JP2003089857A - Negative magnetostrictive material and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the magnetostrictive properties (negative displacement) of a negative magnetostrictive material by making it possible to effectively and uniformly apply tensile strength as preset load to a rare-earth alloy (nega tive magnetostrictive alloy) showing negative magnetostriction. SOLUTION: A preload-applying material 3 composed of at least one kind selected from the particles and fibers of substances having a thermal expansion coefficient lower than that of the rare-earth alloy 2 showing negative magnetostriction is dispersedly arranged in a matrix composed of the rare-earth alloy 2 to manufacture a composite material 4. In the negative magnetostrictive material 1 composed of the composite material 4, tensile stress is allowed to remain at -50 to 200 deg.C in a state free from applied magnetic field in the rare- earth alloy 2, and preset load can be applied by means of this residual tensile stress.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative magnetostrictive material used for a magnetic-mechanical displacement conversion device or the like and a method for manufacturing the same.

[0002]

2. Description of the Related Art Displacement control actuators, magnetostrictive sensors, magnetostrictive filters, ultrasonic transducers, ultrasonic delay lines, etc. are known as devices that apply magnetostriction, which deforms a magnetic body when an external magnetic field is applied to the magnetic body. Has been. In these applications, Ni-based alloys, Fe-Co alloys, ferrites, etc. have been used as magnetostrictive materials.

[0003] In recent years, along with the progress of measurement engineering and the development of precision machinery field, the development of a displacement driving unit which is indispensable for micro displacement control on the order of micron is being advanced, and as one of the mechanisms of such displacement driving unit. , A magneto-mechanical displacement conversion device using a magnetostrictive alloy is regarded as promising. However, the conventional magnetostrictive alloy has an insufficient absolute amount of displacement, and as a micron-order precision drive component material, it is not satisfactory not only in terms of absolute drive displacement, but also in terms of precision control.

In view of this point, a rare earth-transition metal-based magnetostrictive alloy (Japanese Patent Publication No. 61-33892, US Pat. No. 478,
No. 258) has high magnetostriction, and is being put into practical use as a drive unit of a magnetostrictive actuator or a sensor unit of a magnetostrictive sensor. Further, with respect to rare earth-transition metal-based magnetostrictive alloys, various proposals have been made to improve characteristics such as magnetostrictive characteristics, temperature characteristics, operating performance, and mechanical strength (for example, JP-A-10-102218). , JP-A-10-242543, JP-A-11-246948, JP-A-2001-223402, etc.).

When the rare earth-transition metal type magnetostrictive alloy as described above is used as an actuator or the like, an appropriate preset load is applied to the magnetostrictive alloy from the outside in advance, and a magnetic field is applied from this state to displace it. The structure is generally applied, and based on such a structure, a larger amount of displacement can be used. A compressive stress is applied to the preset load in the case of a magnetostrictive alloy exhibiting positive magnetostriction. That is, a larger amount of positive displacement (elongation) can be obtained by applying a magnetic field to the magnetostrictive alloy that has been compressed in advance. The proper preset load in this case indicates a load within a range in which a positive displacement amount can be secured by overcoming the compressive stress generated thereby. In many cases, as the preset load is increased, the amount of displacement obtained when a magnetic field is applied increases, but when it exceeds a certain limit value, the amount of displacement decreases conversely.

On the other hand, when a magnetostrictive alloy exhibiting negative magnetostriction is used, a tensile stress is applied to the magnetostrictive alloy as a preset load in advance, and a magnetic field is applied from this state to displace it, thereby increasing the amount of negative displacement. (Shrinkage) is obtained. However, a rare earth-transition metal-based magnetostrictive alloy is generally strong in compressive stress but weak in tensile stress, and is also brittle in terms of material. Therefore, it is extremely difficult to uniformly apply tensile stress to a negative magnetostrictive alloy from the outside. . Further, unlike compressive stress, it is difficult to maintain a state in which tensile stress is uniformly applied. Under such circumstances, there are few examples in which a negative magnetostrictive alloy is applied with an appropriate preset load (tensile stress) for application.

[0007]

As described above, when a rare earth-transition metal type magnetostrictive alloy is used as an actuator or the like, a preset load should be applied to the magnetostrictive alloy in order to obtain a larger displacement amount. Although it is effective, it is extremely difficult to uniformly apply tensile stress from the outside as a preset load to the negative magnetostrictive alloy, and there is a problem that it is difficult to maintain the state of the tensile stress applied from the outside. . For this reason, there is a strong demand for a technique for uniformly applying an appropriate preset load to the negative magnetostrictive alloy and maintaining the state in a stable manner.

The present invention has been made in order to solve such a problem, and it is possible to effectively and uniformly apply a tensile stress as a preset load to a negative magnetostrictive alloy, thereby obtaining a magnetostrictive characteristic (negative It is an object of the present invention to provide a negative magnetostrictive material having an improved displacement amount) and a manufacturing method thereof.

[0009]

The negative magnetostrictive material of the present invention comprises:
A negative magnetostrictive material comprising a rare earth alloy exhibiting negative magnetostriction, wherein the rare earth alloy is -5.
Tensile stress remains at a temperature in the range of 0 ° C to 200 ° C and in the absence of an applied magnetic field, and a preset load is applied to the rare earth alloy by the residual stress of this tension.

As a more specific constitution of the present invention, as described in claim 2, a base material made of a rare earth alloy exhibiting negative magnetostriction, and a rare earth alloy dispersedly arranged in the base material. Negative magnetostrictive materials that include a preload-applying material that generates tensile residual stress at a temperature in the range of 50 ° C. to 200 ° C. and in the absence of an applied magnetic field and that applies a preset load by the residual stress are included.

In the negative magnetostrictive material of the present invention, tensile stress is retained as internal strain in a rare earth alloy (negative magnetostrictive alloy) exhibiting negative magnetostriction. The residual tensile stress is, for example, a substance having a coefficient of thermal expansion smaller than that of a rare earth alloy, dispersed in a rare earth alloy as a base material under high temperature to form a composite, and the composite material in the high temperature state is cooled to near room temperature. Residual stress consisting of tensile stress can be generated in the rare earth alloy. Since such a tensile stress (residual stress) acts as a preset load for a rare earth alloy exhibiting negative magnetostriction,
By applying a magnetic field in this state to displace the rare earth alloy, an excellent amount of negative displacement (shrinkage) can be obtained.

In the negative magnetostrictive material of the present invention, it is preferable to use, as the preload-applying material, at least one selected from particles and fibers of a substance having a coefficient of thermal expansion smaller than that of the rare earth alloy as described in claim 3. . It is difficult for the preloading material to react with the rare earth alloy at high temperature, for example, tungsten, molybdenum, carbon, silicon nitride, aluminum nitride, titanium nitride, zirconium nitride, boron nitride, silicon carbide, tungsten carbide, Molybdenum carbide,
It is more preferable to use at least one selected from titanium boride, aluminum oxide, silicon oxide, magnesium oxide, aluminum titanate, and rare earth nitrides. Further, in order to obtain an appropriate preset load, the preloading material should be contained in the range of 1 to 10% by volume with respect to the composite material of the rare earth alloy and the preloading material as described in claim 5. Is preferred.

According to the method for producing a negative magnetostrictive material of the present invention, as described in claim 8, in a base material made of a rare earth alloy exhibiting negative magnetostriction, particles of a material having a coefficient of thermal expansion smaller than that of the rare earth alloy and Preloading material consisting of at least one selected from fibers, a step of dispersing and arranging at high temperature to form a composite, and when cooling the composite material in the high temperature state, the rare earth alloy in contact with the preloading material And a step of leaving the tensile stress to remain.

In the method for producing the negative magnetostrictive material of the present invention,
As a concrete step of leaving the tensile stress in the rare earth alloy, for example, the step of casting the molten metal of the rare earth alloy to which the preloading material is added while stirring, or the step of claim 11. In addition, there may be mentioned a step of compacting a mixture of the rare earth alloy powder and the preloading material, sintering the compact, and then cooling the compact.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Modes for carrying out the present invention will be described below. FIG. 1 is a sectional view schematically showing a microstructure of a negative magnetostrictive material according to an embodiment of the present invention. The negative magnetostrictive material 1 shown in the figure is composed of a composite material 4 of a rare earth alloy (negative magnetostrictive alloy) 2 exhibiting negative magnetostriction and a preloading material 3. That is, the rare earth alloy 2 exhibiting negative magnetostriction constitutes the base material of the composite material 4, and the preload applying material 3 is dispersed in the base material.

As the rare earth alloy exhibiting negative magnetostriction, for example, the general formula: R (T _x M _1-x ) _z (1) (wherein R is at least Sm selected from rare earth elements, or 2 or One or more elements, T is at least one element selected from Fe, Co and Ni, and M is the above T
An element selected from transition metal elements other than the element, x
And z are numbers satisfying 0.5 ≦ x ≦ 1 and 1.4 ≦ z ≦ 2.5).

The rare earth element (R) contains at least Sm. An alloy of Sm and a transition metal element becomes a magnetostrictive alloy (negative magnetostrictive alloy) that exhibits negative magnetostriction, that is, a negative displacement amount (contraction) when a magnetic field is applied. As the R element,
Sm may be used alone, or a combination of Sm and another rare earth element may be used. A lanthanoid element containing Y can be appropriately used as the rare earth element other than Sm, and for example, Ce, Nd, Tb, Dy, Ho, Er, T
It is preferable to use m, Pr, Gd, Yb or the like. As for the rare earth element other than Sm, one or more elements can be used. However, if the amount of the rare earth element other than Sm is too large, for example, the negative magnetostriction amount may decrease, so 50% or more of the R element is preferably Sm.

As the transition metal element, at least one T element selected from Fe, Co and Ni is a main constituent element. Among these T elements, Fe is preferably used mainly in order to obtain good negative magnetostriction. In particular,
It is preferable that 50% or more of the T element is Fe. SmF
The e ₂ alloy is known as a typical negative magnetostrictive alloy, and on the basis of this system, a part of Sm is replaced with another rare earth element, and a part of Fe is Co or Ni.
Substitution with an element is preferred.

As described above, part of the T element is an M element selected from transition metal elements other than the T element, if necessary, specifically Mn, Cr, Mg, Al, Ti, V, C.
r, Cu, Zn, Ga, Ge, Zr, Nb, Mo, I
n, Sn, Hf, Ta, W, Re, Ir, B, C, P,
You may substitute by 1 type (s) or 2 or more types of transition metal elements selected from Si etc. By substituting a part of the T element with the M element, magnetostriction characteristics, material strength, corrosion resistance and the like can be improved.

The substitution amount of the M element is the T element (Fe, C
50% or less (0.5 ≦ x ≦ 1) based on the total amount of o and Ni)
It is preferable that The substitution amount of T element by M element is
If it exceeds 50%, the magnetostrictive properties of the rare earth alloy may deteriorate,
Moreover, the Curie temperature may decrease. As the M element (transition metal element) substituting the T element, Mn, Cr,
It is preferable to use Zn, Mo, Al, Ga, Zr or the like.

Rare earth element (R) and transition metal element (T +
The value of z, which is the ratio of M), is preferably in the range of 1.4 to 2.5 as described above. When the value of z is less than 1.4, the ratio of the Laves phase which is the main phase decreases, while when it exceeds 2.5, the generation of different phases increases, so that the magnetostrictive properties deteriorate and the mechanical strength and the like decrease. . z value is 1.7 ~
The range of 2.3 is more preferable.

Representative examples of rare earth alloys exhibiting negative magnetostriction (negative magnetostrictive alloys) are SmFe ₂ , Sm (Fe, Co) ₂ and S.
m (Fe, Ni) ₂ , (Sm _1-a Ce _a ) Fe ₂ , (Sm
_1-a Nd _a ) Fe ₂ , (Sm _1-a Tb _a ) Fe ₂ , (Sm _1-a
Dy _a ) Fe ₂ , (Sm _1-a Ho _a ) Fe ₂ , (Sm _1-a Er
_{a) Fe 2, (Sm 1} -a Tm a) Fe 2, (Sm 1-ab Tb a
_{Dy b) Fe 2, (Sm} 1-ab Tb a Ho b) Fe 2, (Sm
_{1-a Tb a) (Fe} , Co) 2, (Sm 1-a Tb a) (F
e, Ni) _{2 and the} like. In the above formulas, a and b are 0 <a ≦ 0.5, 0 <b ≦ 0.5, 0, respectively.
It is a number that satisfies <a + b ≦ 0.5.

The rare earth alloy exhibiting negative magnetostriction (negative magnetostrictive alloy) may contain at least one selected from nitrogen, hydrogen, boron, carbon, phosphorus and silicon in addition to the above-mentioned main constituent elements. Good. These elements contribute to the improvement of the Curie temperature of the rare earth alloy. However, if the content is too large, the magnetostriction amount is lowered, so that the total content of these elements is preferably 3% by mass or less. In order to obtain the effect of improving the Curie temperature by nitrogen, hydrogen, boron, carbon, phosphorus and silicon, the total content of these elements is preferably 0.0001 mass% or more.

Negative magnetostrictive material 1 comprising composite material 4 shown in FIG.
Has a structure in which the preloading material 3 is dispersedly arranged between particles of the rare earth alloy (negative magnetostrictive alloy) 2 exhibiting negative magnetostriction as described above. Tensile stress remains as internal strain in the rare earth alloy (negative magnetostrictive alloy) 2 based on the preload-applying material 3, and an appropriate preset load (tensile stress) is added by this residual stress of tension. As the preloading material 3 that causes such tensile stress (residual stress), particles or fibers of a material having a smaller coefficient of thermal expansion (coefficient of linear expansion) than a rare earth alloy are used.

The above-mentioned preload-applied material 3 is uniformly dispersed in a rare earth alloy (negative magnetostrictive alloy) 2 which is a base material under high temperature to form a composite, and the composite material in a high temperature state is cooled, A tensile residual stress can be generated in the rare earth alloy 2 near room temperature. That is, internal strain occurs in the composite material based on the difference in thermal expansion between the rare earth alloy 2 as the base material and the preloading material 3. When a substance having a coefficient of thermal expansion smaller than that of the rare earth alloy 2 is applied as the preloading material 3, the internal strain becomes almost minimum when it is compounded at a high temperature, and a part of the strain is released as the temperature lowers. As indicated schematically by the arrow in Fig. 1, tensile stress is exerted on the rare earth alloy 2 as the base material.
Further, compressive stress remains in the preloading material 3. In this way, it becomes possible to generate tensile residual stress as internal strain in the rare earth alloy (negative magnetostrictive alloy) 2 that is in contact with the preloading material 3. The presence or absence of residual stress can be confirmed by X-ray diffraction.

The tensile stress (residual stress) generated in the rare earth alloy (negative magnetostrictive alloy) 2 is the material of the preloading material 3 (elastic constant, etc.), the content in the composite material 4, the particles of the preloading material 3, and the like. The shape and size of the fibers, the orientation based on them, the temperature and time during the high temperature combination of the rare earth alloy 2 and the preloading material 3, and the cooling rate can be controlled to an appropriate value. The alloy 2 can be caused to function as an appropriate preset load. The tensile stress of the rare earth alloy 2 is assumed to remain at a temperature in the range of −50 ° C. to 200 ° C. and in the absence of an applied magnetic field in consideration of, for example, the operating temperature of the actuator. Therefore,
The rare earth alloy 2 and the preloading material 3 are compounded at a temperature higher than that.

As shown in FIG. 2 (a), the coil is formed on the composite material 4 in which the tensile stress remains in the rare earth alloy 2, that is, in the negative magnetostrictive material 1 in which the preset load consisting of the tensile stress is added to the rare earth alloy 2. By applying a magnetic field from 5 or the like and displacing the negative magnetostrictive material 1 made of the composite material 4 in the contraction direction (negative direction) as shown in FIG. 2B, a larger negative displacement amount (negative magnetostriction) Can be obtained. That is,
Since the negative magnetostrictive material 1 is in a state of being stretched by the tensile stress generated in the rare earth alloy 2, it is displaced in the negative direction on the basis of this state, so that it is larger than that in the case where no preset load is added. A negative displacement amount (negative magnetostriction) is obtained.

The internal strain of the rare earth alloy 2 based on the above-mentioned residual stress is preferably set within an appropriate preset load, and specifically, the lattice constant of the crystal of the rare earth alloy 2 mixed with the preloading material 3 is set. From the lattice constant of the crystal before composite
It is preferable to set it so as to increase in the range of 0.005 to 0.15%. If the rate of increase of the crystal lattice constant of the rare earth alloy 2 after the compounding is less than 0.005%, the increase of the magnetostriction amount due to the preset load becomes small and the practical effect cannot be sufficiently obtained. On the other hand, rare earth alloy 2 after compounding
If the increase rate of the crystal lattice constant of is more than 0.15%, the preset load may be too large and the amount of magnetostriction may be decreased. The increase rate of the crystal lattice constant of the rare earth alloy 2 after the combination is more preferably in the range of 0.01 to 0.1%, further preferably 0.01 to 0.05%. The crystal lattice constant of the rare earth alloy 2 can be obtained by X-ray diffraction.

Preloading material 3 compounded with rare earth alloy 2
As described above, a substance having a coefficient of thermal expansion smaller than that of the rare earth alloy 2 is used as described above. In order to allow the tensile stress to remain in the rare earth alloy 2 more effectively, the difference in the coefficient of thermal expansion from the rare earth alloy 2 is used. It is preferable to use a substance having a viscosity of 4 × 10 ⁻⁶ / ° C. or higher. Although it depends on the content of the preload-applying material 3, by using the preload-applying material 3 having the difference in thermal expansion as described above, the internal strain based on the temperature difference can be effectively generated. The tensile stress can be more effectively retained in the rare earth alloy 2 in contact with the preloading material 3.

Further, it is preferable that the preload-applying material 3 has a smaller coefficient of thermal expansion than the rare earth alloy 2 and that it is difficult to react with the rare earth alloy 2 when it is compounded at a high temperature. When the reaction with the rare earth alloy 2 progresses, not only the residual stress decreases but also the magnetostrictive property itself of the rare earth alloy 2 may deteriorate. Note that even a substance that easily reacts with the rare earth alloy 2 can be used by inactivating the surface of the preloading material 3 with a coating or the like. Further, since the preloading material 3 is hardly deformed by the magnetic field,
In order to prevent this from interfering with the displacement of the rare earth alloy 2, it is preferable to use a substance having a small elastic constant for the preloading material 3.

For the reason described above, the preloading material 3
Is specifically tungsten, molybdenum, carbon, silicon nitride, aluminum nitride, titanium nitride, zirconium nitride, boron nitride, silicon carbide, tungsten carbide, molybdenum carbide, titanium boride, aluminum oxide, silicon oxide, magnesium oxide, titanic acid. It is preferable to contain at least one selected from aluminum and rare earth nitrides. The preloading material 3 is a rare earth alloy 2 as a base material.
It is preferable that the particles have a shape such as particles or fibers that can be easily dispersed uniformly therein.

The particle shape of the preloading material 3 may be needle-like, granular, lump-like, or flake-like.
In particular, it is preferable to use particles having a large aspect ratio (length in the lengthwise direction / length in the direction perpendicular thereto) and orient the lengthwise direction in the utilization direction of magnetostriction (mainly the displacement direction). This makes it possible to obtain a favorable effect of improving the magnetostriction amount while suppressing the compounding amount of the preloading material 3. For these reasons, it is also effective to use a fibrous substance such as short fibers for the preloading material 3. It is possible to obtain a larger negative displacement amount (negative magnetostriction) by orienting and presenting the preloading material 3 made of short fibers in the base material 2.

The above-mentioned preload-applying material 3 is contained in the range of 1 to 10% by volume with respect to the composite material 4 of the rare earth alloy 2 and the preload-applying material 3, although it varies depending on the material (Young's modulus etc.). Preferably. If the content of the preloading material 3 is less than 1% by volume of the composite material 4, the effect of improving the magnetostriction amount may not be sufficiently obtained. On the other hand, when the content of the preload-applying material 3 exceeds 10% by volume, the preload-applying material 3 that does not change due to the magnetic field may act in the direction of restraining the magnetostriction. Regarding the material of the preload addition material 3,
For example, when a substance having a large Young's modulus is used, it is preferable to set the content to be smaller than that of a substance having a small Young's modulus.

As described above, in the negative magnetostrictive material 1 composed of the composite material 4 shown in FIG. 1, the preloading material 3 is dispersed in the rare earth alloy (negative magnetostrictive alloy) 2 as the base material,
Since a tensile residual stress is generated in the rare earth alloy 2 and an appropriate preset load is uniformly applied to the rare earth alloy 2 by this tensile residual stress, a magnetic field is applied in this state to apply the magnetic field to the rare earth alloy 2. By displacing, it is possible to obtain an excellent negative displacement amount (negative magnetostriction amount). As described above, the negative magnetostrictive material of the present invention is characterized in that an appropriate preset load is added to the rare earth alloy 2 by the residual tensile stress. It has been difficult to uniformly apply an appropriate tensile stress to a rare-earth negative magnetostrictive alloy that is brittle in terms of material load under the conventional external load, but by utilizing internal strain, the rare earth alloy 2 It is possible to uniformly apply an appropriate tensile stress. Even in the case of a positive magnetostrictive material, a preloaded material having a coefficient of thermal expansion larger than that of the magnetostrictive material,
For example, it is possible to add a compressive residual stress by compounding copper powder or the like.

The negative magnetostrictive material 1 shown in FIG. 1 can be manufactured, for example, as follows. First, an alloy containing a rare earth element and a transition metal element as main components is prepared, and the alloy and a particulate or fibrous preloading material are compounded at high temperature.
As the compounding step under high temperature, (1) molten metal casting method, (2) powder metallurgy method, etc. can be applied. The molten metal casting method (1) is a method of obtaining a composite material of a rare earth alloy and a preloading material by adding a preloading material to the molten metal of the rare earth alloy and casting the molten metal while stirring.

At this time, in order to uniformly combine the rare earth alloys having different specific gravities and the preloading material, the temperature of the molten rare earth alloy to which the preloading material is added is lowered to a semi-molten state. Casting the molten metal while stirring, or lowering the temperature of the molten rare earth alloy to a semi-molten state, adding a preloading material to this semi-molten molten metal, and then casting while stirring this semi-molten molten metal It is preferable. Thus, by finally casting the molten metal in a semi-molten state (semi-molten molten metal) while stirring, the preloading material can be uniformly dispersed in the base material made of the rare earth alloy.

As a method for producing a composite material using a molten rare earth alloy, for example, a porous preform is produced with a preloading material in the form of particles or fibers, and the rare earth is added to the preform. It is also possible to apply a method of impregnating a molten alloy and solidifying it. In addition to this, it is possible to use a method of using a molten metal of a rare earth alloy and compounding it with a particulate or fibrous preloading material.

In the process of casting the molten rare earth alloy to which the preloading material has been added as described above in a mold and cooling the molten metal, internal strain is generated based on the difference in the coefficient of thermal expansion between the rare earth alloy and the preloading material. Occurs. Since the preloading material is made of a material having a smaller coefficient of thermal expansion than that of the rare earth alloy as described above, tensile residual stress occurs in the rare earth alloy. By utilizing this residual tensile stress as a preset load, it is possible to increase the magnetostriction amount of the negative magnetostrictive material composed of the composite material of the rare earth alloy and the preloading material. Here, since the internal strain amount also changes depending on the cooling rate after casting, it is preferable to adjust the cooling rate so that residual stress is appropriately generated. Basically, a large internal strain (residual stress) is generated by rapid cooling after casting.

In the powder metallurgy method of (2), the rare earth alloy powder and the particulate or fibrous preloading material are mixed, and the mixture is molded into a desired shape to obtain a powder compact, It is a method of obtaining a composite material by sintering a powder compact at a predetermined temperature.
Also in this case, tensile residual stress is generated in the rare earth alloy during the cooling process after sintering, so by using this residual tensile stress as a preset load, the composite material of the rare earth alloy and the preload addition material can be used. The amount of magnetostriction of the negative magnetostrictive material can be increased. In the sintering process of the green compact, in addition to normal atmospheric pressure sintering, atmospheric pressure sintering, hot pressing, etc.,
Spark plasma sintering or the like can also be applied. Since spark plasma sintering has a short sintering time, it is effective in suppressing the reaction between the rare earth alloy and the preloading material.

The composite material obtained by the molten metal casting method of (1) or the powder metallurgy method of (2) may be used as a negative magnetostrictive material as it is, or may be used by adjusting its shape by hot extrusion. You can also do it. The hot extrusion not only has the effect of shaping the negative magnetostrictive material, but also has the effect of improving the orientation. The composite material that has been subjected to necessary processing and the like is subjected to heat treatment for crystal growth of the rare earth alloy and homogenization of the components, and then rapidly cooled, and is put to practical use as a negative magnetostrictive material. Heat treatment temperature
The temperature is preferably in the range of 500 to 900 ° C., and the heat treatment atmosphere is vacuum or an inert atmosphere. By heat-treating the alloy material at such a temperature, it is possible to obtain good magnetostrictive properties matching the alloy composition and the like with good reproducibility. However, the cooling conditions after the heat treatment are appropriately set so that the residual stress is not excessively relaxed in the cooling process after the heat treatment.

According to the negative magnetostrictive material of the present invention, a magnetostrictive actuator, a magnetostrictive sensor, etc. are constructed by utilizing magnetostriction in the direction of application of a magnetic field. As described above, the negative magnetostrictive material of the present invention is a driving unit of a magnetostrictive actuator utilizing negative magnetostriction,
Alternatively, it is used as a sensor unit of a magnetostrictive sensor.
The negative magnetostrictive material of the present invention is expected to be used in various fields such as precision machinery, industrial machinery, electricity / electronics, resources / energy, civil engineering / construction, aviation / space / vehicles, and medical care.

[0042]

EXAMPLES Next, specific examples of the present invention and evaluation results thereof will be described.

Example 1 First, as a negative magnetostrictive alloy, an SmFe _1.95 alloy powder having an average particle size of 8 μm (coefficient of thermal expansion: 14 × 10 ⁻⁶ / ° C.) and as a preloading material, an agglomerated tungsten powder having an average particle size of 10 μm ( Thermal expansion coefficient: 4.5 × 10 ^-6 / ° C) is prepared for each of these SmF
e _1.95 alloy powder and tungsten powder were mixed in a mass ratio of 97: 3. The mixed powder was molded under a molding pressure of 980 MPa to prepare a green compact having a diameter of 10 mm and a thickness of 10 mm.

The above-mentioned green compact was placed in an Ar gas atmosphere at 73
Sinter at 0 ° C, then lower to 715 ° C, then at this temperature
The homogenization treatment was performed for 10 hours. Then, it was rapidly cooled to room temperature to prepare a negative magnetostrictive material composed of a composite material of SmFe _1.95 alloy and tungsten particles. The abundance ratio of the tungsten particles in this negative magnetostrictive material was 1.5% by volume.
Also, when the structure of the negative magnetostrictive material was observed, the tungsten particles, which maintained the initial particle size, were uniformly dispersed in the base material, and XPS analysis showed that the tungsten particles in the matrix of the SmFe _1.95 alloy were No elution was observed. Such negative magnetostrictive material was subjected to the characteristic evaluation described later.

Example 2 SmFe _1.95 alloy powder (coefficient of thermal expansion: 14 × 10 ⁻⁶ / ° C.) having an average particle size of 8 μm as a negative magnetostrictive alloy and Si ₃ N having an average length of 10 μm and an average diameter of 2 μm as a preloading material. Prepare ₄ whiskers (coefficient of thermal expansion: 2.8 × 10 ^-6 / ° C),
Fe _1.95 alloy powder and Si ₃ N ₄ whiskers in a mass ratio of 9
Mixed at a ratio of 8: 2. The mixed powder was molded under a molding pressure of 980 MPa to prepare a green compact having a diameter of 10 mm and a thickness of 10 mm.

The above-mentioned green compact was put in an Ar gas atmosphere at 73
Sinter at 0 ° C, then lower to 715 ° C, then at this temperature
The homogenization treatment was performed for 10 hours. Then, it was rapidly cooled to room temperature to prepare a negative magnetostrictive material composed of a composite material of SmFe _1.95 alloy and Si ₃ N ₄ whiskers. The abundance ratio of Si ₃ N ₄ whiskers in this negative magnetostrictive material was 5.2% by volume. Such negative magnetostrictive material was subjected to the characteristic evaluation described later.

Example 3 SmFe _1.95 alloy powder having an average particle diameter of 8 μm (coefficient of thermal expansion: 14 × 10 ⁻⁶ / ° C.) as a negative magnetostrictive alloy, and flaky BN powder having an average particle diameter of 3 μm (heat treatment) as a preloading material. Expansion rate: -1.8 × 10
^-6 / ° C.) were prepared, and these SmFe _1.95 alloy powder and BN powder were mixed in a mass ratio of 99: 1. This mixed powder is molded at a molding pressure of 980 MPa and has a diameter of 10 mm and a thickness of 10
mm powder compacts were prepared.

The above-mentioned green compact was placed in an Ar gas atmosphere at 73
Sinter at 0 ° C, then lower to 715 ° C, then at this temperature
The homogenization treatment was performed for 10 hours. Then, it was rapidly cooled to room temperature to prepare a negative magnetostrictive material composed of a composite material of SmFe _1.95 alloy and flaky BN particles. The abundance ratio of BN particles in this negative magnetostrictive material was 4.3% by volume. Such negative magnetostrictive material was subjected to the characteristic evaluation described later.

Comparative Example 1 The same SmFe _1.95 alloy powder as in Examples 1 to 3 was used alone.
It was molded at a molding pressure of 980 MPa to produce a green compact having a diameter of 10 mm and a thickness of 10 mm. The green compact was sintered and heat-treated under the same conditions as in Examples 1 to 3 to prepare a negative magnetostrictive material made of a single substance of SmFe _1.95 alloy. Such negative magnetostrictive material was subjected to the characteristic evaluation described later.

Comparative Example 2 The same SmFe _1.95 alloy powder as in Example 1 and tungsten agglomerate powder were mixed in a mass ratio of 80:20, and then 980MP.
A compact having a diameter of 10 mm and a thickness of 10 mm was molded with the molding pressure of a.
This green compact was sintered and heat-treated under the same conditions as in Example 1 to produce a negative magnetostrictive material. Such negative magnetostrictive material was subjected to the characteristic evaluation described later.

Examples 1 to 3 and Comparative Examples 1 and 2 described above
A magnetic field of 5 kOe was applied to each negative magnetostrictive material at room temperature, and the amount of magnetostriction at that time was measured. As a result, the magnetostrictive value of the negative magnetostrictive material of Comparative Example 1 was 800 ppm in the negative direction, while the magnetostrictive value of the negative magnetostrictive material of Example 1 was 1100 ppm,
The negative magnetostrictive material of Example 2 had a magnetostrictive value of 1080 ppm, and the negative magnetostrictive material of Example 3 had a magnetostrictive value of 960 ppm. As described above, it was confirmed that the negative magnetostrictive materials made of the composite materials according to Examples 1 to 3 have an improved amount of negative magnetostriction as compared with the negative magnetostrictive material according to Comparative Example 1 including only the SmFe _1.95 alloy. The magnetostrictive value of the negative magnetostrictive material of Comparative Example 2 was 200 ppm.

Further, in order to confirm the presence or absence of residual stress of each negative magnetostrictive material, X-ray diffraction of each negative magnetostrictive material was carried out at room temperature. SmFe _1.95 in the negative magnetostrictive materials of Examples 1 to 3
The diffraction peak of the alloy was found to be wider and moved than the diffraction peak of the SmFe _1.95 alloy of Comparative Example 1 alone, which confirmed that nonuniform expansion of the crystal lattice, that is, tensile residual stress occurred. It was Further, the crystal lattice constants of the SmFe _1.95 alloys of the composite materials of Examples 1 to 3 are 0.036% in Example 1 and 0.034% in Example 2 as compared with the crystal lattice constants of the SmFe _1.95 alloy of Comparative Example 1. In Example 3, it was confirmed that the amount increased by 0.019%.

Regarding the negative magnetostrictive material according to Comparative Example 2, a larger shift of the diffraction peak than that of Example 1, that is, a larger expansion of the crystal lattice was recognized, and the residual stress itself exceeded the range of the appropriate preset load. It was confirmed. The crystal lattice constant of the SmFe _1.95 alloy made of the composite material of Comparative Example 2 was increased by 0.22% as compared with the crystal lattice constant of the SmFe _1.95 alloy of Comparative Example 1. by this,
It is considered that the negative magnetostrictive material of Comparative Example 2 had a greatly reduced magnetostriction value. As described above, the tensile residual stress generated in the rare earth alloy needs to be within a proper preset load range.

Example 4 First, in a melting crucible, SmFe _1.9 (coefficient of thermal expansion: 14 × 10
^-6 / ℃) About 10 kg of negative magnetostrictive alloy melt is melted, and the temperature of this alloy melt is adjusted to 1080 ℃ to make it a semi-molten state, then in a semi-molten melt while stirring with a tungsten stirrer. As a preloading material, 300 g of tungsten agglomerate powder (coefficient of thermal expansion: 4.5 × 10 ⁻⁶ / ° C.) having an average particle diameter of 15 μm was added, and these were mixed and immediately cast. The casting process was carried out by closing the pouring port at the bottom of the crucible with a stopper in advance, adding and mixing tungsten agglomerate powder, and then opening the stopper and casting in a mold.

The ingot thus obtained was
In contrast, homogenization at 715 ° C for 24 hours in Ar gas atmosphere
After the treatment, by cooling to room temperature, Sm
Fe _1.9Negative made of composite material of alloy and tungsten particles
A magnetostrictive material was produced. Tongue in this negative magnetostrictive material
The abundance ratio of stainless particles was 1.5% by volume. Also negative
Observation of the structure of the magnetostrictive material revealed that the initial grain size was almost constant.
Hold the tungsten particles evenly dispersed in the base material.
, XPS analysis shows SmFe_1.9Tan to the base of the alloy
No elution of gustene was observed. Such negative magnetostriction
The material was subjected to the characteristic evaluation described below.

Comparative Example 3 SmFe _1.9 (coefficient of thermal expansion: 1.4 × 10 ⁻⁶ / in a molten crucible)
Approximately 10 kg of a negative magnetostrictive alloy having a composition of ℃) was melted, the temperature of the alloy melt was adjusted to 1080 ° C. to make a semi-molten state, and then immediately cast. Ingot obtained in this way
After homogenizing under the same conditions as in Example 4, the sample was rapidly cooled to room temperature to prepare a negative magnetostrictive material composed of a single substance of SmFe _1.9 alloy. Such negative magnetostrictive material was subjected to the characteristic evaluation described later.

A magnetic field of 5 kOe was applied to each negative magnetostrictive material according to Example 4 and Comparative Example 3 at room temperature, and the magnetostriction amounts at that time were measured. As a result, the magnetostriction value of the negative magnetostrictive material of Comparative Example 3 was 900 ppm in the negative direction,
The negative magnetostrictive material of Example 4 had a magnetostriction value of 1150 ppm. As described above, it was confirmed that the negative magnetostrictive material formed of the composite material according to Example 4 has an improved amount of negative magnetostriction as compared with the negative magnetostrictive material according to Comparative Example 3 including only the SmFe _1.9 alloy.

Further, in order to confirm the presence or absence of residual stress of each negative magnetostrictive material, X-ray diffraction of each negative magnetostrictive material was carried out at room temperature. The diffraction peak of the SmFe _1.9 alloy in the negative magnetostrictive material of Example 4 was found to spread and move as compared with the diffraction peak of the SmFe _1.9 alloy alone of Comparative Example 3, which resulted in uneven expansion of the crystal lattice, that is, tension. It was confirmed that residual stress was generated. In addition, the crystal lattice constant of the SmFe _1.95 alloy made of the composite material of Example 4 is S of Comparative Example 3.
It was confirmed that the crystal lattice constant was increased by 0.042% as compared with the crystal lattice constant of the mFe _1.9 alloy.

Example 5 SmFe _1.95 alloy powder having an average particle size of 8 μm was used as a negative magnetostrictive alloy, and carbon fiber chops having an average length of 2 mm and having a surface plated with Ni were prepared as preloading materials. These SmFe _1.95 alloys were prepared. Mass ratio of powder and carbon fiber chop
Mixed at a ratio of 98: 2. The mixed powder was molded under a molding pressure of 980 MPa to prepare a green compact having a diameter of 10 mm and a thickness of 10 mm.

The above-mentioned green compact was placed in an Ar gas atmosphere at 73
After sintering at 0 ° C., it was rapidly cooled to room temperature. Then, the obtained sintered body was heated to 700 ° C. and extruded through a hole having an inner diameter of 6 mm to obtain a wire having a diameter of 6 mm. This wire was homogenized at 715 ° C for 10 hours. After this, quickly cool to room temperature,
A negative magnetostrictive material (wire having a diameter of 6 mm) made of a composite material of SmFe _1.95 alloy and tungsten particles was produced.

The carbon fiber content in the negative magnetostrictive material thus obtained was 6.2% by volume. Further, when the structure of the wire-shaped negative magnetostrictive material was observed, it was confirmed that the crystal grains of the carbon fibers and the SmFe _1.95 alloy were oriented in the longitudinal direction (extrusion direction) of the wire. Next, a magnetic field of 5 kOe was applied to this negative magnetostrictive material at room temperature, and the magnetostriction amount at that time was measured. As a result, the magnetostrictive value was 1200 ppm in the negative direction.

Further, in order to confirm the presence or absence of residual stress in the negative magnetostrictive material, X-ray diffraction of the negative magnetostrictive material was carried out at room temperature. The diffraction peak of the SmFe _1.9 alloy in the negative magnetostrictive material of Example 5 was found to spread and move as compared with the diffraction peak of the SmFe _1.9 alloy of Comparative Example 1 alone, which resulted in uneven expansion of the crystal lattice, that is, in tensile. It was confirmed that residual stress was generated. In addition, the crystal lattice constant of the SmFe _1.95 alloy made of the composite material of Example 5 is Sm of Comparative Example 1
It was confirmed that the crystal lattice constant was increased by 0.048% as compared with the crystal lattice constant of the Fe _1.9 alloy.

Example 6 About 10 kg of a negative magnetostrictive alloy of SmFe _1.9 composition was melted in a melting crucible, and the temperature of the alloy melt was adjusted to 1080 ° C. to make a semi-molten state, and then a tungsten agitator was used. Average particle size of 15μm as a preloading material in semi-molten molten metal while stirring
300 g of the tungsten agglomerate powder of 1. was added, and these were mixed and immediately cast.

Next, the obtained ingot (ingot) is cooled to 700
Heat up to ℃, extrude through a hole with an inner diameter of 6 mm, and
mm wire rod. This wire is homogenized at 715 ℃ for 24 hours and then rapidly cooled to room temperature to obtain SmF
A negative magnetostrictive material (wire having a diameter of 6 mm) made of a composite material of _e1.9 alloy and tungsten particles was produced.

In the negative magnetostrictive material thus obtained,
The abundance ratio of the tungsten particles was 1.5% by volume. Well
In addition, when the structure of the wire-shaped negative magnetostrictive material was observed, it was found that Sm
Fe _1.95Alloy crystal grains are in the longitudinal direction of the wire (extrusion direction)
It was confirmed that they were oriented in the direction. Next, this negative magnetostrictive material
Apply a magnetic field of 5 kOe to the material at room temperature and measure the amount of magnetostriction at that time.
As a result of the determination, the magnetostriction value was 1150 ppm in the negative direction.

Further, in order to confirm the presence or absence of residual stress in the negative magnetostrictive material, X-ray diffraction of the negative magnetostrictive material was carried out at room temperature. The diffraction peak of the SmFe _1.9 alloy in the negative magnetostrictive material of Example 6 was found to spread and move as compared with the diffraction peak of the SmFe _1.9 alloy of Comparative Example 3 alone, whereby uneven expansion of the crystal lattice, that is, tensile It was confirmed that residual stress was generated. In addition, the crystal lattice constant of the SmFe _1.95 alloy made of the composite material of Example 6 is Sm of Comparative Example 3
It was confirmed that the crystal lattice constant was increased by 0.042% as compared with the crystal lattice constant of the Fe _1.9 alloy.

Examples 7 to 15 First, the rare earth alloys and preloading materials shown in Table 1 were prepared, and using these, negative magnetostrictive materials made of composite materials were prepared according to the manufacturing methods shown in Table 2. The manufacturing conditions of each of these negative magnetostrictive materials were the same as in Example 1 for the powder metallurgy method and the same as in Example 4 for the semi-molten casting method. For each negative magnetostrictive material obtained in this way,
The magnetostriction value when the magnetic field of Oe was applied was obtained as the ratio (magnetostriction change ratio) to the magnetostriction value of the negative magnetostrictive material produced by using the rare earth alloy alone without using the preloading material. The measurement results are shown in Table 2. Further, Table 2 also shows the rate of change (increase rate) of the crystal lattice constant of the rare earth alloy.

[0068]

[Table 1]

[0069]

[Table 2]

[0070]

As described above, according to the negative magnetostrictive material of the present invention, since an appropriate preset load is effectively and uniformly applied to the rare earth alloy by residual tensile stress, the magnetostrictive property (negative The amount of displacement) can be improved. Further, according to the method for producing a negative magnetostrictive material of the present invention, it becomes possible to obtain such a negative magnetostrictive material having excellent magnetostrictive characteristics with good reproducibility.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a microstructure of a negative magnetostrictive material according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining displacement characteristics (negative magnetostriction characteristics) of a negative magnetostrictive material of the present invention due to a magnetic field.

[Explanation of symbols]

1 ... Negative magnetostrictive material, 2 ... Rare earth alloy showing negative magnetostriction (negative magnetostrictive alloy), 3 ... Preloading material, 4 ... Composite material

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C22C 1/04 C22C 1/04 F 28/00 28/00 A H01L 41/20 H01L 41/20 // H01F 1/053 H01F 1/04 A (72) Hideki Yamamiya Inventor Hideki Yamamiya 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Stock Company Toshiba Yokohama Works (72) Inventor Tadahiko Kobayashi, Saiwai-ku, Kawasaki-shi, Kanagawa 1F Kobayashi-shi, Toshiba-cho F-term in Toshiba R & D Center (reference) 4K018 AA08 AA11 AA27 AA40 AB01 AB02 AB03 AB04 AB08 AB10 AC01 CA00 DA00 KA42 5E040 AA03 CA20 NN01 NN18

Claims (13)

[Claims] 1. A negative magnetostrictive material comprising a rare earth alloy exhibiting negative magnetostriction, wherein tensile stress remains in the rare earth alloy at a temperature in the range of −50 ° C. to 200 ° C. and in the absence of an applied magnetic field. The negative magnetostrictive material is characterized in that a preset load is applied to the rare earth alloy due to the tensile residual stress. 2. A base material made of a rare earth alloy exhibiting negative magnetostriction, and dispersedly arranged in the base material, wherein the rare earth alloy has a temperature of −50 ° C. to 2 ° C.
A negative magnetostrictive material, comprising: a preload-applying material that produces a tensile residual stress at a temperature in the range of 00 ° C. and in the absence of an applied magnetic field and applies a preset load by the residual stress. 3. The negative magnetostrictive material according to claim 2, wherein the preloading material comprises at least one selected from particles and fibers of a substance having a coefficient of thermal expansion smaller than that of the rare earth alloy. Magnetostrictive material. 4. The negative magnetostrictive material according to claim 3, wherein the preloading material is tungsten, molybdenum, carbon, silicon nitride, aluminum nitride, titanium nitride, zirconium nitride, boron nitride, silicon carbide, tungsten carbide,
A negative magnetostrictive material containing at least one selected from molybdenum carbide, titanium boride, aluminum oxide, silicon oxide, magnesium oxide, aluminum titanate, and rare earth nitrides. 5. The negative magnetostrictive material according to claim 2, wherein the preload-applying material has a volume of 1 to 10 with respect to the composite material of the rare earth alloy and the preload-applying material. A negative magnetostrictive material characterized by being contained in the range of%. 6. The negative magnetostrictive material according to any one of claims 1 to 5, wherein the rare earth alloy is of the general formula: R (T _x M _1-x ) _z (where R is a rare earth element). One or more elements containing at least Sm selected from the above, T is at least one element selected from Fe, Co and Ni, and M is the aforementioned T
An element selected from transition metal elements other than the element, x
And z are numbers satisfying 0.5 ≦ x ≦ 1 and 1.4 ≦ z ≦ 2.5), which is a negative magnetostrictive material. 7. The negative magnetostrictive material according to claim 1, wherein a crystal lattice constant of the rare earth alloy compounded with the preloading material is composite with the preloading material. A negative magnetostrictive material characterized by increasing the lattice constant of the crystal before 0.005 to 0.15%. 8. A preloading material comprising at least one selected from particles and fibers of a substance having a coefficient of thermal expansion smaller than that of the rare earth alloy in a base material made of a rare earth alloy exhibiting negative magnetostriction under high temperature. Negative magnetostriction, characterized by comprising a step of dispersively arranging and compounding, and a step of leaving a tensile stress in the rare earth alloy in contact with the preloading material when cooling the high temperature composite material. Material manufacturing method. 9. The method for producing a negative magnetostrictive material according to claim 8, further comprising a step of casting the molten metal of the rare earth alloy to which the preload-applying material is added while stirring the negative magnetostrictive material. Production method. 10. The method for manufacturing a negative magnetostrictive material according to claim 9, wherein in the casting step, the molten metal of the rare earth alloy to which the preloading material is added is made into a semi-molten state, and the semi-molten molten metal is stirred. A method for manufacturing a negative magnetostrictive material, which comprises a step of casting while performing 11. The method for manufacturing a negative magnetostrictive material according to claim 8, wherein a mixture of the rare earth alloy powder and the preloading material is compacted, and the compacted body is sintered at a predetermined temperature. A method for producing a negative magnetostrictive material, which comprises a step of cooling after performing. 12. The method for producing a negative magnetostrictive material according to claim 8, wherein the rare earth alloy is at a temperature in the range of −50 ° C. to 200 ° C. and has no applied magnetic field. A method for producing a negative magnetostrictive material, characterized in that a tensile stress is left and a preset load is applied to the rare earth alloy by the residual tensile stress. 13. The method for manufacturing a negative magnetostrictive material according to claim 8, wherein the rare earth alloy is R (T _x M _1-x ) _z (wherein R Is at least one element containing at least Sm selected from rare earth elements, T is at least one element selected from Fe, Co and Ni, and M is the above T
An element selected from transition metal elements other than the element, x
And z are numbers satisfying 0.5 ≦ x ≦ 1 and 1.4 ≦ z ≦ 2.5), the method for producing a negative magnetostrictive material.