JP4058510B2 - Giant magnetostrictive material and manufacturing method thereof - Google Patents

Description

【００６５】
Ｃｒが添加されていない比較例１及び２の場合、主原料粉末中に含まれる酸素量は、それぞれ０．５９％及び０．４９％であった。また、主原料粉末中に含まれる窒素量は、それぞれ、０．０２％及び０．１０％であった。さらに、１００ｋＡ／ｍの磁場中における磁歪は、３７０〜３８０ｐｐｍであり、高い値を示した。しかしながら、比較例１及び２は、いずれも圧縮強度測定用治具を試料上に載せた際に、治具の自重により試料が破壊したために、圧縮強度を測定できなかった。
【００６６】
一方、ＣｒによるＦｅの置換量を５〜１０ａｔ％とした比較例３〜５は、圧縮強度が２５０〜３００ＭＰａに向上した。しかしながら、主原料粉末中に１．５ｍａｓｓ％を超える酸素、及び１．５ｍａｓｓ％を超える窒素が含まれていたために、１００ｋＡ／ｍの磁場中における磁歪は、２００ｐｐｍ未満であった。また、磁歪は、主原料粉末中の酸素量又は窒素が多くなるほど低下する傾向を示した。
【００６７】
さらに、比較例６の場合、高濃度の酸素及び窒素が含まれる雰囲気下で機械的合金化処理を行ったために、主原料粉末中には、５．０ｍａｓｓ％の酸素と、９．８５ｍａｓｓ％の窒素が含まれていた。また、得られた焼結体の１００ｋＡ／ｍの磁場中における磁歪は、３０ｐｐｍまで低下した。さらに、高濃度の酸素及び窒素を含んでいるために、焼結体が脆化しており、圧縮強度を測定できなかった。
【００６８】
これに対し、主原料粉末中の酸素量を１．５ｍａｓｓ％以下、窒素量を１．５ｍａｓｓ％以下とし、Ｆｅの一部をＣｒで置換した実施例１〜３は、いずれも１００ｋＡ／ｍの磁場中における磁歪は、２００ｐｐｍを超え、圧縮強度は３００ＭＰａを超えた。磁歪は、Ｃｒ置換量が少なくなるほど増加する傾向を示し、Ｃｒ置換量を１０ａｔ％以下とすると、磁歪は、Ｃｒ無添加の比較例１及び２と同等となった。一方、圧縮強度は、Ｃｒ置換量が多くなるほど増加する傾向を示し、Ｃｒ置換量を２０ａｔ％とすると、圧縮強度は、４００ＭＰａまで向上した。
【００６９】
以上、本発明の実施の形態について詳細に説明したが、本発明は、上記実施の形態に何ら限定されるものではなく、本発明の要旨を逸脱しない範囲内で種々の改変が可能である。例えば、加熱と同時に加圧を行う方法（方法Ｂ）を用いて超磁歪材料を製造する場合、加圧は、焼結温度に到達したと同時に行っても良く、あるいは、焼結温度に到達する以前から行っても良い。
【００７０】
また、主原料粉末の作製は、機械的合金化処理を用いるのが好ましいが、磁歪合金を構成する金属元素を含有する２種以上の粗粉末を、それぞれ別個に不活性雰囲気下において粉砕し、これらを所定の比率で混合する方法を用いても良い。
【００７１】
【発明の効果】
本発明に係る超磁歪材料は、所定の合金組成を有する磁歪合金の多結晶体からなるので、低磁界おける磁歪特性に優れ、しかも高い圧縮強度を示すという効果がある。また、高強度かつ均質であるので、２次加工が容易化するという効果がある。
【００７２】
また、本発明に係る超磁歪材料の製造方法は、所定の組成並びに酸素量及び窒素量を有する主原料粉末を用いて成形及び焼結を行うので、上述のような優れた特性を有する磁歪材料を効率よく製造できるという効果がある。また、得られる焼結体は、２次加工も容易であるので、従来の方法では得られない複雑形状を有する製品であっても、高い生産性で製造できるという効果がある。
【図面の簡単な説明】
【図１】 通電焼結法の概略構成図である。
【図２】 実施例１で得られた焼結体の磁界と磁歪の関係を示す図である。
【符号の説明】
１０ 型
１２ 主原料粉末
１４、１６ パンチ[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a giant magnetostrictive material and a manufacturing method thereof, and more particularly to a giant magnetostrictive material used for a magneto-mechanical conversion device such as a magnetostrictive actuator, a magnetostrictive vibrator, a filter, and a sensor, and a method of manufacturing the same.
[0002]
[Prior art]
  When a demagnetized ferromagnetic material is magnetized, its size and shape generally change. Such a phenomenon is called a magnetostrictive effect, and a material exhibiting the magnetostrictive effect is called a magnetostrictive material. Specific examples of magnetostrictive materials include Ni, Ni-base alloys, ferrites, and rare earth-iron-based intermetallic compounds.
[0003]
  Among these, a rare earth-iron-based intermetallic compound (Laves phase compound) is 10% at room temperature.^-3It is known as a giant magnetostrictive material exhibiting a huge magnetostriction. Therefore, rare earth-iron-based intermetallic compounds are various magneto-mechanical conversion devices (for example, magnetostrictive actuators, ultrasonic waves used in VTRs, cameras, computer equipment, etc.) for mutually converting magnetic energy and mechanical energy. Magnetostrictive vibrators used in welding machines, cutters, sonars, medical scalpels, pulverizers, various filters such as mechanical filters, variable frequency converters, delay circuit elements, various sensors such as pressure sensors, knock sensors, and sound pressure sensors Application) is expected.
[0004]
  Examples of rare earth-iron-based intermetallic compounds exhibiting the largest magnetostriction include A. E. TbFe reported by Clark et al.₂(A.E.Clark and H.S.Belson: “Giant Room-Temperature Magnetostrictions in TbFe₂ and DyFe₂"Pys. Rev. B, 5 (1972) 3642-3644). However, this TbFe₂However, there is a problem that a large magnetic field is required to obtain a large magnetostriction. Considering the practical use of magnetostrictive materials, it is preferable to obtain a large magnetostriction with a small magnetic field rather than a large magnetostriction with a large magnetic field. Therefore, in order to improve the magnetostriction characteristics of the rare earth-iron-based intermetallic compound, various proposals have conventionally been made regarding the alloy composition and manufacturing method.
[0005]
  For example, as a rare earth-iron super magnetostrictive alloy having a large magnetostriction amount, Tb_0.27Dy_0.73Fe_2.0(Terphenol D) is known. Since terphenol D requires crystal orientation to obtain a large amount of magnetostriction, a single crystal growth method is usually used for its production.
[0006]
  Further, for example, Japanese Patent Laid-Open No. 5-148594 discloses RE (Fe) in order to improve magnetostriction characteristics in a low magnetic field._1-q-rMn_qM_r)_s(RE is at least one kind of rare earth element, M is one metal element selected from C, Mg, Al, Si, Ca, Zr, Y, Ga and B, 0.005 ≦ q ≦ 0.5, 0.005 ≦ r ≦ 0.2, 1.90 ≦ s ≦ 2.10), and a giant magnetostrictive alloy is disclosed in which the content of the 1-3 phase as a different phase is 5% by volume or less.
[0007]
  Further, JP-A-7-286249 discloses a raw material A containing predetermined Tb, Dy and T (T is at least one element selected from Fe, Co and Ni) and having a large magnetic anisotropy. The raw material B containing predetermined Dy, Tb and T and acting as a flux during sintering and a raw material C substantially composed of T as necessary are mixed with the powder of A method for producing a magnetostrictive material in which the mixture is sintered in a magnetic field and then sintered is disclosed. In this publication, the easy magnetization axis is aligned in one direction by this method, and (Tb_vDy_1-v) T_w(However, it is disclosed that a magnetostrictive material having a composition represented by 0.27 ≦ v <0.50, 1.70 ≦ w ≦ 2.00) can be obtained.
[0008]
[Problems to be solved by the invention]
  TbFe₂Substituting all or part of Tb with other rare earth elements such as Dy or substituting all or part of Fe with other elements such as Mn may improve magnetostriction characteristics in a low magnetic field. it can. In addition, when the easy magnetization axis is aligned in one direction, a material having a large magnetostriction amount can be obtained. Therefore, the magnetostrictive material is usually manufactured using a single crystal growth method, a unidirectional solidification method, or a molding-sintering method in a magnetic field. Has been.
[0009]
  However, the single crystal growth method and the unidirectional solidification method have a problem that productivity is extremely poor. In addition, conventional rare earth-iron-based intermetallic compounds are inherently fragile, so that they may be damaged when used under high load conditions, and secondary processing is also difficult. Therefore, the conventional alloy composition and manufacturing method have a problem that there are limitations on the use conditions and the shape that can be manufactured.
[0010]
  In addition, the conventional rare earth-iron-based intermetallic compound has the property of being easily oxidized or nitrided because it contains a rare earth element as a constituent element. Therefore, there is a problem that a desired magnetostrictive characteristic cannot be obtained if the raw material is oxidized or nitrided in the manufacturing process. Further, when oxidation or nitridation progresses during use, there is a problem that the magnetostrictive characteristics deteriorate.
[0011]
  Further, conventional rare earth-iron-based magnetostrictive materials have a property of high thermal conductivity. Therefore, in the conventional material, when the ambient temperature of the magnetostrictive element increases during use, the magnetostrictive material may exceed the Curie temperature, and the magnetostrictive characteristics may be lost.
[0012]
  Furthermore, the magnetostrictive material may be required to be light and wear resistant depending on its application. However, conventional rare earth-iron-based magnetostrictive materials contain heavy elements and thus have a large specific gravity and insufficient wear resistance.
[0013]
  The problem to be solved by the present invention is to provide a giant magnetostrictive material having a high magnetostriction characteristic in a low magnetic field, excellent in productivity, and capable of producing even a component having a complicated shape, and a method for producing the same. It is in. Another problem to be solved by the present invention is to provide a giant magnetostrictive material that is less likely to be damaged even when used under high load conditions, and a method for producing the same.
[0014]
  Another object of the present invention is to provide a giant magnetostrictive material that suppresses the temperature rise of the material itself during use and is unlikely to lose its magnetostrictive characteristics. Another object of the present invention is to provide a super magnetostrictive material capable of suppressing oxidation and nitridation of the material surface during use and maintaining high magnetostriction characteristics over a long period of time. is there. Furthermore, another problem to be solved by the present invention is to provide a giant magnetostrictive material having a small specific gravity and excellent wear resistance.
[0015]
[Means for Solving the Problems]
  In order to solve the above problems, the giant magnetostrictive material according to the present invention has a general formula: (Tb_xDy_1-x) (Fe_yCr_1-y)_z(However, it has a composition represented by 0 ≦ x ≦ 0.8, 0.8 ≦ y ≦ 0.95, 1.5 ≦ z ≦ 3.0)mainIt is made of a magnetostrictive alloy polycrystal having a phase and inevitable impurities, an oxygen content of 1.5 mass% or less, and a nitrogen content of 1.5 mass% or less, and is a sintered body having a compressive strength of 300 MPa or more. This is the gist.
[0016]
  In a magnetostrictive alloy whose main phase is a Laves phase compound containing Tb, Dy, and Fe, if a part of Fe is replaced with predetermined Cr and polycrystallized, the compressive strength is improved without deteriorating the magnetostrictive properties. be able to. Therefore, it can be used under a high load, and secondary processing is facilitated.
[0017]
  In addition, the method of manufacturing a giant magnetostrictive material according to the present invention has a general formula: (Tb_xDy_1-x) (Fe_yCr_1-y)_z(However, it has a composition represented by 0 ≦ x ≦ 0.8, 0.8 ≦ y ≦ 0.95, 1.5 ≦ z ≦ 3.0)mainA powder production process for producing a main raw material powder comprising a magnetostrictive alloy comprising a phase and inevitable impurities and / or a precursor thereof and having an oxygen content of 1.5 mass% or less and a nitrogen content of 1.5 mass% or less; And a sintered body manufacturing process for manufacturing a polycrystalline body using raw material powder.In the powder production process, two or more kinds of coarse powders containing the metal elements constituting the magnetostrictive alloy are mechanically alloyed in an inert atmosphere.This is the gist.
[0018]
  In this case, the sintered body manufacturing step may be one in which the main raw material powder is molded and the obtained molded body is heated, or the main raw material powder is filled in a mold and heated simultaneously. Pressurization may be performed.
[0019]
  When a main raw material powder made of a magnetostrictive alloy having a predetermined composition or a precursor thereof is molded and sintered, a giant magnetostrictive material made of a magnetostrictive alloy polycrystal having a predetermined composition is obtained. Further, by optimizing the manufacturing conditions, a homogeneous giant magnetostrictive material with little anisotropy can be obtained. Therefore, even a part having a complicated shape can be manufactured with high productivity. Further, since the obtained giant magnetostrictive material is high in strength and homogeneous, secondary processing is also facilitated.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, an embodiment of the present invention will be described in detail. The giant magnetostrictive material according to the first embodiment of the present invention has a phase having a composition represented by the following chemical formula 1 as a main phase, an oxygen content of 1.5 mass% or less, and a nitrogen content of 1.5 mass. % Or less magnetostrictive alloy polycrystal.
[0021]
[Chemical 1]
        (Tb_xDy_1-x) (Fe_yCr_1-y)_z
(However, 0 ≦ x ≦ 1.0, 0.8 ≦ y ≦ 0.95, 1.5 ≦ z ≦ 3.0)
[0022]
  In the formula (1), the value of x representing the ratio of Tb and Dy is preferably 0 or more and 0.8 or less in order to reduce magnetic anisotropy and improve magnetostriction characteristics in a low magnetic field. More preferably, it is 0 or more and 0.5 or less.
[0023]
  Cr is a substitution element for Fe and has the effect of improving the compressive strength without adversely affecting the magnetostriction characteristics. Cr also has the effect of increasing the corrosion resistance of the giant magnetostrictive material. The value of y that represents a measure of the amount of substitution of Fe with Cr is preferably 0.8 or more and 0.95 or less. If the value of y is less than 0.8, the magnetostriction characteristics in a low magnetic field are deteriorated, which is not preferable. On the other hand, if the value of y exceeds 0.95, the compressive strength decreases, which is not preferable. In order to achieve both excellent magnetostriction characteristics and high compressive strength, the value of y is more preferably 0.85 or more and 0.95 or less.
[0024]
  Furthermore, in the formula (1), the value of z representing the ratio of (Fe + Cr) to (Tb + Dy) is preferably 1.5 or more and 3.0 or less. If the value of z is less than 1.5, the ratio of Laves phase compounds exhibiting giant magnetostriction in the super magnetostrictive material is decreased, and the magnetostrictive characteristics are deteriorated, which is not preferable. On the other hand, if the value of z exceeds 3.0, the ratio of the Laves phase compound similarly decreases, and the magnetostrictive characteristics deteriorate, which is not preferable. The value of z is more preferably 1.6 or more and 2.2 or less.
[0025]
  The giant magnetostrictive material according to the present embodiment is preferably composed of only a phase having a composition represented by the formula 1 (ie, “main phase”), but inevitably contains impurities. Also good. In order to obtain high magnetostriction characteristics, the main phase is preferably 80 mass% or more, and more preferably 90 mass% or more.
[0026]
  Of the impurities, oxygen and nitrogen are particularly strong in reducing the magnetostriction characteristics, so that the smaller the amount of oxygen and nitrogen contained in the sintered body, the better. In order to obtain a giant magnetostrictive material having high magnetostrictive properties, the oxygen content is preferably 1.5 mass% or less, and more preferably 1.0 mass% or less. Further, the amount of nitrogen is preferably 1.5 mass% or less, and more preferably 1.0 mass% or less.
[0027]
  Such a giant magnetostrictive material with a small amount of oxygen and nitrogen is represented by the formula 1 below.MoneyContains genus elementsTwo or moreMain raw material powder (especially main raw material powder having an oxygen content of 1.5 mass% or less and a nitrogen content of 1.5 mass% or less) obtained by pulverizing (or pulverizing and mixing) coarse powder in an inert atmosphere. It is obtained by tying. This point will be described later.
[0028]
  Furthermore, in the giant magnetostrictive material according to the present embodiment, each crystal grain constituting the polycrystal may be oriented in one direction or non-oriented. However, in order to facilitate the secondary processing, it is desirable that the giant magnetostrictive material is homogeneous. For this purpose, it is preferable that each crystal grain constituting the polycrystalline body is non-oriented.
[0029]
  Moreover, in order to suppress the damage of the giant magnetostrictive material under high load conditions, the higher the compressive strength, the better. Specifically, the compressive strength of the giant magnetostrictive material is preferably 300 MPa or more. For this purpose, it is preferable to reduce the average crystal size of the polycrystal in addition to optimizing the material composition. In order to obtain a giant magnetostrictive material having excellent durability under high load conditions, the average crystal size is preferably 100 μm or less, and more preferably 50 μm or less.
[0030]
  Next, the operation of the giant magnetostrictive material according to the present embodiment will be described. Laves phase (AB₂) Type intermetallic compound TbFe₂Is a giant magnetostrictive material exhibiting giant magnetostriction, but has poor magnetostriction characteristics in a low magnetic field due to its large magnetic anisotropy. This TbFe₂When a part of Tb contained in is replaced with Dy, the magnetic anisotropy energy is reduced, and the magnetostriction characteristics in a low magnetic field are improved.
[0031]
  Further, the Tb—Dy—Fe-based magnetostrictive alloy has a property of being essentially brittle. Therefore, in the conventional alloy composition, there is a risk of breakage under use conditions where a high load acts, not only when used as a single crystal but also when used as a polycrystal.
[0032]
  On the other hand, when a part of Fe of the Tb—Dy—Fe-based magnetostrictive alloy is replaced with predetermined Cr, the compressive strength can be improved without deteriorating the magnetostrictive characteristics. Further, the compressive strength can be further improved by polycrystallizing the magnetostrictive alloy having such a composition. Therefore, it can be used under a high load, and secondary processing is facilitated.
[0033]
  Further, by making the amount of oxygen and nitrogen contained in the magnetostrictive alloy not more than predetermined values, the magnetostriction characteristics in a low magnetic field are further improved, and the magnetostriction material having a magnetostriction amount in a magnetic field of 100 kA / m is 200 ppm or more. Is obtained.
[0034]
  Next, a method for manufacturing a giant magnetostrictive material according to the first embodiment of the present invention will be described. The manufacturing method according to the present embodiment includes a powder manufacturing process and a sintered body manufacturing process.
[0035]
  First, the powder manufacturing process will be described. The powder manufacturing process has a composition represented by the following chemical formula 2mainThis is a step of producing a main raw material powder comprising a magnetostrictive alloy and / or a precursor thereof composed of a phase and inevitable impurities and having an oxygen content of 1.5 mass% or less and a nitrogen content of 1.5 mass% or less.
[0036]
[Chemical formula 2]
        (Tb_xDy_1-x) (Fe_yCr_1-y)_z
(However, 0 ≦ x ≦ 0.8, 0.8 ≦ y ≦ 0.95, 1.5 ≦ z ≦ 3.0)
[0037]
  Here, the “precursor” refers to a material that is not completely alloyed but can be a magnetostrictive alloy having a desired composition by a realistic heat treatment (for example, a powder that has been subjected to mechanical alloying treatment).
[0038]
  The main raw material powder is preferably made of a magnetostrictive alloy and / or its precursor composed of only the phase (main phase) represented by the formula 2 but may contain impurities inevitably included. However, in order to obtain high magnetostriction characteristics, the main phase is preferably 80 mass% or more, and more preferably 90 mass% or more.
[0039]
  The smaller the amount of oxygen and nitrogen in the main raw material powder, the better. When the amount of oxygen or nitrogen increases, the sinterability decreases, and the magnetostrictive properties of the resulting sintered body also decrease, which is not preferable. Specifically, the amount of oxygen in the main raw material powder is preferably 1.5 mass% or less, and more preferably 1.0 mass% or less. Further, specifically, the amount of nitrogen in the main raw material powder is preferably 1.5 mass% or less, and more preferably 1.0 mass% or less.
[0040]
  The average particle size of the main raw material powder is not particularly limited. In general, the smaller the average particle size, the better the sinterability, but the moldability and handleability tend to decrease. Therefore, the composition of the main raw material powder, the method for producing the sintered body, The optimum average particle diameter may be selected according to the manufacturing conditions, characteristics required for the giant magnetostrictive material, and the like.
[0041]
  Moreover, the method of pulverizing the raw material is not particularly limited, and various methods can be used. Specifically, it constitutes a magnetostrictive alloyContains metal elementsA method of simply pulverizing two or more kinds of coarse powders in an inert atmosphere, a method of rapidly solidifying a molten magnetostrictive alloy, and a magnetostrictive alloyContains metal elementsSuitable examples include a method of mechanically alloying two or more kinds of coarse powders in an inert atmosphere, a water or gas spraying method, and the like.
[0042]
  Among them, it constitutes a magnetostrictive alloy represented by the formula 2MoneyA method of mechanically alloying two or more kinds of coarse powders containing a genus element in an inert atmosphere is mainly composed of a magnetostrictive alloy having a predetermined composition and a small amount of oxygen and nitrogen, or a precursor thereof. Since raw material powder can be manufactured efficiently, it is particularly suitable.
[0043]
  In this case, each coarse powder may be blended at a ratio that provides the desired composition of the magnetostrictive alloy. In addition, “inert atmosphere” means oxidation, nitridation of main raw material powder obtained after roughing and / or mechanical alloying as a starting material in vacuum, reduced pressure, reducing atmosphere, inert gas atmosphere, etc. An atmosphere in which carbonization or the like does not occur.
[0044]
  Next, the sintered body manufacturing process will be described. A sintered compact manufacturing process is a process of manufacturing a polycrystal using the main raw material powder manufactured in the powder manufacturing process. Various methods can be used as a method for producing the polycrystalline body, and it is not particularly limited. Specifically, the main raw material powder is molded, and then the resulting molded body is heated (hereinafter referred to as “Method A”), the main raw material powder is filled in a mold, and the pressure is applied simultaneously with heating. Suitable examples include a method of carrying out (hereinafter referred to as “method B”), a method of filling the main raw material powder in a sealed container, and a hydrostatic heat treatment.
[0045]
  When Method A is used as a method for producing a sintered body, the main raw material powder is preferably molded (molding step) at a molding pressure of 98 MPa or more and 980 MPa or less. When the molding pressure is less than 98 MPa, the density of the molded body is lowered, and a high-density sintered body cannot be obtained. On the other hand, even if the molding pressure is increased more than necessary, the influence on the sintered body density is small, and the durability of the mold is rather lowered, which is not preferable. The molding pressure is more preferably 98 MPa or more and 490 MPa or less.
[0046]
  Moreover, it is preferable to perform sintering (sintering process) of the obtained molded body by heating at a temperature of 500 ° C. or higher and 1200 ° C. or lower. A sintering temperature of less than 500 ° C. is not preferable because a high-density sintered body cannot be obtained in a short time. Further, if the sintering temperature exceeds 1200 ° C., the main raw material powder may be melted during sintering, which is not preferable. The sintering temperature is more preferably 800 ° C. or higher and 1100 ° C. or lower.
[0047]
  In the case of using the method A, the sintering is preferably performed in an inert atmosphere in order to prevent oxidation and nitridation of the molded body. Further, the heating rate and the holding time at the sintering temperature are not particularly limited, and are mainly set so that predetermined characteristics (for example, sintered body density, average crystal size, magnetostrictive characteristics, etc.) can be obtained. It can be arbitrarily selected according to the composition of the raw material powder, the sintering temperature and the like.
[0048]
  When Method B is used as a method for producing a sintered body, specifically, after filling the main raw material powder in a mold, the temperature is raised to a sintering temperature at a predetermined temperature raising rate, and at the same time the temperature reaches the sintering temperature. The main raw material powder may be pressurized and held for a predetermined time.
[0049]
  In this case, the pressure applied to the main raw material powder filled in the mold is preferably 19.6 MPa or more and 980 MPa or less. A pressure of less than 19.6 MPa is not preferable because a high-density sintered body cannot be obtained. On the other hand, when the pressure exceeds 980 MPa, the durability of the mold decreases, which is not preferable. More preferably, the pressure applied to the main raw material powder is 39.2 MPa or more and 490 MPa or less.
[0050]
  In Method B, the higher the temperature increase rate, the better. This is because pressurization during sintering does not reduce the density of the sintered body even if the heating rate is increased, but rather by increasing the heating rate, the sintered body has a small average crystal size. Is obtained. However, if the rate of temperature rise is excessive, the heating of the main raw material powder filled in the mold becomes non-uniform and the sinterability is lowered, which is not preferable. In order to obtain a sintered body having a small average crystal size and high density, the temperature rising rate is preferably 20 ° C./min or more and 200 ° C./min or less, more preferably 30 ° C./min or more and 150 ° C./min. It is below min.
[0051]
  Also in this case, the sintering temperature is preferably 500 ° C. or more and 1200 ° C. or less. A sintering temperature of less than 500 ° C. is not preferable because a high-density sintered body cannot be obtained in a short time. Further, if the sintering temperature exceeds 1200 ° C., the main raw material powder may be melted during sintering, which is not preferable. The sintering temperature is more preferably 800 ° C. or higher and 1100 ° C. or lower.
[0052]
  Furthermore, various methods can be used as a method for heating the main raw material powder filled in the mold, and the method is not particularly limited. Specific examples of the heating method include a method of heating the mold from the outside using a heater, a method of flowing a current directly into the mold through upper and lower punches (electric current sintering method), and the like. Among them, the electric current sintering method is particularly suitable as a method for sintering a giant magnetostrictive material because a high-density sintered body can be efficiently produced.
[0053]
  In the case of using method B, the sintering is preferably performed in an inert atmosphere in order to prevent oxidation and nitridation of the main raw material powder. In addition, the holding time at the sintering temperature is not particularly limited, and the composition of the main raw material powder so that predetermined characteristics (for example, sintered body density, average crystal size, magnetostrictive characteristics, etc.) can be obtained. It can be arbitrarily selected depending on the sintering temperature and the like.
[0054]
  The sintered body obtained through such a process may be used as it is as a magnetostrictive element after being subjected to finish processing as necessary, but secondary processing is applied to the obtained sintered body. Also good. Specific examples of the secondary processing method include extrusion, rolling, forging, and the like. These may be used singly or in combination of two or more according to the final shape of the product.
[0055]
  Next, the operation of the manufacturing method according to the present embodiment will be described. Using a method of forming a main raw material powder having a predetermined composition and sintering the resulting molded body, a magnetostrictive element having a complicated shape that cannot be obtained by a single crystal growth method or a unidirectional solidification method is efficiently obtained. Can be manufactured. Also, the main raw material powder having a predetermined composition is filled in the mold, heated to a sintering temperature at a predetermined heating rate, and then held for a predetermined time while applying a predetermined pressure to the main raw material powder. When this method is used, a sintered body having a high sintered body density and a small average crystal size can be efficiently produced.
[0056]
  In addition, since the sintered body obtained in this way has a predetermined alloy composition, it exhibits excellent magnetostriction characteristics in a low magnetic field and high compressive strength. Therefore, according to the method of the present invention, a giant magnetostrictive material excellent in durability under high load conditions can be obtained. Moreover, since the obtained sintered body is high-strength and homogeneous, secondary processing is also facilitated. Therefore, even a magnetostrictive element having a complicated shape that cannot be obtained by a conventional method can be efficiently manufactured.
[0057]
【Example】
Example 1
  Tb, Dy, Fe, and Cr coarse powders having a particle size of 500 μm or less are used as (Tb_0.5Dy_0.5) (Fe_0.95Cr_0.05)_2.0The composition was blended and subjected to mechanical alloying treatment for 100 hours using a planetary ball mill. The mechanical alloying treatment was performed in an argon atmosphere, and the weight ratio of the coarse powder to the ball was about 0.04.
[0058]
  Next, as shown in FIG. 1, the main raw material powder 12 obtained was put into a carbon mold 10 having an inner diameter of 20 mm, and current sintering was performed. Sintering is performed in a vacuum of 10 Pa under conditions of a heating rate of 40 ° C./min, a sintering temperature of 1000 ° C., a pressing force of 39.2 MPa, a holding time of 20 minutes, and the pressurization is performed at 1000 ° C. Just after reaching.
[0059]
  About the obtained sintered compact, the magnetic field from which a magnitude | size differs was provided, and the change of the magnetostriction which arises in that case was measured. FIG. 2 shows the result. FIG. 2 shows that the sintered body obtained in this example exhibits excellent magnetostriction characteristics in a low magnetic field. The magnetostriction of the obtained sintered body in a magnetic field of 100 kA / m was 360 ppm.
[0060]
(Examples 2 and 3)
  A sintered body was produced according to the same procedure as in Example 1 except that the amount of substitution of Fe by Cr was 10 at% (Example 2) and 20 at% (Example 3), respectively.
[0061]
(Comparative Examples 1 and 2)
  A sintered body was produced according to the same procedure as in Example 1 except that the amount of substitution of Fe with Cr was 0 at%.
[0062]
(Comparative Examples 3-6)
  A sintered body was produced according to the same procedure as in Example 1 except that a predetermined amount of oxygen and nitrogen was added to the argon gas filled in the pot during the mechanical alloying treatment (Comparative Examples 3 and 4). ). Similarly, the same amount as in Example 1 except that the substitution amount of Fe with Cr is 10 at% and a predetermined amount of oxygen and nitrogen is added to the argon gas filled in the pot during the mechanical alloying process. A sintered body was produced according to the procedure (Comparative Examples 5 and 6).
[0063]
  About the main raw material powder after the mechanical alloying treatment obtained in Examples 1 to 3 and Comparative Examples 1 to 6, the oxygen content and the nitrogen content were measured. The obtained sintered body was measured for magnetostriction in a magnetic field of 100 kA / m. Furthermore, a jig was placed on the obtained sintered body, and a compression test was performed under the condition of a crosshead speed of 1 mm / min. Table 1 shows the results.
[0064]
[Table 1]

[0065]
  In the case of Comparative Examples 1 and 2 to which no Cr was added, the amounts of oxygen contained in the main raw material powder were 0.59% and 0.49%, respectively. Further, the amounts of nitrogen contained in the main raw material powder were 0.02% and 0.10%, respectively. Furthermore, the magnetostriction in a magnetic field of 100 kA / m was 370 to 380 ppm, indicating a high value. However, in both Comparative Examples 1 and 2, the compressive strength could not be measured because the sample was broken by the weight of the jig when the compressive strength measuring jig was placed on the sample.
[0066]
  On the other hand, in Comparative Examples 3 to 5 in which the substitution amount of Fe with Cr was 5 to 10 at%, the compressive strength was improved to 250 to 300 MPa. However, since the main raw material powder contained oxygen exceeding 1.5 mass% and nitrogen exceeding 1.5 mass%, the magnetostriction in a magnetic field of 100 kA / m was less than 200 ppm. In addition, the magnetostriction tended to decrease as the amount of oxygen or nitrogen in the main raw material powder increased.
[0067]
  Furthermore, in the case of Comparative Example 6, since mechanical alloying treatment was performed in an atmosphere containing high concentrations of oxygen and nitrogen, 5.0 mass% oxygen and 9.85 mass% were contained in the main raw material powder. Nitrogen was included. Further, the magnetostriction of the obtained sintered body in a magnetic field of 100 kA / m was reduced to 30 ppm. Furthermore, since the high concentration oxygen and nitrogen were contained, the sintered compact was embrittled and the compressive strength could not be measured.
[0068]
  On the other hand, in Examples 1-3 in which the oxygen content in the main raw material powder was 1.5 mass% or less, the nitrogen content was 1.5 mass% or less, and a part of Fe was replaced with Cr, all were 100 kA / m. The magnetostriction in the magnetic field exceeded 200 ppm and the compressive strength exceeded 300 MPa. The magnetostriction showed a tendency to increase as the Cr substitution amount decreased. When the Cr substitution amount was 10 at% or less, the magnetostriction was equivalent to Comparative Examples 1 and 2 without addition of Cr. On the other hand, the compressive strength tended to increase as the Cr substitution amount increased. When the Cr substitution amount was 20 at%, the compressive strength was improved to 400 MPa.
[0069]
  The embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention. For example, when a giant magnetostrictive material is manufactured using a method (Method B) in which pressurization is performed simultaneously with heating, pressurization may be performed simultaneously with reaching the sintering temperature, or the sintering temperature is reached. You can do it before.
[0070]
  The production of the main raw material powder preferably uses a mechanical alloying treatment, but constitutes a magnetostrictive alloy.Contains metal elementsTwo or more kinds of coarse powders may be separately pulverized under an inert atmosphere and mixed at a predetermined ratio.
[0071]
【The invention's effect】
  Since the super magnetostrictive material according to the present invention is made of a magnetostrictive alloy polycrystal having a predetermined alloy composition, it has an effect of being excellent in magnetostriction characteristics in a low magnetic field and exhibiting a high compressive strength. Moreover, since it is high intensity | strength and homogeneous, there exists an effect that secondary processing becomes easy.
[0072]
  In addition, since the method for producing a giant magnetostrictive material according to the present invention performs molding and sintering using a main raw material powder having a predetermined composition, oxygen content and nitrogen content, the magnetostrictive material having the excellent characteristics as described above. Can be produced efficiently. Further, since the obtained sintered body can be easily subjected to secondary processing, there is an effect that even a product having a complicated shape that cannot be obtained by a conventional method can be manufactured with high productivity.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an electric current sintering method.
2 is a diagram showing the relationship between the magnetic field and magnetostriction of the sintered body obtained in Example 1. FIG.
[Explanation of symbols]
Type 10
12 Main raw material powder
14,16 punch

Claims (8)

General formula: (Tb _x Dy _1-x ) (Fe _y Cr _1-y ) _z
(However, 0 ≦ x ≦ 0.8, 0.8 ≦ y ≦ 0.95, 1.5 ≦ z ≦ 3.0)
Consists main phase and incidental impurities having a composition expressed in and oxygen content less 1.5 mass%, nitrogen content consists polycrystal magnetostrictive alloy is less than 1.5 mass%,
A giant magnetostrictive material which is a sintered body and has a compressive strength of 300 MPa or more.   The giant magnetostrictive material according to claim 1, wherein the average crystal size is 100 µm or less.   The giant magnetostrictive material according to claim 1 or 2, wherein each crystal grain constituting the polycrystal is non-oriented. 3 two or more kinds of coarse powders containing metallic elements constituting the magnetostrictive alloy claims 1 obtained by molding and sintering a main raw material powder obtained by treating the mechanical alloying in an inert atmosphere The giant magnetostrictive material according to any of the above. General formula: (Tb _x Dy _1-x ) (Fe _y Cr _1-y ) _z
(However, 0 ≦ x ≦ 0.8, 0.8 ≦ y ≦ 0.95, 1.5 ≦ z ≦ 3.0)
A main raw material powder comprising a magnetostrictive alloy and / or a precursor thereof composed of a main phase and inevitable impurities having a composition represented by formula (1) and having an oxygen content of 1.5 mass% or less and a nitrogen content of 1.5 mass% or less. Powder manufacturing process to
A sintered body production process for producing a polycrystalline body using the main raw material powder ,
The said powder manufacturing process is a manufacturing method of the giant magnetostrictive material which carries out the mechanical alloying process of 2 or more types of coarse powder containing the metal element which comprises the said magnetostriction alloy in inert atmosphere . The sintered body manufacturing step includes a molding step of molding the main raw material powder at a molding pressure of 98 MPa or more and 980 MPa or less,
The method for producing a giant magnetostrictive material according to claim 5 , comprising a sintering step in which the molded body obtained in the molding step is heated at 500 ° C. to 1200 ° C. and held for a predetermined time. In the sintered body manufacturing step, the main raw material powder is filled in a mold and heated to a sintering temperature of 500 ° C. or more and 1200 ° C. or less at a temperature rising rate of 20 ° C./min to 200 ° C./min, The method for producing a giant magnetostrictive material according to claim 5 , wherein the material is held for a predetermined time while a pressure of 19.6 MPa to 980 MPa is applied to the main raw material powder in a state where the sintering temperature is maintained. The production of a giant magnetostrictive material according to any one of claims 5 to 7 , further comprising a secondary processing step of performing extrusion, rolling and / or forging on the sintered body obtained in the sintered body production step. Method.

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