Magnetostrictive member and method of manufacturing the same

Abstract

To provide: a magnetostrictive member having a high magnetostrictive constant and parallel magnetostriction, with little variation in the magnetostrictive constant and parallel magnetostriction between members; and a method for producing a magnetostrictive member.SOLUTION: This magnetostrictive member is a plate-shaped body that is composed of crystals of an iron-based alloy having magnetostrictive characteristics and that has front and rear surfaces. In one of the front and rear surfaces, the surface roughness Ra and the thickness of the magnetostrictive member satisfy formula (1). Formula (1): log Ra≥0.48t-0.62 (in formula (1), log represents a common logarithm, Ra represents the surface roughness (μm), and t represents the thickness (mm) 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 a single crystal with the same orientation is the best material for the magnetostrictive member.

[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 (A) (for example, Patent Document 4, Non-Patent Document 2).

[0005] 3 / 2λ 100 =ε( / / )― ε(⊥) ···Formula (A) 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 [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 amount of parallel magnetostriction. As a result of the inventor's investigation, it was found that magnetostrictive members manufactured as described above have variations in the amount of parallel magnetostriction (or the amount of perpendicular magnetostriction) even if the magnetostriction constant is uniform.

[0011] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a magnetostrictive member having a high magnetostriction constant and a high amount of parallel magnetostriction, and having little variation in the magnetostriction constant and amount of parallel magnetostriction between members, and a method for manufacturing the magnetostrictive member. [Means for solving the problem]

[0012] According to one aspect of the present invention, there is provided a magnetostrictive member which is a plate-shaped body made of crystals of an iron-based alloy having magnetostrictive properties, and has a front and back surface, and one of the front and back surfaces has a thickness and a surface roughness Ra of the magnetostrictive member which satisfy the following formula (1): logRa≧0.48t-0.62...Equation (1) (In the above formula (1), log is the common logarithm, Ra is the surface roughness (μm), and t is the thickness (mm) of the magnetostrictive member.)

[0013] Furthermore, according to an embodiment of the present invention, when the thickness of the magnetostrictive member is 0.3 mm or more and 0.75 mm or less, the surface roughness Ra may be 1.0 μm or less, and when the thickness of the magnetostrictive member is more than 0.75 mm, the surface roughness Ra may be 8.6 μm or less.

[0014] Furthermore, when the thickness of the magnetostrictive member is more than 0.3 mm and not more than 0.75 mm, the surface roughness Ra may be 0.5 μm or more; when the thickness of the magnetostrictive member is more than 0.75 mm and not more than 1.0 mm, the surface roughness Ra may be 1.0 μm or more; when the thickness of the magnetostrictive member is more than 1.0 mm and not more than 1.5 mm, the surface roughness Ra may be 1.3 μm or more; when the thickness of the magnetostrictive member is more than 1.5 mm and not more than 2.0 mm, the surface roughness Ra may be 2.5 μm or more; and when the thickness of the magnetostrictive member is more than 2.0 mm and not more than 2.5 mm, the surface roughness Ra may be 4.0 μm or more.

[0015] In addition, when the thickness of the magnetostrictive member is 0.5 mm or more and 0.75 mm or less, the thickness and surface roughness Ra of the magnetostrictive member satisfy the following formula (2): When the thickness of the magnetostrictive member is more than 0.75 mm and not more than 1.0 mm, the thickness and surface roughness Ra of the magnetostrictive member satisfy the following formula (3): The thickness of the magnetostrictive material is over 1.0 mm 1.5 In the case where the thickness is equal to or less than mm, the thickness and surface roughness Ra of the magnetostrictive member may satisfy the following formula (4). logRa≦0.92t-0.45...Equation (2) logRa≦1.48t-1.01...Equation (3) logRa≦0.40t-0.20...Equation (4) (In the above formulas (2) to (4), log represents the common logarithm, Ra represents the surface roughness Ra (μm), and t represents the thickness (mm) of the magnetostrictive member.)

[0016] The magnetostrictive member may have a ratio of parallel magnetostriction to magnetostriction constant of 80% or more. The magnetostrictive constant may be 250 ppm or more, and the parallel magnetostriction may be 250 ppm or more. The iron-based alloy may be an Fe—Ga alloy single crystal. The magnetostrictive member may have a thickness of 0.3 mm or more and 2.5 mm or less.

[0017] Furthermore, according to an aspect of the present invention, there is provided a method for manufacturing a magnetostrictive member, which is a plate-shaped body having a front and back surface and made of crystals of an iron-based alloy having magnetostrictive properties, and at least one of the front and back surfaces is processed so that the thickness and surface roughness Ra of the magnetostrictive member satisfy the following formula (1). logRa≧0.48t-0.62...Equation (1) (In the above formula (1), log is the common logarithm, Ra is the surface roughness (μm), and t is the thickness (mm) of the magnetostrictive member.)

[0018] According to another aspect of the present invention, the processing may be a grinding process. The grinding process may be a surface grinding process. The surface grinding process may be performed using a grinding stone of #40 or more and #500 or less, and may include selecting a grinding stone with a size that satisfies the formula (1) between the thickness and surface roughness Ra of the magnetostrictive member. The processing may also include processing the magnetostriction constant to be 250 ppm or more and the parallel magnetostriction to be 250 ppm or more. [Effects of the Invention]

[0019] The magnetostrictive member of the present invention has the characteristics of a high magnetostriction constant and a high parallel magnetostriction amount, and small variations in the magnetostriction constant and the parallel magnetostriction amount between members. The method for manufacturing a magnetostrictive member of the present invention can easily manufacture a magnetostrictive member having a high magnetostriction constant and a high parallel magnetostriction amount, and small variations in the magnetostriction constant and the parallel magnetostriction amount between members.

[0020] Furthermore, by setting the surface roughness of the magnetostrictive member in a predetermined direction within a predetermined appropriate range relative to the plate thickness of the magnetostrictive member, it is possible to achieve a high level of stable improvement in the magnetostriction constant and parallel magnetostriction amount. [Brief explanation of the drawings]

[0021] [Figure 1] 1A and 1B are diagrams showing an example of a magnetostrictive member according to an embodiment. [Figure 2] 3 is a flowchart showing an example of a method for manufacturing a magnetostrictive member according to an embodiment. [Figure 3] 1A and 1B are diagrams showing a first example of a single crystal, a thin plate member, and a magnetostrictive member. [Figure 4] 10A and 10B are diagrams showing a second example of a single crystal, a thin plate member, and a magnetostrictive member. [Figure 5] 10A and 10B are diagrams showing a third example of a single crystal, a thin plate member, and a magnetostrictive member. [Figure 6] FIG. 1 is a diagram showing the strain gauge method used in the examples. [Figure 7] FIG. 4 is a diagram showing the relationship between the plate thickness and surface roughness of a magnetostrictive member. [Figure 8] FIG. 4 is a diagram showing the relationship between the plate thickness and surface roughness of a magnetostrictive member. DETAILED DESCRIPTION OF THE INVENTION

[0022] Specific embodiments of the present invention will be described in detail below. The present invention is not limited to the following embodiments, and can be modified as appropriate without departing from the spirit of the present invention. In the drawings, some or all of the drawings are shown schematically and scales are changed as appropriate. In the following description, the expression "A to B" means "A or more and B or less."

[0023] The magnetostrictive member of this embodiment and the method for manufacturing the magnetostrictive member will be described below. First, the magnetostrictive member of this embodiment will be described. Fig. 1 is a diagram showing an example of a magnetostrictive member according to an embodiment.

[0024] The magnetostrictive member 1 is a plate-like body as shown in Fig. 1. The plate-like body has a front surface 3 and a back surface 4. The front surface 3 and the back surface 4 are preferably parallel to each other, but they do not have to be parallel to each other.

[0025] The magnetostrictive member 1 is made of a crystal of an iron-based alloy. The iron-based alloy is not particularly limited as long as it has magnetostrictive properties. Magnetostrictive properties refer to the property of undergoing a change in shape when a magnetic field is applied. Examples of the iron-based alloy include Fe-Ga, Fe-Ni, Fe-Al, Fe-Co, Tb-Fe, Tb-Dy-Fe, Sm-Fe, and Pd-Fe alloys. The above alloys may also be alloys to which a third component has been added. For example, an Fe-Ga alloy may be alloyed to which Ba, Cu, or the like has been added. Among these iron-based alloys, Fe-Ga alloys have greater magnetostrictive properties and are easier to process than other alloys. Therefore, they are used in vibration power generation materials in the energy harvesting field, wearable devices, sensors, and the like. In the following explanation, an example of the magnetostrictive member 1 will be described in which the magnetostrictive member 1 is made of a single crystal of an Fe-Ga alloy.

[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 Figures 3 to 5) are equivalent, and the first to third {100} planes (see Figures 3 to 5) among the plane indices in Miller indices are equivalent (i.e., (100), (010), and (001) are equivalent).

[0027] Furthermore, Fe-Ga alloys have the property of producing large magnetostriction in a specific orientation of the crystal. When using this property in a magnetostrictive vibration power generation device, it is desirable to align the direction in which magnetostriction of the magnetostrictive member 1 is required in the device with the orientation (direction) in which the magnetostriction of the crystal is at its maximum. Specifically, as mentioned above, the direction in which magnetization is easy in a single crystal is <100> It is desirable to set the direction of magnetization in the longitudinal direction of the magnetostrictive member 1. <100> The direction can be set to the longitudinal direction of the magnetostrictive member 1, for example, by calculating the crystal orientation of the single crystal using known crystal orientation analysis and cutting the single crystal based on the calculated crystal orientation of the single crystal.

[0028] The crystal that can be used for the magnetostrictive member 1 of this embodiment may be a single crystal or a polycrystal. <100> In order to increase the degree of orientation integration in the direction and improve the properties of the magnetostrictive material, it is advantageous to use a single crystal rather than a polycrystal. Although polycrystals have inferior magnetostrictive properties to single crystals, they can be produced at low cost, so polycrystals are sometimes used.

[0029] 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 terminals 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. In this magnetostrictive vibration power generation device, 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 coil. 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 shape in a plan view. There are no particular limitations on the thickness of the magnetostrictive member 1. The lower limit of the thickness is preferably 0.3 mm or more, more preferably 0.5 mm or more. The upper limit of the thickness of the magnetostrictive member 1 is preferably less than 3 mm, more preferably 2.5 mm or less, and even more preferably 2 mm or less. The thickness of the magnetostrictive member 1 is preferably 0.3 mm or more and less than 3 mm, and more preferably 0.5 mm or more and 2.5 mm or less. As explained above, the mechanism by which the magnetostrictive member 1 generates electricity is a mechanism in which stress (vibration) is applied to the magnetostrictive member to generate electricity through the inverse magnetostriction effect. If the thickness of the magnetostrictive member 1 is less than 0.3 mm, it is more likely to be damaged during vibration. Conversely, if the thickness of the magnetostrictive member 1 exceeds 2 mm, the stress caused by vibration must be increased, resulting in poor efficiency.

[0030] The shape and dimensions of the magnetostrictive member 1 are not particularly limited. They are set appropriately depending on the size of the intended device. 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 elliptical, track-shaped, or irregular in plan view. When the shape of the magnetostrictive member 1 is other than rectangular in plan view, the longitudinal direction is the long diameter direction, major axis direction, etc., and the short direction is the direction perpendicular to the longitudinal direction.

[0031] As described above, the present inventors have developed a single crystal of an Fe—Ga alloy, the principal plane of which is the {100} plane, and the direction of easy magnetization. <100> A number of plate-shaped magnetostrictive members were fabricated, each having a rectangular shape in plan view with the direction parallel to the longitudinal direction of the magnetostrictive member. The magnetostrictive properties of a number of magnetostrictive members fabricated by cutting them from a single crystal of an Fe-Ga alloy with a uniform Ga concentration were confirmed. It was found that the magnetostrictive constants of the fabricated magnetostrictive members were high, but that there was a large variation in the amount of parallel magnetostriction. Further investigation revealed that the magnetostrictive constant and amount of parallel magnetostriction are related to the grinding direction (the direction of the grinding process) of the magnetostrictive member, and also to the plate thickness of the magnetostrictive member. The present invention was made based on the above findings.

[0032] This will be explained in more detail below.

[0033] As shown in FIG. 3, the first <100> Parallel to the axis (single crystal growth direction) and the third <100> The thin plate members were cut out by wire cutting parallel to the axial direction with a loose abrasive multi-wire saw. The thickness of the thin plate members was set to be 0.2 mm thicker than the predetermined plate thickness so that the thickness after surface grinding would be 0.3 mm to 3.0 mm. Next, both sides of the thin plate members were mirror polished, and then cut into pieces measuring 10 mm x 10 mm. The magnetostriction properties of the cut samples were measured, and five samples were selected for each thin plate member so as to include areas with large to small parallel magnetostriction. At this time, the first <100> The direction parallel to the axial direction (single crystal growth direction) was taken as the parallel magnetostriction.

[0034] Next, surface grinding was performed while changing the grit size (grit) of the grinding stone to obtain a predetermined plate thickness. At this time, the grinding direction of the surface grinding (the direction in which multiple grooves extend) was the first <100> The magnetostriction characteristics of the sample were measured after grinding the front and back surfaces.

[0035] The magnetostriction properties were measured by attaching a strain gauge to the surface of a sample of the magnetostrictive member, and measuring the magnetostriction constant in the growth axis direction and the amount of parallel magnetostriction before and after surface grinding. The results are shown in Tables 1 to 3. The measurement of the magnetostriction constant and amount of parallel magnetostriction will be described later.

[0036] As can be seen from Table 1, samples obtained by processing grown crystals from thin plate members, such as samples Nos. 1 to 5 in Example 1, in which the front and back surfaces are mirror-finished, have a magnetostriction constant of 290 ppm to 301 ppm, but the parallel magnetostriction varies from 13 to 279 ppm. In Example 2, the magnetostriction constant is also 295 ppm to 301 ppm, but the parallel magnetostriction varies from 102 to 290 ppm. The same is true for other examples, where the magnetostriction constant is stable but the parallel magnetostriction tends to vary.

[0037] Next, a plurality of grooves 2 were formed on the front and back surfaces of the sample, which had been mirror-finished, by surface grinding. The grinding direction (the direction in which the plurality of grooves extend) was the same as that of the first <100> The axial direction (single crystal growth direction) was the same as the measurement direction of the parallel magnetostriction. As a result, as shown in Example 1, in samples No. 3 and No. 4, which had low parallel magnetostriction before grinding (before forming the multiple grooves 2), the parallel magnetostriction after grinding (after forming the multiple grooves 2) changed from low to high, at 297 ppm and 300 ppm, respectively, and remained stable at a high level. The parallel magnetostriction significantly increased by forming the multiple grooves 2. Furthermore, for samples No. 1, No. 2, and No. 5 of Example 1, the parallel magnetostriction remained stable at a high level, ranging from 289 ppm to 299 ppm, with no change in the parallel magnetostriction value. As a result, it was found that the magnetostriction constant and parallel magnetostriction of samples No. 1 to No. 5 of Example 1, which were surface ground in the same direction as the measurement direction of the parallel magnetostriction, were improved to be stable at a high level with little variation between members (samples). This tendency was also found to be similar in other Examples.

[0038] Furthermore, it was found that the effect of this modification depends on the thickness of the plate, and on the same surface, there is an optimum value for the surface roughness Ra (hereinafter sometimes abbreviated as "surface roughness Ra") in the direction perpendicular to the grinding direction (hereinafter sometimes abbreviated as "perpendicular direction"). It was found that it is preferable to set the surface roughness Ra small when the plate thickness is thin, and to set the surface roughness Ra large when the plate thickness is thick.

[0039] In Examples 1 to 12 and Comparative Examples 1 to 5, magnetostrictive members were measured before and after surface grinding using various thicknesses of 0.3 mm to 3 mm and grindstones with various grit sizes (grits). The magnetostrictive constant and parallel magnetostriction were measured before and after surface grinding, and the surface roughness Ra after surface grinding was also measured. The results are shown in Tables 1 to 3. Surface roughness Ra was measured perpendicular to the grinding direction at five points on the surface of the magnetostrictive member, and the average value was used as the surface roughness Ra of the member. In each Example and Comparative Example, five samples were selected to include areas with large and small parallel magnetostriction values ​​measured before processing. As mentioned above, samples with high parallel magnetostriction values ​​before processing remained stable at a high level, while samples with low parallel magnetostriction values ​​before processing were improved to a high level by surface grinding. Therefore, in this study, to clarify the effect of the improvement, only samples with parallel magnetostriction values ​​less than 80% of the magnetostriction constant before processing were included. The results are shown in Figures 7 and 8. 7 and 8, the surface roughness Ra on the vertical axis is expressed in log (common logarithm). In addition, in Figures 7 and 8, circles indicate examples in which a modification effect was observed, and crosses indicate comparative examples in which the modification effect was small, with the parallel magnetostriction amount being less than 80% of the magnetostriction constant after processing.

[0040] As can be seen from Figure 7, it was found that the effect of the modification depends on the plate thickness and the appropriate surface roughness Ra. When the plate thickness is thin, it was found that the modification effect is achieved even if the surface roughness Ra is small. As the plate thickness increases, it was found that the effect of the modification cannot be obtained unless the surface roughness Ra is increased. There is a correlation between the plate thickness and surface roughness Ra of the magnetostrictive member and the result was obtained that when the modification effect is good, the following formula (1) is satisfied, as shown by the straight line in Figure 7. logRa≧0.48t-0.62...Equation (1) (In formula (1), log is the common logarithm, Ra is the surface roughness (μm), and t is the thickness (mm) of the magnetostrictive member.)

[0041] When grinding is performed using a surface grinder or the like, the surface roughness Ra increases in the vertical direction (hereinafter sometimes simply referred to as the vertical direction) perpendicular to the grinding direction. Therefore, the numerical value of the surface roughness Ra in this embodiment is the value in the direction perpendicular to the grinding direction. In other words, the surface roughness Ra in the magnetostrictive member 1 of this embodiment and the manufacturing method of the magnetostrictive member of this embodiment described later is the value in the direction in which it is maximum within one surface.

[0042] That is, the magnetostrictive member 1 of this embodiment is a plate-like body made of iron-based alloy crystals having magnetostrictive properties and having a front and back, and the thickness and surface roughness Ra of the magnetostrictive member satisfy the above formula (1). Due to the above configuration, the magnetostrictive member 1 of this embodiment has the characteristics of having a high magnetostriction constant and parallel magnetostriction amount, and little variation in the magnetostriction constant and parallel magnetostriction amount between members. Note that in the magnetostrictive member 1 of this embodiment and in the manufacturing method of the magnetostrictive member of this embodiment described below, the measurement direction of the parallel magnetostriction amount is the grinding direction.

[0043] If the above formula (1) is not satisfied, the effect of the modification cannot be obtained. As shown in Comparative Examples 1 to 5 in Table 3, those having a high parallel magnetostriction before processing maintained that high level even after processing.

[0044] For these reasons, when the magnetostrictive member 1 is subjected to grinding, such as surface grinding, processing stress is generated on the surface of the magnetostrictive member 1. In particular, large tensile stress is generated in the direction perpendicular to the grinding direction. The variation in the magnetostrictive properties of the magnetostrictive member 1 is thought to be due to variations in the magnetization direction. However, it is presumed that the above-mentioned modification occurs because the tensile stress is aligned in the direction perpendicular to the grinding direction on the surface of the magnetostrictive member 1, and this stress aligns the magnetization direction of the magnetostrictive member 1 in a fixed direction. As the thickness of the magnetostrictive member 1 increases, the volume of the magnetization direction that needs to be aligned increases (due to the increase in thickness). Therefore, to achieve the above-mentioned modification effect, the tensile stress in the direction perpendicular to the grinding direction on the surface of the magnetostrictive member 1 must be increased, resulting in a larger surface roughness Ra. If the surface roughness Ra is small and does not satisfy the above formula (1), the processing stress on the surface becomes small, resulting in an insufficient modification effect and a state close to the state before processing.

[0045] There is no particular upper limit for the surface roughness Ra of the magnetostrictive member 1, but if the plate thickness of the magnetostrictive member 1 is 1.2 mm or less, if the surface roughness is large, excessive processing stress may be applied to the surface of the magnetostrictive member 1, and the magnetostriction constant itself may decrease.

[0046] Furthermore, even if the thickness of the magnetostrictive member is 2.5 mm or more, it is possible to accommodate this by increasing the surface roughness Ra. However, care must be taken when using a magnetostrictive member with a large thickness, as this will increase the stress caused by vibrations and reduce efficiency when used in vibration power generation, etc.

[0047] Therefore, the surface roughness Ra of the magnetostrictive member 1 is preferably 1.0 μm or less when the thickness of the magnetostrictive member is 0.3 mm or more and 0.75 mm or less, and is preferably 8.6 μm or less when the thickness of the magnetostrictive member is more than 0.75 mm.

[0048] Furthermore, when the thickness of the magnetostrictive member is more than 0.3 mm and not more than 0.75 mm, the surface roughness Ra is preferably 0.5 μm or more, when the thickness of the magnetostrictive member is more than 0.75 mm and not more than 1.0 mm, the surface roughness Ra is preferably 1.0 μm or more, when the thickness of the magnetostrictive member is more than 1.0 mm and not more than 1.5 mm, the surface roughness Ra is preferably 1.3 μm or more, when the thickness of the magnetostrictive member is more than 1.5 mm and not more than 2.0 mm, the surface roughness Ra is preferably 2.5 μm or more, and when the thickness of the magnetostrictive member is more than 2.0 mm and not more than 2.5 mm, the surface roughness Ra is preferably 4.0 μm or more. This makes it possible to more reliably achieve the effects of the above-mentioned modification.

[0049] 8, when the thickness of the magnetostrictive member is 0.5 mm or more and 0.75 mm or less, it is more preferable that the thickness of the magnetostrictive member and the surface roughness Ra satisfy the following formula (2): when the thickness of the magnetostrictive member is more than 0.75 mm and 1.0 mm or less, it is more preferable that the thickness of the magnetostrictive member and the surface roughness Ra satisfy the following formula (3): when the thickness of the magnetostrictive member is more than 1.0 mm and 1.5 mm or less, it is more preferable that the thickness of the magnetostrictive member and the surface roughness Ra in the direction perpendicular to the grinding direction satisfy the following formula (4): This makes it possible to more reliably achieve the effect of the above-mentioned modification. logRa≦ 0.40t-0.20 ...Equation (2) logRa≦1.48t-1.01...Equation (3) logRa≦ 0.92t-0.45 ...Equation (4) (In the above formulas (2) to (4), log is the common logarithm, Ra is the surface roughness Ra (μm) in the direction perpendicular to the grinding direction, and t is the thickness (mm) of the magnetostrictive member.)

[0050] Therefore, by setting the surface roughness Ra within the above range relative to the thickness of the magnetostrictive member 1, the effect of improving the magnetostriction constant and the amount of parallel magnetostriction can be achieved stably at a high level.

[0051] From the viewpoint of achieving the above-mentioned modification effect more reliably and with an easier manufacturing method, the magnetostrictive member 1 preferably has a ground surface that has been subjected to grinding, and in particular, a surface that has been subjected to surface grinding is preferable. The grinding is preferably a process in which grinding is performed in one direction. That is, the magnetostrictive member 1 preferably has a processed surface that has been ground in one direction (a one-way ground surface), and more preferably has a processed surface that has been subjected to surface grinding (a surface ground surface). The grinding direction of the magnetostrictive member 1 is not particularly limited, but is preferably a direction along the longitudinal direction of the magnetostrictive member 1. Here, the direction along the longitudinal direction includes a direction that intersects with the longitudinal direction at an angle of 40° or less.

[0052] Furthermore, a high modification effect can be achieved, with the ratio of the parallel magnetostriction to the magnetostriction constant after modification being preferably 80%, more preferably 90% or more. Furthermore, the magnetostriction constant itself can be a high and stable value of 250 ppm or more in the case of an Fe-Ga alloy, for example.

[0053] As described above, the magnetostrictive member 1 of this embodiment is a plate-like body made of iron-based alloy crystals having magnetostrictive properties and having front and back surfaces 3 and 4. The thickness and surface roughness Ra of one of the front and back surfaces satisfy the above-mentioned formula (1). The magnetostrictive member 1 of this embodiment may have any configuration other than that described above. Due to the above configuration, the magnetostrictive member 1 of this embodiment has a high magnetostriction constant and parallel magnetostriction, and exhibits small variations in the magnetostriction constant and parallel magnetostriction between members. Furthermore, the magnetostrictive member 1 of this embodiment can stably and highly exhibit the effect of improving the magnetostriction constant and parallel magnetostriction by setting the surface roughness in a predetermined direction of the magnetostrictive member within a predetermined appropriate range relative to the plate thickness of the magnetostrictive member. For example, the magnetostrictive member 1 of this embodiment preferably has a magnetostriction constant of 200 ppm or more, more preferably 250 ppm or more, more preferably 280 ppm or more, and more preferably 290 ppm or more. Furthermore, the magnetostrictive member 1 has a parallel magnetostriction constant of preferably 200 ppm or more, more preferably 250 ppm or more, more preferably 270 ppm or more, more preferably 280 ppm or more, and more preferably 290 ppm or more. The magnetostrictive member 1 also has a parallel magnetostriction / magnetostriction constant ratio of preferably 80% or more, more preferably 90% or more, and more preferably 95% or more. Because the magnetostrictive member 1 of this embodiment has a high magnetostriction constant as described above, it can be suitably used as a final product of a member (material) that exhibits excellent magnetostriction effect and inverse magnetostriction effect.

[0054] Next, a method for manufacturing the magnetostrictive member of this embodiment will be described.

[0055] The method for manufacturing the magnetostrictive member of this embodiment is the method for manufacturing the magnetostrictive member 1 of this embodiment described above. The method for manufacturing the magnetostrictive member of this embodiment is a plate-shaped body made of iron-based alloy crystals having magnetostrictive properties and having front and back surfaces, and includes processing at least one of the front and back surfaces 3 and 4 so that the thickness and surface roughness Ra of the magnetostrictive member satisfy the following formula (1): logRa≧0.48t-0.62...Equation (1) (In the above formula (1), log represents the common logarithm, Ra represents the surface roughness (μm), and t represents the thickness (mm) of the magnetostrictive member.) In the following explanation, a method for manufacturing the magnetostrictive member 1 from a single crystal ingot of an Fe-Ga alloy will be described as an example, but the manufacturing method of the magnetostrictive member of this embodiment is not limited to the following explanation. Furthermore, any description in this specification that is applicable to the manufacturing method of the magnetostrictive member of this embodiment will also be applied to the manufacturing method of the magnetostrictive member of this embodiment. Furthermore, any description of the manufacturing method of the magnetostrictive member of this embodiment that is applicable to the magnetostrictive member of this embodiment will also be applied to the magnetostrictive member of this embodiment. Furthermore, the method for manufacturing the magnetostrictive member 1 of this embodiment is not limited to the manufacturing method of the magnetostrictive member of this embodiment described below, and it may be manufactured by other manufacturing methods.

[0056] Fig. 2 is a flowchart showing an example of a method for manufacturing a magnetostrictive member of this embodiment. Figs. 3 to 5 are diagrams showing first to third examples of a single crystal, a thin plate member, and a magnetostrictive member. The method for manufacturing a magnetostrictive member of this embodiment includes a crystal preparation step (step S1), a crystal cutting step (step S2), a surface processing step (step S3), and a cutting step (step S4).

[0057] 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 prepared crystal may be a single crystal or a polycrystal. Furthermore, the prepared crystal may be a grown crystal or a commercially available crystal. For example, in the crystal preparation step, a single crystal of an Fe-Ga alloy is prepared. There are no particular limitations on the method for growing the single crystal of an Fe-Ga alloy. The method for growing the single crystal of an Fe-Ga alloy may be 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.

[0058] 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, the Fe—Ga alloy single crystal is preferably grown so that the gallium content is 16.0 to 20.0 at% or 25.0 to 29.0 at%, and more 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 predetermined diameter of the single crystal) with a cutting device. The size of the grown single crystal is not particularly limited as long as the magnetostrictive member can be secured in the predetermined direction. When growing an Fe—Ga alloy single crystal, the growth axis direction 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.

[0059] 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 prepare a thin plate member. The thin plate member is a member that will be the material for the magnetostrictive member 1 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 prepare a thin plate member having 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 use of a multi-wire saw is particularly preferable because it can cut multiple thin plate members simultaneously. The cutting direction of the single crystal is, in the case of a single crystal of an Fe-Ga alloy, <100> The cutting is performed so that the cut surface, i.e., the main surface of the thin plate member, is the {100} plane. The cutting direction of the single crystal is not particularly limited. For example, as shown in Figures 3 to 5, the cutting direction of the single crystal may be perpendicular or parallel to the growth direction of the single crystal (the direction in which the crystal is grown).

[0060] Following the crystal cutting step (step S2), a surface processing step (step S3) is performed. In the surface processing step, as described above, at least one of the front and back surfaces 3 and 4 is processed so that the relationship between the plate thickness and the surface roughness Ra satisfies the relationship of the above formula (1). The magnetostrictive member 1 of this embodiment can be obtained by the surface processing step. The processing is preferably a grinding process, and more preferably a surface grinding process. For example, in the surface processing step, multiple grooves 2 are formed on at least one of the front and back surfaces 3 and 4 of the obtained thin plate member. The direction in which the multiple grooves 2 are formed is not particularly limited, but in the surface processing step, it is preferable to form multiple grooves 2 in the thin plate member so that when the thin plate member is finally cut into the magnetostrictive member 1, multiple grooves 2 extending in the longitudinal direction of the magnetostrictive member 1 are formed. As described above, multiple grooves 2 can be formed by performing surface grinding on at least one of the front and back surfaces of the thin plate member obtained by the crystal cutting step. In this case, the multiple grooves 2 extend in the grinding direction. Hereinafter, an example will be described in which the surface processing step is performed by surface grinding of a thin plate member. When a plurality of grooves 2 are formed by surface grinding, the effect of improving the magnetostriction constant and the amount of parallel magnetostriction can be efficiently achieved.

[0061] The surface grinding process is performed using a surface grinding machine. In order to efficiently achieve the effect of modifying the magnetostriction constant and the amount of parallel magnetostriction, it is preferable that the direction of the multiple grooves 2 (grinding marks) formed in the thin plate member be parallel to the longitudinal direction of the magnetostrictive member 1. For this reason, it is preferable that the grinding marks be linear. When making the grinding marks linear, it is preferable that the surface grinding machine be a type in which the grinding wheel or processing table moves in a linear direction, and it is preferable to use a surface grinding machine that uses a flat grinding wheel and has a processing table that moves back and forth. It is also possible to use a surface grinding machine that uses a cup grinding wheel and has a processing table that rotates, but when using such a surface grinding machine, the grinding marks will be curved, so it is preferable to set the curvature of the grinding marks to be small (the degree of curvature is small).

[0062] Furthermore, the grinding marks must be formed on the surface (surface) of the magnetostrictive member 1. For this reason, when processing the thin plate member to adjust its thickness, etc., it is possible to perform predetermined processing using a processing machine other than a surface grinder, such as a double-sided lapping machine or a surface grinder using a cup grinding wheel, and then perform surface grinding or other processing. Alternatively, it is possible to perform polishing as in the conventional method to mirror-finish the surface of the thin plate member (magnetostrictive member), and then perform surface grinding or other processing. It is preferable to perform surface grinding or other processing on both the front and back surfaces of the thin plate member, from the viewpoint of efficiently achieving the effect of modifying the magnetostriction constant and parallel magnetostriction.

[0063] The grinding stone used in the surface grinding process is selected to match the thickness of the magnetostrictive member so that the surface roughness Ra falls within the range specified above. For example, when processing a magnetostrictive member with a surface grinder, the grinding stone grit size is #200 or more and #500 or less if the thickness of the magnetostrictive member is 0.3 mm to 0.75 mm, #60 or more and #100 or less if the thickness of the magnetostrictive member is 1.0 mm, and #40 or more and #50 or less if the thickness of the magnetostrictive member is 2.0 mm. When the thickness of the magnetostrictive member is 2.5 mm or more, the grinding stone grit size is preferably #40 or less.

[0064] Furthermore, the multiple grooves 2 are preferably formed in the magnetostrictive member 1 so that the magnetostriction constant and parallel magnetostriction amount fall within the above-mentioned ranges. For example, the multiple grooves 2 are preferably formed in the magnetostrictive member 1 so that the magnetostriction constant is 200 ppm or more and the parallel magnetostriction amount is 200 ppm or more. Furthermore, as described above, the roughness (grit) of the grinding stone is appropriately selected based on the plate thickness of the magnetostrictive member so that the relationship between the plate thickness and the surface roughness Ra falls within the above-mentioned range. This preferably results in the magnetostrictive member 1 having a magnetostriction constant of 250 ppm or more and a parallel magnetostriction amount of 250 ppm or more. The multiple grooves 2 having the above-mentioned preferred ranges of surface roughness Ra, magnetostriction constant, and parallel magnetostriction amount can be formed by the above-mentioned surface grinding process. Note that the surface processing step may be performed by a method other than surface grinding, as long as it is possible to form the multiple grooves 2 on at least one of the front surface 3 and the back surface 4 of the obtained thin plate member. For example, the thin plate member may be produced using a fixed abrasive wire saw. That is, grooves formed when slicing a crystal with a fixed abrasive wire saw to produce a thin plate member may be used as multiple grooves 2. Cutting with a wire saw involves pressing the workpiece against a series of parallel, uniformly spaced, ultra-fine wires. Wires with abrasive grains such as diamonds fixed by electrodeposition or adhesive are fed in the linear direction to cut the workpiece. In this case, grinding marks are generated in the wire feed direction, making it possible to form multiple grooves 2 similar to those formed by the surface grinding process described above. When cutting with a wire saw, the crystal cutting process (step S2) and the surface processing process (step S3) can be performed simultaneously, allowing for efficient production of thin plate members. Alternatively, multiple grooves 2 may be formed by applying a constant pressure with sandpaper or the like. The surface processing process may involve electrical discharge machining to achieve a predetermined surface roughness Ra. For example, the predetermined surface roughness may be achieved by adjusting the processing conditions in a wire electrical discharge machining device. In the surface processing process of magnetostrictive members, grinding, which has a high processing speed, is more preferable. For example, the grinding process is preferably wire saw grinding or surface grinding.

[0065] After the surface processing step (step S3), a cutting step (step S4) is carried out. The cutting step is a step in which the thin plate member in which the plurality of grooves 2 have been formed in the surface processing step is cut to obtain the magnetostrictive member 1 of this embodiment.

[0066] In the cutting process, when cutting a thin plate member having a plurality of grooves 2 formed therein to form magnetostrictive members 1, the thin plate member is cut so as to form a plurality of grooves 2 extending in the longitudinal direction of the magnetostrictive member 1. In the cutting process, the thin plate member is cut to a predetermined size. In the cutting process, the thin plate member is cut into magnetostrictive members 1 so that the magnetostrictive members 1 become rectangular plate-like bodies in a plan view. In the cutting process, the thin plate member is cut using a cutting device. The cutting device used in the cutting process is not particularly limited, and for example, a peripheral blade cutting device, a wire electric discharge machine, a wire saw, etc. can be used. There is no particular limit to the direction in which the magnetostrictive members are extracted from the thin plate member, and for example, it may be set to a direction that allows for efficient extraction based on the size of the magnetostrictive members, etc.

[0067] As described above, the method for manufacturing a magnetostrictive member of this embodiment is a plate-shaped body made of iron-based alloy crystals having magnetostrictive properties and having a front and back surface, and comprises processing at least one of the front and back surfaces so that the thickness and surface roughness Ra of the magnetostrictive member satisfy the following formula (1). logRa≧0.48t-0.62...Equation (1) (In the above formula (1), log is the common logarithm, Ra is the surface roughness (μm), and t is the thickness (mm) of the magnetostrictive member.)

[0068] The manufacturing method of the magnetostrictive member of this embodiment has any configuration other than that described above. The manufacturing method of the magnetostrictive member of this embodiment can easily manufacture magnetostrictive members with high magnetostriction constants and parallel magnetostriction amounts, and with little variation in the magnetostriction constants and parallel magnetostriction amounts between members. By setting the surface roughness of the magnetostrictive member in a predetermined direction within a predetermined appropriate range relative to the plate thickness of the magnetostrictive member, the effect of improving the magnetostriction constant and parallel magnetostriction amount can be achieved at a high level and in a stable manner. [Example]

[0069] The present invention will be explained in more detail below by way of examples and comparative examples, but the present invention is not limited to the following examples in any way.

[0070] [Example 1] The raw materials were prepared with a stoichiometric ratio of iron to gallium of 81:19, and a cylindrical Fe-Ga alloy single crystal was grown by 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%.

[0071] A magnetostrictive member was manufactured from the grown single crystal as follows. First, a free abrasive grain wire saw was used to cut the single crystal in a direction parallel to the direction of growth ( <100> parallel to the direction) and the third <100> The single crystal was cut parallel to the axial direction to produce a thin plate member with a cut surface, i.e., the main surface, in the {100} direction. The thickness of the thin plate member was set to 1.2 mm, 0.2 mm thicker than the plate thickness, so that the thickness after surface grinding would be 1.0 mm. Next, both sides of the thin plate member were mirror-polished, and then cut into pieces measuring 10 mm x 10 mm. The magnetostrictive properties of the cut magnetostrictive members, which will be described later, were measured, and five pieces were selected so as to include areas with large to small parallel magnetostriction. Next, the obtained magnetostrictive members were subjected to surface grinding on a surface grinder using a #100 flat grinding wheel to adjust the thickness of the magnetostrictive member to 1 mm, and multiple grooves (grinding marks) were formed on the front and back surfaces. At this time, the grinding direction of the surface grinding (the direction in which the multiple grooves extend) was set to the first <100> The direction was the axial direction (single crystal growth direction).

[0072] Next, the magnetostrictive properties of the cut-out magnetostrictive member were measured before and after surface grinding. The magnetostrictive properties were measured using a strain gauge method. As shown in Figure 6, 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. Note that the longitudinal direction of the strain gauge is the direction of magnetostriction detection, so the longitudinal direction of the strain gauge was aligned with the first side of the magnetostrictive member. <100> The specimen was bonded so that the direction was parallel to the axial direction (single crystal growth direction) and the direction in which the parallel magnetostriction was measured was the grinding direction in the surface grinding process.

[0073] 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.

[0074] The amount of magnetostriction was determined by correcting the actual strain detection value with the gauge factor. The gauge factor was calculated using the following formula (5). ε=2.00 / Ks × εi...Equation (5) (ε: gauge factor, εi: measured strain value, Ks: gauge factor of the gauge used)

[0075] At this time, the first <100> The direction parallel to the axial direction (the direction of growth of the single crystal) was defined as the parallel magnetostriction. The magnetostriction when the magnetic field direction was parallel to the longitudinal direction of the strain gauge was defined as the parallel magnetostriction. On the other hand, the magnetostriction when the magnetic field direction was perpendicular to the longitudinal direction of the strain gauge was defined as the perpendicular magnetostriction. The magnetostriction constant was determined by the difference between the parallel magnetostriction and the perpendicular magnetostriction according to formula (A). The surface grinding direction was determined by the first magnetostrictive element. <100> This is the axial direction (the direction in which the single crystal is grown), and this direction is the amount of parallel magnetostriction.

[0076] In addition, after the surface grinding process of the magnetostrictive member, the surface roughness Ra of the surface was measured at five points in each direction perpendicular to the grinding direction of the surface grinding of the magnetostrictive member using a surface roughness meter (Keyence Corporation, VK-X1050) at a magnification of 20 times, and the average value was taken as the surface roughness Ra. The manufacturing conditions and evaluation results are shown in Table 1.

[0077] [Examples 2 to 12] [Comparative Examples 1 to 5] In Examples 2 to 12 and Comparative Examples 1 to 5, surface grinding was carried out by varying the thickness of the magnetostrictive member from 0.3 mm to 3 mm and the grit size (number) of the grindstone from #40 to #500. Other than the above, the same procedures were followed as in Example 1. The thickness of the magnetostrictive member, the grit size (number) of the grindstone, and the evaluation results are shown in Tables 1 to 3.

[0078] [Table 1]

[0079] [Table 2]

[0080] [Table 3]

[0081] [summary] From the results of the above examples and comparative examples, as shown in Tables 1 to 3 and Figures 7 to 8, it is confirmed that by setting the surface roughness Ra in the short direction relative to the thickness of the magnetostrictive member within the above range, the effect of improving the magnetostriction constant and parallel magnetostriction can be achieved at a high level and in a stable manner.

[0082] The technical scope of the present invention is not limited to the aspects described in the above-mentioned embodiments. One or more of the requirements described in the above-mentioned embodiments may be omitted. The requirements described in the above-mentioned embodiments may be combined as appropriate. Furthermore, to the extent permitted by law, the disclosures of all documents cited in the above-mentioned embodiments are incorporated by reference into this specification. [Explanation of symbols]

[0083] 1: Magnetostrictive material 2:Groove 3: Surface 4: Back side S1: Crystal preparation process S2: Crystal cutting process S3: Surface Finishing Engineering S4: Cut-off Engineering

Claims

1. It is made of Fe—Ga alloy crystals having magnetostrictive properties, It is a plate-like body having a front and a back, The magnetostrictive member has a plurality of grooves on the front and back surfaces, and the thickness and surface roughness Ra of the magnetostrictive member satisfy the following formula (1): logRa≧0.48t-0.62...Formula (1) (In the above formula (1), log represents common logarithm, Ra represents surface roughness (μm), and t represents the thickness (mm) of the magnetostrictive member.)

2. When the thickness of the magnetostrictive member is 0.3 mm or more and 0.75 mm or less, the surface roughness Ra is 1.0 μm or less, 2. The magnetostrictive member according to claim 1, wherein when the thickness of the magnetostrictive member exceeds 0.75 mm, the surface roughness Ra is 8.6 μm or less.

3. When the thickness of the magnetostrictive member is more than 0.3 mm and not more than 0.75 mm, the surface roughness Ra is 0.5 μm or more, When the thickness of the magnetostrictive member is more than 0.75 mm and not more than 1.0 mm, the surface roughness Ra is 1.0 μm or more, When the thickness of the magnetostrictive member is more than 1.0 mm and not more than 1.5 mm, the surface roughness Ra is 1.3 μm or more, When the thickness of the magnetostrictive member is more than 1.5 mm and not more than 2.0 mm, the surface roughness Ra is 2.5 μm or more, and When the thickness of the magnetostrictive member is more than 2.0 mm and not more than 2.5 mm, the surface roughness Ra is 4.0 μm or more. The magnetostrictive member according to claim 2 .

4. When the thickness of the magnetostrictive member is 0.5 mm or more and 0.75 mm or less, the thickness of the magnetostrictive member and the surface roughness Ra satisfy the following formula (2): When the thickness of the magnetostrictive member is more than 0.75 mm and 1.0 mm or less, the thickness of the magnetostrictive member and the surface roughness Ra satisfy the following formula (3): When the thickness of the magnetostrictive member is more than 1.0 mm and not more than 1.5 mm, the thickness of the magnetostrictive member and the surface roughness Ra satisfy the following formula (4): The magnetostrictive member according to any one of claims 1 to 3. logRa≦0.40t-0.20...Formula (2) logRa≦1.48t-1.01...Formula (3) logRa≦0.92t-0.45...Formula (4) (In the above formulas (2) to (4), log represents common logarithm, Ra represents surface roughness Ra (μm), and t represents the thickness (mm) of the magnetostrictive member.)

5. 5. The magnetostrictive member according to claim 1, wherein the ratio of the parallel magnetostriction amount to the magnetostriction constant of the magnetostrictive member is 80% or more.

6. The magnetostriction constant is 250 ppm or more, 6. The magnetostrictive member according to claim 1, wherein the amount of parallel magnetostriction is 250 ppm or more.

7. A magnetostrictive member described in any one of claims 1 to 6, wherein the Fe-Ga alloy is a single crystal.

8. 8. The magnetostrictive member according to claim 1, wherein the magnetostrictive member has a thickness of 0.3 mm or more and 2.5 mm or less.

9. A method for manufacturing a magnetostrictive member, comprising: processing a plate-shaped body having front and back surfaces, the plate-shaped body being made of Fe-Ga alloy crystals having magnetostrictive properties, to form a plurality of grooves on the front and back surfaces, the grooves satisfying the following formula (1) in terms of the thickness and surface roughness Ra of the magnetostrictive member: logRa≧0.48t-0.62...Formula (1) (In the above formula (1), log represents common logarithm, Ra represents surface roughness (μm), and t represents the thickness (mm) of the magnetostrictive member.)

10. The method for manufacturing a magnetostrictive member according to claim 9 , wherein the processing is a grinding process.

11. The method for manufacturing a magnetostrictive member according to claim 10 , wherein the grinding process is a surface grinding process.

12. The method for manufacturing a magnetostrictive member according to claim 11, wherein the surface grinding is performed using a grinding wheel of #40 or more and #500 or less, and includes selecting a grinding wheel of a size such that the thickness of the magnetostrictive member and the surface roughness Ra satisfy the formula (1).

13. 13. The method for manufacturing a magnetostrictive member according to claim 9, wherein the processing includes processing the magnetostrictive member so that the magnetostriction constant is 250 ppm or more and the parallel magnetostriction amount is 250 ppm or more.

Images