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Investigation on the formation of the preferred orientations in a TbDyFe alloy with directional solidification
Materials Science and Engineering B58 (1999) 191 – 194
Investigation on the formation of the preferred orientations in a TbDyFe alloy with directional solidification Chengbao Jiang a,*, Shouzeng Zhou b, Huibin Xu a, Run Wang b a
Department of Materials Science and Engineering, Beijing Uni6ersity of Aeronautics and Astronautics, Beijing 100083, People’s Republic of China b State Key Laboratory for Ad6anced Materials, Uni6ersity of Science and Technology Beijing, Beijing 100083, People’s Republic of China Received 6 May 1997; received in revised form 20 October 1998; accepted 23 October 1998
Abstract The formation of the preferred orientations in a TbDyFe alloy was studied by transmission electron microscopy (TEM). It was found that there were several different preferred orientations in the experimental TbDyFe alloy with directional solidification. 110, 112 and 113 preferred orientations were observed in this alloy solidified by our self-made super high gradient temperature directional solidification device. The preferred orientations changed with the variation of the solidification conditions. Two {111} twinning systems resulted in the 110 preferred orientation and a single {111} twinning system resulted in the 112 preferred orientation. The twinning displacement was observed and this formatted the 113 preferred orientation. © 1999 Published by Elsevier Science S.A. All rights reserved. Keywords: TnDyFe alloy; Transmission electron microscopy; Orientations
1. Introduction Due to the strong magnetostriction anisotropy in the TbDyFe magnetostrictive alloys [1,2], the crystals solidified with different preferred orientations would exhibit a giant difference in the magnetostrictive property. Previous studies observed 112 preferred orientation in the alloys solidified with the methods of Bridgman, Czochralski and floating zone [3 – 7]. Our investigations indicate that there are several preferred orientations in the alloys with directional solidification and these preferred orientations change with the variation of the crystal growth conditions. The unstable magnetostriction has been measured in the samples with different preferred orientations, which has a negative influence on their application. Verheoven et al. [7] had observed the lamellar twins structure by optical and scanning electron microscopy in TbDyFe alloys solidified with 112 preferred orientation. Bi [6] researched the microstructural defects of * Corresponding author. E-mail address: [email protected] (C. Jiang)
TbDyFe alloys by TEM. He observed the twins lying in the alloys. But very little work has been published on the formation of the preferred orientations in TbDyFe alloys by TEM. In this paper, we carried out the detailed studies on the formation of the different preferred directions in TbDyFe alloys.
2. Experimental A master alloy of Tb0.3Dy0.7Fe1.95 was prepared by vacuum induction melting from commercial quality(3N, REP) start materials. The self-made super high temperature gradient directional solidification device was used to produce the experimental rod samples, which were uniform of the composition and magnetostriction along the axis. The crystal growth velocity (6) changed in the range of 1–20 mm min − 1 with the temperature gradient GL : 700 K cm − 1. The dimension of the samples were f8× 120 mm. The preferred growth directions were detected by X-ray diffraction from the transverse sections of the samples, which were 80 mm apart from the solidification starting positions. Thin disc for TEM
0921-5107/99/$ - see front matter © 1999 Published by Elsevier Science S.A. All rights reserved. PII: S 0 9 2 1 - 5 1 0 7 ( 9 8 ) 0 0 3 1 9 - 5
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C. Jiang et al. / Materials Science and Engineering B58 (1999) 191–194
were prepared from the longitudinal sections of the rod samples by ion beam thinned. TEM work was carried out on a H800 Transmission Electron Microscope.
3. Results and discussion
3.1. The different preferred growth directions with the 6ariation of the solidification conditions in the TbDyFe alloy X-ray diffraction studies demonstrated that the preferred directions of the TbDyFe alloy changed with the variation of the solidification parameters. Fig. 1 shows that there were three different preferred directions in the samples. For the temperature gradient GL :700 K cm − 1 and the crystal growth velocity 6B 6 mm min − 1,
Fig. 1. The different preferred growth directions appeared in the TbDyFe alloy.
Fig. 2. Two {111} twinning systems result in 110 preferred growth direction: (a) bright-field micrograph showing twin traces in two directions; (b) electron diffraction pattern; (c) interpretation of 011 diffraction pattern for twinning on two {111} twinning system; (d) schematic diagram of the 110 preferred growth direction.
Fig. 2.
C. Jiang et al. / Materials Science and Engineering B58 (1999) 191–194
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the crystals preferentially grew along 110 orientation (as Fig. 1a); 8B6 B12 mm min − 1, the crystals were 112 preferred orientation (as Fig. 1b); and 6 \15 mm min − 1, the degree of 112 preferred orientation decreased. Sometimes, near the value of 8 mm min − 1, the preferred orientation appeared along 113 (as Fig. 1c).
3.2. The formation of the different preferred growth directions TEM observations showed that two {111} twinning systems existed in the samples with 110 preferred growth direction (as shown in Fig. 2). The angle between the two twin planes is 109.5°. Optical microscope observation on the 110 oriented samples showed that the twin A, B and C almost had the same volume and the actual growth direction was the orientation of the symmetric axis [2], which was [110] A along the angle bisection of the twin traces in Fig. 2a. An interpretation of the relationship between two {111} twins growth pattern and 110 preferred orientation was given in Fig. 2d. In the lower part of Fig. 2d, the local growth direction is [112]A and [112]B The nucleation of twin A and C appeared on the uppermost twin A(111) surface, giving the alternative growth direction [112]A and [112]C Nucleation of original A and B on a C(111) surface then allowed resumption of the first direction, and so on. If each type of nucleation event occurs with equal frequency and each growth segment is of equal length, the resultant growth direction is [110]A in terms of the common twin A orientation. Optical microscope observation confirmed this pattern of two {111}twin systems with equal volume growth [2]. In the samples with 112 growth direction, only a single {111} twinning system was observed. Fig. 3a shows twin traces only in a direction. The internal twin planes are designated as (111)A and (111)B. The re-entrant edge at the growth tip is assumed to form by (111)A and (111)B which are cozonal, i.e. they share a common [110] axis with (111) (as shown in Fig. 3b), only twin A and B orientation are present and the preferred growth direction is strictly [112]B. This is consistent with the X-ray diffraction results shown in Fig. 1b. Optical microscope observation confirmed that there were only one direction of the twin traces along the axis of 112 oriented samples [2]. Fig. 4a shows the twins with steps morphology which results in 113 preferred orientation as Fig. 1c. The nucleation of twin B appeared on the (111)A, and then, the [111]A direction became more thick, twinning steps existed at the (111)A face. The diffraction pattern across the twinning step is identical with Fig. 2b. Fig. 4b shows the twinning steps schematically. This twinning displacement resulted in 113 preferred growth direction.
Fig. 3. A single {111} twinning system results in B112\ preferred growth direction: (a) bright-field micrograph showing twin traces in only one directio; (b) electron diffraction pattern; (c) interpretation of 011 diffraction pattern for twinning on one {111} twinning system; (d) schematic diagram of the 112 preferred direction.
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C. Jiang et al. / Materials Science and Engineering B58 (1999) 191–194
tion. 110; 112 and 113 preferred directions appeared with different solidification conditions. 2. Two {111} twinning systems resulted in the 110 preferred growth direction, and a single {111} twinning system could retain the preferred growth direction along 112 orientation. The twinning displacement resulted in 113 preferred growth direction.
Acknowledgements This work is partially supported by the National Natural Science Foundation of China.
References Fig. 4. The twinning displacement formats the 113 preferred growth direction; (a) the twins morphology; (b) schematic diagram of the 113 preferred growth direction.
4. Conclusions 1. Several preferred growth directions existed in the experimental TbDyFe alloy with directional solidifica-
.
[1] A.E. Clark, Ferromagnetic materials, vol. 1, North-Holland, Amsterdam, 1980, p. 595. [2] C. Jiang, Doctoral dissertation of University of Science and Technology Beijing, China 1996, p. 86. [3] A.E. Clark, J.D. Verhoeven, O.D. McMasters, E.D. Gibson, IEEE Trans. Mag. 22 (1986) 973. [4] J.D. Verhoeven, J.E. Ostenson, E.D. Gibson, O.D. McMasters, J. Appl. Phys. 66 (1989) 772. [5] M.A. Jiboory, D.G. Lord, Y.J. Bi, J.S. Abell, A.M.H. Hwang, J.P. Teter, J. Appl. Phys. 73 (1993) 6168. [6] Y.J. Bi, J.S. Abell, A.M.H. Hwang, J. Mag. Mater. 99 (1991) 159. [7] J.D. Verhoever, E.D. Gibson, O.D. McMasters, H.H. Baker, Metall. Trans. 18A (1987) 223.
Investigation on the formation of the preferred orientations in a TbDyFe alloy with directional solidification Chengbao Jiang a,*, Shouzeng Zhou b, Huibin Xu a, Run Wang b a
Department of Materials Science and Engineering, Beijing Uni6ersity of Aeronautics and Astronautics, Beijing 100083, People’s Republic of China b State Key Laboratory for Ad6anced Materials, Uni6ersity of Science and Technology Beijing, Beijing 100083, People’s Republic of China Received 6 May 1997; received in revised form 20 October 1998; accepted 23 October 1998
Abstract The formation of the preferred orientations in a TbDyFe alloy was studied by transmission electron microscopy (TEM). It was found that there were several different preferred orientations in the experimental TbDyFe alloy with directional solidification. 110, 112 and 113 preferred orientations were observed in this alloy solidified by our self-made super high gradient temperature directional solidification device. The preferred orientations changed with the variation of the solidification conditions. Two {111} twinning systems resulted in the 110 preferred orientation and a single {111} twinning system resulted in the 112 preferred orientation. The twinning displacement was observed and this formatted the 113 preferred orientation. © 1999 Published by Elsevier Science S.A. All rights reserved. Keywords: TnDyFe alloy; Transmission electron microscopy; Orientations
1. Introduction Due to the strong magnetostriction anisotropy in the TbDyFe magnetostrictive alloys [1,2], the crystals solidified with different preferred orientations would exhibit a giant difference in the magnetostrictive property. Previous studies observed 112 preferred orientation in the alloys solidified with the methods of Bridgman, Czochralski and floating zone [3 – 7]. Our investigations indicate that there are several preferred orientations in the alloys with directional solidification and these preferred orientations change with the variation of the crystal growth conditions. The unstable magnetostriction has been measured in the samples with different preferred orientations, which has a negative influence on their application. Verheoven et al. [7] had observed the lamellar twins structure by optical and scanning electron microscopy in TbDyFe alloys solidified with 112 preferred orientation. Bi [6] researched the microstructural defects of * Corresponding author. E-mail address: [email protected] (C. Jiang)
TbDyFe alloys by TEM. He observed the twins lying in the alloys. But very little work has been published on the formation of the preferred orientations in TbDyFe alloys by TEM. In this paper, we carried out the detailed studies on the formation of the different preferred directions in TbDyFe alloys.
2. Experimental A master alloy of Tb0.3Dy0.7Fe1.95 was prepared by vacuum induction melting from commercial quality(3N, REP) start materials. The self-made super high temperature gradient directional solidification device was used to produce the experimental rod samples, which were uniform of the composition and magnetostriction along the axis. The crystal growth velocity (6) changed in the range of 1–20 mm min − 1 with the temperature gradient GL : 700 K cm − 1. The dimension of the samples were f8× 120 mm. The preferred growth directions were detected by X-ray diffraction from the transverse sections of the samples, which were 80 mm apart from the solidification starting positions. Thin disc for TEM
0921-5107/99/$ - see front matter © 1999 Published by Elsevier Science S.A. All rights reserved. PII: S 0 9 2 1 - 5 1 0 7 ( 9 8 ) 0 0 3 1 9 - 5
192
C. Jiang et al. / Materials Science and Engineering B58 (1999) 191–194
were prepared from the longitudinal sections of the rod samples by ion beam thinned. TEM work was carried out on a H800 Transmission Electron Microscope.
3. Results and discussion
3.1. The different preferred growth directions with the 6ariation of the solidification conditions in the TbDyFe alloy X-ray diffraction studies demonstrated that the preferred directions of the TbDyFe alloy changed with the variation of the solidification parameters. Fig. 1 shows that there were three different preferred directions in the samples. For the temperature gradient GL :700 K cm − 1 and the crystal growth velocity 6B 6 mm min − 1,
Fig. 1. The different preferred growth directions appeared in the TbDyFe alloy.
Fig. 2. Two {111} twinning systems result in 110 preferred growth direction: (a) bright-field micrograph showing twin traces in two directions; (b) electron diffraction pattern; (c) interpretation of 011 diffraction pattern for twinning on two {111} twinning system; (d) schematic diagram of the 110 preferred growth direction.
Fig. 2.
C. Jiang et al. / Materials Science and Engineering B58 (1999) 191–194
193
the crystals preferentially grew along 110 orientation (as Fig. 1a); 8B6 B12 mm min − 1, the crystals were 112 preferred orientation (as Fig. 1b); and 6 \15 mm min − 1, the degree of 112 preferred orientation decreased. Sometimes, near the value of 8 mm min − 1, the preferred orientation appeared along 113 (as Fig. 1c).
3.2. The formation of the different preferred growth directions TEM observations showed that two {111} twinning systems existed in the samples with 110 preferred growth direction (as shown in Fig. 2). The angle between the two twin planes is 109.5°. Optical microscope observation on the 110 oriented samples showed that the twin A, B and C almost had the same volume and the actual growth direction was the orientation of the symmetric axis [2], which was [110] A along the angle bisection of the twin traces in Fig. 2a. An interpretation of the relationship between two {111} twins growth pattern and 110 preferred orientation was given in Fig. 2d. In the lower part of Fig. 2d, the local growth direction is [112]A and [112]B The nucleation of twin A and C appeared on the uppermost twin A(111) surface, giving the alternative growth direction [112]A and [112]C Nucleation of original A and B on a C(111) surface then allowed resumption of the first direction, and so on. If each type of nucleation event occurs with equal frequency and each growth segment is of equal length, the resultant growth direction is [110]A in terms of the common twin A orientation. Optical microscope observation confirmed this pattern of two {111}twin systems with equal volume growth [2]. In the samples with 112 growth direction, only a single {111} twinning system was observed. Fig. 3a shows twin traces only in a direction. The internal twin planes are designated as (111)A and (111)B. The re-entrant edge at the growth tip is assumed to form by (111)A and (111)B which are cozonal, i.e. they share a common [110] axis with (111) (as shown in Fig. 3b), only twin A and B orientation are present and the preferred growth direction is strictly [112]B. This is consistent with the X-ray diffraction results shown in Fig. 1b. Optical microscope observation confirmed that there were only one direction of the twin traces along the axis of 112 oriented samples [2]. Fig. 4a shows the twins with steps morphology which results in 113 preferred orientation as Fig. 1c. The nucleation of twin B appeared on the (111)A, and then, the [111]A direction became more thick, twinning steps existed at the (111)A face. The diffraction pattern across the twinning step is identical with Fig. 2b. Fig. 4b shows the twinning steps schematically. This twinning displacement resulted in 113 preferred growth direction.
Fig. 3. A single {111} twinning system results in B112\ preferred growth direction: (a) bright-field micrograph showing twin traces in only one directio; (b) electron diffraction pattern; (c) interpretation of 011 diffraction pattern for twinning on one {111} twinning system; (d) schematic diagram of the 112 preferred direction.
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tion. 110; 112 and 113 preferred directions appeared with different solidification conditions. 2. Two {111} twinning systems resulted in the 110 preferred growth direction, and a single {111} twinning system could retain the preferred growth direction along 112 orientation. The twinning displacement resulted in 113 preferred growth direction.
Acknowledgements This work is partially supported by the National Natural Science Foundation of China.
References Fig. 4. The twinning displacement formats the 113 preferred growth direction; (a) the twins morphology; (b) schematic diagram of the 113 preferred growth direction.
4. Conclusions 1. Several preferred growth directions existed in the experimental TbDyFe alloy with directional solidifica-
.
[1] A.E. Clark, Ferromagnetic materials, vol. 1, North-Holland, Amsterdam, 1980, p. 595. [2] C. Jiang, Doctoral dissertation of University of Science and Technology Beijing, China 1996, p. 86. [3] A.E. Clark, J.D. Verhoeven, O.D. McMasters, E.D. Gibson, IEEE Trans. Mag. 22 (1986) 973. [4] J.D. Verhoeven, J.E. Ostenson, E.D. Gibson, O.D. McMasters, J. Appl. Phys. 66 (1989) 772. [5] M.A. Jiboory, D.G. Lord, Y.J. Bi, J.S. Abell, A.M.H. Hwang, J.P. Teter, J. Appl. Phys. 73 (1993) 6168. [6] Y.J. Bi, J.S. Abell, A.M.H. Hwang, J. Mag. Mater. 99 (1991) 159. [7] J.D. Verhoever, E.D. Gibson, O.D. McMasters, H.H. Baker, Metall. Trans. 18A (1987) 223.