JP7533135B2 - Magnetostrictive member and method for manufacturing the same - Google Patents

Description

The present invention relates to a magnetostrictive member and a method for manufacturing a magnetostrictive member.

Magnetostrictive materials have been attracting attention as functional materials. For example, Fe-Ga alloys, which are iron-based alloys, are materials that exhibit magnetostrictive and inverse magnetostrictive effects, and exhibit large magnetostriction of about 100 to 350 ppm. For this reason, they have been attracting attention in recent years as vibration power generation materials in the energy harvesting field, and are expected to be applied to wearable devices and sensors. As a method for manufacturing single crystals of Fe-Ga alloys, a method for growing single crystals by the pulling method (Czochralski method, hereinafter abbreviated as "Cz method") is known (for example, Patent Document 1). In addition to the Cz method, other manufacturing methods such as the vertical Bridgman method (VB method) and the vertical temperature gradient solidification method (VGF method) are known (for example, Patent Document 2 and Patent Document 3).

Fe-Ga alloys have an easy axis of magnetization in the <100> crystal direction, and can produce large magnetostriction in this direction. Conventionally, magnetostrictive members of Fe-Ga alloys have been manufactured by cutting a single crystal portion oriented in the <100> direction from Fe-Ga polycrystals to the desired size (for example, Non-Patent Document 1). However, since the crystal orientation has a large effect on the magnetostrictive properties, it is believed that the optimal material for magnetostrictive members is a single crystal in which the direction in which magnetostriction is required matches the <100> crystal direction in which the magnetostriction is maximized.

When a magnetic field is applied parallel to the <100> orientation of a single crystal of an Fe-Ga alloy, positive magnetostriction appears (hereinafter referred to as "parallel magnetostriction"). On the other hand, when a magnetic field is applied perpendicular to the <100> orientation, negative magnetostriction appears (hereinafter referred to as "perpendicular magnetostriction"). When the strength of the applied magnetic field is gradually increased, the parallel magnetostriction and the perpendicular magnetostriction are saturated, respectively. The magnetostriction constant (3/2λ ₁₀₀ ) is determined by the difference between the saturated parallel magnetostriction and the saturated perpendicular magnetostriction, and is calculated by the following formula (1) (for example, Patent Document 4 and Non-Patent Document 2).

3/2λ ₁₀₀ = ε (//) - ε (⊥) ...Formula (1)
3/2λ ₁₀₀ : Magnetostriction constant ε(//): Parallel magnetostriction amount when saturated by applying a magnetic field parallel to the <100> direction ε(⊥): Parallel magnetostriction amount when a magnetic field is applied perpendicular to the <100> direction Vertical magnetostriction when saturated

The magnetostrictive properties of Fe-Ga alloys are believed to affect the magnetostrictive and inverse magnetostrictive effects and the properties of magnetostrictive vibration power generation devices, and are an important parameter in device design (e.g., Non-Patent Document 4). In particular, it is known that the magnetostrictive constant depends on the Ga composition of the Fe-Ga alloy single crystal, and that the magnetostrictive constant is maximized at Ga compositions of 18-19 at% and 27-28 at% (e.g., Non-Patent Document 2), and 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 amount of parallel magnetostriction, the higher the device properties such as output voltage tend to be (e.g., Non-Patent Document 3).

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 a field magnet (for example, Patent Document 5 and Non-Patent Document 4). In this magnetostrictive vibration power generation device, when the yoke of 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 magnetic flux density of the coil wound around the Fe-Ga magnetostrictive member changes due to the inverse magnetostrictive effect, generating an electromagnetically induced electromotive force and generating electricity. In a magnetostrictive vibration power generation device, vibration occurs when a force is applied to the yoke in the longitudinal direction, so it is desirable to process the Fe-Ga magnetostrictive member used in the device so that the easy magnetization axis <100> is in the longitudinal direction.

JP 2016-28831 A JP 2016-138028 A Japanese Unexamined Patent Publication No. 4-108699 Special table 2015-517024 publication International Publication No. 2011-158473

Etrema, State of the Art of Galfenol Processing. A. E. Clark et al. , Appl. Phys. 93 (2003) 8621. Jung Jin Park, Suok-Min Na, Ganesh Raghunath, and Alison B. Flatau. , AIP ADVANCES 6, 056221 (2016). Toshiyuki Ueno, Journal of the Japan Society for Precision Engineering, Vol. 79, No. 4, (2013) 305-308.

The device characteristics of magnetostrictive vibration power generation devices and the like are affected by the magnetostrictive properties of the magnetostrictive member, so the magnetostrictive member is required to have high magnetostrictive properties and little variation in the magnetostrictive properties. In this context, it was thought that if the crystal orientation of the Fe-Ga alloy single crystal was <100> and the Ga concentration was uniform, a magnetostrictive member with a uniform magnetostrictive constant could be obtained. However, as described in Non-Patent Document 3, it is disclosed that device characteristics are influenced not only by the magnetostrictive constant but also by the amount of parallel magnetostriction. As a result of the inventor's investigation, it was found that the magnetostrictive member manufactured as described above has variation in the amount of parallel magnetostriction (or the amount of perpendicular magnetostriction) even if the magnetostrictive constant is uniform, and that the magnetostrictive constant itself varies.

The present invention aims to provide a magnetostrictive member and a method for manufacturing a magnetostrictive member that has a high magnetostriction constant and a high amount of parallel magnetostriction and has little variation in the magnetostriction constant and amount of parallel magnetostriction between members.

According to an aspect of the present invention, a magnetostrictive member is provided that is a plate-like body made of crystals of an iron-based alloy having magnetostrictive properties, has a longitudinal direction and a transverse direction, and has a plurality of first grooves extending in the longitudinal direction on the front and back surfaces of the plate-like body, and a plurality of second grooves extending in the longitudinal direction and deeper than the first grooves on the front and back surfaces of the plate-like body.

The second grooves may be formed periodically at a predetermined interval in the short direction of the magnetostrictive member. The predetermined interval in the plurality of second grooves may be 5 μm or more and 30 μm or less. The angle between the first groove and the second groove may be within 15°. The surface having the first groove and the second groove may be configured such that the surface roughness Ra in the longitudinal direction is smaller than the surface roughness Ra in the short direction. The surface roughness Ra in the longitudinal direction may be 0.3 μm or more and 1.5 μm or less, and the surface roughness Ra in the short direction may be 0.6 μm or more and 4.5 μm or less. The magnetostriction constant may be 200 ppm or more, and the parallel magnetostriction amount, which is the amount of magnetostriction when a magnetic field parallel to the longitudinal direction is applied and the amount of magnetostriction in the longitudinal direction is saturated, may be 200 ppm or more. The first and second grooves may each be formed by cutting using a multi-wire saw.

In addition, according to an aspect of the present invention, a method for manufacturing a magnetostrictive member is provided, which comprises forming a plurality of first grooves extending in the longitudinal direction on the front and back surfaces of a plate-like body made of crystals of an iron-based alloy having magnetostrictive properties and having a longitudinal direction and a transverse direction, and forming a plurality of second grooves extending in the longitudinal direction deeper than the first grooves on the front and back surfaces of the plate-like body.

The method for manufacturing a magnetostrictive member may also include forming the first groove and the second groove with a multi-wire saw. The formation of the first groove and the second groove with a multi-wire saw may also be configured to use a fixed abrasive wire method in which the wire used in the multi-wire saw is a fixed abrasive wire with abrasive grains fixed to the wire. The formation of the first groove and the second groove with a multi-wire saw may also be configured to include forming the groove by tilting the wire within a range of ±5° relative to the workpiece.

The magnetostrictive member of the present invention has a high magnetostriction constant and a high amount of parallel magnetostriction, and has a small variation in the magnetostriction constant and the amount of parallel magnetostriction between members, and can be easily manufactured. The manufacturing method of the magnetostrictive member of the present invention can easily manufacture a magnetostrictive member having a high magnetostriction constant and a high amount of parallel magnetostriction, and has a small variation in the magnetostriction constant and the amount of parallel magnetostriction between members.

1A is a perspective view showing an example of a magnetostrictive member according to an embodiment, and FIG. 1B is an example of a drawing substitute photograph showing an enlarged portion of a surface portion of the magnetostrictive member according to an embodiment, and a cross-sectional view of the surface portion of the magnetostrictive member. FIG. 1 is a diagram illustrating an example of a wire saw device. FIG. 2 is a diagram showing an example of a swing mechanism in a wire saw device. 3 is a flowchart showing an example of a method for manufacturing a magnetostrictive member according to the embodiment. 1A and 1B are diagrams showing a first example of a single crystal, a thin plate member, and a magnetostrictive member. 1A and 1B are diagrams showing a second example of a single crystal, a thin plate member, and a magnetostrictive member. 11A and 11B are diagrams showing a third example of a single crystal, a thin plate member, and a magnetostrictive member. FIG. 1 is a diagram showing the strain gauge method used in the examples.

The following description will be given with reference to the drawings. In each drawing, some or all of the drawings are shown in schematic form and the scale is changed as appropriate. In this specification, "A-B" means greater than or equal to A and less than or equal to B.

[Embodiment]
The magnetostrictive member and the method for manufacturing the magnetostrictive member of this embodiment will be described below.

First, the magnetostrictive member of this embodiment will be described. FIG. 1(A) is a perspective view showing an example of a magnetostrictive member according to an embodiment. FIG. 1(B) is an example of a drawing substitute photograph showing an enlarged portion of a surface portion of the magnetostrictive member according to an embodiment, and a cross-sectional view of the surface portion of the magnetostrictive member.

As shown in FIG. 1(A), the magnetostrictive member 1 is a plate-like body having a longitudinal direction D1 and a lateral direction D2. The plate-like body is rectangular in a plan view. The plate-like body has a front surface 4 and a back surface 5. The front surface 4 and the back surface 5 are preferably parallel to each other, but do not have to be parallel to each other.

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. The magnetostrictive properties refer to the property of changing the shape when a magnetic field is applied. The iron-based alloy is, for example, an alloy such as Fe-Ga, Fe-Ni, Fe-Al, Fe-Co, Tb-Fe, Tb-Dy-Fe, Sm-Fe, or Pd-Fe. The above alloy may also be an alloy to which a third component is added. For example, an Fe-Ga alloy may be an alloy to which Ba, Cu, or the like is added. Among these iron-based alloys, the Fe-Ga alloy has a large magnetostrictive property and is easy to process compared to other alloys, and is therefore applied to vibration power generation materials in the energy harvesting field, wearable terminals, sensors, and the like. In the following explanation, as an example of the magnetostrictive member 1, an example of a configuration in which the magnetostrictive member 1 is made of a single crystal of an Fe-Ga alloy will be explained.

The Fe-Ga alloy single crystal has a body-centered cubic lattice structure, and is based on the fact that the first to third <100> axes (see Figures 5 to 7) among the directional indices in the Miller index are equivalent, and the first to third {100} faces (see Figures 5 to 7) among the plane indices in the Miller index are equivalent (i.e., (100), (010) and (001) are equivalent). In addition, the Fe-Ga alloy has the property of exhibiting large magnetostriction in a specific orientation of the crystal. When using this property in a magnetostrictive vibration power generation device, it is desirable to match the direction in the device that requires magnetostriction of the magnetostrictive member 1 with the orientation (direction) in which the magnetostriction of the crystal is maximized. Specifically, as described above, it is desirable to set the <100> direction, which is the magnetization easy direction in the single crystal, to the longitudinal direction D1 of the magnetostrictive member 1. The <100> direction, which is the direction of easy magnetization in a single crystal, can be set to the longitudinal direction D1 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.

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

The magnetostrictive member 1 is used, for example, as a material (part) for vibration power generation devices in the energy harvesting field, and as a material (part) for wearable terminals and sensors. For example, the magnetostrictive vibration power generation device shown in the above Patent Document 5 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, and the magnetic flux density of the coil wound around the magnetostrictive member changes due to the inverse magnetostrictive effect, and electromagnetic induction electromotive force is generated, thereby generating electricity. When used in such a mechanism, the shape of the magnetostrictive member 1 is preferably a thin plate shape and is set to a long and narrow rectangular shape in a plan view. There is no particular limit to the thickness of the magnetostrictive member 1. The lower limit of the thickness is preferably 0.3 mm or more, more preferably 0.4 mm or more, and even more preferably 0.5 mm or more. The upper limit of the thickness of the magnetostrictive member 1 is preferably 2 mm or less, more preferably 1.8 mm or less, and even more preferably 1.5 mm or less. The thickness of the magnetostrictive member 1 is preferably 0.3 mm or more and 2 mm or less, more preferably 0.4 mm or more and 1.8 mm or less, and even more preferably 0.5 mm or more and 1.5 mm or less. As described above, the mechanism of power generation by the magnetostrictive member 1 is a mechanism of generating power by applying stress (vibration) to the magnetostrictive member through the inverse magnetostrictive effect. If the thickness of the magnetostrictive member 1 is less than 0.3 mm, it is likely to be damaged during vibration. Conversely, if the thickness of the magnetostrictive member 1 exceeds 2 mm, it is necessary to increase the stress due to vibration, which reduces efficiency. The shape and size of the magnetostrictive member 1 are appropriately set according to the size of the target 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 lateral direction D2, and 1 mm in thickness.

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 elliptical, track-shaped, or amorphous in plan view. When the shape of the magnetostrictive member 1 is other than rectangular in plan view, the longitudinal direction D1 is the long diameter direction, long axis direction, etc., and the short direction D2 is a direction perpendicular to the longitudinal direction D1.

As described above, the inventors produced a number of plate-shaped magnetostrictive members made of single crystals of Fe-Ga alloy, with the main surface being a {100} plane, and with the magnetization easy direction being the <100> direction as the longitudinal direction of the magnetostrictive member, and with a rectangular shape in plan view. As a result of checking the magnetostrictive properties of a number of magnetostrictive members cut from single crystals of Fe-Ga alloys with a uniform Ga concentration, it was found that the magnetostrictive constants of the created magnetostrictive members were high, but the amount of parallel magnetostriction was highly variable. In addition, it was found that the magnetostrictive constants of these magnetostrictive members themselves vary, and that the magnetostrictive constants vary depending on the position at which the magnetostrictive members are cut from the single crystal. As a result of further investigation, it was found that the magnetostrictive constant and the amount of parallel magnetostriction are related to the grinding direction of the magnetostrictive member. The present invention was made based on the above findings.

Magnetostrictive members are manufactured, for example, by cutting grown iron-based alloy crystals in a certain direction to create a thin plate-like member, and then cutting the thin plate-like member to a specified size.

As shown in Figs. 1(A) and (B), the magnetostrictive member 1 of this embodiment is characterized by having a plurality of first grooves 2 extending in the longitudinal direction D1 on the front surface 4 and the back surface 5 (sometimes referred to collectively as "front and back surfaces" and "front and back surfaces 4, 5"), and a plurality of second grooves 3 deeper than the first grooves 2 and extending in the longitudinal direction D1 on the front surface 4 and the back surface 5 of the plate-like body. A detailed explanation will be given below. (In the following explanation, the first grooves 2 and the second grooves 3 may sometimes be referred to collectively as "grooves" and "grooves 2, 3.")

As described above, the magnetostrictive properties of a number of magnetostrictive members cut from Fe-Ga single crystals with a uniform Ga concentration were confirmed, and it was found that the magnetostrictive constant was high, but the parallel magnetostriction amount varied. According to this embodiment, even in magnetostrictive members with such a variation in the parallel magnetostriction amount, by forming a number of first grooves 2 extending in the longitudinal direction D1 on the front surface 4 and back surface 5, and a number of second grooves 3 deeper than the first grooves 2 and extending in the longitudinal direction D1 on the front surface 4 and back surface 5 of the plate-shaped body, both the magnetostrictive constant and the parallel magnetostriction amount can be modified to be high and have little variation between members (also referred to as "modification of the magnetostrictive constant and the parallel magnetostriction amount"). In particular, the parallel magnetostriction amount can be modified. It is presumed that this modification phenomenon occurs because the formation of a number of first grooves 2 in particular applies stress such as residual strain within the crystal, which uniformly rearranges the magnetic moment and uniformizes the magnetostrictive properties.

The following describes the modification of the magnetostriction constant and the amount of parallel magnetostriction. In this embodiment, as shown in the examples described later, samples of magnetostrictive members having front and back surfaces cut from a single crystal using a multi-wire saw device were examined for the changes in the magnetostriction constant and the amount of parallel magnetostriction due to the formation of multiple grooves 2 and 3 for samples (Examples 1 to 4) in which multiple first grooves 2 extending in the longitudinal direction D1 and multiple second grooves 3 extending in the longitudinal direction D1 deeper than the first grooves 2 were formed on both the front and back surfaces of the magnetostrictive member, and for a sample (Comparative Example 1) in which multiple first grooves extending in the lateral direction D2 and multiple second grooves extending in the lateral direction D2 deeper than the first grooves were formed. The results are shown in Table 1.

As shown in Examples 1 to 4, in the samples in which multiple first grooves 2 extending in the longitudinal direction D1 and multiple second grooves extending in the longitudinal direction deeper than the first grooves are formed on both the front and back surfaces of the magnetostrictive member, the magnetostriction constant and the amount of parallel magnetostriction are both 200 ppm or more in all ten samples, and are stable at a high level.

In contrast, in the case of a sample in which a plurality of first grooves extending in the short direction D2 and a plurality of second grooves extending deeper in the short direction D2 are formed on both the front and back surfaces of the magnetostrictive member, as shown in Comparative Example 1, in all ten samples, the magnetostriction constant is stable at 200 ppm or more, but the parallel magnetostriction amount is low and stable at 100 ppm or less.

Furthermore, in Example 1, the front and back surfaces of the magnetostrictive member 1 were further ground using a lapping device, and then polished using a polishing device to mirror finish the front and back surfaces. The grooves 2 and 3 on the front and back surfaces of the magnetostrictive member were removed by this mirror finish, and the amount of parallel magnetostriction was checked again. As a result, the amount of parallel magnetostriction varied widely, from 34 to 290 ppm. In particular, the amount of parallel magnetostriction in eight out of ten samples fell to less than 200 ppm, increasing the variation. The amount of parallel magnetostriction in the remaining two samples was almost the same as before grinding, with no change. From the above situation, it can be inferred that by forming a plurality of first grooves 2 extending in the longitudinal direction D1 on the front surface 4 and back surface 5, and a plurality of second grooves 3 that are deeper than the first grooves 2 and extend in the longitudinal direction D1, it is possible to improve both the magnetostriction constant and the amount of parallel magnetostriction to a high level with less variation between components (also referred to as "improving the magnetostriction constant and the amount of parallel magnetostriction").

The parallel magnetostriction amount is the amount of magnetostriction when a magnetic field parallel to the longitudinal direction D1 of the magnetostrictive member 1 is applied and the amount of magnetostriction in the longitudinal direction D1 is saturated. The perpendicular magnetostriction amount is the amount of magnetostriction when a magnetic field parallel to the transverse direction D2 of the magnetostrictive member 1 is applied and the amount of magnetostriction in the transverse direction D2 is saturated. The magnetostriction constant, parallel magnetostriction amount, and perpendicular magnetostriction amount in the magnetostrictive member 1 of this embodiment are values obtained as described in the examples described later, and the amount of magnetostriction is a value obtained by correcting the actual strain detection value with the gauge factor according to formula (3), the amount of magnetostriction when the magnetic field direction is parallel to the longitudinal direction of the strain gauge is the amount of parallel magnetostriction, the amount of magnetostriction when the magnetic field direction is perpendicular to the longitudinal direction of the strain gauge is the amount of perpendicular magnetostriction, and the magnetostriction constant is a value obtained by the difference between the amount of parallel magnetostriction and the amount of perpendicular magnetostriction according to formula (1). In addition, the angle between the extension direction of the multiple grooves 2 and 3 and the longitudinal direction D1 is the average value of the values for multiple different grooves.

Next, we will explain the multiple first grooves 2 and the multiple second grooves 3 that are deeper than the first grooves 2 and extend in the longitudinal direction D1. Since the multiple first grooves 2 and the multiple second grooves 3 are related to the manufacturing method of the magnetostrictive member, we will first explain the multi-wire saw device that processes the front and back surfaces of the magnetostrictive member.

In the manufacturing of the magnetostrictive member 1 of this embodiment, a multi-wire saw device (wire saw device) is used as the cutting device in the cutting process. The multi-wire saw device is described below.

2 is a diagram showing an example of a multi-wire saw device (wire saw device). The wire saw device 20 is equipped with a wire array 26 consisting of wires 25 arranged at a predetermined interval, and is an apparatus for grinding and cutting the single crystal C into a plurality of thin plate members PL (see Figs. 5 to 7) by moving the single crystal C having a cylindrical shape or the like and the wire array 26 relatively. As shown in Fig. 2, the wire saw device 20 is equipped with a slice table holder 21, a slice table 22, a plurality of rollers R (three in the example of Fig. 2, two in the example of Fig. 3), and a wire array 26 stretched between the plurality of rollers R at a predetermined interval. As shown in Fig. 2, the wire saw device 20 moves the single crystal C upward or downward to move the wire array 26 and the single crystal C in a relative direction. The wire saw device 20 moves the wire array 26 and the single crystal C in a relative direction, and by running the wire array 26 in one direction or a reciprocating direction while pressing the single crystal C against the wire array 26, the single crystal C is simultaneously cut into a plurality of thin plate members PL (see Figures 5 to 7). The wire saw device 20 may be configured to move the wire array 26 relative to the fixed single crystal C, or may be configured to move the single crystal C while the wire array 26 is fixed.

In cutting processes using the wire saw device 20, there are two methods: a free abrasive method, in which the single crystal C is pressed against a row of ultra-fine wires 26 arranged in parallel at a constant pitch, and a machining liquid (also called a slurry) containing abrasive grains is supplied between the single crystal C and the wire 25 while the wire 25 is fed in the linear direction to cut the single crystal C; and a fixed abrasive method, in which the workpiece is cut while the wire 25, to which abrasive grains such as diamond are fixed by electroplating or adhesive, is fed in the linear direction. In this embodiment, the fixed abrasive method is used. Details will be described later.

In addition, the direction of travel of the wire 25 when cutting the single crystal C with the wire saw device 20 (traveling method) can be either a method in which the wire 25 travels in only one direction to perform cutting (hereinafter referred to as the "unidirectional cutting method") or a method in which the wire 25 travels back and forth to perform cutting (hereinafter referred to as the "reciprocating cutting method"). The unidirectional cutting method allows for long-term travel at a high linear speed, resulting in high processing efficiency, but when the single crystal diameter is large, several hundred kilometers of wire 25 are required to perform one cut, which is expensive. Generally, the reciprocating cutting method is used. In the reciprocating cutting method, when the wire 25 travels back and forth to cut the single crystal C, the wire 25 is temporarily stopped every time the traveling direction of the wire 25 is changed, and the linear speed becomes zero. For this reason, the cut thin plate member PL has a step (groove) due to a saw mark as shown by the symbol "3" in FIG. 1 (B). This phenomenon occurs as the wire 25 travels back and forth, resulting in steps (grooves) at a certain pitch P1 (see Figure 1 (B)) perpendicular to the direction in which the wire 25 travels.

Furthermore, the wire saw device 20 may have a swing mechanism. FIG. 4 is a diagram showing an example of a swing mechanism of the wire saw device. The swing mechanism is a mechanism for cutting the single crystal C by tilting the entire roller R from a horizontal state of the wire row 26 arranged on the multiple rollers R of the wire saw device 20 as shown in FIG. 3 (hereinafter, tilting the entire roller R from a horizontal state may be abbreviated as "swing"). By applying a swing motion while cutting the single crystal C with the wire 25, the contact surface (contact portion) between the wire 25 and the single crystal C can be changed from a line contact in the absence of a swing mechanism to a state close to point contact. For this reason, a substantially higher load can be applied to the contact portion between the wire 25 and the single crystal C, and the abrasive grains used for cutting act efficiently on the contact portion. This swing is preferably performed within a range of ±15° with respect to the horizontal. More preferably, it is within a range of ±5°. That is, the angle θ of the inclination of the wire row 26 during swing (hereinafter, sometimes referred to as the "swing angle" or "swing angle") is preferably within a range of ±15°. It is more preferable that the angle θ of the oscillation is in the range of ±5°. The signs ("+", "-") in the oscillation angle θ are positive (+) and negative (-) in the clockwise direction and counterclockwise direction, respectively, on a plane parallel to the running direction of the wire 25 (wire row 26) (see FIG. 3). In this specification, the "range of ±n°" means a range of -n° to +n°, in other words, less than |n|° (|n| indicates an absolute value). If the oscillation angle θ exceeds the above range, it is known that the surface roughness of the cut surface is reduced by the oscillation motion, and the effect of improving the magnetostriction constant and the amount of parallel magnetostriction may be reduced. For this reason, it is more preferable that the oscillation angle θ is in the range of ±3° with respect to the horizontal. The oscillation speed is not particularly limited, but is, for example, 3° to 10°/sec.

The above-mentioned oscillation is repeated at a constant speed by setting the oscillation angle θ while cutting the single crystal C with the wire saw device 20. Note that this wire oscillation is not linked to the wire reciprocating mechanism described above, but can be set separately. Note that there is no particular limitation on the wire saw device 20 that can be used in this embodiment, and any known device can be used. For example, the wire saw device described in JP 2008-229752 A can be used as a wire saw device equipped with the above-mentioned oscillation mechanism.

The front and back surfaces of the magnetostrictive member 1 in this embodiment are the processed surfaces by the multi-wire saw device 20, and the wire 25 is processed using a fixed abrasive cutting method, in which the wire 25 is moved back and forth to perform cutting.

The first groove 2 in the magnetostrictive member 1 of this embodiment is a groove formed when ground by a fixed abrasive fixed to the wire 25. As shown in FIG. 1B, the first groove 2 needs to be formed in a plurality of grooves in a certain direction. By using the wire 25 of the fixed abrasive type, it is possible to reliably form a plurality of grooves in a direction parallel to the running direction of the wire 25. This groove is affected by the abrasive fixed to the wire 25. The abrasive fixed to the wire 25 is generally made of diamond abrasive grains, but is not limited to diamond abrasive grains. It is preferable to use a grain size of 6 to 40 μm for the abrasive fixed to the wire 25. When the grain size of the abrasive grains is within the above range, the first groove 2 and the second groove 3 can be formed more reliably. If the abrasive grains are small, the life of the wire will be shortened due to abrasive grain wear, which increases costs, and if the abrasive grains are large, the processing-affected layer will be deep and the directionality will be small, resulting in insufficient processing of the grooves (groove formation). There are no particular limitations on the diameter of the wire 25, but a diameter of 0.1 to 0.3 mm is generally preferred.

The second groove 3 (see FIG. 1(B)) in the magnetostrictive member 1 of this embodiment is due to a saw mark formed when cutting is performed by a reciprocating cutting method in which the wire 25 of the wire saw device 20 is moved back and forth to perform cutting. As described above, when the wire 25 is moved back and forth to cut the single crystal C, the wire 25 pauses each time the running direction of the wire 25 changes and the linear speed becomes zero. Since processing is resumed from that point, a difference occurs between the forward and backward paths, resulting in a saw mark, which becomes the second groove 3. The saw mark (second groove 3) is deeper than the first groove (see FIG. 1(B)).

The saw marks (second grooves 3) are formed at regular intervals perpendicular to the wire travel direction, depending on the number of times the wire 25 goes back and forth, the feed speed of the single crystal C, etc. For example, the saw marks are formed to a depth of 0.5 μm to 3.0 μm, with a pitch P1 of 5 μm to 30 μm (see FIG. 1(B)). The depth and pitch of the saw marks can be controlled by the processing conditions when cutting the single crystal C with the wire saw device 20 (the feed speed of the single crystal C, the number and speed of the wire going back and forth, etc.).

Furthermore, the extension direction of the first groove 2 and the extension direction of the second groove 3 may be the same direction, or the angle at which the extension direction of the first groove 2 and the extension direction of the second groove 3 intersect (also called the "intersection angle") may be within a range of ±15° (the intersection angle may be 15° or less). As described above, the wire 25 is arranged on a plurality of rollers R, and the plurality of rollers R are oscillated at an angle within a predetermined range from the horizontal with respect to the single crystal C by the oscillating mechanism to cut the single crystal C. When this oscillating motion is used, since it is not linked to the reciprocation of the wire 25 described above, the angle at which the extension direction of the first groove 2 and the extension direction of the second groove 3 intersect (intersection angle) fluctuates within the set oscillating angle range on the front and back surfaces of the thin plate member PL in which the single crystal C is cut by the wire saw device 20. In Example 2, Example 3, and Comparative Example 3, the rocking motion was performed at rocking angles θ (see FIG. 3) of ±3° and ±10°. In Example 2 and Example 3, as in Example 1, the magnetostriction constant and the parallel magnetostriction amount were both 200 ppm or more in 10 samples, and were stable at a high level. In contrast, as shown in Example 4, at a rocking angle θ of ±10°, the crossing angle is large, so although there is an effect of improving the parallel magnetostriction amount, it is slightly inferior to Examples 2 and 3. Thus, it can be seen that the effect of improving the magnetostriction constant and the parallel magnetostriction amount is expressed if the extension direction of the first groove and the extension direction of the second groove are the same direction, or if the angle (crossing angle) at which the extension direction of the first groove 2 and the extension direction of the second groove 3 intersect is within the range of ±15°. If it is within the range of ±5°, the effect of improving the magnetostriction constant and the parallel magnetostriction amount is more reliably expressed.

The grooves 2, 3 (grooves 2, 3) are formed to extend in the longitudinal direction D1. Each groove 2, 3 is linear (stripe-like). The grooves 2, 3 are preferably linear from the viewpoint of efficiently expressing the effect of modifying the magnetostriction constant and the amount of parallel magnetostriction. The grooves 2, 3 may be curved. The length of the longitudinal direction D1 of the grooves 2, 3 is not particularly limited. The grooves 2, 3 are preferably formed over the entire surface from the viewpoint of efficiently expressing the effect of modifying the magnetostriction constant and the amount of parallel magnetostriction. As described above, in the magnetostrictive member 1 cut using the wire saw device 20, the grooves 2, 3 are formed over the entire front and back surfaces. In this embodiment, the magnetostrictive member 1 may include grooves extending in other directions than the longitudinal direction as long as the effect of the present invention is not impaired, and such magnetostrictive members are not excluded, but it is ideal that there are no grooves extending in other directions than the longitudinal direction.

On each surface of the front and back surfaces of the magnetostrictive member 1, the surface roughness Ra in the longitudinal direction D1 is preferably smaller than the surface roughness Ra in the transverse direction D2. On each surface of the front and back surfaces of the magnetostrictive member 1, the surface roughness Ra in the longitudinal direction D1 is preferably at least 0.3 μm in lower limit, and preferably at most 1.5 μm in upper limit, more preferably at least 0.3 μm and at most 1.5 μm. Also, on each surface of the front and back surfaces of the magnetostrictive member 1, the surface roughness Ra in the transverse direction D2 is preferably at least 0.6 μm in lower limit, more preferably at least 0.7 μm in higher limit, and preferably at most 4.5 μm in upper limit, and preferably at most 0.6 μm and at most 4.5 μm in higher limit, more preferably at most 0.7 μm and at most 4.5 μm in higher limit. When the surface roughness Ra in the longitudinal direction D1 or the lateral direction D2 of each of the front and back surfaces of the magnetostrictive member 1 is within the above range, the effect of improving the magnetostriction constant and the amount of parallel magnetostriction can be efficiently achieved. In this embodiment, the surface roughness Ra is the average value obtained by measuring multiple different parts of one magnetostrictive member 1.

In this embodiment, the grooves 2 and 3 extending in the longitudinal direction D1 includes the grooves 2 and 3 extending in a direction parallel to the longitudinal direction D1 and the grooves 2 and 3 extending in a direction intersecting the longitudinal direction D1 at an angle of less than 40°. If the extension direction (extension direction) of the grooves 2 and 3 deviates from a direction parallel to the longitudinal direction D1, the amount of parallel magnetostriction decreases (see Comparative Example 1), so it is preferable that the extension direction of the grooves 2 and 3 is a direction parallel to the longitudinal direction D1. The grooves 2 may include grooves extending in different directions, or grooves having shapes with different lengths or depths. The grooves 3 may include grooves extending in different directions, or grooves having shapes with different lengths or depths.

The characteristics of the magnetostrictive member 1 of this embodiment will be described. The magnetostrictive member 1 of this embodiment can have a magnetostriction constant of 200 ppm or more, preferably 250 ppm or more, due to the above configuration. In addition, the magnetostrictive member 1 can have a parallel magnetostriction amount of 200 ppm or more, preferably 250 ppm or more, due to the above configuration. When the magnetostrictive constant and parallel magnetostriction amount of the magnetostrictive member 1 are to be within the above ranges, it is preferable to form the magnetostrictive member 1 from a single crystal of an Fe-Ga alloy.

In addition, the magnetostrictive member 1 of this embodiment is modified (corrected) so that both the magnetostrictive constant and the amount of parallel magnetostriction are high and have little variation between members by forming the above-mentioned first groove 2 and second groove 3. The grooves 2 and 3 in the magnetostrictive member 1 of this embodiment are capable of modifying both the magnetostrictive constant and the amount of parallel magnetostriction (at least the amount of parallel magnetostriction), and the grooves 2 and 3 can make the magnetostrictive constant preferably 200 ppm or more, more preferably 250 ppm or more, and the amount of parallel magnetostriction preferably 200 ppm or more, more preferably 250 ppm or more. Therefore, in the case of multiple magnetostrictive members 1 manufactured from one crystal, the magnetostrictive member 1 of this embodiment can make the coefficient of variation of the magnetostrictive constant in the multiple magnetostrictive members 1 preferably 0.1 or less, more preferably 0.06 or less, more preferably 0.04 or less, and the coefficient of variation of the amount of parallel magnetostriction preferably 0.1 or less, more preferably 0.06 or less. Note that a single grown crystal is the effective crystal (the part that is actually used as a part) that is used as a magnetostrictive member. For example, crystals grown by the BV method have a solidification rate in the range of 10% to 85%, while crystals grown by the CZ method have a uniform diameter (excluding the growth shoulder, etc.).

As described above, the magnetostrictive member 1 of this embodiment is a plate-shaped body made of crystals of an iron-based alloy having magnetostrictive properties and having a longitudinal direction D1 and a transverse direction D2, and has a plurality of first grooves D1 extending in the longitudinal direction D1 on the front surface 4 and back surface 5 of the plate-shaped body, and a plurality of second grooves 3 deeper than the first grooves 2 and extending in the longitudinal direction D1 on the front surface 4 and back surface 5 of the plate-shaped body. Note that in the magnetostrictive member 1 of this embodiment, the configuration other than the above is optional. The magnetostrictive member 1 of this embodiment has a high magnetostriction constant and parallel magnetostriction amount, and has a characteristic of small variation in the magnetostriction constant and parallel magnetostriction amount between members. In addition, the magnetostrictive member 1 of this embodiment is presumed to have the above grooves modify the magnetostriction constant and parallel magnetostriction amount, and since the variation in the magnetostriction constant and parallel magnetostriction amount in magnetostrictive members manufactured from the same conventional single crystal is corrected, it can be produced stably with high yield. The magnetostrictive member 1 of this embodiment has a high magnetostriction constant and a high amount of parallel magnetostriction, and can therefore be suitably used as a final product of a member (material) that exhibits excellent magnetostriction and inverse magnetostriction effects. In addition, the magnetostrictive member 1 of this embodiment can be easily manufactured because it can be manufactured simply by cutting a single crystal with a wire saw device, as will be explained later in the manufacturing method of the magnetostrictive member of this embodiment.

Next, a method for manufacturing the magnetostrictive member of this embodiment will be described. 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 comprises forming a plurality of first grooves 2 extending in the longitudinal direction D1 on the front surface 4 and back surface 5 of a plate-like body made of crystals of an iron-based alloy having magnetostrictive properties and having a longitudinal direction D1 and a lateral direction D2, and forming a plurality of second grooves 3 extending in the longitudinal direction D1 deeper than the first grooves 2 on the front surface 4 and back surface 5 of the plate-like body.

In the following explanation, a method for manufacturing the magnetostrictive member 1 from a single crystal ingot of an Fe-Ga alloy is described as an example, but the manufacturing method of the magnetostrictive member of this embodiment is not limited to the following explanation. In addition, any description in this specification that is applicable to the manufacturing method of the magnetostrictive member of this embodiment is also applicable to the manufacturing method of the magnetostrictive member of this embodiment.

Figure 4 is a flow chart showing an example of a method for manufacturing a magnetostrictive member of this embodiment. Figures 5 to 7 are diagrams showing first to third examples of a single crystal, a thin plate member, and a magnetostrictive member. For example, the method for manufacturing a magnetostrictive member of this embodiment includes a crystal preparation step (step S1), a crystal cutting step (step S2), and a cutting step (step S3) (see Figure 4).

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, but the following explanation will focus on an example in which the crystal is a single crystal. The prepared crystal may be grown or a commercially available product. For example, in the crystal preparation step, a single crystal of an Fe-Ga alloy is prepared. There is no particular limitation on the method of growing the single crystal of an Fe-Ga alloy. The method of growing the single crystal of an Fe-Ga alloy may be, for example, a pulling method or a unidirectional solidification method. The Cz method can be used for the pulling method, and the VB method, VGF method, and micro-pulling down method can be used for the unidirectional solidification method.

The magnetostriction constant of the Fe-Ga alloy single crystal is maximized by setting the gallium content to 18.5 at% or 27.5 at%. For this reason, the Fe-Ga single crystal is preferably grown to have a gallium content of 16.0 to 20.0 at% or 25.0 to 29.0 at%, and more preferably to have a gallium content of 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 by cutting the seed crystal, the diameter-increasing portion, or the shoulder portion (the portion that increases the diameter from the seed crystal to a specified single crystal diameter) with a cutting device as necessary. The size of the grown single crystal is not particularly limited as long as the magnetostrictive member can be secured in a specified direction. When growing Fe-Ga single crystals, they are grown using a seed crystal whose top or bottom surface is machined to a {100} plane so that the growth axis direction is <100>. The grown Fe-Ga alloy single crystal grows perpendicular to the top or bottom surface of the seed crystal, and inherits the orientation of the seed crystal.

After the crystal preparation step (step S1), the crystal cutting step (step S2) is performed. The crystal cutting step is a step of cutting the crystal C to produce a thin plate member PL. The thin plate member PL is a member that will be the material of the magnetostrictive member 1 of this embodiment. As described above, the crystal cutting step is preferably performed using a multi-wire saw device 20 (wire saw device). In addition, the crystal cutting step forms grooves that will become the first groove 2 and the second groove 3. By using a wire saw device, the first groove 2 and the second groove 3 (the grooves that will become them) can be more reliably formed, and the magnetostrictive member 1 can be easily manufactured. Note that cutting devices include, for example, peripheral blade cutting devices and wire electric discharge machines, but in the case of such devices, it is difficult to form multiple grooves (machining marks) in a fixed direction as described above.

It is also preferable to use a wire 25 (fixed abrasive wire) in which abrasive grains such as diamond are fixed by electrochemical deposition or adhesive (fixed abrasive wire method). When using a fixed abrasive wire (fixed abrasive wire method), the first groove 2 and the second groove 3 can be reliably formed along the running direction of the wire. In addition, in the free abrasive method in which cutting is performed by supplying a machining liquid (also called a slurry) containing abrasive grains between the single crystal C and the wire 25 while feeding the wire 25 in the linear direction, the degree of freedom of the abrasive grains is high and it is not possible to form a groove that is constant in one direction. For this reason, as shown in Comparative Example 2, there is variation in the magnetostriction constant and the amount of parallel magnetostriction.

When cutting single crystal C with the wire saw device 20, the direction of travel of the wire 25 (travel method) is preferably a method in which the wire 25 travels back and forth to perform the cutting (reciprocating cutting method).

The wire saw device 20 that can be used in this embodiment is not particularly limited and any known device can be used. For example, the wire saw device described in JP 2008-229752 A can be used as a wire saw device equipped with the above-mentioned oscillation mechanism. Note that in this embodiment, a wire saw device that does not have the above-mentioned oscillation mechanism may also be used.

The cutting direction of the single crystal C when cutting the single crystal C with the wire saw device 20 is not particularly limited. As shown in FIG. 7, the wire 25 may be arranged so that the running direction is perpendicular to the growth direction of the single crystal C, and cutting may start from the circumferential side of the single crystal C. The wire 25 may also be arranged so that the running direction is perpendicular to the growth direction of the single crystal C, and cutting may start from the top and bottom surfaces of the single crystal. Furthermore, as shown in FIG. 5 and FIG. 6, the wire 25 may be arranged so that the growth direction of the single crystal C is parallel to the growth direction of the single crystal, and cutting may be started. FIG. 5 is a diagram showing cutting starting from the third <100> axis side on the circumferential side of the single crystal C. FIG. 6 is a diagram showing cutting starting from the second <100> axis side on the circumferential side of the single crystal C.

The thickness of the thin plate member PL is set to be the same as the thickness of the magnetostrictive member 1. For example, it is 0.5 mm to 3.0 mm. By appropriately adjusting the diameter of the wire 25 and the pitch P1 between the wires 25 (the distance between the wires 25, see FIG. 1(B)), the single crystal C can be cut into thin plate members PL of a predetermined thickness. At this time, the thin plate members PL are produced with the {100} plane as the main surface. Note that other conditions for cutting the single crystal C using the wire saw device 20 are as described above and will not be described here.

Next, a cutting process (step S3) is carried out. In the cutting process, the thin plate member PL in which the multiple first grooves 2 and the multiple second grooves 3 that are deeper than the first grooves and extend in the longitudinal direction are formed by the crystal cutting process is cut to obtain the magnetostrictive member 1 of this embodiment.

In the cutting process (step S3), when cutting the thin plate member PL to make the magnetostrictive member 1, the thin plate member PL is cut so that a plurality of first grooves 2 extending in the longitudinal direction D1 are formed on the front surface 4 and back surface 5 of the magnetostrictive member finally obtained, and a plurality of second grooves 3 extending in the longitudinal direction D1 deeper than the first grooves 2 are formed on the front surface 4 and back surface 5 of the plate-like body. In the cutting process, the thin plate member PL is cut to a predetermined size. In the cutting process, the thin plate member PL is cut as the magnetostrictive member 1 so that the magnetostrictive member 1 becomes a rectangular plate-like body in a plan view. In the cutting process, the thin plate member PL 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 member is extracted from the thin plate member, and for example, it may be set to a direction that allows efficient acquisition based on the size of the magnetostrictive member.

The effect of modifying the magnetostriction constant and the amount of parallel magnetostriction occurs by forming grooves 2, 3 extending in the longitudinal direction D1 on the front and back surfaces of the magnetostrictive member 1. In the manufacturing method of this embodiment, however, by using a multi-wire saw device 20 (wire saw device), it is not necessary to perform a new process of processing the front and back surfaces to form the multiple grooves 2, 3 after manufacturing the thin plate member PL or the magnetostrictive member 1, so it is possible to efficiently manufacture the magnetostrictive member 1.

As described above, the manufacturing method of the magnetostrictive member of this embodiment comprises forming a plurality of first grooves extending in the longitudinal direction on the front and back surfaces of a plate-shaped body made of crystals of an iron-based alloy having magnetostrictive properties and having a longitudinal direction and a lateral direction, and a plurality of second grooves extending in the longitudinal direction deeper than the first grooves on the front and back surfaces of the plate-shaped body. Note that in the manufacturing method of the magnetostrictive member of this embodiment, the configuration other than the above is optional. The manufacturing method of the magnetostrictive member of this embodiment can manufacture a magnetostrictive member having a high magnetostriction constant and parallel magnetostriction amount, and a small variation in the magnetostriction constant and parallel magnetostriction amount between members. The manufacturing method of the magnetostrictive member of this embodiment can be easily carried out because it is only necessary to form a plurality of grooves 2 and 3 in a material having magnetostrictive properties, and the processing steps are easy and few as described above. The magnetostrictive member 1 of this embodiment has a high magnetostriction constant and parallel magnetostriction amount, and can be suitably used as a final product of a member (material) exhibiting excellent magnetostrictive effect and inverse magnetostrictive effect.

Conventionally, magnetostrictive members taken from the same single crystal have variations in the amount of parallel magnetostriction depending on the position where the magnetostrictive member is taken from the single crystal, and magnetostrictive members with a high amount of parallel magnetostriction have been selected. However, in the manufacturing method of magnetostrictive members of this embodiment, the above-mentioned magnetostriction constant and parallel magnetostriction amount are modified to correct the variation in the magnetostrictive constant and parallel magnetostriction amount in magnetostrictive members made from the same single crystal in the past. This makes it possible to produce magnetostrictive members with characteristics of high magnetostriction constant and parallel magnetostriction amount and small variation in the magnetostrictive constant and parallel magnetostriction amount between members in a simple manufacturing method, with high yield and stable production.

The present invention will be explained in detail below using examples, but the present invention is not limited to these examples.

[Example 1]
The raw materials were adjusted to a stoichiometric ratio of iron and gallium of 81:19, and a cylindrical Fe-Ga alloy single crystal was prepared by growing using the vertical Bridgman (VB) method. The growth axis direction of the single crystal was set to <100>. The orientation of the {100} plane on the top or bottom surface of the single crystal perpendicular to the crystal growth axis direction was confirmed by X-ray diffraction. At this time, the top and bottom samples of the crystal were measured using a Shimadzu sequential plasma emission spectrometer (ICPS-8100), and the concentration of the single crystal was found to be 17.5 to 19.0 at% gallium.

A magnetostrictive member was manufactured from the grown single crystal as follows. The single crystal was cut by a reciprocating cutting method using a fixed abrasive grain type multi-wire saw device. As shown in Figure 7, the single crystal was arranged so that the wire travel direction was perpendicular to the single crystal growth direction (the crystal's <100> orientation direction) and the single crystal was cut from the circumferential side of the single crystal, and a thin plate member was manufactured by cutting. The abrasive grain size was 30 to 40 μm, the wire diameter was 180 μm, the new wire supply rate was 6.8 m/min, and the wire oscillation angle (see Figure 3) was 0°. The wire reciprocating cycle was 3 times per minute, and the wire feed rate was 1000 m/min. The speed (feed rate) at which the single crystal was pressed against the wire was 3.3 mm/hour. Next, the obtained thin plate member was cut out using an outer peripheral blade cutting device so that the wire travel direction when the thin plate member was manufactured was aligned with the longitudinal direction of the magnetostrictive member. As a result, ten magnetostrictive members were obtained, each having a longitudinal dimension of 16 mm, a transverse dimension of 4 mm, and a thickness of 1 mm. The obtained magnetostrictive member was a plate-like body having a longitudinal direction and a transverse direction, as shown in the example in Figures 1 (A) and (B), and had a plurality of first grooves extending in the longitudinal direction on the front and back surfaces of the plate-like body, and a plurality of second grooves extending in the longitudinal direction and deeper than the first grooves on the front and back surfaces of the plate-like body. In addition, the angle (intersection angle) at which the extension direction of the first grooves intersects with the extension direction of the second grooves was 15° or less.

Next, the magnetostrictive properties of the cut magnetostrictive members were measured. The magnetostrictive properties were measured using a strain gauge method. As shown in Figure 8, a strain gauge (manufactured by Kyowa Electric Industries, Ltd.) was attached with an adhesive to the {100} plane, which is the main surface of the manufactured magnetostrictive member. Note that since the longitudinal direction of the strain gauge is the direction in which magnetostriction is detected, the strain gauge was attached so that its longitudinal direction was parallel to the longitudinal direction of the magnetostrictive member and the <100> orientation.

The magnetostriction measuring device (manufactured by Kyowa Electric Industry Co., Ltd.) consists of a neodymium permanent magnet, a bridge box, a compact recording system, a strain unit, and dynamic data acquisition software.

The amount of magnetostriction was determined by correcting the actual detected strain value with the gauge factor.
The gauge factor was determined by the following formula (3).
ε=2.00/Ks × εi...Formula (3)
(ε: gauge factor, εi: measured strain value, Ks: gauge factor of the gauge used)

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 magnetostriction constant was determined by the difference between the parallel magnetostriction and the perpendicular magnetostriction according to formula (1). As a result of measuring 10 pieces, when the longitudinal direction was processed to be parallel to the extension direction of the first groove and the second groove, the parallel magnetostriction of this magnetostrictive member was 262 to 314 ppm (average 282 ppm) and the magnetostriction constant was 271 to 295 ppm (average 284 ppm).

The surface of the magnetostrictive member was also measured at five locations in each of the two directions, the longitudinal direction and the lateral direction, 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 surface roughness Ra in the longitudinal direction was 0.3 to 0.4 μm, and the surface roughness Ra in the lateral direction was 0.7 to 0.8 μm. The manufacturing conditions and evaluation results are shown in Table 1. The second grooves were formed with a pitch of 17 μm and a depth of 1.5 μm.

Furthermore, the front and back surfaces of the magnetostrictive member were ground using a lapping device, and then polished using a polishing device to give them a mirror finish. The first and second grooves on the front and back surfaces of the magnetostrictive member were removed, and the amount of parallel magnetostriction was checked again. As a result, the amount of parallel magnetostriction varied greatly, from 34 to 290 ppm. In particular, the amount of parallel magnetostriction was significantly reduced in eight out of ten samples, causing large variations. The remaining two samples were almost identical and showed no variation.

[Example 2]
In Example 2, the swing angle θ (see FIG. 3) of the wire in Example 1 was changed to ±3°, and the rest of the experiment was carried out in the same manner as in Example 1. The manufacturing conditions and evaluation results of the obtained magnetostrictive member are shown in Table 1. The obtained magnetostrictive member was a plate-like body having a longitudinal direction and a lateral direction, as in the example shown in FIGS. 1(A) and (B), and had a plurality of first grooves extending in the longitudinal direction on the front and back surfaces of the plate-like body, and a plurality of second grooves deeper than the first grooves and extending in the longitudinal direction on the front and back surfaces of the plate-like body. In addition, the angle at which the extension direction of the first groove intersects with the extension direction of the second groove (intersection angle) was 15° or less. The surface roughness Ra was 0.3 to 0.4 μm in the longitudinal direction and 0.6 to 0.7 μm in the lateral direction, and the surface roughness Ra in the lateral direction was greater than that in the longitudinal direction.

[Example 3]
In Example 3, the abrasive grain size of the abrasive grains fixed to the wire in Example 2 was changed to 6 to 12 μm, and the wire diameter was changed to 120 μm, and the rest of the experiment was carried out in the same manner as in Example 2. The manufacturing conditions and evaluation results of the obtained magnetostrictive member are shown in Table 1. The obtained magnetostrictive member was a plate-like body having a longitudinal direction and a lateral direction, as shown in the example in FIG. 1 (A) and (B), and had a plurality of first grooves extending in the longitudinal direction on the front and back surfaces of the plate-like body, and a plurality of second grooves extending in the longitudinal direction and deeper than the first grooves on the front and back surfaces of the plate-like body. In addition, the angle (intersection angle) at which the extension direction of the first grooves intersects with the extension direction of the second grooves was 15° or less. The surface roughness Ra was 0.3 to 0.4 μm in the longitudinal direction and 0.6 to 0.7 μm in the lateral direction, and the surface roughness in the lateral direction was greater than that in the longitudinal direction.

[Example 4]
Example 4 is an example in which the thickness of the magnetostrictive member in Example 3 was changed to 0.5 mm and the swing angle θ of the wire (see FIG. 3) was changed to ±10°, and otherwise the same as Example 3 was carried out. The manufacturing conditions and evaluation results of the obtained magnetostrictive member are shown in Table 1. The obtained magnetostrictive member was a plate-like body having a longitudinal direction and a lateral direction as shown in the example of FIG. 1 (A) and (B), and had a plurality of first grooves extending in the longitudinal direction on the front and back surfaces of the plate-like body, and a plurality of second grooves deeper than the first grooves and extending in the longitudinal direction on the front and back surfaces of the plate-like body. In addition, the angle (intersection angle) at which the extension direction of the first groove intersected with the extension direction of the second groove was 15° or less. The surface roughness Ra was 0.1 to 0.2 μm in the longitudinal direction and 0.2 to 0.3 μm in the lateral direction, and the surface roughness in the lateral direction was greater than that in the longitudinal direction.

[Comparative Example 1]
In Comparative Example 1, the single crystal was cut into thin plate members using a fixed abrasive wire saw device in Example 1, and then cut out using a peripheral blade cutting device so that the running direction of the wire was aligned with the "short side direction" of the magnetostrictive member. Ten magnetostrictive members with a longitudinal dimension of 16 mm x short side dimension of 4 mm x thickness of 1 mm were obtained. The obtained magnetostrictive member had a plurality of first grooves extending in the "short side direction" and a plurality of second grooves extending in the "short side direction" on the front and back surfaces of the plate-like body. The manufacturing conditions and evaluation results of the obtained magnetostrictive member are shown in Table 1. As a result of evaluating the obtained 10 magnetostrictive members, the parallel magnetostriction amount of this magnetostrictive member was 27 to 70 ppm (average 40 ppm) and the magnetostriction constant was 70 to 300 ppm (average 284 ppm). The surface roughness Ra was 0.7 to 0.8 μm in the longitudinal direction and 0.3 to 0.4 μm in the lateral direction.

[Comparative Example 2]
Comparative Example 2 is an example in which the wire saw device in Example 1 was changed to a "free abrasive type" wire saw device and cutting processing was performed, and other than these, it is an example that was performed in the same manner as in Example 1. Ten magnetostrictive members having a size of 16 mm in the longitudinal direction × 4 mm in the transverse direction × 1 mm in thickness were obtained. The wire diameter and the wire swing angle θ (see FIG. 3) were also changed from Example 1. The manufacturing conditions and evaluation results of the obtained magnetostrictive members are shown in Table 1. As a result of evaluating the obtained 10 magnetostrictive members, the parallel magnetostriction amount of the magnetostrictive members was 22 to 270 ppm (average 103 ppm), and the magnetostriction constant was 270 to 318 ppm (average 287 ppm). In addition, the surface roughness Ra was 0.4 to 0.5 μm in the longitudinal direction and 0.4 to 0.5 μm in the transverse direction. In addition, the shape of the front and back surfaces of the obtained magnetostrictive members was matte.

[summary]
The results of the examples confirm the above-mentioned improvement of the magnetostriction constant and the parallel magnetostriction amount. The results of the examples also confirm that the magnetostrictive member 1 of this embodiment has a high magnetostriction constant and parallel magnetostriction amount, and has a property of small variation in the magnetostriction constant and parallel magnetostriction amount between members. The results of the examples also confirm that the manufacturing method of the magnetostrictive member of the aspect of the present invention can easily manufacture a magnetostrictive member having a high magnetostriction constant and parallel magnetostriction amount, and small variation in the magnetostriction constant and parallel magnetostriction amount between members.

In addition, as shown in Examples 1 to 4 and Comparative Examples 1 and 2, it has been confirmed that the magnetostrictive member of this embodiment can be manufactured more reliably by using a fixed abrasive wire cutting device and setting the wire oscillation angle θ to less than |15|° (|n| indicates an absolute value), and more preferably, by setting the wire oscillation angle θ to less than |5|° (|n| indicates an absolute value).

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. In addition, to the extent permitted by law, the disclosures of all documents cited in the above-mentioned embodiments are incorporated by reference and made part of the description in this text.

1: Magnetostrictive member 2: First groove 3: Second groove 4: Front surface 5: Back surface D1: Longitudinal direction D2: Shortitudinal direction C: Crystal (single crystal, polycrystal)
S1: Crystal preparation process S2: Crystal cutting process S3: Cutting process

Claims (6)

The plate-shaped body is made of crystals of an Fe—Ga alloy, which is an iron-based alloy having magnetostrictive properties, and has a longitudinal direction and a lateral direction.
the main surface of the plate-like body is a {100} plane of the crystal,
the longitudinal direction is the <100> direction, which is the direction of easy magnetization in the crystal;
A plurality of first grooves extending in the longitudinal direction on the front and back surfaces of the plate-like body;
a plurality of second grooves on the front and back surfaces of the plate-like body, the second grooves being deeper than the first grooves and extending in the longitudinal direction;
the angle between the first groove and the second groove is within 15°;
The surface roughness Ra in the longitudinal direction of the plate-like body is smaller than the surface roughness Ra in the lateral direction, the surface roughness Ra in the longitudinal direction is 0.1 μm or more and 0.4 μm or less, and the surface roughness Ra in the lateral direction is 0.2 μm or more and 0.8 μm or less,
The magnetostriction constant is 200 ppm or more,
A magnetic field parallel to the longitudinal direction is applied, and the amount of parallel magnetostriction, which is the amount of magnetostriction when the amount of magnetostriction in the longitudinal direction is saturated, is 200 ppm or more.
Magnetostrictive material. The magnetostrictive member according to claim 1, wherein the second grooves are formed periodically at predetermined intervals in the short direction of the magnetostrictive member. 3. The magnetostrictive member according to claim 2 , wherein the predetermined interval between the second grooves is not less than 5 μm and not more than 30 μm. The method comprises obtaining a magnetostrictive member having a front and rear surface of a plate-like body made of crystals of an Fe-Ga alloy, which is an iron-based alloy having magnetostrictive properties, the plate-like body having a longitudinal direction and a lateral direction, the front and rear surface of the plate-like body being provided with a plurality of first grooves extending in the longitudinal direction, and a plurality of second grooves extending in the longitudinal direction and deeper than the first grooves on the front and rear surface of the plate-like body ,
a main surface of the magnetostrictive member is a {100} plane of the crystal,
the longitudinal direction is the <100> direction, which is the direction of easy magnetization in the crystal;
the angle between the first groove and the second groove is within 15°;
In the magnetostrictive member, a surface roughness Ra in the longitudinal direction is smaller than a surface roughness Ra in the lateral direction, the surface roughness Ra in the longitudinal direction is 0.1 μm or more and 0.4 μm or less, and the surface roughness Ra in the lateral direction is 0.2 μm or more and 0.8 μm or less,
The magnetostrictive member has a magnetostriction constant of 200 ppm or more,
In the magnetostrictive member, a parallel magnetostriction amount, which is the amount of magnetostriction when a magnetic field parallel to the longitudinal direction is applied and the amount of magnetostriction in the longitudinal direction is saturated, is 200 ppm or more.
A manufacturing method of a magnetostrictive member. the first groove and the second groove are formed by a multi-wire saw;
The method for manufacturing a magnetostrictive member according to claim 4 , wherein the wire used in the multi-wire saw is a fixed abrasive wire having abrasive grains fixed to the wire. 6. The method for manufacturing a magnetostrictive member according to claim 5 , wherein the formation of the first groove and the second groove includes forming the wire by tilting it within a range of ±5° with respect to the workpiece.

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