Magnetostrictive member and method of manufacturing the same

Abstract

To easily and securely manufacture a magnetostrictive member with increased parallel magnetostriction and reduced variation in parallel magnetostriction between members.SOLUTION: A manufacturing method for a magnetostrictive member is for manufacturing a magnetostrictive member composed of a crystal of an iron-based alloy having magnetostrictive properties and having a shape having a longitudinal direction and a shortitudinal direction. The manufacturing method for a magnetostrictive member includes measuring the parallel and perpendicular magnetostrictive quantities on one surface of the crystal, and cutting the crystal such that the direction in which the measured parallel and perpendicular magnetostrictive quantities become larger is the longitudinal direction of the magnetostrictive member.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a magnetostrictive member and a method for manufacturing a magnetostrictive member. [Background technology]

[0002] Magnetostrictive materials have been attracting attention as functional materials. For example, Fe-Ga alloys, which are iron-based alloys, exhibit magnetostrictive and inverse magnetostrictive effects, exhibiting large magnetostriction of approximately 100 to 350 ppm. Therefore, in recent years, they have attracted attention as vibration-powered energy harvesting materials in the energy harvesting field, and are expected to be applied to wearable devices, sensors, and the like. A single crystal growth method using the Czochralski method (hereinafter abbreviated as the "Cz method") is known as a method for producing Fe-Ga alloy single crystals (e.g., Patent Document 1). Other known production methods besides the Cz method include the vertical Bridgman method (VB method) and the vertical gradient freezing method (VGF method) (e.g., Patent Documents 2 and 3).

[0003] Fe-Ga alloys are crystalline <100> The magnetostrictive material has an easy axis of magnetization in the direction of the Fe-Ga alloy, and can exhibit large magnetostriction in this direction. <100> Magnetostrictive materials are manufactured by cutting a single crystal portion oriented in a certain direction to the desired size (for example, Non-Patent Document 1). However, since the crystal orientation has a large effect on the magnetostrictive properties, the direction in which the magnetostriction of the magnetostrictive material is required and the direction in which the magnetostriction of the crystal is greatest are also important. <100> It is believed that single crystals with the same orientation are the best material for magnetostrictive members (magnetostrictive elements).

[0004] Fe-Ga alloy single crystals are <100> When a magnetic field is applied parallel to the direction, positive magnetostriction appears (hereinafter referred to as "parallel magnetostriction"). <100> When a magnetic field is applied perpendicular to the orientation, negative magnetostriction appears (hereinafter referred to as "perpendicular magnetostriction"). When the strength of the applied magnetic field is gradually increased, the parallel magnetostriction or perpendicular magnetostriction saturates. The magnetostriction constant (3 / 2λ 100) is determined by the difference between the saturated parallel magnetostriction amount and the saturated perpendicular magnetostriction amount, and is calculated by the following formula (1) (for example, Patent Document 4, Non-Patent Document 2).

[0005] 3 / 2λ 100 =ε( / / )― ε(⊥) ···Equation (1) 3 / 2λ 100 : Magnetostriction constant ε( / / ): <100> Parallel magnetostriction when saturated by applying a magnetic field parallel to the direction ε(⊥): <100> Amount of perpendicular magnetostriction when saturated by applying a magnetic field perpendicular to the direction

[0006] The magnetostrictive properties of Fe-Ga alloys are believed to affect the magnetostrictive and inverse magnetostrictive effects and the characteristics of magnetostrictive vibration power generation devices, and are an important parameter in device design (e.g., Non-Patent Document 4). In particular, the magnetostrictive constant depends on the Ga composition of the Fe-Ga alloy single crystal, and it is known that the magnetostrictive constant is maximized at Ga compositions of 18-19 at% and 27-28 at% (e.g., Non-Patent Document 2). It is considered desirable to use Fe-Ga alloys with such Ga concentrations in devices. Furthermore, in recent years, it has been reported that in addition to a large magnetostrictive constant, the greater the parallel magnetostriction, the better the device characteristics, such as output voltage, tend to be (e.g., Non-Patent Document 3).

[0007] A magnetostrictive vibration power generation device is composed of, for example, an Fe-Ga magnetostrictive member wound around a coil, a yoke, and a permanent magnet for the field magnet (for example, Patent Document 5 and Non-Patent Document 4). In this magnetostrictive vibration power generation device, when the yoke, which is the moving part of the device, is vibrated, the Fe-Ga magnetostrictive member fixed to the center of the yoke vibrates in conjunction with it, and the inverse magnetostrictive effect changes the magnetic flux density of the coil wound around the Fe-Ga magnetostrictive member, generating an electromagnetically induced electromotive force and generating electricity. In a magnetostrictive vibration power generation device, a force is applied in the longitudinal direction of the yoke, causing vibration, so the Fe-Ga magnetostrictive member used in the device must be aligned along the easy axis of magnetization. <100> It is desirable to process it so that the direction of the arrow is in the longitudinal direction. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2016-28831 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-138028 [Patent Document 3] Japanese Patent Application Publication No. 4-108699 [Patent Document 4] Special Publication No. 2015-517024 [Patent Document 5] International Publication No. 2011 / 158473 [Patent Document 6] Patent Publication No. 2021-088471 [Patent Document 7] Japanese Patent Publication No. 2020-136594 [Non-patent literature]

[0009] [Non-Patent Document 1] Etrema, State of the Art of Galfenol Processing. [Non-patent document 2] AE Clark et al., Appl. Phys. 93(2003)8621. [Non-patent document 3] Jung Jin Park, Suok-Min Na, Ganesh Raghunath, and Alison B. Flatau., AIP ADVANCES 6, 056221(2016). [Non-patent document 4] Toshiyuki Ueno, Journal of the Japan Society for Precision Engineering, Vol. 79, No. 4, (2013) 305-308. Summary of the Invention [Problem to be solved by the invention]

[0010] Since the device characteristics of magnetostrictive vibration power generation devices are affected by the magnetostrictive properties of the magnetostrictive member, the magnetostrictive member is required to have high magnetostrictive properties and little variation in the magnetostrictive properties. <100> It was thought that if the Ga concentration was uniform, a magnetostrictive member with a uniform magnetostriction constant would be obtained. However, as described in Non-Patent Document 3, it has been disclosed that device characteristics are affected not only by the magnetostriction constant but also by the parallel magnetostriction. As a result of the inventor's investigation, it was found that magnetostrictive members manufactured as described above have variations in the parallel magnetostriction (or perpendicular magnetostriction) even if the magnetostriction constant is uniform. This is thought to be due to variations in the magnetostriction (or magnetic domain structure) of the members cut out from the grown single crystal. Patent Document 6 describes a method in which both sides of a flat plate cut out from a single crystal are mirror-polished, the magnetic domain structure is observed using the Bitter method, and the position and direction for cutting out members from the flat plate are determined. Patent Document 7 describes a method in which the magnetic domain structure is observed using the KeRR method and then members are cut out.

[0011] However, in the above-mentioned methods such as the Bitter method and the KeRR method, the surface of the component must be mirror-finished in order to observe the magnetic domain structure, which requires a lot of man-hours. Furthermore, depending on the processing method of the component surface, residual stress may be applied to the component surface, resulting in a magnetic domain structure different from the observed magnetic domain structure, and the desired magnetostriction characteristics may not be obtained. Therefore, wire electrical discharge machining, which is said to have no effect on the magnetic domain structure, has often been used for processing the component surface.

[0012] Therefore, an object of the present invention is to provide a magnet that has a high parallel magnetostriction amount, has little variation in the parallel magnetostriction amount between members, and is easily and reliably manufactured. [Means for solving the problem]

[0013] According to an aspect of the present invention, there is provided a method for manufacturing a magnetostrictive member made of a crystal of an iron-based alloy having magnetostrictive properties and having a shape with a longitudinal direction and a lateral direction, the method comprising: measuring the parallel magnetostriction and the perpendicular magnetostriction on one face of the crystal; and cutting the crystal so that the direction in which the measured parallel magnetostriction and the perpendicular magnetostriction are larger is parallel to the longitudinal direction of the magnetostrictive member.

[0014] In the manufacturing method of a magnetostrictive member according to this aspect of the present invention, measuring the magnetostriction may include measuring the magnetostriction of one surface of a flat, thin plate member obtained by cutting the crystal. The crystal may be a single crystal, and the surface of the single crystal from which the magnetostriction is measured may have an in-plane crystal orientation of {100}. The surface of the magnetostrictive member may be the same machined surface as the surface from which the magnetostriction is measured. The surface of the crystal from which the magnetostriction is measured may be a wire-electric discharge machined surface or a wire-saw machined surface. The iron-based alloy crystal may be an Fe-Ga alloy. The magnetostrictive member may have a longitudinal parallel magnetostriction of 200 ppm or more.

[0015] Furthermore, according to an aspect of the present invention, there is provided a magnetostrictive member cut into a shape having a longitudinal direction and a lateral direction from a thin plate member made of crystals of an iron-based alloy having magnetostrictive properties, wherein the longitudinal direction of the magnetostrictive member is the direction in which the magnetostriction amount is greater than the parallel magnetostriction amount and the perpendicular magnetostriction amount measured in the thin plate member.

[0016] Furthermore, according to an aspect of the present invention, there is provided a magnetostrictive member which is made of crystals of an iron-based alloy having magnetostrictive properties and has a shape having a longitudinal direction and a lateral direction, and on one surface of the magnetostrictive member, the ratio of parallel magnetostriction (ppm) in the longitudinal direction to perpendicular magnetostriction (ppm) is 3.0 or more.

[0017] The iron-based alloy crystal may be a single crystal of an Fe--Ga alloy, and the crystal orientation of the surface of the magnetostrictive member may be {100}. [Effects of the Invention]

[0018] The method for manufacturing a magnetostrictive member according to an aspect of the present invention allows for easy and reliable manufacturing of a magnetostrictive member with a high parallel magnetostriction and little variation in the parallel magnetostriction between members. The magnetostrictive member according to an aspect of the present invention has a high parallel magnetostriction and little variation in the parallel magnetostriction between members. [Brief explanation of the drawings]

[0019] [Figure 1] 3 is a flowchart showing an example of a method for manufacturing a magnetostrictive member according to an embodiment. [Figure 2] 1A and 1B are diagrams illustrating examples of a single crystal ingot and a thin plate member. [Figure 3] 1A and 1B are diagrams showing an example of a magnetostrictive member according to an embodiment. [Figure 4] FIG. 2 is a diagram showing measurement positions of parallel magnetostriction and perpendicular magnetostriction in a thin plate member in an example and a comparative example. [Figure 5] FIG. 1 is a diagram showing the strain gauge method used in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0020] The following description will be made with reference to the drawings. In each drawing, some or all of the components are shown in schematic form and scaled as appropriate.

[0021] [Embodiment] The magnetostrictive member and the manufacturing method of the magnetostrictive member of this embodiment will be described below. Fig. 1 is a flowchart showing an example of the manufacturing method of the magnetostrictive member of this embodiment. Fig. 2 is a diagram showing an example of a single crystal ingot and a thin plate member. Fig. 2 is a diagram showing an example of the magnetostrictive member of this embodiment. The manufacturing method of the magnetostrictive member of this embodiment includes a crystal preparation step (step S1), a crystal cutting step (step S2), a magnetostriction amount measurement step (step S3), and a cutting step (step S4).

[0022] The magnetic domain structure will be explained. As mentioned above, the inventors have determined that the principal plane is the {100} plane and the direction of easy magnetization is <100> We fabricated plate-shaped magnetostrictive members that were rectangular in plan view, with the direction parallel to the longitudinal direction of the magnetostrictive member. We examined the magnetostrictive properties of several magnetostrictive members cut from single crystals of an Fe-Ga alloy with a uniform Ga concentration. We found that there was little variation in the magnetostriction constant, but some variation in the parallel magnetostriction. In particular, we found that the parallel magnetostriction varied depending on the position at which the magnetostrictive member was cut from the single crystal. It is known that this variation in parallel magnetostriction is influenced by the magnetic domain structure. Patent Documents 6 and 7 describe methods for mirror-finishing both sides of a flat plate cut from a single crystal, observing the magnetic domain structure using the Bitter method or the KeRR method, and then cutting out the member.

[0023] The magnetic domain structure can be obtained, for example, using the Bitter method. The Bitter method is a method for observing the magnetic domain structure (magnetic domains) using magnetic colloid particles. Thin plates cut from single crystal ingots, which are used as materials for magnetostrictive members, have variations in their magnetic domain structure.

[0024] However, in the Bitter and Kerr methods, the surface of the component must be mirror-finished to observe the magnetic domain structure, which requires a lot of labor (effort). Furthermore, depending on the method used to process the component surface, residual stress may be applied to the component surface, resulting in a magnetic domain structure different from the observed magnetic domain structure, making it impossible to obtain the desired magnetostriction characteristics. Therefore, in this invention, we have investigated a method that can simply measure magnetostriction without observing the magnetic domains, and as a result, we have arrived at the present invention.

[0025] In the manufacturing method of the magnetostrictive member of this embodiment, first, in the crystal preparation step (step S1), a crystal of an iron-based alloy having magnetostrictive properties is prepared. The crystal used in the manufacturing method of the magnetostrictive member of this embodiment and in the magnetostrictive member of this embodiment may be a single crystal or a polycrystal. In order to increase the orientation concentration of the magnetization easy direction of the magnetostrictive member and improve its properties as a magnetostrictive material, it is preferable to use a single crystal rather than a polycrystal. Although polycrystals have inferior magnetostrictive properties compared to single crystals, they can be produced at low cost, so polycrystals may also be used. The iron-based alloy is not particularly limited as long as it has magnetostrictive properties. Magnetostrictive properties refer to the property of changing shape when a magnetic field is applied. Examples of iron-based alloys include alloys such as Fe-Ga, Fe-Ni, Fe-Al, Fe-Co, Tb-Fe, Tb-Dy-Fe, Sm-Fe, and Pd-Fe. Among these iron-based alloys, Fe-Ga alloys have greater magnetostriction properties and are easier to process than other alloys, and are therefore applied to vibration power generation materials in the energy harvesting field, wearable devices, sensors, etc. In the following explanation, as an example of a magnetostrictive member, an example of a configuration in which the magnetostrictive member is made of a single crystal of an Fe-Ga alloy will be described, but this is just one example, and the crystal of this embodiment is not limited to this example.

[0026] The single crystal of the Fe-Ga alloy has a body-centered cubic lattice structure, and the first to third directional indices in the Miller indices <100> The basis is that the axes (see Figure 2) are equivalent, and the first to third {100} planes (see Figure 2) among the plane indices in the Miller index are equivalent (i.e., (100), (010), and (001) are equivalent). Furthermore, Fe-Ga alloys have the property of producing large magnetostriction in a specific orientation of the crystal. When this property is utilized in a magnetostrictive vibration power generation device, it is desirable to match the direction in the device where magnetostriction of the magnetostrictive member is required with the orientation (direction) where the magnetostriction of the crystal is at its maximum. Specifically, as mentioned above, the direction of easy magnetization in a single crystal is <100> It is desirable to set the direction of magnetostriction in the longitudinal direction of the magnetostrictive member from the viewpoint of magnetostriction characteristics. Also, it is desirable to set the crystal orientation of the surface of the magnetostrictive member to {100} from the viewpoint of magnetostriction characteristics. <100> The direction of the magnetostrictive member can be set to the longitudinal direction of the magnetostrictive member, and the crystal orientation of the surface of the magnetostrictive member can be set to {100}, for example, by obtaining the crystal orientation of the single crystal using known crystal orientation analysis, and cutting the single crystal based on the obtained crystal orientation of the single crystal.

[0027] The prepared crystal may be grown or commercially available. For example, in the crystal preparation step, a single crystal of an Fe-Ga alloy is prepared. The method for growing the single crystal of an Fe-Ga alloy is not particularly limited. The method for growing the single crystal of an Fe-Ga alloy may be, for example, a pulling method or a unidirectional solidification method. For example, the Cz method may be used as the pulling method, and the VB method, VGF method, and micro-pulling down method may be used as the unidirectional solidification method.

[0028] The magnetostriction constant of the Fe—Ga alloy single crystal is maximized by adjusting the gallium content to 18.5 at% or 27.5 at%. Therefore, it is preferable that the Fe—Ga alloy single crystal is grown so that the gallium content is 16.0 to 20.0 at% or 25.0 to 29.0 at%, preferably 17.0 to 19 at% or 26.0 to 28.0 at%. The shape of the grown single crystal is not particularly limited, and may be, for example, cylindrical or rectangular prism. The grown single crystal may be cut into a cylindrical single crystal as needed by cutting the seed crystal, the diameter-increasing portion, or the shoulder portion (the portion that increases from the seed crystal to the diameter of the specified single crystal) with a cutting device. The size of the grown single crystal is not particularly limited as long as it is large enough to secure the magnetostrictive member. When growing an Fe—Ga alloy single crystal, the direction of the growth axis of the single crystal is <100> The seed crystal is grown using a seed crystal whose top or bottom surface is machined to a {100} plane so that the Fe-Ga alloy single crystal grows in a direction perpendicular to the top or bottom surface of the seed crystal, and inherits the orientation of the seed crystal.

[0029] Following the crystal preparation step (step S1), a crystal cutting step (step S2) is carried out. The crystal cutting step is a step of cutting a crystal to create a thin plate member. The thin plate member obtained by cutting the crystal is a member that will be the material for the magnetostrictive member of this embodiment. The crystal cutting step is, for example, a step of cutting a single crystal of an Fe-Ga alloy having magnetostrictive properties using a cutting device to create a thin plate member with a {100} plane as the main surface. The cutting device may be a wire electric discharge machine, an inner diameter blade cutting device, a wire saw, or other cutting device. Among these, the crystal cutting step is preferably wire electric discharge machining or wire saw machining. When a multi-wire saw is used, it is preferable because it can cut multiple thin plate members at the same time. The thin plate member is preferably flat. In the case of a single crystal of an Fe-Ga alloy, the cutting direction of the crystal is as follows: <100> From the viewpoint of improving magnetostriction characteristics, it is preferable to cut the thin plate member so that the cut surface, i.e., the main surface, is a {100} plane. The cutting direction of the crystal may be perpendicular or parallel to the growth direction of the single crystal (the direction in which the crystal is grown), as shown in Fig. 2, for example, but it is preferable to cut the single crystal parallel to the growth direction (the direction in which the crystal is grown).

[0030] Following the crystal cutting step (step S2), a magnetostriction measurement step (step S3) is performed. The magnetostriction measurement step is a step of measuring the magnetostriction on one surface of a thin plate member (crystal). The magnetostriction measurement step can be performed, for example, using a strain gauge method. Measurement using the strain gauge method involves attaching a strain gauge to the thin plate member. This method allows the strain gauge to be attached directly to the processed surface of the thin plate member. Therefore, mirror finishing is not required to observe the measurement surface, as in Patent Documents 6 and 7, and measurements can be performed efficiently without the need for processing the measurement surface. Furthermore, the measurements in Patent Documents 6 and 7 involve observing magnetic domains on the mirror-finished surface of the member, which differs from the processed surface of the magnetostrictive member actually used. Depending on the surface processing method, residual stress may be applied to the surface of the magnetostrictive member, resulting in a magnetic domain structure different from the observed magnetic domain structure, and the desired magnetostriction characteristics may not be obtained. In this embodiment, the surface on which the magnetostriction is measured on the thin plate member is the same as the surface that will become the magnetostrictive member, thereby improving reliability. The measurement method using the strain gauge method will be described in detail later.

[0031] In this embodiment, the magnetostriction is measured as a parallel magnetostriction or a perpendicular magnetostriction. <100> As described above, the thin plate member is preferably cut so that the main surface of the thin plate member is the {100} plane, and the magnetostriction is preferably measured in a direction perpendicular or parallel to the single crystal growth direction (the direction in which the crystal is grown).

[0032] For example, as shown in Figures 2(a) and 2(b), when measuring the magnetostriction of a thin plate member obtained by cutting a grown single crystal in a direction parallel to the crystal growth direction, the magnetostriction in the crystal growth direction may be taken as the parallel magnetostriction. The magnetostriction of a thin plate member is preferably measured at multiple locations within the plane. For a thin plate member such as that shown in Figures 2(a) and 2(b), it is preferable to measure in a matrix at predetermined intervals in the direction perpendicular to the crystal growth direction and in the growth direction, as this allows for understanding the magnetostriction status of the entire thin plate member. The interval at which magnetostriction is measured is not particularly limited. For example, it is preferable to measure magnetostriction at intervals of 5 mm to 30 mm. Because magnetostriction measurements vary significantly, particularly in the growth direction, it is preferable to measure at intervals narrower in the growth direction than in other directions. Note that parallel magnetostriction and perpendicular magnetostriction are generally correlated; when parallel magnetostriction is low, perpendicular magnetostriction is high, and when parallel magnetostriction is high, parallel magnetostriction is low.

[0033] Table 1 shows an example (Example) of the results of measuring the magnetostriction of the thin plate member shown in FIG. 2. The direction of parallel magnetostriction was the crystal growth direction. In Table 1 shown later, the parallel magnetostriction was high and stable in the regions of measurement positions 1 to 6. On the other hand, the parallel magnetostriction was low and stable in the regions of measurement positions 7 to 14. Although not shown in Table 1, variations in the parallel magnetostriction were also observed in the middle or on the left and right sides of the thin plate member. In this example, the parallel magnetostriction was high or low and stable in the regions of measurement positions 1 to 14, and it is preferable to use these regions as magnetostrictive members. The parallel magnetostriction and perpendicular magnetostriction are generally correlated; when the parallel magnetostriction is low, the perpendicular magnetostriction is high, and when the parallel magnetostriction is high, the parallel magnetostriction is low. In the regions of measurement positions 7 to 14, the parallel magnetostriction was low and stable, which means that the perpendicular magnetostriction was high and stable.

[0034] The magnetostriction measurement process allows accurate understanding of the magnetostriction state throughout the entire thin plate member. While magnetostriction measurements may be performed on both sides of the thin plate member, because the thickness of the thin plate member is thin and nearly identical on both sides, measuring only one of the front and back sides of the thin plate member allows for sufficient understanding of the magnetostriction of the thin plate member. The magnetostriction characteristics of a thin plate member tend to exhibit similar trends in adjacent portions of the thin plate member. Due to this tendency, magnetostriction measurements may be performed on each consecutively cut thin plate member. Alternatively, magnetostriction measurements may be performed on multiple thin plate members selected from multiple different positions on the crystal, and the magnetostriction distribution of the entire crystal may be predicted from the results. For example, when a crystal (crystal ingot) is made into multiple thin plate members, the magnetostriction of sampled thin plate members at predetermined intervals may be measured, and the magnetostriction distribution of the entire crystal may be predicted from the results. Furthermore, magnetostriction may be measured on one surface of the crystal, rather than on the thin plate members. For example, if the magnetostrictive member is not plate-shaped but rectangular, it is possible to measure the magnetostriction of one surface of the single crystal and determine the area from which to cut out the rectangular magnetostrictive member. It is preferable that the surface of the crystal (thin plate member) whose magnetostriction is measured in the magnetostriction measurement step is non-mirror-finished (a surface other than a mirror-finished surface), and more preferably a cut-machined surface such as a wire-electric discharge machined surface or a wire-saw machined surface. It is also preferable that the surface whose magnetostriction is measured in the magnetostriction measurement step and the surface of the magnetostrictive member are the same machined surface. This eliminates the need for mirror-finishing, which is required in the magnetic domain observation method described above.

[0035] Following the magnetostriction amount measuring step (step S3), a cutting step (step S4) is carried out. The cutting step is a step in which the thin plate member is cut to obtain the magnetostrictive member of this embodiment. The cutting step is carried out using, for example, a cutting device. The cutting device is not particularly limited, and for example, a peripheral blade cutting device, a wire electric discharge machine, a wire saw, etc. can be used.

[0036] As mentioned above, in the cutting process, the direction in which the magnetostrictive member is extracted becomes important based on the results of measuring the magnetostriction of the thin plate member (crystal). In the cutting process, the magnetostrictive member is cut out from the thin plate member so that the direction with the larger parallel or perpendicular magnetostriction is the longitudinal direction of the magnetostrictive member based on the results of measuring the magnetostriction in the magnetostriction measurement process. In this specification, "so that the X direction is the longitudinal direction" means "so that the X direction is parallel to the longitudinal direction and forms an angle of less than 20 degrees with the longitudinal direction."

[0037] Furthermore, it is preferable that the surface of the magnetostrictive member obtained by the cutting process is the same processed surface as the surface on which the magnetostriction was measured. This ensures that the magnetostriction measured in the magnetostriction measurement process is more reliably reflected in the magnetostrictive member after cutting. In the cutting process, it is more preferable to sample the magnetostrictive member from a region of the thin plate member where the parallel magnetostriction or perpendicular magnetostriction is stable as a result of measuring the magnetostriction in the magnetostriction measurement process. By sampling the magnetostrictive member from such a region of the thin plate member, it is possible to obtain a magnetostrictive member with a high parallel magnetostriction in the longitudinal direction and little variation between members.

[0038] In the cutting process, it is preferable from the viewpoint of magnetostriction characteristics to cut the thin plate member so that the longitudinal direction of the magnetostrictive member is parallel to the axis of easy magnetization. The shape of the magnetostrictive member obtained by the cutting process is not particularly limited as long as it does not deviate from the spirit of the present invention, and for example, it may be rectangular or square in plan view, or the overall shape may be plate-like, cylindrical, or amorphous. From the viewpoint of magnetostriction characteristics, it is preferable that the shape of the magnetostrictive member is plate-like, which is rectangular in plan view. Furthermore, the size of the magnetostrictive member obtained by the cutting process is not particularly limited as long as it does not deviate from the spirit of the present invention.

[0039] Next, the magnetostrictive member of this embodiment will be described. The magnetostrictive member of this embodiment can be obtained by the manufacturing method of the magnetostrictive member of this embodiment described above. Fig. 3 is a diagram showing an example of the magnetostrictive member of this embodiment. Note that the magnetostrictive member of this embodiment and the manufacturing method of the magnetostrictive member described above are subject to the applicable configurations described in this specification.

[0040] As shown in FIG. 3, the magnetostrictive member 1 of this embodiment is made of iron-based alloy crystals having magnetostrictive properties and is cut out from a thin plate member into a shape having a longitudinal direction D1 and a transverse direction D2, and the direction in which the magnetostriction increases in the thin plate member is the longitudinal direction D1 of the magnetostrictive member. Furthermore, the magnetostrictive member 1 of this embodiment is made of iron-based alloy crystals having magnetostrictive properties and is a magnetostrictive member having a shape having a longitudinal direction D1 and a transverse direction D2, and on one surface of the magnetostrictive member, the parallel magnetostriction and perpendicular magnetostriction in the longitudinal direction D1 are preferably such that the value of "parallel magnetostriction in the longitudinal direction (ppm) / perpendicular magnetostriction (ppm)" is larger, but is preferably 3.0 or more, more preferably 5.0 or more, and even more preferably 7.0 or more. As shown in the examples, the manufacturing method of this embodiment makes it possible to manufacture a magnetostrictive member whose "parallel magnetostriction in the longitudinal direction (ppm) / perpendicular magnetostriction (ppm)" satisfies the above range.

[0041] The shape of the magnetostrictive member 1 is, for example, as shown in FIG. 3, a plate-like body having a longitudinal direction D1 and a lateral direction D2. The plate-like body is, for example, rectangular in plan view. The plate-like body has a front surface (front face) 2 and a back surface 3. The front surface 2 and the back surface 3 are preferably parallel to each other, but do not have to be parallel to each other. As will be explained later, the magnetostrictive member 1 may not be plate-shaped, but may be a rod-like body such as a rectangular parallelepiped or a cylinder having a longitudinal direction D1 and a lateral direction D2. An example of a plate-like body will be explained in FIG. 3 etc.

[0042] Magnetostrictive members 1 are used, for example, as materials (components) for vibration power generation devices in the energy harvesting field, as well as for wearable devices and sensors. For example, a magnetostrictive vibration power generation device such as that shown in Patent Document 5 above is composed of a coil, a magnetostrictive member made of an Fe-Ga alloy wound around the coil, a yoke, and a permanent magnet for a field magnet. When the yoke, which is the moving part of the device, is vibrated, the magnetostrictive member fixed to the center of the yoke vibrates in conjunction with the yoke. The inverse magnetostrictive effect changes the magnetic flux density of the coil wound around the magnetostrictive member, generating electromagnetically induced electromotive force, thereby generating electricity. When used in such a mechanism, the magnetostrictive member 1 is preferably thin and rectangular in plan view. The shape and size of the magnetostrictive member 1 are appropriately determined depending on the size of the intended device. For example, the size of the magnetostrictive member 1 is 16 mm in length (dimension) in the longitudinal direction D1, 4 mm in width (dimension) in the transverse direction D2, and 0.5 mm in thickness.

[0043] The shape and dimensions of the magnetostrictive member 1 are not particularly limited. For example, the magnetostrictive member 1 does not have to be rectangular in plan view; for example, the shape of the magnetostrictive member 1 may be square, elliptical, track-shaped, or irregular in plan view. The shape of the magnetostrictive member 1 is not limited to a plate-like body, and may be, for example, cylindrical. Note that, when the shape of the magnetostrictive member 1 is square in plan view, the longitudinal direction D1 and the lateral direction D2 may be the same. Note that, when the shape of the magnetostrictive member 1 is other than rectangular in plan view, the longitudinal direction D1 is the major axis direction, the major axis direction, etc., and the lateral direction D2 is the direction perpendicular to the longitudinal direction D1. The shape and dimensions of the magnetostrictive member 1 can be set appropriately depending on the shape of the thin plate member and the cutting process.

[0044] Furthermore, the higher the parallel magnetostriction amount in the longitudinal direction D1 of the magnetostrictive member 1, the more preferable, but in the magnetostrictive member 1 of this embodiment, the parallel magnetostriction amount in the longitudinal direction D1 can be made high, for example, as shown in the examples, 200 ppm or more, more preferably 250 ppm or more, and more preferably 270 ppm or more. Furthermore, the lower the perpendicular magnetostriction amount to the longitudinal direction of the magnetostrictive member 1, the more preferable, but for example, as shown in the examples, it can be made 100 ppm or less, more preferably 70 ppm or less, more preferably 50 ppm or less, and more preferably 40 ppm or less.

[0045] Furthermore, it is preferable that the surface of the magnetostrictive member 1 is the same processed surface as the surface (the surface of the thin plate member) whose magnetostriction is measured in the magnetostriction measurement step. It is preferable that the surface of the magnetostrictive member 1 is a non-mirror surface. This eliminates the need for mirror finishing required in the magnetic domain observation method described above.

[0046] As described above, the manufacturing method of a magnetostrictive member of this embodiment is a manufacturing method of a magnetostrictive member made of a crystal of an iron-based alloy having magnetostrictive properties and having a shape with a longitudinal direction and a lateral direction. The method includes measuring the parallel magnetostriction and the perpendicular magnetostriction on one face of the crystal, and cutting the crystal so that the direction in which the measured parallel magnetostriction and the perpendicular magnetostriction are larger is the longitudinal direction of the magnetostrictive member. Note that in the manufacturing method of a magnetostrictive member of this embodiment, any configuration other than that described above is optional. The manufacturing method of a magnetostrictive member of this embodiment can easily and reliably manufacture a magnetostrictive member having a high parallel magnetostriction and little variation in parallel magnetostriction between members. In the manufacturing method of this embodiment, magnetostriction is measured by directly attaching a strain gauge to the machined surface of a thin plate member. Therefore, unlike Patent Documents 6 and 7, there is no need to mirror-finish the measurement surface to observe it, and magnetostriction can be measured efficiently because there is no need to machine the measurement surface. Furthermore, the measurement in Patent Document 7 involves observing the magnetic domains after mirror-finishing the member surface, which differs from the machined surface of the magnetostrictive member actually used. Depending on the surface processing method, magnetostrictive members may have residual stress on the member surface, resulting in a magnetic domain structure different from the one observed above, and the desired magnetostrictive characteristics may not be obtained. In this embodiment, the surface of the thin plate member on which the magnetostriction amount is measured can be the same as the surface that becomes the magnetostrictive member, thereby improving reliability.

[0047] The magnetostrictive member of this embodiment is a magnetostrictive member cut into a shape having a longitudinal direction and a lateral direction from a thin plate member made of crystals of an iron-based alloy having magnetostrictive properties, and the longitudinal direction of the magnetostrictive member is the direction in which the magnetostriction is larger among the parallel magnetostriction and perpendicular magnetostriction measured in the thin plate member. The magnetostrictive member of this embodiment is a magnetostrictive member made of crystals of an iron-based alloy having magnetostrictive properties and has a shape having a longitudinal direction and a lateral direction, and on one surface of the magnetostrictive member, the parallel magnetostriction (ppm) in the longitudinal direction / perpendicular magnetostriction (ppm) is 3.0 or more. Note that the configuration of the magnetostrictive member of this embodiment other than the above is optional. The magnetostrictive member of this embodiment has a high parallel magnetostriction and little variation in parallel magnetostriction between members. The magnetostrictive member of this embodiment can be easily and reliably manufactured by the manufacturing method of the magnetostrictive member of this embodiment. [Example]

[0048] The present invention will be specifically explained below using examples, but the present invention is not limited to these examples.

[0049] [Examples and Comparative Examples] The raw materials were prepared with a stoichiometric ratio of iron to gallium of 81:19, and a cylindrical Fe-Ga alloy single crystal ingot was prepared by growing it using the vertical Bridgman (VB) method. The growth axis of the single crystal was <100> The orientation of the {100} plane on the top or bottom surface of the single crystal, which was perpendicular to the crystal growth axis, was confirmed by X-ray diffraction. At this time, measurements of the top and bottom surface samples of the crystal using a Shimadzu sequential plasma emission spectrometer (ICPS-8100) revealed that the gallium content of the single crystal was 17.5 to 19.0 at%.

[0050] A magnetostrictive member was manufactured from the grown single crystal as follows. First, a wire saw with a free abrasive grain type was used to cut the single crystal in a direction parallel to the direction of growth ( <100> The single crystal was cut in a direction parallel to the {100} crystal orientation to produce thin plate members with a cut surface, i.e., a main surface, of {100}, as shown in Figure 2(a). The size of the thin plate members was 60 mm in length (growth direction), 45 mm in width, and 0.5 mm in thickness, and multiple pieces were produced.

[0051] Next, two adjacent sheets were taken from the obtained thin plate members, and the parallel and perpendicular magnetostriction amounts were measured. The parallel magnetostriction was measured in the single crystal growth direction.

[0052] As shown in Figure 4, the magnetostriction of the thin plate member was measured at positions in a matrix, with the final growth stage portion being the upper side of the thin plate member, and measurements were taken at positions 5 mm apart from the upper end face of the thin plate member, downward, and 10 mm inward from the left and right end faces in the width direction.

[0053] The magnetostriction properties were measured using a strain gauge method. As shown in Figure 5, a strain gauge (manufactured by Kyowa Electronics Co., Ltd.) was attached with an adhesive to the {100} plane, which is the main surface of the manufactured magnetostrictive member. Since the longitudinal direction of the strain gauge is the direction in which magnetostriction is detected, the longitudinal direction of the strain gauge was aligned with the longitudinal direction of the magnetostrictive member and <100> It was glued so that it was parallel to the direction.

[0054] The magnetostriction measuring device (manufactured by Kyowa Electronics Co., Ltd.) consisted of a neodymium permanent magnet, a bridge box, a compact recording system, a strain unit, and dynamic data acquisition software.

[0055] The amount of magnetostriction was determined by correcting the actual strain detection value with the gauge factor. The gauge factor was determined by the following formula (2). ε=2.00 / Ks × εi...Equation (2) (ε: gauge factor, εi: measured strain value, Ks: gauge factor of the gauge used)

[0056] Furthermore, the amount of magnetostriction when the magnetic field direction is parallel to the longitudinal direction of the strain gauge was defined as the parallel magnetostriction. On the other hand, the amount of magnetostriction when the magnetic field direction is perpendicular to the longitudinal direction of the strain gauge was defined as the perpendicular magnetostriction. The results are shown in Table 1. The magnetostriction constants of the magnetostrictive members of the examples and comparative examples were stable at 250 ppm or more. The parallel magnetostriction and perpendicular magnetostriction varied greatly depending on the position of the thin plate member. The measurements of the thin plate members were performed on two adjacent thin plate members, and the results of one of the two adjacent members were as shown in Table 1, and the results of the other were almost identical to those of Table 1.

[0057] Next, magnetostrictive members were cut out based on the results of the measurements of parallel and perpendicular magnetostriction from the region where the parallel and perpendicular magnetostriction of the thin plate member shown in Table 1 were measured. The size of the cut magnetostrictive member was 16 mm in the longitudinal direction, 4 mm in the lateral direction, and 0.5 mm in thickness. In the example, the thin plate member was cut out using a peripheral blade cutting device so that the larger of the parallel and perpendicular magnetostriction amounts measured was in the longitudinal direction of the magnetostrictive member.

[0058] As a comparative example, a magnetostrictive member was cut out from the region where the parallel and perpendicular magnetostriction were measured on another thin plate member adjacent to the thin plate member used in the examples, so that the larger of the measured parallel and perpendicular magnetostriction amounts was in the transverse direction of the magnetostrictive member based on the measurement results of the parallel and perpendicular magnetostriction amounts. The size of the magnetostrictive member was the same as in the examples, with a longitudinal direction of 16 mm, a transverse direction of 4 mm, and a thickness of 0.5 mm.

[0059] Next, the magnetostriction characteristics of the cut-out magnetostrictive members were measured. The measurement method was the same as that for the thin plate members. The longitudinal direction of the magnetostrictive members was taken as the parallel magnetostriction amount. The results are shown in Table 1. In the examples, it was confirmed that the parallel magnetostriction amount in the longitudinal direction of the magnetostrictive members was stable at 250 ppm or more. In contrast, in the comparative examples, the parallel magnetostriction amount in the longitudinal direction of the magnetostrictive members was 100 ppm or less, indicating that the magnetostriction characteristics were low.

[0060] [Table 1]

[0061] In Table 1, the notation "the cutting direction of the magnetostrictive member is the growth direction" means that the magnetostrictive member was cut out so that its longitudinal direction was the growth direction, and the notation "the cutting direction of the magnetostrictive member is the radial direction" means that the cutting direction of the magnetostrictive member is perpendicular to the growth direction. Also, in Table 1, the notation "measurement position number" of the thin plate member indicates the area in the thin plate member where the magnetostriction was measured and the area from which the magnetostrictive member was cut out, and when the measurement position number is the same (for example, in Example 1 and Comparative Example 1), this means that the area in the thin plate member where the magnetostriction was measured and the area from which the magnetostrictive member was cut out are the same area.

[0062] From the results of the above examples and comparative examples, it is confirmed that the method for manufacturing a magnetostrictive member according to the present invention has a high parallel magnetostriction amount, little variation in the parallel magnetostriction amount between members, and can easily and reliably manufacture magnetostrictive members, and that the magnetostrictive member according to the present invention has a high parallel magnetostriction amount, and little variation in the parallel magnetostriction amount between members. [Explanation of symbols]

[0063] 1. Magnetostrictive member 2...Surface 3...Back side D1: Longitudinal direction D2...Short direction S1: Crystal preparation process S2...Crystal cutting process S3...Magnetostriction measurement process S4...Cutting process

Claims

1. A method for manufacturing a magnetostrictive member made of crystals of an iron-based alloy having magnetostrictive properties and having a shape having a longitudinal direction and a lateral direction, Measuring the parallel magnetostriction and the perpendicular magnetostriction on one surface of a flat thin plate member obtained by cutting the crystal; and obtaining a magnetostrictive member by cutting the thin plate member so that the magnetic field direction during measurement for the measured parallel magnetostriction amount or perpendicular magnetostriction amount that showed the larger magnetostriction amount is the longitudinal direction of the magnetostrictive member to be obtained.

2. 2. The method for manufacturing a magnetostrictive member according to claim 1, wherein the crystal is a single crystal, and the crystal plane on which the magnetostriction is measured has an in-plane crystal orientation of {100}.

3. 3. The method for manufacturing a magnetostrictive member according to claim 1, wherein the surface of the magnetostrictive member is the same processed surface as the surface on which the magnetostriction amount is measured.

4. The method for manufacturing a magnetostrictive member according to any one of claims 1 to 3, wherein the surface of the thin plate member for measuring the amount of magnetostriction is a wire-electric discharge machined surface or a wire-saw machined surface.

5. 5. The method for manufacturing a magnetostrictive member according to claim 1, wherein the iron-based alloy crystal is an Fe--Ga alloy.

6. The method for manufacturing a magnetostrictive member according to claim 1 , wherein the magnetostrictive member has a parallel magnetostriction amount in the longitudinal direction of 200 ppm or more.

7. A plurality of magnetostrictive members formed from the same crystal ingot of an iron-based alloy having magnetostrictive properties. Each magnetostrictive member is a plate having a longitudinal direction and a lateral direction, Both surfaces of each magnetostrictive member are cut surfaces, A magnetostrictive member, wherein the ratio of parallel magnetostriction (ppm) to perpendicular magnetostriction (ppm) in the longitudinal direction on one surface of each magnetostrictive member is 3.0 or more.

8. the iron-based alloy crystal is a single crystal of an Fe—Ga alloy, 8. The magnetostrictive member according to claim 7, wherein the crystal orientation on both surfaces of each of said magnetostrictive members is {100}.

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