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High performance giant magnetostrictive alloy with 〈1 1 0〉 crystal orientation
Journal of Alloys and Compounds 381 (2004) 226–228
High performance giant magnetostrictive alloy with 1 1 0 crystal orientation Maocai Zhang∗ , Xuexu Gao, Shou Zeng Zhou, Zhenhua Shi State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, PR China Received 16 January 2004; received in revised form 28 February 2004; accepted 28 February 2004
Abstract High magnetostrictive strains have been obtained in Tb0.29 Dy0.61 Pr0.1 Fe1.97 Be0.05 polycrystalline samples with 1 1 0 crystal orientation. The λ40 and λ80 values are 1380 and 1560 ppm respectively under a pressure of 6 MPa, which is better than that of samples with 1 1 2 crystal orientation. The observed morphologies indicate that the grains with 1 1 0 axial orientation grow in the form of sheet-like cellular crystals. A rare-earth rich phase (R: Tb, Dy), is distributed along the boundaries of the cellular crystals. The excellent magnetostrictive properties originate from the matrix RFe2 phase and are related to texture. © 2004 Elsevier B.V. All rights reserved. Keywords: 1 1 0 Crystal orientation; Giant magnetostrictive strain; Sheet-like cellular crystal
1. Introduction Recently, much attention has been paid to rare earth giant magnetostrictive material, (Tb, Dy)Fe2 , because of an advanced functional material, its fields of application have become wider. Materials research [1–5] and applied research [6–9] have been prolific. But still, there are several technological details that need improvement. The Laves phase (Tb, Dy)Fe2 compound has MgCu2 structure type. Its magnetic easy axis is the 1 1 1 direction and the magnetostrictive strain along this direction is 16.6 times larger than along the 1 0 0 direction because of the highly anisotropic magnetostriction. Therefore, the preparation of defect-free single crystals with 1 1 1 orientation is ideal for reaching maximum magnetostrictive strain. But due to very low growing rate of single crystals, this is not economical for products. Fortunately, as Verhoeven et al. [10] and Clark et al. [11] reported, the preferential growth direction of (Tb, Dy)Fe2 crystals is the 1 1 2 direction. It has 19.5◦ deviation from the 1 1 1 orientation and the magnetostriction is λ112 = 94% λ111 along this direction. So 1 1 2 aligned polycrystalline rod samples have good magnetostrictive properties. Because the 1 1 2 crystals can be obtained easily, many authors focused on how to prepare ∗
Corresponding author. E-mail address: [email protected] (M. Zhang).
0925-8388/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2004.02.056
ideal materials with 1 1 2 alignment. We found that other crystal growth directions can be obtained by changing the solidification conditions. In this paper, we report results on (Tb, Dy)Fe2 crystals with 1 1 0 alignment.
2. Experimental Tb0.29 Dy0.61 Pr0.1 Fe1.97 Be0.05 master rod samples with dimensions of φ20 mm × 120 mm were prepared by vacuum induction melting. The starting materials and their purities in wt.% were Tb (99.8%), Dy (99.8%), Pr (99.6%), Fe (99.9%), and Be (99.8%). The master alloy rods were directionally solidified in the zone melting directional equipment with a temperature gradients GL of 200–600 K/cm and solidification rates of 1–20 mm/min. The specimens for crystal orientation determination and metallographic examination were cut from the end of grain-aligned rods. Then, the aligned alloy rods were heat treated at 1273–1373 K for 3–48 h in an argon atmosphere. The dimensions of the sample for λ measurement are (φ20 mm × 100 mm) and (φ20 mm × 120 mm). Magnetostrictive properties were measured by means of standard strain gauge technique. Microstructure and morphology observations were carried out using SEM and metallography. The crystal orientation analysis was performed by using of a DMAXRBX diffractometer.
M. Zhang et al. / Journal of Alloys and Compounds 381 (2004) 226–228
227
Fig. 1. X-ray diffraction patterns of the transverse section of the 1 1 0 axial aligned rod (a) bottom of sample (in contact with cooling end) and (b) top of sample.
3. Results and discussion 3.1. Crystal orientation The XRD spectra of the bottom and top transverse section of the directional solidified samples are shown in Fig. 1. It can be seen that there are almost only the 2 2 0 and 4 4 0 peaks present at the bottom of the rod sample. It indicates that all grains of the rod aligned along the 1 1 0 direction. For the top of the alloy rod, the diffraction intensity of the 3 1 1 peak is about 20% of that of the 2 2 0 peak, indicating that a part of the grains is aligned along the 1 1 3 direction. The reason why the (311) peak appears is that the temperature gradient changed a little because the power supply was not very stable.
Fig. 2. λ vs. H curves of the 1 1 0 axial aligned sample after heat treatment with (a) 0 MPa pre-stress and (b) 6 MPa pre-stress.
3.2. The magnetostrictive strains As shown in Table 1, the magnetostrictive strains of the 1 1 0 axial grain oriented sample are 650 × 10−6 and 1380 × 10−6 in a magnetic field of 40 kA/m with respect to a pre-stress of 0 and 6 MPa. Compared with the 1 1 2 aligned sample, the magnetostrictive properties of the 1 1 0 aligned samples are better. The λversus H curves of the aligned rod without and with pre-stress are shown in Fig. 2. The curve under pre-stress shows a marked “jump effect”, indicating excellent megnetostrictive properties under low magnetic field. The giant magnetostrictive properties in low magnetic field are very important for the application of this kind of material, because the higher the magnetostrictive properties, the lower
Fig. 3. Illustration of the rod sample with six locations for strain measurement.
are the bias field or the applied field needed. In this case, the size of the equipment to generate a magnetic field may be reduced. In order to check the strain homogeneity of the 120 mm long rod sample, we measured magnetostrictive properties at six points along the rod, as shown in Fig. 3. The strains in a magnetic field of 80 kA/m under 6 MPa pre-stress are almost same, indicating the strains in the whole sample are homogeneous.
Table 1 Comparisons between the magnetostrictive properties of Tb0.29 Dy0.61 Pr0.1 Fe1.97 Be0.05 polycrystal samples with 1 1 0 axial alignment and other axial orientations Crystal orientation
Pre-stress (MPa)
λ (10−6 ) (40 kA/m)
λ (10−6 ) (80 kA/m)
d33 (nm A−1 )
k33
1 1 0 1 1 0 1 1 2 1 1 1 (Single crystal)
0 6 7 6
650 1380 1200 1500
1100 1560 1490 1800
20 38
0.72
Source This work This work [10] [12]
228
M. Zhang et al. / Journal of Alloys and Compounds 381 (2004) 226–228
Fig. 4. Micrographs of an 1 1 0 axial oriented sample (a) transverse and (b) vertical. Table 2 The magnetostrictive properties of samples manufactured by our method Furnace number
Sample number
SA SA SA SA SA SA
S01 S02 S03 S04 S05 S06
λ/ppm (pre-stress 6 MPa) 40 kA/m
80 kA/m
1057 1050 1104 1072 1044 1040
1555 1343 1378 1404 1344 1361
By means of these results, we have shown that the new method to prepare high performance samples is effective. The magnetostrictive properties of the samples manufactured by this method are high and uniform. The data are tabulated in Table 2. 3.3. The crystal morphologies The metallographic examination of an aligned rod shows that the grains grow in the form of sheet-like cellular crystals, as depicted in Fig. 4. The average thickness of the sheets is about 60 m. The rare-earth rich phase which is distributed along the boundaries of the cellular crystals, forms a ductile skeleton network. The excellent magnetostrictive properties originated from the matrix RFe2 phase and are related to its texture. 4. Conclusions 1. Tb0.29 Dy0.61 Pr0.1 Fe1.97 Be0.05 alloy crystals with 1 1 0 orientation were obtained successfully by adjusting the temperature gradient and the crystal growth rate during solidification.
2. The samples with 1 1 0 alignment have excellent magnetostrictive properties in low magnetic fields. They can be used conveniently in devices. 3. The excellent magnetostrictive properties originate from the matrix RFe2 phase and are related to its texture. 4. The magnetostrictive properties of 1 1 0 aligned samples are better than those of samples with 1 1 2 alignment and the strains of samples are homogeneous and uniform.
References [1] P. Westwood, J.S. Abell, K.C. Pitman, J. Appl. Phys. 67 (9) (1990) 4998. [2] M. Al-Jiboory, D.G. Lord, Y.J. Bi, J.S. Abell, A.M.H. Hwang, J.P. Teter, J. Appl. Phys. 73 (10) (1993) 6168. [3] X. Zhao, G. Wu, J. Wang, K. Jia, W. Zan, J. Appl. Phys. 79 (8) (1996) 6225. [4] W. Mei, T. Umeda, S. Zhou, R. Wang, J. Magn. Magn. Mater. 147 (1997) 100. [5] W. Mei, T. Okane, T. Umeda, S. Zhou, J. Alloys Compd. 248 (1997) 151. [6] R.W. Timme, S.W. Meeks, J. de Physique Coll. C5, Tome 40 (Suppl. 5) (1979) 280. [7] F. Claeyseen, Proceedings of the Actuator 94th Conference, Axon, Bremen (G), 1994, p. 203. [8] L. Sandlung, Proceedings of the Third International Workshop on Power Transducers for Sonics & Ultrosonics, vol. F1, Springer, 1992 p. 113. [9] F. Goldie, Spie 3675 (1999) 223. [10] J.D. Verhoeven, E.D. Gibson, O.D. McMasters, H.H. Baker, Metall. Trans. 18A (1987) 223. [11] A.E. Clark, J.D. Verhoeven, O.D. McMasters, E.D. Gibson, IEEE Trans. Magn. 22 (5) (1986) 973. [12] O.D. McMasters, Proceedings of International Symposium on Giant Magnetostrictive Material and their Applications, Tokyo 21 (1992) pp. 5–6.
High performance giant magnetostrictive alloy with 1 1 0 crystal orientation Maocai Zhang∗ , Xuexu Gao, Shou Zeng Zhou, Zhenhua Shi State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, PR China Received 16 January 2004; received in revised form 28 February 2004; accepted 28 February 2004
Abstract High magnetostrictive strains have been obtained in Tb0.29 Dy0.61 Pr0.1 Fe1.97 Be0.05 polycrystalline samples with 1 1 0 crystal orientation. The λ40 and λ80 values are 1380 and 1560 ppm respectively under a pressure of 6 MPa, which is better than that of samples with 1 1 2 crystal orientation. The observed morphologies indicate that the grains with 1 1 0 axial orientation grow in the form of sheet-like cellular crystals. A rare-earth rich phase (R: Tb, Dy), is distributed along the boundaries of the cellular crystals. The excellent magnetostrictive properties originate from the matrix RFe2 phase and are related to texture. © 2004 Elsevier B.V. All rights reserved. Keywords: 1 1 0 Crystal orientation; Giant magnetostrictive strain; Sheet-like cellular crystal
1. Introduction Recently, much attention has been paid to rare earth giant magnetostrictive material, (Tb, Dy)Fe2 , because of an advanced functional material, its fields of application have become wider. Materials research [1–5] and applied research [6–9] have been prolific. But still, there are several technological details that need improvement. The Laves phase (Tb, Dy)Fe2 compound has MgCu2 structure type. Its magnetic easy axis is the 1 1 1 direction and the magnetostrictive strain along this direction is 16.6 times larger than along the 1 0 0 direction because of the highly anisotropic magnetostriction. Therefore, the preparation of defect-free single crystals with 1 1 1 orientation is ideal for reaching maximum magnetostrictive strain. But due to very low growing rate of single crystals, this is not economical for products. Fortunately, as Verhoeven et al. [10] and Clark et al. [11] reported, the preferential growth direction of (Tb, Dy)Fe2 crystals is the 1 1 2 direction. It has 19.5◦ deviation from the 1 1 1 orientation and the magnetostriction is λ112 = 94% λ111 along this direction. So 1 1 2 aligned polycrystalline rod samples have good magnetostrictive properties. Because the 1 1 2 crystals can be obtained easily, many authors focused on how to prepare ∗
Corresponding author. E-mail address: [email protected] (M. Zhang).
0925-8388/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2004.02.056
ideal materials with 1 1 2 alignment. We found that other crystal growth directions can be obtained by changing the solidification conditions. In this paper, we report results on (Tb, Dy)Fe2 crystals with 1 1 0 alignment.
2. Experimental Tb0.29 Dy0.61 Pr0.1 Fe1.97 Be0.05 master rod samples with dimensions of φ20 mm × 120 mm were prepared by vacuum induction melting. The starting materials and their purities in wt.% were Tb (99.8%), Dy (99.8%), Pr (99.6%), Fe (99.9%), and Be (99.8%). The master alloy rods were directionally solidified in the zone melting directional equipment with a temperature gradients GL of 200–600 K/cm and solidification rates of 1–20 mm/min. The specimens for crystal orientation determination and metallographic examination were cut from the end of grain-aligned rods. Then, the aligned alloy rods were heat treated at 1273–1373 K for 3–48 h in an argon atmosphere. The dimensions of the sample for λ measurement are (φ20 mm × 100 mm) and (φ20 mm × 120 mm). Magnetostrictive properties were measured by means of standard strain gauge technique. Microstructure and morphology observations were carried out using SEM and metallography. The crystal orientation analysis was performed by using of a DMAXRBX diffractometer.
M. Zhang et al. / Journal of Alloys and Compounds 381 (2004) 226–228
227
Fig. 1. X-ray diffraction patterns of the transverse section of the 1 1 0 axial aligned rod (a) bottom of sample (in contact with cooling end) and (b) top of sample.
3. Results and discussion 3.1. Crystal orientation The XRD spectra of the bottom and top transverse section of the directional solidified samples are shown in Fig. 1. It can be seen that there are almost only the 2 2 0 and 4 4 0 peaks present at the bottom of the rod sample. It indicates that all grains of the rod aligned along the 1 1 0 direction. For the top of the alloy rod, the diffraction intensity of the 3 1 1 peak is about 20% of that of the 2 2 0 peak, indicating that a part of the grains is aligned along the 1 1 3 direction. The reason why the (311) peak appears is that the temperature gradient changed a little because the power supply was not very stable.
Fig. 2. λ vs. H curves of the 1 1 0 axial aligned sample after heat treatment with (a) 0 MPa pre-stress and (b) 6 MPa pre-stress.
3.2. The magnetostrictive strains As shown in Table 1, the magnetostrictive strains of the 1 1 0 axial grain oriented sample are 650 × 10−6 and 1380 × 10−6 in a magnetic field of 40 kA/m with respect to a pre-stress of 0 and 6 MPa. Compared with the 1 1 2 aligned sample, the magnetostrictive properties of the 1 1 0 aligned samples are better. The λversus H curves of the aligned rod without and with pre-stress are shown in Fig. 2. The curve under pre-stress shows a marked “jump effect”, indicating excellent megnetostrictive properties under low magnetic field. The giant magnetostrictive properties in low magnetic field are very important for the application of this kind of material, because the higher the magnetostrictive properties, the lower
Fig. 3. Illustration of the rod sample with six locations for strain measurement.
are the bias field or the applied field needed. In this case, the size of the equipment to generate a magnetic field may be reduced. In order to check the strain homogeneity of the 120 mm long rod sample, we measured magnetostrictive properties at six points along the rod, as shown in Fig. 3. The strains in a magnetic field of 80 kA/m under 6 MPa pre-stress are almost same, indicating the strains in the whole sample are homogeneous.
Table 1 Comparisons between the magnetostrictive properties of Tb0.29 Dy0.61 Pr0.1 Fe1.97 Be0.05 polycrystal samples with 1 1 0 axial alignment and other axial orientations Crystal orientation
Pre-stress (MPa)
λ (10−6 ) (40 kA/m)
λ (10−6 ) (80 kA/m)
d33 (nm A−1 )
k33
1 1 0 1 1 0 1 1 2 1 1 1 (Single crystal)
0 6 7 6
650 1380 1200 1500
1100 1560 1490 1800
20 38
0.72
Source This work This work [10] [12]
228
M. Zhang et al. / Journal of Alloys and Compounds 381 (2004) 226–228
Fig. 4. Micrographs of an 1 1 0 axial oriented sample (a) transverse and (b) vertical. Table 2 The magnetostrictive properties of samples manufactured by our method Furnace number
Sample number
SA SA SA SA SA SA
S01 S02 S03 S04 S05 S06
λ/ppm (pre-stress 6 MPa) 40 kA/m
80 kA/m
1057 1050 1104 1072 1044 1040
1555 1343 1378 1404 1344 1361
By means of these results, we have shown that the new method to prepare high performance samples is effective. The magnetostrictive properties of the samples manufactured by this method are high and uniform. The data are tabulated in Table 2. 3.3. The crystal morphologies The metallographic examination of an aligned rod shows that the grains grow in the form of sheet-like cellular crystals, as depicted in Fig. 4. The average thickness of the sheets is about 60 m. The rare-earth rich phase which is distributed along the boundaries of the cellular crystals, forms a ductile skeleton network. The excellent magnetostrictive properties originated from the matrix RFe2 phase and are related to its texture. 4. Conclusions 1. Tb0.29 Dy0.61 Pr0.1 Fe1.97 Be0.05 alloy crystals with 1 1 0 orientation were obtained successfully by adjusting the temperature gradient and the crystal growth rate during solidification.
2. The samples with 1 1 0 alignment have excellent magnetostrictive properties in low magnetic fields. They can be used conveniently in devices. 3. The excellent magnetostrictive properties originate from the matrix RFe2 phase and are related to its texture. 4. The magnetostrictive properties of 1 1 0 aligned samples are better than those of samples with 1 1 2 alignment and the strains of samples are homogeneous and uniform.
References [1] P. Westwood, J.S. Abell, K.C. Pitman, J. Appl. Phys. 67 (9) (1990) 4998. [2] M. Al-Jiboory, D.G. Lord, Y.J. Bi, J.S. Abell, A.M.H. Hwang, J.P. Teter, J. Appl. Phys. 73 (10) (1993) 6168. [3] X. Zhao, G. Wu, J. Wang, K. Jia, W. Zan, J. Appl. Phys. 79 (8) (1996) 6225. [4] W. Mei, T. Umeda, S. Zhou, R. Wang, J. Magn. Magn. Mater. 147 (1997) 100. [5] W. Mei, T. Okane, T. Umeda, S. Zhou, J. Alloys Compd. 248 (1997) 151. [6] R.W. Timme, S.W. Meeks, J. de Physique Coll. C5, Tome 40 (Suppl. 5) (1979) 280. [7] F. Claeyseen, Proceedings of the Actuator 94th Conference, Axon, Bremen (G), 1994, p. 203. [8] L. Sandlung, Proceedings of the Third International Workshop on Power Transducers for Sonics & Ultrosonics, vol. F1, Springer, 1992 p. 113. [9] F. Goldie, Spie 3675 (1999) 223. [10] J.D. Verhoeven, E.D. Gibson, O.D. McMasters, H.H. Baker, Metall. Trans. 18A (1987) 223. [11] A.E. Clark, J.D. Verhoeven, O.D. McMasters, E.D. Gibson, IEEE Trans. Magn. 22 (5) (1986) 973. [12] O.D. McMasters, Proceedings of International Symposium on Giant Magnetostrictive Material and their Applications, Tokyo 21 (1992) pp. 5–6.