KR20040021213A - Magnetostrictive composites of transition metal based alloys and their manufacturing method - Google Patents

Abstract

PURPOSE: A method is provided to reduce eddy current losses and achieve improved characteristics even in the high frequency. CONSTITUTION: A method comprises a step of designing an alloy by reflecting magnetic and mechanical properties; a step of forming Fe-Al based and Fe-Co based alloy ingots by using a vacuum induction melting system or a vacuum arc melting system; a step of grinding the alloy ingots into lamellar powder; a step of mixing a polymer binder and the lamellar powder; and a step of compacting and hardening the mixture.

Description

Magnetostrictive composites of transition metal based alloys and their manufacturing method

The present invention relates to a method for producing a transition metal-based magnetostrictive composite, in particular, a composite having a high saturation magnetization of a transition metal-based powder using a polymer binder has a large magnetostriction sensitivity even at a low magnetic field. The magnetostrictive composite according to the present invention is slightly lower in performance compared to the conventional rare earth-based giant magnetostrictive composite, but the price is relatively inexpensive, and thus high commercial / applicability due to high performance / price ratio.

Magnetostrictive materials can be classified into two types, rare earth type and transition metal type. In general, the rare earth type has a much higher magnetostriction than the transition metal type, but is limited to a wide range of applications because it contains a very expensive element such as Tb. Therefore, except for special fields such as space, aviation, medical, defense, transition metal-based materials are used a lot.

The main applications of magnetostrictive materials are actuators and sensors. In particular, magnetostrictive materials have superior characteristics as actuators because of their higher output than conventional materials (eg piezoelectric ceramics). Applications of magnetostrictive actuators include high-speed precision position control, sonic and ultrasonic oscillators, active vibration and noise control, and these applications are mainly used in dynamic (high frequency) applications.

However, both rare earth-based and transition metal-based magnetostrictive materials are metals, which have low resistivity and large eddy current loss, which causes great problems in high frequency applications. Currently used in bulk metal form, the frequency of use is up to 1kHz. Existing methods for solving this problem are different depending on the alloy system, Figure 1 summarizes the existing process sequence for the rare earth-based alloy, and Figure 2 for the transition metal-based alloy.

As summarized in FIG. 1, in the case of a rare earth-based alloy, an alloy having a desired composition is prepared through a conventional dissolution process such as vacuum induction melting and vacuum arc dissolving, and then the directional solidification method is used to improve the magnetostriction characteristics. Align or prepare a single crystal. In the case of the rare earth-based alloy, since the magnetostriction in the <111> crystal direction is much larger than that in the <100> direction, the crystal direction is grown as close to the <111> direction as possible [A. E. Clark, in E. P. Wohlfarth (Ed.), Ferromagnetic Materials, chapter 7, volume 1, North-Holland, Amsterdam, 1980]. However, the crystals produced by conventional directional solidification processes are in the <112> direction rather than the <111> direction [E.D. Gibson, J.D. Verhoeven, F.A. Schmidt, O. D. McMasters, Continuous Method for Manufacturing Grain-Oriented Magnetostrictive Bodies, US Patent 4,770,704, Japanese Patent 2,020,420. It is known that it is possible to align in the <111> direction using a special method, but [W. Mei, M. Yoshizumi, T. Okane and T. Umeda, "Crystal growth of giant magnetostrictive Tb-Dy-Fe alloy", Journal of Alloys and Compounds, 258, pp. 34-38 (1997)], the commercial applicability is very low because the process is complex and therefore expensive. These directional solidified crystals, as already mentioned, have a low resistivity and, due to the skin effect, limit the usable frequency up to 1 kHz. To solve this problem, the crystals are sliced to a thickness of 1 mm or less to form a thin plate. In this case, the specific thickness is determined in consideration of the surface effect according to the frequency of use and the magnetic properties of the material. The sliced material is made into a laminated structure using an insulating binder, and then processed into a final shape.

As shown in FIG. 2, in the case of the transition metal alloy, an alloy ingot of a desired composition is first produced by a conventional dissolution process as in the rare earth alloy. The ingot is hot-rolled and cold-rolled several times to produce a plate having a desired thickness. Most transition metal magnetostrictive materials are too brittle mechanically for rolling and add a third element to solve this, which greatly degrades the magnetic properties. One example is an alloy with the commercial name Supermendur with the addition of V to the Fe—Co alloy (Fe ₄₉ Co ₄₉ V ₂ alloy). The transition metal-based magnetostrictive alloy sheet is laminated using an insulating binder, and then processed into a final shape.

Existing methods applied to both rare earth systems and transition metal systems include many processes, and many process parameters have to be controlled very precisely, so devices manufactured through such processes have a disadvantage of being very expensive. As an example, the directional solidification process used in rare earth-based alloys is very expensive, and the process of slicing highly brittle directional solidified crystals to 1 mm or less is also difficult and a lot of material is wasted in such a process. In the case of transition metal alloys, hot and cold rolling have to be repeatedly performed, resulting in high process costs. In particular, the third element added to improve the mechanical ductility greatly deteriorates the magnetic properties.

For this reason, although the magnetostrictive material has superior characteristics as a high power actuator compared to piezoelectric ceramics, its application range has been limited. In order to solve this problem, a recent patent of the laboratory has prepared a magnetostrictive composite by preparing an ingot from a rare earth magnetostrictive alloy through a conventional dissolution process, pulverizing it to form a powder, and then combining it with a polymer binder. [Sang-Ho Lim, Sang-Rok Kim, Seok-Ik Kang, Jong-Koo Park, Method for manufacturing Tb-Dy-Fe magnetostrictive alloy composite, Korean Patent Registration No. 10-0302583 (4 July 2001). A schematic diagram of the process used to prepare the rare earth-based magnetostrictive composite by this method is shown in FIG. 3. Binding technology is the key to making magnetostrictive composites using magnetostrictive powders and polymeric binders. As shown in FIG. 3, the number of processes is greatly reduced and does not include expensive processes as compared with the conventional method shown in FIG. 1. In particular, since it is possible to manufacture directly to a desired shape, it is possible to minimize the waste of material according to the process. Therefore, magnetostrictive composites according to past patents are very advantageous for commercial applications. In other words, the rare earth magnetostrictive composite according to the past patent is significantly improved performance / price ratio, which means that the commercial applicability is greatly improved.

As known conventional techniques, rare earth-based magnetostrictive composites have shown excellent magnetostrictive properties. In particular, it showed high magnetostriction sensitivity in the low magnetic field region. When using the commercially well-known Terfenol-D alloy ((Tb, Dy) Fe ₂ ) as a rare earth magnetostrictive alloy, 536 ppm magnetostriction at 1.1 kOe applied magnetic field and high magnetostrictive sensitivity of 1.3 ppm / Oe This was achieved.

It would be possible to produce transition metal based magnetostrictive composites using similar techniques. However, unlike rare earth magnetostrictive composites, it is difficult to achieve excellent magnetostrictive properties with the same method in the case of transition metal magnetostrictive composites. The reason for this is because the saturation magnetic flux density of the transition metal alloy is high, so that the semi-magnetic field is large when it is made of a conventional powder as in the rare earth alloy. This deteriorates the susceptibility of magnetostriction in the low magnetic field region, which is important for applications. Let's take an example. Assuming that the powder is fully spherical, Terfenol-D powder with 10 kG saturation magnetization is 3.3 kOe in size of a diamagnetic field, while Fe ₅₀ Co ₅₀ alloy with 24 KG saturation magnetization is 8 kOe. That is, even if a rare earth alloy having a small saturation magnetization and a small semi-magnetic field is made of a conventional powder, and then a magnetostrictive composite is prepared using a polymer binder, it is possible to prepare a magnetostrictive composite having relatively good magnetostrictive properties. In the case of transition metal alloys, this method is not possible.

The main technical problem to be achieved by the present invention is to produce a magnetostrictive composite obtained with excellent magnetostrictive properties even for transition metal alloys with high saturation magnetization. The transition metal-based alloy is inferior in performance to the rare earth-based alloy, but does not contain expensive elements, and thus has a good commercial / applicability ratio due to its high performance / price ratio.

The technical problem to be achieved by the present invention is mainly achieved through the following three main technical matters. The first is to prepare the shape of the powder in the form of a plate rather than a spherical shape. The second is to greatly reduce the diamagnetic field by aligning the face of the powder parallel to the magnetic field applied during the compaction of the powder. Finally, a binding technology is developed to allow deformation between powders to be transferred through the polymer binder in the form of a plate-like powder so that the deformation of the entire composite can be achieved.

In summary, the present invention relates to a transition metal magnetostrictive composite having excellent magnetostrictive properties even for a transition metal alloy having a high saturation magnetization and a manufacturing technique thereof. This is mainly achieved through the technique of producing a plate-like powder to reduce the semi-magnetic field even though it has a high saturation magnetization, and aligning the plate-like powder so as to be parallel to the magnetic field applied during molding and binding the plate-shaped powder. The magnetostrictive composite according to the present invention has a high magnetostriction sensitivity even at a low magnetic field, and because the metal magnetostrictive powder is insulated by the polymer binder, the resistance is large and thus the eddy current loss is small, thereby showing excellent characteristics even at high frequencies.

1 is a process flow diagram of a conventional method for increasing the use frequency for rare earth magnetostrictive alloys.

2 is a process flowchart of an existing method for increasing the use frequency for a transition metal-based magnetostrictive alloy.

3 is a process flow diagram of an existing method used to prepare rare earth-based magnetostrictive composites.

Figure 4 is a scanning electron micrograph of the Fe ₃₆ Co ₆₂ Ge ₂ alloy powder having an average particle size of 23 ㎛ prepared according to the present invention. The shape of powder is thin plate shape, and thickness is about 3-5 micrometers.

5 is a scanning electron micrograph of the Fe ₃₆ Co ₆₂ Ge ₂ alloy powder having an average particle size of 73 ㎛ prepared according to the present invention. The shape of powder is thin plate shape, and thickness is about 3-5 micrometers.

6 is a scanning electron micrograph of the Fe ₃₆ Co ₆₂ Ge ₂ alloy powder having an average particle size of 125 ㎛ prepared according to the present invention. The shape of powder is thin plate shape, and thickness is about 3-5 micrometers.

7 is a scanning electron micrograph of the Fe ₃₆ Co ₆₂ Ge ₂ alloy powder having an average particle size of 175 ㎛ prepared according to the present invention. The shape of powder is thin plate shape, and thickness is about 3-5 micrometers.

FIG. 8 shows the results of X-ray diffraction patterns of Fe ₃₆ Co ₆₂ Ge ₂ alloy powders for various particle sizes. (a) is a powder having an irregular shape produced by a conventional powder production method, and (b) is a plate-like powder produced by the present invention. The average particle size of the powders for both kinds of powders is 23, 73, 125, 175 and 225 μm.

FIG. 9 shows the result that the magnetostriction (λ) obtained in the applied magnetic field of 8 kOe in the binary Fe-Co alloy fast solidification ribbon is changed according to the composition of the alloy. λ is Obtained by the relation of Wow Are the magnetostriction values measured in the direction parallel to the length direction, respectively, while applying the magnetic fields in the parallel and transverse directions in the plane of the ribbon.

FIG. 10 shows that when substituting a third element instead of a Co atom in a binary Fe ₃₆ Co ₆₄ alloy rapid solidification ribbon, the value of λ obtained at an applied magnetic field of 8 kOe is dependent on the amount of the substituted third element. An example is shown.

Figure 11 shows the result of the saturation magnetization and density change with the average particle size of the powder for the magnetostrictive composite according to the present invention. Results for composites prepared with a phenol content of 10% by weight and a molding pressure of 0.5 GPa.

Figure 12 shows the result of the saturation magnetization and density change depending on the phenol content for the magnetostrictive composite according to the present invention. This is the result for the composite prepared with the average particle size of the powder 73 µm and the molding pressure being 0.5 GPa.

Figure 13 shows the result of the saturation magnetization and density changes with pressure during molding for the magnetostrictive composite according to the present invention. Results are for composites prepared with a mean particle size of 73 μm and a phenol content of 7 weight%.

Figure 14 shows the result that the compressive strength of the composite according to the present invention changes depending on the molding pressure. Results obtained from average particle size (125 μm) and phenol content (10 wt%) of certain powders.

Figure 15 shows the result that the compressive strength of the composite according to the present invention changes depending on the average size of the powder. Result obtained at constant molding pressure (0.67 GPa) and phenol content (10% by weight).

16 is a scanning electron micrograph of the cross section of the Fe ₃₆ Co ₆₂ Ge ₂ magnetostrictive composite prepared according to the present invention. Results were obtained for composites prepared at 73 μm powder average particle size, phenol content of 10% by weight and molding pressure of 0.5 GPa. No magnetic field is applied during molding.

Figure 17 shows the result of the coercive force of the composite according to the present invention changes depending on the average particle size of the powder.

Figure 18 shows the result of the coercive force of the composite according to the present invention changes depending on the molding pressure of the powder.

Figure 19 shows the result of the λ value for the Fe ₃₆ Co ₆₂ Ge ₂ alloy ribbon prepared by the rapid solidification method according to the present invention changes with the magnetic field.

FIG. 20 is a sample of a Fe ₃₆ Co ₆₂ Ge ₂ alloy ingot prepared by a conventional vacuum induction melting method or vacuum arc melting method according to the present invention in a square column shape of 3.5 mm * 3.5 mm * 10 mm. Shows the result of changing according to the magnetic field.

21 is for the Fe ₃₆ Co ₆₂ Ge ₂ magnetostrictive composite prepared by molding under applied magnetic field in accordance with the present invention Shows the result of changing according to the magnetic field. Sample dimensions are 3.5 mm * 3.5 mm * 10 mm.

22 is measured at a magnetic field of 4.3 kOe for the Fe ₃₆ Co ₆₂ Ge ₂ magnetostrictive composite prepared according to the present invention. It shows the result that the value changes according to the average particle size. To investigate the effect of applied magnetic field on the magnetostriction during molding, we compared the results of composites molded with magnetic field and those molded without magnetic field.

23 is measured at a magnetic field of 4.3 kOe for the Fe ₃₆ Co ₆₂ Ge ₂ magnetostrictive composite prepared according to the present invention. The result shows that the value changes according to the phenol content. The result is obtained from the average particle size (125 ㎛) and molding pressure (0.5 GPa) of a certain powder.

24 is measured at a magnetic field of 4.3 kOe for the Fe ₃₆ Co ₆₂ Ge ₂ magnetostrictive composite prepared according to the present invention. The value is changed according to the molding pressure. Results obtained from average particle size (125 μm) and phenol content (10 wt%) of certain powders.

FIG. 25 shows a magnetic history curve for a Fe ₃₆ Co ₆₂ Ge ₂ magnetostrictive composite prepared by molding under an applied magnetic field according to the present invention.

26 is a view of the Fe ₅₂ Co ₄₈ magnetostrictive composite prepared using the spherical powder according to the comparative example of the present invention Shows the result of changing according to the magnetic field. Sample dimensions are 3.5 mm * 3.5 mm * 10 mm.

FIG. 27 shows a magnetic history curve of a Fe ₅₂ Co ₄₈ magnetostrictive composite prepared using spherical powder according to the comparative example of the present invention.

The process for producing the transition metal magnetostrictive composite according to the present invention is similar to that of the rare earth magnetostrictive composite shown in FIG. 3. The main difference is that the rare earth magnetostrictive composite was prepared by a conventional method, but in the present invention, the powder is prepared in a plate-like form and is aligned with the known prior art.

In the present invention, as the transition metal magnetostrictive alloy, Fe-Al and Fe-Co alloys were selected. Specifically, in the case of the Fe-Al alloy, the Al content was changed from 18 atomic% to 40 atomic%, and in the case of Fe-Co alloy, the Co content was changed from 30 atomic% to 75 atomic%.

Since alloys having the above composition range are too ductile to prepare powders, it is very difficult to prepare powders in a conventional powder manufacturing process. In particular, even when the powder is produced, the shape of the powder is very irregular, which is not suitable for producing a magnetostrictive composite. Therefore, a third element was added to the Fe-Al and Fe-Co-based alloys to produce a plate-like powder by a conventional powder manufacturing process.

Referring to the process for producing the transition metal-based magnetostrictive composite according to the present invention in more detail, the step of designing the alloy in consideration of the magnetic properties (including magnetostrictive properties) and mechanical properties (easiness of plate-like powder production) of the alloy Preparing an alloy ingot by a conventional vacuum induction melting method or vacuum arc melting method, pulverizing the ingot into a plate-like powder, mixing the polymer binder with the powder, and molding and curing the mixture. .

The third element added to facilitate the plate-like powder from the Fe-Al and Fe-Co alloy ingots is as follows. In the case of the Fe-Al alloy system, as the third element, B, C, Si, Ge, Ga, Tb, Dy, and Sm were added, and the maximum amount was 4 atomic%. In the case of the Fe-Co alloy system, B, C, Si, Ge, Ga, Al, Tb, Dy, and Sm were added as the third element, and the maximum amount was 6 atomic%. The addition of the third element increased the brittleness of most of the alloys and facilitated powder production. In addition, in most cases, the addition of a third element produces a more regular, easier-to-control plate-like powder. The third element is a nonmagnetic material at room temperature, and since the magnetic properties of the alloy are mostly degraded by the addition of such an element, it is necessary to minimize the addition amount as much as possible. Among the third elements, the effect of adding Ge was very good. In other words, when Ge was added as the third element, a plate-like powder suitable for the magnetostrictive composite could be produced with minimal deterioration of magnetic properties.

The plate-like powder thus prepared was mixed with a polymer binder. Phenol-based resins, urea-formaldehyde-based resins, melamine-formaldehyde-based resins, polyester-based resins, epoxy-based resins, polyimide-based resins, etc., which have a relatively low curing temperature and high mechanical strength after curing, are preferable. And, the mixing amount is preferably 3 to 15% by weight.

In order to uniformly apply the polymer binder to the surface of the powder, the polymer binder is preferably dissolved in a polar solvent such as methanol, ethanol, and tetrahydrofuran (THF), and then mixed with the powder. If the content of the polymer binder is too large, the magnetostriction value of the composite is greatly reduced by the dilution effect, and if it is too small, the mechanical strength of the composite is small, which is not preferable.

The molding of the powder used a conventional press. The molding pressure is appropriately 0.1 to 2.0 GPa. Although it is also possible to shape | mold without applying a magnetic field at the time of shaping | molding of a powder, it is more preferable to apply a magnetic field. The direction of the applied magnetic field is perpendicular to the pressing direction by the press. The applied magnetic field helps to align the plate-like surface of the powder and the direction of the magnetic field to be parallel by the electromagnetic interaction. In the case of a magnetostrictive composite in which a plate-like powder is aligned by applying a magnetic field, when the magnetic field is applied in a direction parallel to the plane during application, the size of the diamagnetic field is reduced, so that the sensitivity of the magnetostriction can be increased even at a low magnetic field.

Curing of the molded powder is achieved by maintaining a few minutes to several tens of minutes in the temperature range of 100 ^° C. to 200 ^° C.

In the following, in order to more clearly understand the present invention, one preferred embodiment according to the manufacturing method of the present invention will be described. The following examples are merely exemplary, and various modifications other than the present embodiment can be made within the scope of the present invention.

<Example>

An alloy ingot having a composition of Fe ₃₆ Co ₆₂ Ge ₂ was prepared by a conventional vacuum induction melting method or a vacuum arc melting method. The composition selected in this embodiment is one of the compositions optimized through systematic investigation. More specifically, first, the change in the magnetostriction properties of binary Fe-Co alloys was systematically investigated, and the effects of the type and amount of the third element on the magnetic and mechanical properties were also systematically investigated. Based on these results, Fe ₃₆ Co ₆₂ Ge ₂ alloy was selected as the optimal composition.

The molten alloy ingot was pulverized to about 1 mm in diameter using a pulverizer, and then the final powder was prepared using a spex mill (a kind of high energy ball mill). When the powder was prepared by using a spex mill, milling balls having a composition similar to that of the powder were used, and the sizes were 4.7 mm, 6.3 mm and 9.5 mm in diameter. The amount of the sample to be crushed was about five times the weight of the milling ball. At the time of milling, isopropyl alcohol was used as a solvent and milling time was varied from 2 hours to 10 hours. The powder thus prepared was separated into several powder groups having similar sizes by using a sieve to compare the characteristics according to the size of the powder. In this embodiment, the powder group is the average particle size of the powder ( (Similar to diameter) were classified into five types of 23 µm, 73 µm, 125 µm, 175 µm and 225 µm, respectively. 4-7 shows micrographs observed by scanning electron microscopy for powders having an average particle size of 23 μm, 73 μm, 125 μm, and 175 μm, respectively. As shown in Figure 4-7, the powder shows a very thin plate-like shape, the plate-like thickness is about 3 to 5 ㎛.

FIG. 8 shows the results of X-ray diffraction on powders having various particle sizes shown in FIGS. 4-7. Figure 8 (a) shows the X-ray diffraction results of the powder prepared by a conventional powder manufacturing method, (b) is for the plate-shaped powder prepared according to the present invention, and shown in Figure 4-7 X-ray diffraction results are shown. In general, alloys having a body-centered cubic lattice (BCC) structure are first grown to (110) plane except for single crystal growth such as unidirectional solidification. In the case of (a), it can be observed that the (110) plane is preferentially developed compared to other planes regardless of the size of the powder. This is in good agreement with the general case seen in alloys with polycrystalline phases. However, in the case of the plate-shaped powder prepared according to the present invention, the peaks corresponding to the (200) plane (Fig. (B)) were found to be similar to the peaks corresponding to the (110) plane across all the powders. As the average particle size increases, the (200) peak tends to increase, while the peak on the (110) plane gradually disappears. From the X-ray diffraction analysis results, it can be seen that the plate-shaped powder is crushed to the (200) plane. Relatively large (110) plane peaks at small powder particle sizes indicate that the smaller the particle size, the more randomly the powder accumulates when charged with the powder for X-ray diffraction analysis. It seems to exist.

The pulverization of the plate-like powder to the (200) plane also plays a positive role in the magnetostriction properties. Because of the FeCo-based magnetostrictive alloy having a body-centered cubic lattice, the magnetostriction in the <100> direction is significantly higher than that of the <111> direction. The pulverized plate-like powder is expected to have large magnetostriction even at low magnetic fields.

This plate-like powder was combined with a polymer binder. As the polymer binder, a phenolic resin having a relatively low curing temperature and high mechanical strength was used. A mixing amount of the phenolic resin was mixed in various amounts in the range of 3% by weight to 10% by weight. In order to distribute the phenol evenly on the surface of the powder, the phenol was first dissolved in ethanol or THF solvent and then mixed with the powder.

The phenol mixed powder was molded at various pressures in the range of 0.25 to 0.75 GPa using conventional presses. The magnetic field was applied by attaching Nd-Fe-B permanent magnet to the molding die in order to observe the effect of the magnetic field applied to the powder during molding. The magnitude of the applied magnetic field is on the order of 2 kOe. The molded article prepared by this process was cured at 150 ^° C for several minutes to several ten minutes to produce a high mechanical strength Fe ₃₆ Co ₆₂ Ge ₂ magnetostrictive composite. The composites prepared were mainly cylindrical in shape 5 mm in diameter and 10-12 mm in height, or in the shape of a square column of 3.5 mm * 3.5 mm * 10 mm.

Magnetostriction was measured not only in samples prepared in the form of a composite, but also before the composite was prepared to investigate the inherent magnetostrictive properties of the alloy. This is necessary not only in the step to determine the optimum alloy, but also to investigate how the magnetostrictive properties changed by the formation of the composite. In the case of preparing the composite, the ingot prepared by the conventional vacuum induction melting method or the vacuum arc melting method is measured by machining to the same size as the shape of the composite, or by reintegrating and rapidly solidifying it by vacuum induction method. Was measured. In the latter case, in order to rapidly solidify the re-dissolved molten metal, the molten metal was sprayed onto a rotating copper roll at a linear speed of 10-50 m / sec. By such a rapid solidification process, a ribbon having very fine grains can be obtained. The quick-curing ribbons produced are 20-50 μm thick and 1-2 mm wide. The magnetostriction of the ingots machined to the same dimensions as the composite and the composite according to the invention was measured under a magnetic field of up to 4.3 kOe using a strain gauge. Ribbons prepared by rapid solidification were measured under capacities up to 8 kOe using capacitive method. Magnetic properties were measured using a vibration sample magnetometer while applying a magnetic field of 15 kOe. In order to measure the mechanical properties of the composite, especially the compressive strength, a tester capable of measuring the mechanical properties was used. Measurement results of the respective physical properties are shown in FIGS. 9 to 27, which will be described below.

The results shown in FIGS. 9 and 10 show some of the composition optimization efforts made in this example. FIG. 9 shows the result of the change of magnetostriction (λ) according to the composition of the alloy in the binary Fe-Co alloy. FIG. 9 shows an example of a result in which the lambda value is changed depending on the amount of the substituted third element when the third element is substituted for the Co atom in the binary Fe ₃₆ Co ₆₄ alloy. As the third element, B, Si, Ge, Ga, Al, Tb, and Dy were added. The results shown in FIGS. 9 and 10 are for rapid coagulation samples. The magnetostriction value was obtained at a maximum magnetic field of 8 kOe. Since the magnetic saturation occurred at the maximum magnetic field of 8 kOe in most samples, the magnetostriction values shown in FIGS. 9 and 10 are almost the same as the saturation magnetostriction. Magnetostriction λ is Obtained by the relation of Wow Are the magnetostriction values measured in the direction parallel to the longitudinal direction, respectively, while applying a magnetic field in the parallel and transverse directions in the plane of the ribbon. Normal Wow The value is sensitive to the sample's magnetic structure, but the difference between these two values, When the magnetic field is applied large enough to magnetically saturate, it is measured a lot to investigate the inherent magnetostriction of the material because it is independent of the structure and depends on the composition of the material.

As shown in FIG. 9, the maximum magnetostriction in the binary Fe-Co alloy was obtained when the Co content was 60-70 atomic%. From the results for FIG. 10, the magnetostriction monotonously decreases as a non-magnetic third element is added to the Fe—Co alloy. However, the extent to which the magnetostriction decreases depends on the type of the third element. When Ge was added as the third element, the decrease in magnetostriction was rather small. In particular, the addition of 2 atomic% Ge showed little decrease in magnetostriction. In addition, unlike other third elements, it was possible to easily prepare a plate-like powder having properties suitable for the magnetostrictive composite even with a small addition of 2 atomic% in the case of Ge. From these magnetic and mechanical properties, the Fe ₃₆ Co ₆₂ Ge ₂ alloy containing 2 atomic% of Ge was selected as the optimal composition.

Figure 11 shows the result of the saturation magnetization and density changes with the average particle size of the powder for the magnetostrictive composite according to the present invention. The results in FIG. 11 are the results for the composite prepared in a state in which the phenol content is 10% by weight and the molding pressure is 0.5 GPa.

Figure 12 shows the result of the saturation magnetization and density change depending on the phenol content for the magnetostrictive composite according to the present invention. The result of FIG. 12 is a result of the composite prepared in a state in which the average particle size of the powder is 73 μm and the molding pressure is 0.5 GPa.

Figure 13 shows the result of the saturation magnetization and density changes with pressure during molding for the magnetostrictive composite according to the present invention. The result of FIG. 13 is a result for the composite prepared in a state in which the average particle size of the powder was 73 μm and the phenol content was constant at 7% by weight.

From the results of Figs. 11-13, the saturation magnetization and the behavior of density change are very similar. In other words, if the density is high, the saturation magnetization is high. On the contrary, if the density is low, the saturation magnetization is also low. This is easily expected because the density of the ferromagnetic Fe ₃₆ Co ₆₂ Ge ₂ alloy is approximately 7.99 g / cc, which is higher than 1.28 g / cc of the non-magnetic phenol. In FIG. 11, as the average particle size of the powder increases from 23 μm to 225 μm, the saturation magnetization decreases from 10.36 kG to 9.01 kG, and the density decreases from 4.61 g / cc to 4.04 g / cc. Despite the constant phenol content and pressure during molding, the decrease in saturation magnetization and density of the composite as the average particle size of the powder increases, the rate of filling of the magnetostrictive alloy of the composite as the average particle size of the powder increases. It means lowering. In FIG. 12, the saturation magnetization decreases from 13.22 kG to 10.03 kG and the density decreases from 5.72 g / cc to 4.45 g / cc as the phenol content increases from 3% to 10% by weight. The saturation magnetization and density of the composites decrease with increasing phenolic content because the phenols are nonmagnetic and have a very low density compared to magnetostrictive alloys. In FIG. 13, as the forming pressure increases from 0.25 GPa to 0.75 GPa, the saturation magnetization increases from 10.62 kG to 12.24 kG, and the density increases from 4.54 g / cc to 5.39 g / cc. Although the average particle size and phenol content of the powder are constant, the saturation magnetization and density of the composite increase with the molding pressure because the filling rate of the composite increases as the molding pressure of the powder increases.

It can be expected from the results of FIGS. 11-13 that the characteristics of the composite are excellent because the smaller the average particle size, the smaller the phenol content, and the higher the molding pressure, the higher the saturation magnetization and density of the composite are. However, the optimization of these process parameters should be determined taking into account the magnetostriction and mechanical properties of these parameters. First consider the case of phenol content. If the phenol content is very low, the saturation magnetization and density are high, but the mechanical strength is low enough to be unsuitable for the application, and the low resistivity will result in poor high frequency characteristics. On the other hand, if the phenol content is high, it will show excellent high frequency characteristics because of its high strength and high resistivity, but excessive phenol content will degrade the magnetic properties due to the dilution effect of the non-magnetic phenol.

In the case of the molding pressure, since the saturation magnetization and the density increase linearly as the molding pressure increases in the result of FIG. 13, it is expected that the higher the molding pressure, the better the properties of the composite. Figure 14 shows the result that the compressive strength of the composite according to the present invention changes depending on the molding pressure. The results in FIG. 14 are obtained from the average particle size (125 μm) and phenol content (10 wt%) of the constant powder. As shown in FIG. 14, the compressive strength is maximum at 0.5-0.6 GPa. This means that the optimum molding pressure in terms of compressive strength is 0.5-0.6 GPa. The reduction in compressive strength at very large molding pressures is presumed to be due to the fact that the polymeric binders present between the plate-like powders in these molding pressure ranges leak out of the powder and are not properly bonded. In addition, the polymer binders leaking out between the surface and the surface of the powder are expected to play a role of deteriorating the compressive stress because they exist in the form of segregation as they aggregate together.

Figure 15 shows that unlike the molding pressure, as the average particle size of the powder decreases, the saturation magnetization and density increase, and the compressive strength also increases. In the case of the average particle size of 125-225 ㎛, the compressive strength is similar as 35-36 MPa, but in the case of 75 ㎛ is rapidly increased to 65 MPa. When the plate-like powder embedded in the polymer binder matrix is regarded as a sharp and long crack, the thickness / diameter ratio of the powder increases as the average particle size of the powder decreases, so that the compressive strength of the powder in the plane direction is determined by brittle fracture under uniaxial stress. Increase on the basis of In addition, as the average particle size of the powder increases, the surface area of each powder particle also increases, requiring a more uniform and greater adhesive strength between the polymer binder and the powder. Therefore, the binding force between powders decreases with increasing average particle size.

FIG. 16 is a photograph illustrating a cross section of a composite having an average particle size of 75 μm in FIG. 15 with a scanning electron microscope. FIG. The powder is grayed out and the binder is black. The powder is mostly aligned in the direction perpendicular to the molding direction since the cross section of the powder is observed in the cut section parallel to the molding direction. In other words, by forming, the plate-like powders are generally aligned in a direction perpendicular to the forming direction, and some of the polymer binders are aggregated, but the binders are uniformly distributed between the powders as a whole.

17 and 18 show the result of the coercive force of the composites varying with the average size and molding pressure of the powder, respectively. The coercive force of the composite does not change much according to the average size of the powder and the molding pressure, but decreases as the size of the powder increases and increases as the molding pressure increases. The coercive force of the complex is almost independent of the phenol content. The coercive force of the composite in the range of process parameters performed in the present invention was relatively small as 50 Oe-57 Oe.

FIG. 19 shows the result of λ value change according to the magnetic field for the Fe ₃₆ Co ₆₂ Ge ₂ alloy ribbon prepared at the rotational roll speed of 30 m / s by the rapid solidification method. 9 and 10, the lambda value is It was obtained by the relational formula of. As shown in FIG. 19, the value of λ increases to a magnetic field of 1 kOe, but gradually increases in an applied magnetic field thereafter, and is substantially saturated at 8 kOe, the largest magnetic field applied in the present invention. The average lambda value at this time is about 76 ppm.

FIG. 20 illustrates a sample in which a Fe ₃₆ Co ₆₂ Ge ₂ alloy ingot prepared by a conventional vacuum induction melting method or vacuum arc melting method is machined into a square pillar shape having a size of 3.5 mm * 3.5 mm * 10 mm. Results in a change depending on the magnetic field. Like the quick-curing ribbon Wow Once all of the results are obtained, and the λ values irrelevant to the magnetic domain of the material are obtained from these results, a direct comparison with the results for the ribbon of FIG. 10 may be possible. But Unlike the rapid solidification ribbon, the semi-magnetic field due to the shape of the sample is very large and therefore it is difficult to accurately predict the magnetic field actually applied to the material. Only the results for At a magnetic field of 2 kOe The saturation of the value indicates the effect of shape anisotropy and was nearly saturated at 108 ppm. At low magnetic fields (below 1 kOe) The lower value of is considered to be due to the residual stress of the machined sample.

21 is for the Fe ₃₆ Co ₆₂ Ge ₂ magnetostrictive composite prepared by molding under applied magnetic field in accordance with the present invention Has changed according to the magnetic field. The dimensions of the sample were 3.5 mm * 3.5 mm * 10 mm, which is the same as the machined alloy ingot of FIG. therefore When calculating the value, the semi-magnetic field due to the shape of the sample is very large and therefore it is difficult to accurately predict the magnetic field actually applied to the material. Only the results for Similar to the result of FIG. 20, at a magnetic field of 2 kOe It can be seen that is saturated. This indicates that there is little influence of the diamagnetic field due to the shape of the powder, and proves that the diamagnetic field appears by the shape of the pure sample. Therefore, if you adjust the shape of the sample, under much lower magnetic field It is thought that the saturation value of can be obtained.

22 is measured at a magnetic field of 4.3 kOe for the Fe ₃₆ Co ₆₂ Ge ₂ magnetostrictive composite prepared according to the present invention. The result shows that the value changes according to the average particle size. In FIG. 22, in order to investigate the effect of the applied magnetic field on the magnetic deformation during molding, the results of the composite molded with the magnetic field and the composite molded without the magnetic field were compared. As shown in the result of FIG. 22, when the average particle size of the powder is low, the presence or absence of the magnetic field does not significantly affect the magnetostriction. However, as the average particle size of the powder was increased, the magnetostriction was greatly increased by applying a magnetic field during molding, and this tendency was more pronounced as the average particle size of the powder was increased. This result is considered that when the average particle size of the powder is small, the plate-shaped powder is aligned by the pressure at the time of molding, but when the average particle size of the powder is large, the plate-shaped powder is not aligned by the pressure at the time of molding. In this case, when a magnetic field is applied from the outside, the surface of the plate-shaped powder is arranged to be parallel to the magnetic field by the static magnetic interaction, which reduces the size of the semi-magnetic field.

23 is measured at a magnetic field of 4.3 kOe for the Fe ₃₆ Co ₆₂ Ge ₂ magnetostrictive composite prepared according to the present invention. The results show that the value changes with the phenol content. As shown in the results of FIG. 23, the phenol content was increased from 3% to 7% by weight from 63.3 ppm to 102.7 ppm, while the phenol content was continuously increased to 10% by weight and decreased to 92.8 ppm. In general, when the phenol content is reduced, the volume fraction of the magnetostrictive material is increased, thereby reducing the dilution effect due to the binder. However, considering the reduction of the magnetostriction at the low phenol content, the phenol content is 3 and At 5% by weight, it is believed that the binder has not been applied sufficiently to deliver the magnetostriction of the powder. Therefore, in the Fe ₃₆ Co ₆₂ Ge ₂ magnetostrictive composite, the phenol content to transfer the magnetostrictive powder displacement most effectively is 7% by weight. These results correspond to the case where the average particle size of the powder is 125 μm. As the average particle size increases, the optimum phenol content is expected to increase.

24 is measured at a magnetic field of 4.3 kOe for the Fe ₃₆ Co ₆₂ Ge ₂ magnetostrictive composite prepared according to the present invention. It is shown that the value changes with the pressure during molding. As shown in the results of FIG. 24, as the forming pressure increases from 0.25 GPa to 0.61 GPa The value increases from 72.2 ppm to 94.8 ppm. Increasing the molding pressure above 0.61 GPa resulted in a slight decrease of 92 ppm at 0.67 GPa. If you continue to increase beyond that The value will gradually decrease. This is related to the distribution of the polymeric binder considering that the compressive strength decreases when the molding pressure exceeds 0.5-0.6 GPa in the change of compressive strength according to the molding pressure shown in FIG. Prove that there is a direct association with the value.

25 is a magnetic history curve for a Fe ₃₆ Co ₆₂ Ge ₂ magnetostrictive composite prepared by molding under an applied magnetic field in accordance with the present invention. From the results in FIG. 25, the magnetization is nearly saturated at 4 kOe and the coercive force is 50 Oe. The composite made of plate-like powder had little effect of the diamagnetic field due to the powder, but exhibited a semi-magnetic field due to the shape of the entire composite, thereby increasing the sensitivity of magnetization due to the magnetic field. Particularly, the magnetic susceptibility was 10 times 1.4 times higher than that of the spherical powder, which was prepared under the low magnetic field of 1 kOe. The poor squareness until saturation above 1 kOe is due to the powder being not perfectly aligned. These results indicate that the sensitivity of magnetic and magnetic strain to the magnetic field of the composite is important to the shape of the powder unaffected by the anti-magnetic field and to the alignment in the direction parallel to the applied magnetic field.

<Comparative Example>

A bimodal Fe-Co alloy was prepared by vacuum induction melting or vacuum arc dissolving, and a magnetostrictive composite was prepared in the same manner as in Example except that a spherical powder was used using an atomization method. The composition of the alloy selected in this comparison is Fe ₅₂ Co ₄₈ . The size of the powder is 75 μm in average diameter.

26 is a FeCo magnetostrictive composite prepared using the spherical powder according to the comparative example Has changed according to the magnetic field. The dimensions of the sample are 3.5 mm * 3.5 mm * 10 mm. As shown in FIG. 21, the magnetostriction in the same magnetic field is somewhat lower than the magnetostrictive composite prepared using the plate-shaped powder according to the embodiment of the present invention. In particular, magnetostriction sensitivity at low magnetic fields, which is important for applications, is very poor. this is It can be clearly seen that saturation is not achieved even at a high magnetic field of 2 kOe.

FIG. 27 is a magnetic history curve of a FeCo magnetostrictive composite prepared using a spherical powder according to a comparative example. FIG. As shown in FIG. 25, magnetization in the same magnetic field is lower than in the magnetostrictive composite prepared using the plate-shaped powder according to the embodiment of the present invention. That is, although the intrinsic properties of the material are very similar, many applied magnetic fields are required to magnetize the composite because the semi-magnetic field by shape is large when the powder is spherical. The coercive force is 56 Oe, which is almost the same.

In the above, as shown in the embodiment of the present invention, the alloy composition having excellent magnetic and mechanical properties was optimized, and in this alloy, a plate-like powder having suitable properties for the magnetostrictive composite was prepared by a conventional powder manufacturing process. A magnetostrictive composite was prepared by combining the prepared powder with a polymer binder, and excellent magnetostrictive properties were achieved in this composite.

The transition metal magnetostrictive composite according to the present invention has a high magnetostriction sensitivity even at a low magnetic field, and because the metal magnetostrictive powder is insulated by the polymer binder, the resistance is high and thus the eddy current loss is small, thereby showing excellent characteristics even at high frequencies. The transition metal-based magnetostrictive composite according to the present invention has a lower performance than the conventional rare earth-based magnetostrictive composite, but has a high performance / price ratio because the price of the material is significantly lower than that of the rare earth-based composite, and thus the commercial applicability is very high.

The present invention is not limited only to the above embodiments, and it is apparent that many modifications are possible by those skilled in the art within the technical spirit of the present invention.

Claims (8)

In the method of producing a magnetostrictive composite having excellent magnetostrictive properties for the transition metal alloy, Designing the alloy to reflect magnetic and mechanical properties; Forming Fe-Al and Fe-Co-based alloy ingots by vacuum induction melting or vacuum arc melting; Grinding the alloy ingot into a plate-like powder; Mixing a polymer binder with the pulverized plate-shaped powder; And Transforming metal-based magnetostrictive composite manufacturing method comprising the step of molding and curing the resulting mixture. The method according to claim 1, wherein the third element consisting of B, C, Si, Ge, Ga, Tb, Dy, Sm group is added so that a plate-like powder is easily formed from the Fe-Al alloy ingot, and the maximum amount Method for producing a transition metal-based magnetostrictive composite, characterized in that 4 atomic%. The method according to claim 1, wherein a third element consisting of B, C, Si, Ge, Ga, Al, Tb, Dy, Sm group is added so that a plate-like powder is easily formed from the Fe-Co alloy ingot. Method for producing a transition metal-based magnetostrictive composite, characterized in that the addition amount is 6 atomic%. The method of claim 1, wherein the polymer binder to be mixed with the plate-like powder is a phenol resin, urea-formaldehyde resin, melamine-formaldehyde resin, polyester resin, Epoxy resin, polyimide resin, etc. are used, and the mixing amount is 3-15 weight%, The transition metal type magnetostrictive composite manufacturing method characterized by the above-mentioned. The method according to claim 1 or 4, wherein the polymer binder is first dissolved in a polar solvent such as methanol, ethanol, THF (tetrahydrofuran), and then mixed with the powder so that the polymer binder is uniformly applied to the surface of the plate-like powder Transition metal-based magnetostrictive composite manufacturing method. The method of claim 1, wherein the molding of the mixture using a press, the molding pressure is a transition metal-based magnetostrictive composite manufacturing method, characterized in that 0.1 to 2.0 GPa. The transition metal-based magnetostriction according to claim 1 or 6, wherein the molding of the mixture is performed without directly applying a magnetic field or applying a magnetic field, and the direction of the applied magnetic field is perpendicular to the pressing direction by a press. Composite manufacturing method. The method of claim 1, wherein the curing of the molded mixture is maintained for several minutes to several tens of minutes at a temperature range of 100 ^° C. to 200 ^° C.