FIG 1 - uploaded by Tianli Zhang
Content may be subject to copyright.
͑ Color online ͒ ͑ a ͒ Transverse section micrograph of the polished ingot by etching with 60% volume fraction natal, ͑ b ͒ Fractograph of the ingot observed by scanning electron microscope, ͑ c ͒ Morphology of the crushed particles with a size distribution of 200– 300 m.
Source publication
A strong < 111 > preferred orientation is induced along the axis of the TbDyFe/epoxy bonded giant magnetostrictive rods by curing the epoxy under a moderate magnetic field. TbDyFe particles with a size distribution of 200-300 mu m align in an epoxy matrix, showing an approximate chain structure. A high magnetostrictive performance resulting from th...
Contexts in source publication
Context 1
... composites have attracted considerable attentions since they posses the distinct advantages of reduc- ing both eddy current losses and intrinsic brittleness compa- 1,2 rable to monolithic TbDyFe giant magnetostrictive alloy. Laminated composites were initially studied by sticking the 3 sheets of TbDyFe alloys with epoxy. However, due to the brittleness, the cutting thickness of TbDyFe alloy sheets was limited to about 1 mm, hindering their application at higher operation frequency. ͗ 112 ͘ -oriented Terfenol-D/epoxy composites were also developed by using short needle-shape fi- 4,5 bers cut from the directional solidified crystal. Another process was recently introduced by removing the eutectic phase from a grain-aligned TbDyFe rod and infiltrating the 6,7 epoxy to the sites of removed eutectic phase. Most researches performed the crushed particle compos- 8,9 ites since the simple process and lower cost. But the strain levels of the crushed particle composites were far be- low the monolithic TbDyFe. Because of the strong magnetostriction anisotropy in TbDyFe alloys, a drastic difference of magnetostriction exists along specific crystallographic orientations. 10 It keeps active to obtain ͗ 111 ͘ preferred orientation in the magnetostrictive composites although it is 11 seem to be difficult in the aspect of crystal growth and the composite preparation in the previous reports. In this letter grains alignment with ͗ 111 ͘ orientation was induced in the anisotropic TbDyFe/epoxy bonded giant magnetostrictive materials by curing the epoxy matrix under a moderate applied magnetic field. A sound giant magnetostriction of 1360 ϫ 10 −6 was achieved. High-purity starting element Tb, Dy, and Fe with the purity level of 99.99%, 99.99%, and 99.97%, respectively, were remelted four times by arc melting for preparing the nominally Tb 0.3 Dy 0.7 Fe 1.9 ingots. The ingots were annealed at 1173 K for 4 h. The crushed particles of about 200– 300 m size with 20%–40% volume fraction epoxy were homogenously mixed in a plastic mold. The sealed mold was placed in an electromagnet with a uniform magnetic field ranging from 0 to 12000 Oe along the longitudinal direction of the mold. After aligning, the epoxy was cured at 323 K for 2 h under the applied magnetic field. These cured composites were prepared with the dimension of ⌽ 13.5 mm ϫ 20 mm. Optical metallography and x-ray diffraction were used for checking the particle alignment and orientation by a Neophot II optical microscope and a Regaku D/max2200 PC x-ray diffractometer with Cu K ␣ radiation. Magnetostriction was measured by using a standard resistant strain gauge and a gas pressure cell was used for applying the compressive prestress along the axis of the rods. The grain size of the annealed TbDyFe ingot was checked by metallograph with the average value of more than 300 m, as shown in Fig. 1 ͑ a ͒ . An intergranular frac- ture character can be monitored from the fractograph, as shown in Fig. 1 ͑ b ͒ . The photograph for the crushed particles is also shown in Fig. 1 ͑ c ͒ . The crushed particles should be single crystal though it was not checked by the accessible facilities. Figure 2 illustrates the x-ray diffraction patterns for the composites with a 20% volume fraction TbDyFe particles cured under 0, 4000, 8000, and 12000 Oe magnetic fields, respectively. It is reasonable that the x-ray diffraction pattern of the composite cured without the applied magnetic field is 12 the same as that for the as-cast monolithic TbDyFe alloy, since the random crystallographic orientations exhibit in the composites. When the magnetic field is applied during the curing process, under the action of the static magnetic energy, the particles should rotate with the easy axis ͗ 111 ͘ along the direction of the applied field if the magnetocrystalline anisotropy energy is large enough. If the magnetocrystalline anisotropy energy is small the magnetic domains rotate by the reorientation of the electrons orbits, in this case the particles should be magnetized and the particle rotation should not occur. The nominal composition for the present study is Tb 0.3 Dy 0.7 Fe 1.90 , in which the magnetocrystalline anisotropy constant k 1 is −1.6 ϫ 10 5 J / m 3 . 13 From the x-ray pattern in Figs. 2 ͑ b ͒ –2 ͑ d ͒ , the preferred orientation along ͗ 111 ͘ crystallographic direction is obviously observed. That means the particles rotation happen under the applied field during curing and the strongest ͑ 222 ͒ peak is monitored for the sample cured under 8000 Oe. The adhesive force of the uncured resin should be overcome by the driving force of the applied magnetic field. No drastic change is observed in the x-ray patterns for the samples cured at 12000 Oe, as shown in Fig. 2 ͑ d ͒ . In addition, the extent of the preferred orientation declines as the volume fraction of TbDyFe particles increases. The reason is that the irregular particles con- tact each other and hinder the rotation of the particles. Figure 3 shows the comparison of TbDyFe particles alignment with a 20% volume fraction in two samples cured under 0 and 8000 Oe magnetic field, respectively. The particles ͑ bright area ͒ are randomly dispersed in the epoxy matrix ͑ gray-black area ͒ without the applied field, as shown in Fig. 3 ͑ a ͒ . However the particles align regularly with an approximate chain structure under an applied field, as shown in Fig. 3 ͑ b ͒ . The particles can be regarded as tiny magnetic needles. The magnetic field not only forces the rotation of the tiny needles but also leads to the mutual attraction of the magnetic pole. The inset in Fig. 3 ͑ b ͒ shows the sketch-map of the tiny magnetic needles alignment under the applied field. The excessive magnetic field of 12000 Oe results in a nonhomogeneous distribution of the TbDyFe particles in the composite, in which the TbDyFe particles segregate at the end of the sample near the electromagnet. Figure 4 plots the magnetostriction for the composites with 40% volume fraction TbDyFe particles cured at 0 and 8000 Oe, respectively. In Fig. 4 ͑ a ͒ it is evident that there is little stress effect and low saturated magnetostriction. This is attributed to the random orientation of the particles and irregular alignment. When cured at 8000 Oe, as seen in Fig. 4 ͑ b ͒ , the magnetostriction enhances significantly under the compressive prestress, as observed in the directionally solidi- 14 fied oriented crystals of TbDyFe magnetostrictive alloys. The optimized magnetostriction is achieved from 679 ϫ 10 −6 at 0 MPa to 1358 ϫ 10 −6 at 17 MPa, nearly increased by 100%. The outstanding achieved magnetostriction should be attributed to the ͗ 111 ͘ preferred orientation. This is also linked to the chain structure of TbDyFe particles as shown in Fig. 3 ͑ b ͒ , in which magnetostriction could be transferred through the interaction of the neighbor particles. Compara- tively, magnetostriction is restricted by transferring to the epoxy resin in the isotropic composites. There the particles are also not aligned as the chain structure. The results of magnetostriction cured at four different applied fields are summarized in Table I. Contrasted to the specimen cured at 0 Oe, the magnetostriction increases by 26% and 34% cured at applied field of 4000 and 12000 Oe, respectively. This improvement further reflects the important action of 111 preferred orientation of the particles on the magnetostriction. The slightly low extent of the ͗ 111 ͘ preferred orientation for the sample cured at 4000 Oe shows a relatively inferior magnetostriction compared with the sample cured at 8000 Oe. Grain ͗ 111 ͘ preferred orientation and chain structure alignment of the composites cured at a moderate applied field are essential for the improved magnetostriction. At the excessive magnetic field of 12000 Oe, the magnetostriction slightly decreases, since the particles present segregation at the two ends of the sample as the discussion above. This work is supported by Natural Science Foundation of China ͑ NSFC ͒ under Grant Nos. 50925101 and ...
Context 2
... composites have attracted considerable attentions since they posses the distinct advantages of reduc- ing both eddy current losses and intrinsic brittleness compa- 1,2 rable to monolithic TbDyFe giant magnetostrictive alloy. Laminated composites were initially studied by sticking the 3 sheets of TbDyFe alloys with epoxy. However, due to the brittleness, the cutting thickness of TbDyFe alloy sheets was limited to about 1 mm, hindering their application at higher operation frequency. ͗ 112 ͘ -oriented Terfenol-D/epoxy composites were also developed by using short needle-shape fi- 4,5 bers cut from the directional solidified crystal. Another process was recently introduced by removing the eutectic phase from a grain-aligned TbDyFe rod and infiltrating the 6,7 epoxy to the sites of removed eutectic phase. Most researches performed the crushed particle compos- 8,9 ites since the simple process and lower cost. But the strain levels of the crushed particle composites were far be- low the monolithic TbDyFe. Because of the strong magnetostriction anisotropy in TbDyFe alloys, a drastic difference of magnetostriction exists along specific crystallographic orientations. 10 It keeps active to obtain ͗ 111 ͘ preferred orientation in the magnetostrictive composites although it is 11 seem to be difficult in the aspect of crystal growth and the composite preparation in the previous reports. In this letter grains alignment with ͗ 111 ͘ orientation was induced in the anisotropic TbDyFe/epoxy bonded giant magnetostrictive materials by curing the epoxy matrix under a moderate applied magnetic field. A sound giant magnetostriction of 1360 ϫ 10 −6 was achieved. High-purity starting element Tb, Dy, and Fe with the purity level of 99.99%, 99.99%, and 99.97%, respectively, were remelted four times by arc melting for preparing the nominally Tb 0.3 Dy 0.7 Fe 1.9 ingots. The ingots were annealed at 1173 K for 4 h. The crushed particles of about 200– 300 m size with 20%–40% volume fraction epoxy were homogenously mixed in a plastic mold. The sealed mold was placed in an electromagnet with a uniform magnetic field ranging from 0 to 12000 Oe along the longitudinal direction of the mold. After aligning, the epoxy was cured at 323 K for 2 h under the applied magnetic field. These cured composites were prepared with the dimension of ⌽ 13.5 mm ϫ 20 mm. Optical metallography and x-ray diffraction were used for checking the particle alignment and orientation by a Neophot II optical microscope and a Regaku D/max2200 PC x-ray diffractometer with Cu K ␣ radiation. Magnetostriction was measured by using a standard resistant strain gauge and a gas pressure cell was used for applying the compressive prestress along the axis of the rods. The grain size of the annealed TbDyFe ingot was checked by metallograph with the average value of more than 300 m, as shown in Fig. 1 ͑ a ͒ . An intergranular frac- ture character can be monitored from the fractograph, as shown in Fig. 1 ͑ b ͒ . The photograph for the crushed particles is also shown in Fig. 1 ͑ c ͒ . The crushed particles should be single crystal though it was not checked by the accessible facilities. Figure 2 illustrates the x-ray diffraction patterns for the composites with a 20% volume fraction TbDyFe particles cured under 0, 4000, 8000, and 12000 Oe magnetic fields, respectively. It is reasonable that the x-ray diffraction pattern of the composite cured without the applied magnetic field is 12 the same as that for the as-cast monolithic TbDyFe alloy, since the random crystallographic orientations exhibit in the composites. When the magnetic field is applied during the curing process, under the action of the static magnetic energy, the particles should rotate with the easy axis ͗ 111 ͘ along the direction of the applied field if the magnetocrystalline anisotropy energy is large enough. If the magnetocrystalline anisotropy energy is small the magnetic domains rotate by the reorientation of the electrons orbits, in this case the particles should be magnetized and the particle rotation should not occur. The nominal composition for the present study is Tb 0.3 Dy 0.7 Fe 1.90 , in which the magnetocrystalline anisotropy constant k 1 is −1.6 ϫ 10 5 J / m 3 . 13 From the x-ray pattern in Figs. 2 ͑ b ͒ –2 ͑ d ͒ , the preferred orientation along ͗ 111 ͘ crystallographic direction is obviously observed. That means the particles rotation happen under the applied field during curing and the strongest ͑ 222 ͒ peak is monitored for the sample cured under 8000 Oe. The adhesive force of the uncured resin should be overcome by the driving force of the applied magnetic field. No drastic change is observed in the x-ray patterns for the samples cured at 12000 Oe, as shown in Fig. 2 ͑ d ͒ . In addition, the extent of the preferred orientation declines as the volume fraction of TbDyFe particles increases. The reason is that the irregular particles con- tact each other and hinder the rotation of the particles. Figure 3 shows the comparison of TbDyFe particles alignment with a 20% volume fraction in two samples cured under 0 and 8000 Oe magnetic field, respectively. The particles ͑ bright area ͒ are randomly dispersed in the epoxy matrix ͑ gray-black area ͒ without the applied field, as shown in Fig. 3 ͑ a ͒ . However the particles align regularly with an approximate chain structure under an applied field, as shown in Fig. 3 ͑ b ͒ . The particles can be regarded as tiny magnetic needles. The magnetic field not only forces the rotation of the tiny needles but also leads to the mutual attraction of the magnetic pole. The inset in Fig. 3 ͑ b ͒ shows the sketch-map of the tiny magnetic needles alignment under the applied field. The excessive magnetic field of 12000 Oe results in a nonhomogeneous distribution of the TbDyFe particles in the composite, in which the TbDyFe particles segregate at the end of the sample near the electromagnet. Figure 4 plots the magnetostriction for the composites with 40% volume fraction TbDyFe particles cured at 0 and 8000 Oe, respectively. In Fig. 4 ͑ a ͒ it is evident that there is little stress effect and low saturated magnetostriction. This is attributed to the random orientation of the particles and irregular alignment. When cured at 8000 Oe, as seen in Fig. 4 ͑ b ͒ , the magnetostriction enhances significantly under the compressive prestress, as observed in the directionally solidi- 14 fied oriented crystals of TbDyFe magnetostrictive alloys. The optimized magnetostriction is achieved from 679 ϫ 10 −6 at 0 MPa to 1358 ϫ 10 −6 at 17 MPa, nearly increased by 100%. The outstanding achieved magnetostriction should be attributed to the ͗ 111 ͘ preferred orientation. This is also linked to the chain structure of TbDyFe particles as shown in Fig. 3 ͑ b ͒ , in which magnetostriction could be transferred through the interaction of the neighbor particles. Compara- tively, magnetostriction is restricted by transferring to the epoxy resin in the isotropic composites. There the particles are also not aligned as the chain structure. The results of magnetostriction cured at four different applied fields are summarized in Table I. Contrasted to the specimen cured at 0 Oe, the magnetostriction increases by 26% and 34% cured at applied field of 4000 and 12000 Oe, respectively. This improvement further reflects the important action of 111 preferred orientation of the particles on the magnetostriction. The slightly low extent of the ͗ 111 ͘ preferred orientation for the sample cured at 4000 Oe shows a relatively inferior magnetostriction compared with the sample cured at 8000 Oe. Grain ͗ 111 ͘ preferred orientation and chain structure alignment of the composites cured at a moderate applied field are essential for the improved magnetostriction. At the excessive magnetic field of 12000 Oe, the magnetostriction slightly decreases, since the particles present segregation at the two ends of the sample as the discussion above. This work is supported by Natural Science Foundation of China ͑ NSFC ͒ under Grant Nos. 50925101 and ...
Context 3
... composites have attracted considerable attentions since they posses the distinct advantages of reduc- ing both eddy current losses and intrinsic brittleness compa- 1,2 rable to monolithic TbDyFe giant magnetostrictive alloy. Laminated composites were initially studied by sticking the 3 sheets of TbDyFe alloys with epoxy. However, due to the brittleness, the cutting thickness of TbDyFe alloy sheets was limited to about 1 mm, hindering their application at higher operation frequency. ͗ 112 ͘ -oriented Terfenol-D/epoxy composites were also developed by using short needle-shape fi- 4,5 bers cut from the directional solidified crystal. Another process was recently introduced by removing the eutectic phase from a grain-aligned TbDyFe rod and infiltrating the 6,7 epoxy to the sites of removed eutectic phase. Most researches performed the crushed particle compos- 8,9 ites since the simple process and lower cost. But the strain levels of the crushed particle composites were far be- low the monolithic TbDyFe. Because of the strong magnetostriction anisotropy in TbDyFe alloys, a drastic difference of magnetostriction exists along specific crystallographic orientations. 10 It keeps active to obtain ͗ 111 ͘ preferred orientation in the magnetostrictive composites although it is 11 seem to be difficult in the aspect of crystal growth and the composite preparation in the previous reports. In this letter grains alignment with ͗ 111 ͘ orientation was induced in the anisotropic TbDyFe/epoxy bonded giant magnetostrictive materials by curing the epoxy matrix under a moderate applied magnetic field. A sound giant magnetostriction of 1360 ϫ 10 −6 was achieved. High-purity starting element Tb, Dy, and Fe with the purity level of 99.99%, 99.99%, and 99.97%, respectively, were remelted four times by arc melting for preparing the nominally Tb 0.3 Dy 0.7 Fe 1.9 ingots. The ingots were annealed at 1173 K for 4 h. The crushed particles of about 200– 300 m size with 20%–40% volume fraction epoxy were homogenously mixed in a plastic mold. The sealed mold was placed in an electromagnet with a uniform magnetic field ranging from 0 to 12000 Oe along the longitudinal direction of the mold. After aligning, the epoxy was cured at 323 K for 2 h under the applied magnetic field. These cured composites were prepared with the dimension of ⌽ 13.5 mm ϫ 20 mm. Optical metallography and x-ray diffraction were used for checking the particle alignment and orientation by a Neophot II optical microscope and a Regaku D/max2200 PC x-ray diffractometer with Cu K ␣ radiation. Magnetostriction was measured by using a standard resistant strain gauge and a gas pressure cell was used for applying the compressive prestress along the axis of the rods. The grain size of the annealed TbDyFe ingot was checked by metallograph with the average value of more than 300 m, as shown in Fig. 1 ͑ a ͒ . An intergranular frac- ture character can be monitored from the fractograph, as shown in Fig. 1 ͑ b ͒ . The photograph for the crushed particles is also shown in Fig. 1 ͑ c ͒ . The crushed particles should be single crystal though it was not checked by the accessible facilities. Figure 2 illustrates the x-ray diffraction patterns for the composites with a 20% volume fraction TbDyFe particles cured under 0, 4000, 8000, and 12000 Oe magnetic fields, respectively. It is reasonable that the x-ray diffraction pattern of the composite cured without the applied magnetic field is 12 the same as that for the as-cast monolithic TbDyFe alloy, since the random crystallographic orientations exhibit in the composites. When the magnetic field is applied during the curing process, under the action of the static magnetic energy, the particles should rotate with the easy axis ͗ 111 ͘ along the direction of the applied field if the magnetocrystalline anisotropy energy is large enough. If the magnetocrystalline anisotropy energy is small the magnetic domains rotate by the reorientation of the electrons orbits, in this case the particles should be magnetized and the particle rotation should not occur. The nominal composition for the present study is Tb 0.3 Dy 0.7 Fe 1.90 , in which the magnetocrystalline anisotropy constant k 1 is −1.6 ϫ 10 5 J / m 3 . 13 From the x-ray pattern in Figs. 2 ͑ b ͒ –2 ͑ d ͒ , the preferred orientation along ͗ 111 ͘ crystallographic direction is obviously observed. That means the particles rotation happen under the applied field during curing and the strongest ͑ 222 ͒ peak is monitored for the sample cured under 8000 Oe. The adhesive force of the uncured resin should be overcome by the driving force of the applied magnetic field. No drastic change is observed in the x-ray patterns for the samples cured at 12000 Oe, as shown in Fig. 2 ͑ d ͒ . In addition, the extent of the preferred orientation declines as the volume fraction of TbDyFe particles increases. The reason is that the irregular particles con- tact each other and hinder the rotation of the particles. Figure 3 shows the comparison of TbDyFe particles alignment with a 20% volume fraction in two samples cured under 0 and 8000 Oe magnetic field, respectively. The particles ͑ bright area ͒ are randomly dispersed in the epoxy matrix ͑ gray-black area ͒ without the applied field, as shown in Fig. 3 ͑ a ͒ . However the particles align regularly with an approximate chain structure under an applied field, as shown in Fig. 3 ͑ b ͒ . The particles can be regarded as tiny magnetic needles. The magnetic field not only forces the rotation of the tiny needles but also leads to the mutual attraction of the magnetic pole. The inset in Fig. 3 ͑ b ͒ shows the sketch-map of the tiny magnetic needles alignment under the applied field. The excessive magnetic field of 12000 Oe results in a nonhomogeneous distribution of the TbDyFe particles in the composite, in which the TbDyFe particles segregate at the end of the sample near the electromagnet. Figure 4 plots the magnetostriction for the composites with 40% volume fraction TbDyFe particles cured at 0 and 8000 Oe, respectively. In Fig. 4 ͑ a ͒ it is evident that there is little stress effect and low saturated magnetostriction. This is attributed to the random orientation of the particles and irregular alignment. When cured at 8000 Oe, as seen in Fig. 4 ͑ b ͒ , the magnetostriction enhances significantly under the compressive prestress, as observed in the directionally solidi- 14 fied oriented crystals of TbDyFe magnetostrictive alloys. The optimized magnetostriction is achieved from 679 ϫ 10 −6 at 0 MPa to 1358 ϫ 10 −6 at 17 MPa, nearly increased by 100%. The outstanding achieved magnetostriction should be attributed to the ͗ 111 ͘ preferred orientation. This is also linked to the chain structure of TbDyFe particles as shown in Fig. 3 ͑ b ͒ , in which magnetostriction could be transferred through the interaction of the neighbor particles. Compara- tively, magnetostriction is restricted by transferring to the epoxy resin in the isotropic composites. There the particles are also not aligned as the chain structure. The results of magnetostriction cured at four different applied fields are summarized in Table I. Contrasted to the specimen cured at 0 Oe, the magnetostriction increases by 26% and 34% cured at applied field of 4000 and 12000 Oe, respectively. This improvement further reflects the important action of 111 preferred orientation of the particles on the magnetostriction. The slightly low extent of the ͗ 111 ͘ preferred orientation for the sample cured at 4000 Oe shows a relatively inferior magnetostriction compared with the sample cured at 8000 Oe. Grain ͗ 111 ͘ preferred orientation and chain structure alignment of the composites cured at a moderate applied field are essential for the improved magnetostriction. At the excessive magnetic field of 12000 Oe, the magnetostriction slightly decreases, since the particles present segregation at the two ends of the sample as the discussion above. This work is supported by Natural Science Foundation of China ͑ NSFC ͒ under Grant Nos. 50925101 and ...
Citations
... Mei et al. prepared < 111 > granularly oriented Tb-Dy-Fe sintered compacts by a magnetically oriented powder metallurgical process with a magnetostriction of 1400 ppm at 7 kOe for Tb 0.32 Dy 0.68 Fe 2 [8]. In the preparation of Tb-Dy-Fe/ resin-based composites, Meng et al. [9] crushed ingots into 200-300 µm coarse powder and obtained anisotropic composites Wenhao Zhang and Jin Qian contributed equally to this work. ...
In this paper, spherical single-crystal powder of Tb0.35Dy0.65Fe1.9 alloy was prepared by combining solid/liquid unwetting effect and anomalous grain growth, and the Tb0.35Dy0.65Fe1.9/epoxy composite was prepared under an applied magnetic field at 1.0 T. SEM observed that the prepared Tb0.35Dy0.65Fe1.9 alloy powder was spherical (sphere-like). XRD shows that the composites with 50% volume fraction of powder particles have a high < 111 > orientation, magnetostriction measurements showed that the composites prepared from spherical single-crystal powder treated with titanate coupling agent exhibited a high low-field magnetostriction coefficient of 464 ppm at 1 kOe magnetic field, which is 83 ppm higher than the spherical single-crystal powder composites without any treatment, an improvement of 21%.
... At the same time, considering that ferromagnetic particles are sensitive to magnetic fields [44], the effect of whether there is an orientation magnetic field has a great influence on the meso-structure of the composite [45]. Fig. 2 (c) shows that the particles are randomly distributed without an oriented magnetic field, and they are arranged in chains with an oriented magnetic field [46]. Their experimental results have shown that the strain of the composite with an external oriented magnetic field is greater than that without the oriented magnetic field. ...
... here λ s is the saturated magnetostrictive strain. The particles are distributed in the matrix in the form of (a) aggregate (b) random (c) chain [29,46] ...
... Their tendencies to saturation are different for the variant composition x, depending principally on the ratio of magnetostriction to magnetization l/M that resulted from the magnetic anisotropy variation. 26,27 To further understand this magnetoelastic behavior especially for the effect of anisotropy variation on magnetostriction, analogous to M/ M max eH ( Fig. 5(b)), the l a /l max eH curves for different compositions x are shown in Fig. 8(b), where l max denotes the l a value at H ¼ 960 kA/m. As expected, the curve moves to the upper one with increasing Ce content, indicating that it is easier to reach saturation for the samples with larger Ce content. ...
The light rare earth Pr/Ce-contained (Tb0.2Pr0.8)1–xCexFe1.93 (0 ≤ x ≤ 1.0) intermetallics are arc melted and investigated for magnetoelastic properties. The compounds of x ≥ 0.40 are found to stabilize at ambient pressure in a single Laves phase with MgCu2-type C15 structure, which is attributed to the strong Ce 4f bonding. The mixed-valence behavior, with a support of the deviation from the linear Vegard’s law for both lattice parameter a and saturation magnetization MS, is observed at room temperature. The easy magnetization direction (EMD) was determined by the analysis of both the XRD on magnetically aligned samples and the (440) splitting, that is, EMD lies toward <111> axis for x ≤ 0.50 rotating to <110> for x = 0.60, accompanied with the structural distortion from rhombohedral to orthorhombic. The substitution of Ce for Tb/Pr is conductive to the reduction of magnetocrystalline anisotropy, giving rise to an improvement of the low-field magnetostriction. The excellent magnetoelastic properties can be tailored by the Ce introduction, e.g., the spontaneous magnetostriction coefficient λ111 as large as 1150 × 10–6 for x = 0.40, and the low-field induced magnetostriction achieving a high value of λa = 180 × 10–6 at 80 kA/m for x = 0.60. The excellent magnetoelastic properties and the combination in high Pr-content with low cost, suggest promising prospects in applications.
... This transition would generate huge internal stress which always induce the cracks on CoMnSi bulks. Secondly, the texture is important to the magnetostrictive effect [10][11][12][13][14]. On the basis on the anisotropic of the lattice change during the metamagnetic transition, the magnetostriction along h100i crystal direction (a-axis) is probably much higher than the magnetostriction along other directions. ...
Magnetostrictive properties of CoMnSi are generally confined by their intrinsic brittleness and difficulty in growing into anisotropic bulk materials. In this study, we present a new type of 〈100〉-oriented CoMnSi microspheres/epoxy resin composite that exhibits a giant and reversible magnetostriction of 6700 ppm. 〈100〉-textured CoMnSi microspheres were synthesized through the non-wettability between CoMnSi liquid and solid dispersions. The microspheres/epoxy composites with a uniform 〈100〉 orientation were produced by applying a simulating rotating magnetic field. The improved magnetostriction in the composite was associated with microspheres' texture as well as their orientation. This work may shed light on the synthesis of textured metal spheres and the development of magnetic composite materials.
... The existing hybrid composites are usually hierarchical compound, and the first-level composites are usually particles inclusion types, whose effective properties are directly related to the microstructure, which is strongly dependent on the shape of the inclusion, bulk fraction ratio, orientation of magnetic field and other factors. For example, under the action of an oriented magnetic field, the particles will show a chain-like distribution, which is very important to improve the magnetostrictive performance [43,44], and then the ME effect of the hybrid ME composite are significantly affected [45]. How to comprehensively consider the above factors to establish a theoretical model that can reflect the microscopic characteristics of the hybrid ME composite to analyze its ME performance. ...
Polymer-based hybrid magnetoelectric (ME) composites have the advantages of light weight, good flexibility, environmental friendliness and biocompatibility, etc., and have potential applications special in mechanical signal detection and special environments, such as biomimetic robots, medical non-invasive detection, virus monitoring and other fields. The ME performance of this composite is closely related to its microstructure characteristics. In this work, a connection between the effective performance of the chain-arranged magneto-strictive composite and its microscopic properties is presented by the two-step homogenization process. On this basis, a theoretical model of the ME effect is established for the chain-like Terfenol-D/epoxy and PVDF multi-layers, and the analytical expression of its polarized electric field is also obtained. By comparison, our theoretical results agree well with the software calculation results and experimental data. Then the influence of some factors on the ME properties are discussed. The results show that the ME coefficients and resonance frequency strongly depend on the microstructure characteristics of the structure. Besides, the aspect ratio and volume fraction of the magnetostrictive inclusions, the magnetic-field intensity, and the frequency of the magnetic field, all have significant effects on the ME coefficient. This research will provide a theoretical basis for the preparation and application of the hybrid ME composites.
... From the X-ray pattern shown in Fig. 10, it can be seen that the preferred orientation along the 〈1 1 1〉 crystallographic direction (2θ ≈ 21 • ), which is commonly attributed to the giant magnetostriction of Terfenol-D [23][24], is observed only for the unmilled sample, which allows us to conclude that the magnetostriction of the milled sample was affected by the milling process. ...
In this paper, we report a study on optical sensors based on fiber Bragg gratings (FBG) and magnetostrictive composites of Terfenol D applied to magnetic field measurement. The study consisted in determining the sensor's sensitivity influenced by the shape of the magnetostrictive composite with an embedded FBG. The proposed sensors were designed and simulated using finite element method (FEM) in cylindrical, hyperbolic, and conical shapes in order to determine the geometric configuration for best sensitivity using the less amount of Terfenol-D. One prototype of each designed shape was manufactured using powdered Terfenol-D with 200-300 µm grain size and epoxy resin. The experimental results showed that the shape of the magnetostrictive composite influences up to 59% in the sensitivity of the sensors. The results also showed that the smaller sensor, a 1.5 mm x 16 mm cylinder using only 0.052 g of Terfenol-D was the best shape and achieved the highest sensitivity.
... Hao Meng et al. [50] studied the effects of orientation magnetic field and preloading stress on magnetostrictive composites. The grain size of magnetostrictive powder used is 200-300 µm. ...
Optical fiber current sensors are widely used in the online monitoring of a new generation power system because of their high electrical insulation, wide dynamic range, and strong anti-electromagnetic interference ability. Current sensors, based on fiber Bragg grating (FBG) and giant magnetostrictive material, have the advantages of high reliability of FBG and high magnetostrictive coefficient of giant magnetostrictive material, which can meet the monitoring requirements of digital power systems. However, giant magnetostrictive materials are expensive, fragile, and difficult to mold, so giant magnetostrictive composite materials have replaced giant magnetostrictive materials as the sensitive elements of sensors. High sensitivity, high precision, wide working range, low response time, and low-cost optical fiber current sensors based on magnetostrictive composites have become a research hotspot. In this paper, the working principle of the sensor, the structure of the sensor, and the improvement of magnetostrictive composite materials are mainly discussed. At the same time, this paper points out improvements for the sensor.
... The results of the characterization of TD powder by XRD are shown in Fig. 3(a). In this characterization, we found a pattern similar to that described by Meng et al. [12], in which the peak corresponding to crystallographic plane <111> is directly associate with the magnetostrictive property of TD. In addition, the magnetic domains of the composite were oriented during the curing process, since there is an increases in the intensity of the peak corresponding to the magnetostrictive property, which is proved in the Meng et al. [12].The acquisition of the output signals from the proposed FOCS prototypes was performed by an si155 FBG Interrogator (Micron Optics, Inc.) with a resolution of ±10 pm and maximum frequency response of 1kHz. ...
... In this characterization, we found a pattern similar to that described by Meng et al. [12], in which the peak corresponding to crystallographic plane <111> is directly associate with the magnetostrictive property of TD. In addition, the magnetic domains of the composite were oriented during the curing process, since there is an increases in the intensity of the peak corresponding to the magnetostrictive property, which is proved in the Meng et al. [12].The acquisition of the output signals from the proposed FOCS prototypes was performed by an si155 FBG Interrogator (Micron Optics, Inc.) with a resolution of ±10 pm and maximum frequency response of 1kHz. The input signals were acquired by a clamp meter i2000FLEX (Fluke Co.) connected to a digital oscilloscope. ...
This paper presents a novel compact fiber-optic current sensor (FOCS) based on magnetostrictive composites that employ only 1 gram of Terfenol-D. Finite element method (FEM) simulations supported the design and construction of two versions of FOCS, which were capable to measure on a.c. current from 200 to 800 A rms in laboratory.
... Promoting particulate crystallographic orientation along the <111> direction with the maximum magnetostrictive coefficient strongly enhances the magnetostrictive response of the composites. The optimal saturation magnetostriction 1358 ppm at 17 MPa uniaxial pressure preloaded was achieved for static magnetically oriented GMPCs with <111> orientation on a V F 40% [15]. Magnetocrystalline anisotropy playes a key role in the magnetic field orientation process since it provides the driving force to rotate particles and align their easy axes. ...
... Previous research has proved that the Tb-Dy-Fe alloy particles are smaller than the crystallite grain size of the master alloy and the fracture character of the master alloy is intergranular fracture [15], which avoids the crushed particles being polycrystalline. Then the Tb-Dy-Fe alloy particles were evenly mixed with a bisphenol A type E44 epoxy resin in China, whose epoxy content is 0.44 ± 0.03. ...
... The Fe/Ni-based alloys possess superb ductility, allowing them to be processed to thin sheets and wires [9][10][11][12][13], but their magnetostriction does not exceed 100 ppm, which precludes applications where a large value is required. The (TbDy)Fe 2 alloys have been found to offer giant magnetostriction of over 1000 ppm with minimum cubic anisotropy, but at a high cost for the heavy rare earths [8,14,15]. Furthermore, the brittleness of the Laves phase alloys mean that they fracture in tension and cannot be processed into other shapes. They are used in the form of oriented rods prepared by directional solidification [3,16]. ...
New-generation magnetostrictive applications in micromanipulation instruments, torque sensing and transducers require materials that offer a combination of large magnetostriction and good structural properties. Fe100-xGax-based (x = 17-19) alloys are potential candidates. In this work, the solidification behavior of Tb-doped FeGa alloys is investigated by theoretical simulation and experimental observation; directional solidification parameters are optimized to obtain the largest solid solubility of Tb while keeping the <100> preferred orientation. The multiscale evolution of the structure with Tb additions that enhances both magnetostriction and tensile properties is systematically studied in alloys prepared under optimal directional solidification conditions. Magnetostriction of 387 ppm is accompanied by a remarkable tensile fracture strain of 12.5% in 0.05 at.% Tb-doped Fe81Ga19. The values represent an improvement of ~29% in magnetostriction and a sixfold enhancement in tensile fracture strain compared with undoped binary Fe81Ga19. The increase in magnetostriction is attributed to the higher density of tetragonally-modified D03 nanoinclusions induced by traces of Tb. The enhancement in ductility is explained by the dislocation concentration around the submicron-scale Tb-rich precipitates which can effectively hinder their motion. The FeGa alloys doped with traces of Tb can be easily processing to thin sheets or wires and are likely to be extensively applied because they contain only traces of rare-earths.
