuSn,. which have been characterized as pertaining to the 0122~Gd,Cu,Ge, type and to the hP$AIB, type respectively. and two other phases with unknown structure corresponding to the NdCtt,Sn and Nd,Cu,,,Sn, stoichiometries (and probably isostructural with similar phases in the Ce-Cu-Sn and Pr-Cu-Sn systems). Crystal structure data of the ternary compounds are reported in Table I and compared with literature data. Among previously mentioned ternary compounds, NdCu,Sn,. NdCtt,Sn and Nd,Cu,,Sn, may be considered compounds’. NdCu$t, and stoichiometric ‘point Nd,Cu,Sn, are probably characterized by a solubility range whose extension is under study. (These phases actually show different compositions in different samples analyzed by EPMA.) A larger range of homogeneity should finally be attributed to the -Nd,CuSn,
Fig. 2. Electron micrograph of alloy I t 19.7 at.9 Nd. 9.0 at.5 Sn): large quantity of solid solution of NdCu, tgrey) plus ‘TV white) and NdCu, (black).
phase.
1.2. I.torhermal section A partial isothermal section at 400°C obtained in this work is reported in Fig. 1. This has been constructed mainly on the basis of analyses carried out in the three-phase regions in which the different phases have been identified and characterized by means of X-ray and EPMA analysis. The results concerning a number of selected alloys are reported in Table 2. in Fig. 2 Fig. 3 Fig. 4 Fig. 15 Fig. 6. selected scanning electron micrographs of alloys in typical three-phase fields are reported as examples. The following three-phase fields have been observed: Nd+NdCu+Nd,Sn, NdCu+NdCu,+Nd,Sn,. Nd,Sn,+ NdCuz+Nd,Sn,, Nd,Sn,+NdCtt2+NdCttSn, NdCua+ NdCuSn+NdCu,. NdCu,+NdCtt,+NdCttSn, NdCtt,+
Fig.
I. Nd-Cu-Sn
system: p&al
isothermal secdon at 400 “C
Fig. 3. Electron micrograph of alloy 5 (29.0 at.% Nd. 16.4 at.% Sn): white crystals of r, plus N&I,
tgrey) plus binary eutectic tNdCu,+NdCu,).
Fig. 4. Electron micmgrapb of alloy I I (35.8 al.% Nd. 27.2 at.% Sn): white crystals of TV plus NdCu, tgrey) plus Nd,Sn,.
and also the close analogy with other R-Cu-Sn systems when R is a light rare eatih. In particular. from a comparison with the Pr-Cu-Sn system. we may notice that the phases RCusSn, R,Cu, lSn,. RCu,Sn,. RCuSn. R,Cu,Sn,, RCu$n,. R2Cu,Sn,. RCu, ,Srr_, and R,CuSn, are f-d in both systems. The phases R,,Cu,,Sn2, and R,,Cu,,Sn,, reported for Pr have not been identified in the Nd system. Concerning the determination of tie-triangles, it is interesting to notice the difference between Pr and Nd. which can be attributed to the existence of the binary compound Pr,Sn absent in the Nd-Sn system.
Acknowledgments Fig. S. Electron micrograph of alloy
13 tS.Oat.%
Nd. %.5at.%
Snl:
ociculm crystals of T. plus E (black) and T..
We would like to thank the Ministero deR’Universit~ e della Ricerca Scientitica e Tecno!ogica (MURST. 40%) for the hrancial support afforded us.
References
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The
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