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Crystallization behavior of Al100 − xSmx (x = 8–14 at%) amorphous alloys
June 1995
ELSEVIER
Materials Letters 24 (1995) 133-138
Crystallization behavior of AllOO_,Sm, (x = 8-14 at%) amorphous alloys J.Q. Guo a, K. Ohtera b, K. Kita a, J. Nagahora a, N.S. Kazama a aSenaizi Institute of Materials Science and Technology, Research and Development Division, YKK Corporation, 38 Ahzishi, Tomiya, Kurokowa, Miyagi-Ken 981-33, Japan b Research and Development Division, YKK Corporation, 200 Yoshida, Kurobe, Toyama 938, Japan
Received 28 March 1995; accepted 30 March 1995
Abstract Crystallization processes of Al,,_,Sm, (x = 8-14 at%) amorphous alloys were investigated. The alloys were rapidly solidified into ribbons by a single roller method. The rapidly solidified ribbons are composed of mainly amorphous phase and a little crystal phase. Subsequent decomposition behavior of the melt spun ribbons was examined by XRD, TEM and DSC. Three kinds of new phases which are defined as Ml, M2 and S3 were found to appear in the decomposition process of the amorphous ribbons. Ml, M2 and S3 are a metastable hexagonal phase with lattice parameters Q= 0.4597 nm and c = 0.6358 nm, a metastable cubic phase with lattice parameter a = 1.9154 nm and an orthorhombic phase with lattice parameters a = 1.3781 nm, b = 1.1019 nm and c = 0.7303 nm, respectively.
1. Introduction Al-rare earth element amorphous alloys, such as AlLa, Al-Cc, Al-Sm, ,41-Y and so on, can be obtained by rapid solidification [ la]. Through controlling the crystallization process of amorphous alloys, the alloys with different crystal ,structures and microstructures can be attained. To obtain the desired properties, given crystal structures and microstructures are hoped to be gotten. Therefore, it is necessary to know the crystallization behavior of amorphous Al-rare earth element alloys so that their rnicrostructures and crystal structures can be easily controlled and the best properties can be obtained. Crystallization behavior of amorphous Al-La and Al-Cc alloys has been reported in Ref. [ 51 by the present authors. Among binary Al-rare earth element alloys, the Al-Sm system has a wider amorphous formation composition range and its decomposition process is complicated [6]. There are a few 0167-577x/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDIO167-577x(95)00066-6
unknown phases appearing in the decomposition process of Al-Sm amorphous alloys. This paper is intended to investigate crystallization processes of amorphous AIIr,c_xSmx(n= 8-14 at%) alloys.
2. Experimental methods Al,,_,Sm, (x=8-14 at%) alloys were prepared from pure elements by arc melting in an argon atmosphere. The purity was 99.99 wt% for Al and 99.9 wt% for Sm. By using a single roller melt spinning apparatus, the prealloyed ingots were rapidly solidified into a ribbon form at a circumferential speed of 40 m/s in an argon atmosphere. The thickness of these ribbons was in the range 20-30 pm. The thermal stability of these rapidly solidified ribbons was evaluated by DSC to measure phase transformation temperature. Based on the DSC results, the rapidly solidified Al,,_,Sm,
134
J.Q. Guo et al. /Materials L.&en 24 (1995) 133-I38
(x = 8-14 at%) ribbons were annealed for 3.6 ks at different temperatures. Crystal structures and microstructures of the as-rapidly solidified and annealed ribbons were examined by X-ray diffraction and transmission electron microscopy (TJZM). The microstructural change with increasing annealing temperature was examined in situ using a transmission electron microscope with a heating stage.
3. Results and discussion 28 Pegred
3.1. Crystal structures of as-rapidly solid@ed Al,,_*Sm, (x = 8-14 at%) alloys According to the results of X-ray diffraction analysis shown in Figs. 1, 3 and 5, it is known that the rapidly solidified Al$m, ribbon is composed only of amorphous phase, while the Al,,_,Sm, (x= 10-14) ribbons consist of mainly amorphous phase and a little crystal phase.
Cu.Ka
Fig. 1. X-ray diffhction patterns of the A19,Sms alloy.
ml,
,
A186Sml4
’
763.:X m.1x .
0.33Kis Al90SmlO
’
Al92Sm8
.
3.2. Crystallization of Al&3m8 amorphous alloy There are three exothermic peaks in the DSC curve of the Al&ma amorphous ribbon shown in Fig. 2. The exothermic peaks are at 470,541 and 594 K. Based on the DSC results, the amorphous ribbons were annealed for 3.6 ks at 473, 573 and 873 K. X-ray diffraction results for the annealed ribbons are shown in Fig. 1. According to the results, it is known that a-Al phase precipitates from the amorphous phase at 473 K. When the amorphous ribbon is annealed at 573 K for 3.6 ks, the annealed ribbon consist of a-Al and Al$m phases. This means that at 54 1 K, that is the temperature of the second DSC peak, Al,Sm phase forms from the alloy. A1,Sm is a tetragonal phase with lattice parameters a = 0.428 nm and c = 0.990 nm. When the amorphous ribbon is annealed at 873 K, the AL,Sm phase disappears and changes in a new orthorhombic phase. The lattice parameters of the new orthorhombic phase are determined as a=1.3781 nm, b=1.1019 nm and c = 0.7303 run. Here, the new orthorhombic phase is called as S3. Therefore, at the temperature of the third DSC peak, that is 594 K, the phase transformation is a-Al + Al$m + a-Al + S3.
-25c : 173
: 600
.
: 800
Temperature (K)
Fig. 2. DSC curves of rapidly solidified Al-Sm alloys.
if
Cu-Ka
Fig. 3. X-my diffraction patterns of the Al,Sm,,
alloy.
1 873
J.Q. Guo et al. /Materials Letters 24 (1995) 133-138
135
l
001 0000 0
Ml [OlO] Ml [22i]
C
0
0 0
0
0
012 412 0 0 000 400 0 0
s3 [02i] 0
0
331
0 0
0'00
0
iGO
s3 [oi3]
e 5OOnm Fig. 4. Microstrncturs of the AI&m,, alloy annealed at different temperatures and TEM SAD patterns which show that a new hexagonal phase Ml and a new orthorhombic phase S3 exist in the alloy. (a) As-ion milled; (b) annealed for 720 s at 673 K; (c) SAD patterns on matrix of microstructure (a) ; (d) annealed for 720 s at 873 K, (e) SAD patterns on dark compounds of microstructure (d) .
J.Q. Guo et al. /Materials Letters 24 (1995) 133-138
136
IO
>o
10
10
50
60
70
II0
10
100 ,111,
213(Degree) Cl-KU
Fig. 5. X-ray diffraction
patterns of the Al&m,,
alloy.
3.3. Crystallization of rapidly solid@ed Al,$m,, A18,$m12 alloys
and
Crystallization process of the rapidly solidified Aim Sm,, alloy is the same as that of the Al&ml2 alloy. Here Al,Sm,, alloy is taken as an example. Thermal analysis of the rapidly solidified A19,,Sm,, ribbon shows that there exist three peaks in the DSC curve. Their temperature is 507, 580 and 724 K as shown in Fig. 1. X-ray diffraction results for the annealed ribbons in Fig. 3 show that at the temperature corresponding to the first DSC peak, (Y-AI, Al$m and a new hexagonal phase precipitate from the amorphous phase. At the second DSC peak, no new phase appears. This means that at the temperature of the second DSC peak, the phase transformation occurring at the first DSC peak continues going on. It is noticed that the X-ray diffraction intensity of (Y-AI phase is weak in the ribbons annealed at 523 and 623 K. So there is only a little aAl phase in the annealed Al,Sm,e ribbon. When the annealing temperature is higher than that of the third DSC peak, the new hexagonal phase and Al,Sm disappear and S3 phase forms. On the basis of X-ray diffraction data, the lattice parameters of the new hexagonal phase are determined as a = 0.4597 nm, and c = 0.6358 nm. The hexagonal phase is defined here as Ml. To observe the structure change of the alloys with increasing temperature and to verify whether the crystal structures of Ml and S3 phases are right, the rapidly solidified Al,Smn, ribbon was heated and observed in situ using a transmission electron microscope with a heating stage. Fig. 4 shows the microstructures of the
alloy at different temperatures and TEM SAD patterns. Since the TEM sample was made by the ion milling method, we were not able to observe the actual asrapidly solidified structure. The reason is considered to be that when the sample was being thinned by ion milling, the temperature of the sample was increased and phase transformation occurred. Although the ribbon was annealed at 553 K for 720 s, that is, at the temperature above the first DSC peak, no microstructure change was observed. Selected area diffraction patterns of the new phases, shown in Figs. 4c and 4e, prove that the two new phases Ml and S3 do exist in the decomposition processes of the alloy. From Fig. 4, it is known that although no new phase appears at the temperature of the second DSC peak, that is 580 K, compared with the microstructure of Fig. 4a, the microstructure has changed above 580 K. 3.4. Crystallizationof rapidly solidi$ed Al,$m,, alloy On the basis of XRD, DSC data and TEM observation results shown in Figs. 1,5 and 6, the crystallization processes of the Al&m,, alloy are determined as amorphous + a-Al + M2 + Al,Sm --) a-Al + A1,Sm + Ml -+ a-Al + S3. Here M2 is referred to a new metastable cubic phase with lattice parameter a = 1.9 15 nm. The existence of the new cubic phase is also proved by TEM selected areadiffraction analysis as shown in Fig. 6. From SAD patterns and dark-field image it is known that the new metastable cubic phase always coexists with the Al$m phase.
4. Conclusions According to above results, it is known that the crystallization processes of rapidly solidified Alr,,+$m, (x= 8-14) alloys are sensitive to their composition. A little difference in composition leads to very different phase transformation processes. Three kinds of new phases were found to appear in the crystallization processes of these alloys. They are called Ml, M2 and S3, respectively. Ml is a metastable hexagonal phase with lattice parameters a=0.4597 nm and c=O.6358 nm. M2 is a metastable cubic phase with lattice parameter a = 1.9154 nm. S3 is an orthorhombic phase with lattice parameters a=1.3781 nm, b=1.1019 nm and
J.Q. Guo et al. /Materials Letters 24 (1995) 133-138
137
500nm
011
211
a l
Al&m
l
0
M2
@
Al&m [i3ij
h42 [oli]
Al&m M2
Al&m [Ol i]
M2 @ill
l
Al&m
0
M2
Al&m 10211
M2 [2233
C Fig. 6. Bright-field image, dark-field image and SAD patterns of the rapidly solidified Al,,Sm&loy annealed at 523 K for 720 s. SAD patterns show the existence of a metastable cubic phase M2 in the alloy. (a) Bright-field image; (b) Dark-field image on circle mark of SAD pattern; (c) SAD patterns.
c=O.7303 nm. The crystallization processes of Al,oo_xSmx (x= 8-14) alloys can be summarized as follows:
Al, Sm, Am + CY-Al + Am + a--Al+ Al4Sm --, a-Al+ S3 ;
138
J.Q. Guo et al. /Materials Letters 24 (1995) 133-138
AbSmlo Am+a-Al+Al,Sm+Ml+cw-Al+S3
;
48 Smlz
Am+cx-Al+Al,Sm+Ml
Powder Diffraction Data created by Yoshito Takagi et al., Department of ARts and Sciences (Information Science), Osaka Kyoiku University, 4-698, Asahigaoka, Kashiwara-shi 582, Osaka, Japan. We are grateful to Professor Yoshito Takagi and his group.
+c~-Al+S3 ;
Al&ml4
References
Am + (Y-AI+ AL,Sm + M2
[ 1] A. Inoue, T. Zhang, K. Kita and T. Masumoto, Mater. Trans.
+cr-Al+AldSm+M1-,a-Al+S3.
Acknowledgement In the process of identification of phase structures, one of authors applied the Programs for Finding the Unit-Cell Constants and the Space Groups from X-ray
JIM 30 (1989) 870. [2] A. Inoue, K. Ohtera and T. Masumoto, Japan J. Appl. Phys. 27 (1988) L736. [3] A. moue, K. Ohtera, Z. Tao and T. Masumoto, Japan. J. Appl. Phys. 27 (1988) L1583. [4] E. Matsubara,Y. Waseda, A. moue, K. OhteraandT. Masumoto, Z. Naturforsch. 44a (1989) 814. [ 5 ] J.Q. Guo, K. Kita, K. Ohtera, J. Nagahora, A. Inoue and T. Masumoto, Mater. Letters 21 (1994) 279. [6] L. Battezzati, M. Baricco, P. Schumacher, W.C. Shih and A.L. Greer, Mater. Sci. Bng. A 179/180 (1994) 600.
ELSEVIER
Materials Letters 24 (1995) 133-138
Crystallization behavior of AllOO_,Sm, (x = 8-14 at%) amorphous alloys J.Q. Guo a, K. Ohtera b, K. Kita a, J. Nagahora a, N.S. Kazama a aSenaizi Institute of Materials Science and Technology, Research and Development Division, YKK Corporation, 38 Ahzishi, Tomiya, Kurokowa, Miyagi-Ken 981-33, Japan b Research and Development Division, YKK Corporation, 200 Yoshida, Kurobe, Toyama 938, Japan
Received 28 March 1995; accepted 30 March 1995
Abstract Crystallization processes of Al,,_,Sm, (x = 8-14 at%) amorphous alloys were investigated. The alloys were rapidly solidified into ribbons by a single roller method. The rapidly solidified ribbons are composed of mainly amorphous phase and a little crystal phase. Subsequent decomposition behavior of the melt spun ribbons was examined by XRD, TEM and DSC. Three kinds of new phases which are defined as Ml, M2 and S3 were found to appear in the decomposition process of the amorphous ribbons. Ml, M2 and S3 are a metastable hexagonal phase with lattice parameters Q= 0.4597 nm and c = 0.6358 nm, a metastable cubic phase with lattice parameter a = 1.9154 nm and an orthorhombic phase with lattice parameters a = 1.3781 nm, b = 1.1019 nm and c = 0.7303 nm, respectively.
1. Introduction Al-rare earth element amorphous alloys, such as AlLa, Al-Cc, Al-Sm, ,41-Y and so on, can be obtained by rapid solidification [ la]. Through controlling the crystallization process of amorphous alloys, the alloys with different crystal ,structures and microstructures can be attained. To obtain the desired properties, given crystal structures and microstructures are hoped to be gotten. Therefore, it is necessary to know the crystallization behavior of amorphous Al-rare earth element alloys so that their rnicrostructures and crystal structures can be easily controlled and the best properties can be obtained. Crystallization behavior of amorphous Al-La and Al-Cc alloys has been reported in Ref. [ 51 by the present authors. Among binary Al-rare earth element alloys, the Al-Sm system has a wider amorphous formation composition range and its decomposition process is complicated [6]. There are a few 0167-577x/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDIO167-577x(95)00066-6
unknown phases appearing in the decomposition process of Al-Sm amorphous alloys. This paper is intended to investigate crystallization processes of amorphous AIIr,c_xSmx(n= 8-14 at%) alloys.
2. Experimental methods Al,,_,Sm, (x=8-14 at%) alloys were prepared from pure elements by arc melting in an argon atmosphere. The purity was 99.99 wt% for Al and 99.9 wt% for Sm. By using a single roller melt spinning apparatus, the prealloyed ingots were rapidly solidified into a ribbon form at a circumferential speed of 40 m/s in an argon atmosphere. The thickness of these ribbons was in the range 20-30 pm. The thermal stability of these rapidly solidified ribbons was evaluated by DSC to measure phase transformation temperature. Based on the DSC results, the rapidly solidified Al,,_,Sm,
134
J.Q. Guo et al. /Materials L.&en 24 (1995) 133-I38
(x = 8-14 at%) ribbons were annealed for 3.6 ks at different temperatures. Crystal structures and microstructures of the as-rapidly solidified and annealed ribbons were examined by X-ray diffraction and transmission electron microscopy (TJZM). The microstructural change with increasing annealing temperature was examined in situ using a transmission electron microscope with a heating stage.
3. Results and discussion 28 Pegred
3.1. Crystal structures of as-rapidly solid@ed Al,,_*Sm, (x = 8-14 at%) alloys According to the results of X-ray diffraction analysis shown in Figs. 1, 3 and 5, it is known that the rapidly solidified Al$m, ribbon is composed only of amorphous phase, while the Al,,_,Sm, (x= 10-14) ribbons consist of mainly amorphous phase and a little crystal phase.
Cu.Ka
Fig. 1. X-ray diffhction patterns of the A19,Sms alloy.
ml,
,
A186Sml4
’
763.:X m.1x .
0.33Kis Al90SmlO
’
Al92Sm8
.
3.2. Crystallization of Al&3m8 amorphous alloy There are three exothermic peaks in the DSC curve of the Al&ma amorphous ribbon shown in Fig. 2. The exothermic peaks are at 470,541 and 594 K. Based on the DSC results, the amorphous ribbons were annealed for 3.6 ks at 473, 573 and 873 K. X-ray diffraction results for the annealed ribbons are shown in Fig. 1. According to the results, it is known that a-Al phase precipitates from the amorphous phase at 473 K. When the amorphous ribbon is annealed at 573 K for 3.6 ks, the annealed ribbon consist of a-Al and Al$m phases. This means that at 54 1 K, that is the temperature of the second DSC peak, Al,Sm phase forms from the alloy. A1,Sm is a tetragonal phase with lattice parameters a = 0.428 nm and c = 0.990 nm. When the amorphous ribbon is annealed at 873 K, the AL,Sm phase disappears and changes in a new orthorhombic phase. The lattice parameters of the new orthorhombic phase are determined as a=1.3781 nm, b=1.1019 nm and c = 0.7303 run. Here, the new orthorhombic phase is called as S3. Therefore, at the temperature of the third DSC peak, that is 594 K, the phase transformation is a-Al + Al$m + a-Al + S3.
-25c : 173
: 600
.
: 800
Temperature (K)
Fig. 2. DSC curves of rapidly solidified Al-Sm alloys.
if
Cu-Ka
Fig. 3. X-my diffraction patterns of the Al,Sm,,
alloy.
1 873
J.Q. Guo et al. /Materials Letters 24 (1995) 133-138
135
l
001 0000 0
Ml [OlO] Ml [22i]
C
0
0 0
0
0
012 412 0 0 000 400 0 0
s3 [02i] 0
0
331
0 0
0'00
0
iGO
s3 [oi3]
e 5OOnm Fig. 4. Microstrncturs of the AI&m,, alloy annealed at different temperatures and TEM SAD patterns which show that a new hexagonal phase Ml and a new orthorhombic phase S3 exist in the alloy. (a) As-ion milled; (b) annealed for 720 s at 673 K; (c) SAD patterns on matrix of microstructure (a) ; (d) annealed for 720 s at 873 K, (e) SAD patterns on dark compounds of microstructure (d) .
J.Q. Guo et al. /Materials Letters 24 (1995) 133-138
136
IO
>o
10
10
50
60
70
II0
10
100 ,111,
213(Degree) Cl-KU
Fig. 5. X-ray diffraction
patterns of the Al&m,,
alloy.
3.3. Crystallization of rapidly solid@ed Al,$m,, A18,$m12 alloys
and
Crystallization process of the rapidly solidified Aim Sm,, alloy is the same as that of the Al&ml2 alloy. Here Al,Sm,, alloy is taken as an example. Thermal analysis of the rapidly solidified A19,,Sm,, ribbon shows that there exist three peaks in the DSC curve. Their temperature is 507, 580 and 724 K as shown in Fig. 1. X-ray diffraction results for the annealed ribbons in Fig. 3 show that at the temperature corresponding to the first DSC peak, (Y-AI, Al$m and a new hexagonal phase precipitate from the amorphous phase. At the second DSC peak, no new phase appears. This means that at the temperature of the second DSC peak, the phase transformation occurring at the first DSC peak continues going on. It is noticed that the X-ray diffraction intensity of (Y-AI phase is weak in the ribbons annealed at 523 and 623 K. So there is only a little aAl phase in the annealed Al,Sm,e ribbon. When the annealing temperature is higher than that of the third DSC peak, the new hexagonal phase and Al,Sm disappear and S3 phase forms. On the basis of X-ray diffraction data, the lattice parameters of the new hexagonal phase are determined as a = 0.4597 nm, and c = 0.6358 nm. The hexagonal phase is defined here as Ml. To observe the structure change of the alloys with increasing temperature and to verify whether the crystal structures of Ml and S3 phases are right, the rapidly solidified Al,Smn, ribbon was heated and observed in situ using a transmission electron microscope with a heating stage. Fig. 4 shows the microstructures of the
alloy at different temperatures and TEM SAD patterns. Since the TEM sample was made by the ion milling method, we were not able to observe the actual asrapidly solidified structure. The reason is considered to be that when the sample was being thinned by ion milling, the temperature of the sample was increased and phase transformation occurred. Although the ribbon was annealed at 553 K for 720 s, that is, at the temperature above the first DSC peak, no microstructure change was observed. Selected area diffraction patterns of the new phases, shown in Figs. 4c and 4e, prove that the two new phases Ml and S3 do exist in the decomposition processes of the alloy. From Fig. 4, it is known that although no new phase appears at the temperature of the second DSC peak, that is 580 K, compared with the microstructure of Fig. 4a, the microstructure has changed above 580 K. 3.4. Crystallizationof rapidly solidi$ed Al,$m,, alloy On the basis of XRD, DSC data and TEM observation results shown in Figs. 1,5 and 6, the crystallization processes of the Al&m,, alloy are determined as amorphous + a-Al + M2 + Al,Sm --) a-Al + A1,Sm + Ml -+ a-Al + S3. Here M2 is referred to a new metastable cubic phase with lattice parameter a = 1.9 15 nm. The existence of the new cubic phase is also proved by TEM selected areadiffraction analysis as shown in Fig. 6. From SAD patterns and dark-field image it is known that the new metastable cubic phase always coexists with the Al$m phase.
4. Conclusions According to above results, it is known that the crystallization processes of rapidly solidified Alr,,+$m, (x= 8-14) alloys are sensitive to their composition. A little difference in composition leads to very different phase transformation processes. Three kinds of new phases were found to appear in the crystallization processes of these alloys. They are called Ml, M2 and S3, respectively. Ml is a metastable hexagonal phase with lattice parameters a=0.4597 nm and c=O.6358 nm. M2 is a metastable cubic phase with lattice parameter a = 1.9154 nm. S3 is an orthorhombic phase with lattice parameters a=1.3781 nm, b=1.1019 nm and
J.Q. Guo et al. /Materials Letters 24 (1995) 133-138
137
500nm
011
211
a l
Al&m
l
0
M2
@
Al&m [i3ij
h42 [oli]
Al&m M2
Al&m [Ol i]
M2 @ill
l
Al&m
0
M2
Al&m 10211
M2 [2233
C Fig. 6. Bright-field image, dark-field image and SAD patterns of the rapidly solidified Al,,Sm&loy annealed at 523 K for 720 s. SAD patterns show the existence of a metastable cubic phase M2 in the alloy. (a) Bright-field image; (b) Dark-field image on circle mark of SAD pattern; (c) SAD patterns.
c=O.7303 nm. The crystallization processes of Al,oo_xSmx (x= 8-14) alloys can be summarized as follows:
Al, Sm, Am + CY-Al + Am + a--Al+ Al4Sm --, a-Al+ S3 ;
138
J.Q. Guo et al. /Materials Letters 24 (1995) 133-138
AbSmlo Am+a-Al+Al,Sm+Ml+cw-Al+S3
;
48 Smlz
Am+cx-Al+Al,Sm+Ml
Powder Diffraction Data created by Yoshito Takagi et al., Department of ARts and Sciences (Information Science), Osaka Kyoiku University, 4-698, Asahigaoka, Kashiwara-shi 582, Osaka, Japan. We are grateful to Professor Yoshito Takagi and his group.
+c~-Al+S3 ;
Al&ml4
References
Am + (Y-AI+ AL,Sm + M2
[ 1] A. Inoue, T. Zhang, K. Kita and T. Masumoto, Mater. Trans.
+cr-Al+AldSm+M1-,a-Al+S3.
Acknowledgement In the process of identification of phase structures, one of authors applied the Programs for Finding the Unit-Cell Constants and the Space Groups from X-ray
JIM 30 (1989) 870. [2] A. Inoue, K. Ohtera and T. Masumoto, Japan J. Appl. Phys. 27 (1988) L736. [3] A. moue, K. Ohtera, Z. Tao and T. Masumoto, Japan. J. Appl. Phys. 27 (1988) L1583. [4] E. Matsubara,Y. Waseda, A. moue, K. OhteraandT. Masumoto, Z. Naturforsch. 44a (1989) 814. [ 5 ] J.Q. Guo, K. Kita, K. Ohtera, J. Nagahora, A. Inoue and T. Masumoto, Mater. Letters 21 (1994) 279. [6] L. Battezzati, M. Baricco, P. Schumacher, W.C. Shih and A.L. Greer, Mater. Sci. Bng. A 179/180 (1994) 600.