JP3697506B2 - Giant magnetostrictive alloy having excellent oxidation resistance and method for producing the same - Google Patents
Giant magnetostrictive alloy having excellent oxidation resistance and method for producing the same Download PDFInfo
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- JP3697506B2 JP3697506B2 JP2001052042A JP2001052042A JP3697506B2 JP 3697506 B2 JP3697506 B2 JP 3697506B2 JP 2001052042 A JP2001052042 A JP 2001052042A JP 2001052042 A JP2001052042 A JP 2001052042A JP 3697506 B2 JP3697506 B2 JP 3697506B2
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- 229910045601 alloy Inorganic materials 0.000 title claims description 57
- 239000000956 alloy Substances 0.000 title claims description 57
- 230000003647 oxidation Effects 0.000 title claims description 41
- 238000007254 oxidation reaction Methods 0.000 title claims description 41
- 238000004519 manufacturing process Methods 0.000 title claims description 11
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 44
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 41
- 239000011651 chromium Substances 0.000 claims description 35
- 229910052804 chromium Inorganic materials 0.000 claims description 32
- 239000000843 powder Substances 0.000 claims description 32
- KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 claims description 20
- 238000005551 mechanical alloying Methods 0.000 claims description 20
- GZCRRIHWUXGPOV-UHFFFAOYSA-N terbium atom Chemical compound [Tb] GZCRRIHWUXGPOV-UHFFFAOYSA-N 0.000 claims description 18
- 229910052742 iron Inorganic materials 0.000 claims description 14
- 229910052751 metal Inorganic materials 0.000 claims description 11
- 239000002184 metal Substances 0.000 claims description 10
- 238000005245 sintering Methods 0.000 claims description 9
- 229910052692 Dysprosium Inorganic materials 0.000 claims description 7
- 229910052771 Terbium Inorganic materials 0.000 claims description 7
- 238000002156 mixing Methods 0.000 claims description 5
- 239000000470 constituent Substances 0.000 claims description 4
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 12
- 239000003153 chemical reaction reagent Substances 0.000 description 12
- 238000010438 heat treatment Methods 0.000 description 11
- 239000007789 gas Substances 0.000 description 8
- 239000000463 material Substances 0.000 description 8
- 238000000034 method Methods 0.000 description 7
- 229910052786 argon Inorganic materials 0.000 description 6
- 238000005275 alloying Methods 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 238000005485 electric heating Methods 0.000 description 4
- 239000011261 inert gas Substances 0.000 description 4
- 229910000669 Chrome steel Inorganic materials 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- RDTHZIGZLQSTAG-UHFFFAOYSA-N dysprosium iron Chemical compound [Fe].[Dy] RDTHZIGZLQSTAG-UHFFFAOYSA-N 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000001747 exhibiting effect Effects 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- 229910002804 graphite Inorganic materials 0.000 description 3
- 239000010439 graphite Substances 0.000 description 3
- 238000000227 grinding Methods 0.000 description 3
- JSUSQWYDLONJAX-UHFFFAOYSA-N iron terbium Chemical compound [Fe].[Tb] JSUSQWYDLONJAX-UHFFFAOYSA-N 0.000 description 3
- 239000011812 mixed powder Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 239000001307 helium Substances 0.000 description 2
- 229910052734 helium Inorganic materials 0.000 description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 2
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 230000006837 decompression Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000001727 in vivo Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 239000000696 magnetic material Substances 0.000 description 1
- 238000003801 milling Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
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Description
【０００１】
【発明の属する技術分野】
本発明は、耐酸化性に優れる超磁歪合金およびその製造方法に関するものであり、更に詳しくは、本発明は、鉄粉末、クロム粉末、テルビウム粉末、ディスプロシウム粉末を機械的合金化法により合金化し、耐酸化性を改善した超磁歪合金の製造方法及び得られた超磁歪合金に関するものである。本発明は、超磁歪合金を構成する元素にクロムを混合することによって、耐酸化性に優れた超磁歪合金を作製し、提供することを可能にするものである。
【０００２】
【従来の技術】
超磁歪合金は、電流によって発生する磁界によって変位量を精密に制御できるため、その超磁歪素子や磁歪特性の改善が種々検討されている。その中でも、鉄、テルビウム、ディスプロシウムからなる合金は、磁界による寸法変化が大きく、超磁歪素子として注目されている。超磁歪素子は、従来、寸法変化がより大きくなるように、また、より小さい磁界で大きな変化が得られるように開発されてきた。ところで、超磁歪素子の使用が想定されている環境に注目すると、その環境は、エンジンルーム内であったり、宇宙環境あるいは生体内部といった材料にとって厳しい環境である場合が少なくない。そのような環境で超磁歪素子を長期間安定的に使用するためには、超磁歪特性を損なわず、耐酸化性に優れた素子の開発が不可欠である。しかし、これまでのところ、耐酸化性に優れた超磁歪合金の開発は行われていない。
【０００３】
【発明が解決しようとする課題】
このような状況の中で、本発明者らは、上記の問題点を解決するために鋭意研究を重ねた結果、以下の結果を見いだし、本発明を完成するに至った。
まず、超磁歪合金の構成元素である鉄粉末、テルビウム粉末、ディスプロシウム粉末にクロム粉末を加えて、機械的合金化法により合金を合成する。その場合、超磁歪特性を損なわないために、クロムは鉄に置き換える形で混合し、鉄とクロムを合わせた割合の合計が６４原子％から６９原子％とする。更に、クロムの割合を６原子％から２０原子％とする。残りをテルビウムとディスプロシウムが任意の割合となるように配合する。得られた粉末を焼結することにより、超磁歪特性を損なわず、耐酸化性に優れた超磁歪合金が得られることを見いだした。
本発明は、超磁歪合金を構成する元素にクロムを混合することで、超磁歪特性を損なうことなく、耐酸化性を向上させた超磁歪合金を作製し、提供することを目的とする。
【０００４】
【課題を解決するための手段】
上記課題を解決するための本発明は、以下の技術的手段から構成される。
（１）超磁歪特性を損なうことなく、耐酸化性を付与した超磁歪合金を製造する方法であって、１）超磁歪合金の構成元素である鉄粉末、テルビウム粉末、ディスプロシウム粉末と、クロム粉末およびその不可避なる金属元素を機械的合金化法により処理して合金を合成する、２）その場合、クロムは鉄に置き換える形で混合し、鉄とクロムをあわせて全体の６４〜６９原子％とし、かつ、クロムの割合を６〜２０原子％とし、全体の残りをテルビウムとディスプロシウムが任意の割合になるように配合する、３）得られた合金粉末を焼結して焼結体を作製する、４）上記１）〜３）により、超磁歪特性を損なうことなく、耐酸化性を向上させた超磁歪合金を作製する、ことを特徴とする耐酸化性を付与した超磁歪合金の製造方法。
（２）上記合金粉末を加圧しながら成形して焼結体を作製し、これを熱処理して緻密化することを特徴とする前記（１）に記載の耐酸化性を付与した超磁歪合金の製造方法。
（３）超磁歪特性を損なうことなく、耐酸化性を付与した超磁歪合金であって、次の工程；１）超磁歪合金の構成元素である鉄粉末、テルビウム粉末、ディスプロシウム粉末と、クロム粉末およびその不可避なる金属元素を機械的合金化法により処理して合金を合成する、２）その場合、クロムは鉄に置き換える形で混合し、鉄とクロムをあわせて全体の６４〜６９原子％とし、かつ、クロムの割合を６〜２０原子％とし、全体の残りをテルビウムとディスプロシウムが任意の割合になるように配合する、３）得られた合金粉末を焼結して焼結体を作製する、４）上記１）〜３）により、超磁歪特性を損なうことなく、耐酸化性を向上させた超磁歪合金を作製する、により作製したことを特徴とする、耐酸化性を付与した超磁歪合金。
（４）上記合金粉末を加圧しながら成形して焼結体を作製し、これを熱処理して緻密化したことを特徴とする前記（３）に記載の耐酸化性を付与した超磁歪合金。
【０００５】
【発明の実施の形態】
次に、本発明について更に詳細に説明する。
本発明に用いる材料には、市販の鉄粉末、クロム粉末、テルビウム粉末、ディスプロシウム粉末が利用できる。粉末の大きさについては特に指定しないが、一般的には数十ミクロンから数ミリの粉末が利用できる。各粉末の混合の割合は、鉄とクロムをあわせて全体の６４原子％から６９原子％となり、かつ、クロムの割合が６原子％から２０原子％であり、全体の残りをテルビウムとディスプロシウムが任意の割合になるように配合する。鉄とクロムを６４〜６９原子％とした理由は、６４原子％より少ない、あるいは６９原子％より多いと、磁歪を示す結晶相が形成されないためであり、クロムの割合を６〜２０原子％とした理由は、６原子％より少ないと耐酸化性向上の効果が見られない、また、２０原子％より多いと磁歪特性が低下するためである。
【０００６】
機械的合金化処理には乾式の粉砕機が利用でき、好適には振動型ボールミル、遊星型ボールミル、転動型ボールミル、アトライターなどが利用できる。機械的合金化処理時の雰囲気は粉末の酸化を防止するため、不活性ガス雰囲気や減圧雰囲気が好ましい。また、機械的合金化処理時に金属粉末が容器やボールに付着しないように添加するミリング助剤は、合金粉末に炭素が混入し、回収時に合金粉末が燃焼するため使用してはならない。
【０００７】
機械的合金化に供する時間は特に指定しないが、５０時間から１５０時間が好ましい。５０時間より短いと各元素の混合状態が不十分であり、合金化には至っていない可能性がある。また、１５０時間を超えると機械的合金化処理時に粉末の酸化あるいは窒化が多くなり、超磁歪合金の性能劣化をもたらす酸化物や窒化物が生成される。更に、機械的合金化時の圧力伝達媒体としては、鋼球、セラミックス球、超硬球などの一般的な粉砕球が利用できる。
【０００８】
所定の組成に配合された元素の粉末を機械的合金化処理により合金化した粉末は、数マイクロメートル以下の微細な粉末であり、その内部は微細な結晶や非晶質で構成されている。
【０００９】
得られた粉末を固化するための雰囲気は、粉末の酸化を防止するため、不活性ガス雰囲気や減圧あるいは真空雰囲気が好ましい。好適には、不活性ガスとしてアルゴン、ヘリウムなどが用いられる。減圧条件は、１５０ｍｍＨｇから５００ｍｍＨｇ、真空条件は、０．１ｍｍＨｇ以下が好ましい。加熱方法は特に指定しないが、短時間で目的温度に到達する方法が好ましく、例えば、通電加熱や赤外線イメージ炉、高周波加熱炉などが利用できる。焼結の温度条件は、９００℃から１１００℃が好ましい。また、加熱時には成形性を向上するため、加圧しなければならない。加圧方法は特に指定しないが、一般的には油圧や空圧を利用した一軸の加圧や、ガス圧を利用した等方的な加圧が利用される。好適には、加圧として４００ｋｇｆ／ｃｍ2 から５００ｋｇｆ／ｃｍ2 の圧力が用いられる。
【００１０】
得られた焼結体を熱処理するための雰囲気は、焼結体の酸化を防止するため、不活性ガス雰囲気や減圧あるいは真空雰囲気が好ましい。好適には、それらの条件は１５０ｍｍＨｇから５００ｍｍＨｇ程度のアルゴンガスやヘリウムガス雰囲気、あるいは、０．１ｍｍＨｇ以下の真空雰囲気が例示される。加熱方法は特に指定しないが、均熱帯が大きい方法が好ましく、例えば、管状炉や赤外線イメージ炉などが利用できる。熱処理の温度は、８００℃から１０００℃が好ましい。
【００１１】
本発明の作製方法を用いることにより、超磁歪特性を損なうことなく、耐酸化性に優れた超磁歪合金を得ることができる。磁歪合金は電流によって発生する磁界によって変位量を制御できるため、素早い動作と精密な位置ぎめができる。その上、更に耐酸性が改善されると、例えば、ディーゼルエンジンの燃料インジェクターなどにすることによって、燃料の噴射量を厳密に制御し、排気ガスに含まれる環境汚染物質を低減させることができる。更に、今後の宇宙開発において要求される、超精密流量制御バルブなどへの応用が期待される。また、医学分野に視点を移すと、体内で活動するマイクロマシンへの応用が考えられる。生体内は複雑であるため、コードレスで制御可能なアクチュエータとしての磁歪材料が注目されている。しかし、生体内は腐食環境であるため、自在材料の安定的な活動が困難であると考えられている。本発明の方法を用いることにより、耐酸化性が向上するため、このような分野でも応用できる。このように、本発明は、様々な工業分野での発展に貢献できるものと期待される。
【００１２】
【実施例】
以下、実施例に基づいて本発明を更に具体的に説明するが、以下の実施例は本発明の好適な一例を示すものであり、本発明は、該実施例により何ら限定されるものではない。
実施例１
鉄粉末（和光純薬試薬特級）５．１ｇ、テルビウム粉末（レアメタリック試薬特級）４．６ｇ、ディスプロシウム粉末（レアメタリック試薬特級）４．７ｇにクロム粉末（ナカライテスク試薬特級）０．６ｇを添加し、遊星型ボールミルにて１００時間の機械的合金化処理を行った。機械的合金化処理時の雰囲気は１５０ｍｍＨｇの減圧アルゴンガス雰囲気とし、粉末とボールの重量比が約１：２７になるようにした。容器と１０ｍｍ径の粉砕球にはクロム鋼を用いた。得られた材料は数マイクロメートル程度の粉末であった。
【００１３】
鉄粉末、テルビウム粉末、ディスプロシウム粉末とクロム粉末を機械的に合金化した混合粉末６ｇを５×３０ｍｍの黒鉛製の型に入れ、約１ｍｍＨｇの真空中で通電加熱による固化成形を行った。焼結は、４２０ｋｇｆ／ｃｍ2 の加圧下にて１０００℃で５分間保持した。得られた成形体は５×５×３０ｍｍの角柱状になった。
【００１４】
得られた成形体は、超磁歪特性を示す、鉄−テルビウム、鉄−ディスプロシウム化合物からなっており、クロムが微細に分散していた。成形体の磁歪特性はクロムがない場合と比較して同程度であった。また、クロムの添加により酸化による重量増加が約１／７となり、耐酸化性が改善された。図１に、加熱中の試料の重量増加を示す。また、図２に、耐酸化性評価に使用した試料と同じ試料の磁歪特性を示す。図１より、Ｃｒを添加しない試料は酸化（酸素との結合）による重量増加が大きく、Ｃｒを添加すると、酸化が抑制され重量増加が小さいことがわかる。また、図２より、Ｃｒ添加の有無による依存性は見られないことがわかる。
【００１５】
実施例２
鉄粉末（和光純薬試薬特級）５．２ｇ、テルビウム粉末（レアメタリック試薬特級）５．２ｇ、ディスプロシウム粉末（レアメタリック試薬特級）０．９ｇにクロム粉末（ナカライテスク試薬特級）０．６ｇを添加し、遊星型ボールミルにて１００時間の機械的合金化処理を行った。機械的合金化処理時の雰囲気は５００ｍｍＨｇの減圧アルゴンガス雰囲気とし、粉末とボールの重量比が約１：２７になるようにした。容器と１０ｍｍ径の粉砕球にはクロム鋼を用いた。得られた材料は数マイクロメートル程度の粉末であった。
【００１６】
鉄粉末、テルビウム粉末、ディスプロシウム粉末とクロム粉末を機械的に合金化した混合粉末１１ｇを９×３０ｍｍの黒鉛製の型に入れ、約１ｍｍＨｇの真空中で通電加熱による固化成形を行った。焼結は、４２０ｋｇｆ／ｃｍ2 の加圧下にて１０００℃で５分間保持した。得られた成形体は５×９×３０ｍｍの角柱状になった。
【００１７】
得られた成形体は、超磁歪特性を示す、鉄−テルビウム、鉄−ディスプロシウム化合物からなっており、クロムが微細に分散していた。成形体の磁歪特性はクロムがない場合と比較して同程度であった。また、クロムの添加により酸化による重量増加が約１／７となり、耐酸化性が改善された。
【００１８】
実施例３
鉄粉末（和光純薬試薬特級）４．６ｇ、テルビウム粉末（レアメタリック試薬特級）２．７ｇ、ディスプロシウム粉末（レアメタリック試薬特級）６．５ｇにクロム粉末（ナカライテスク試薬特級）１．１ｇを添加し、遊星型ボールミルにて１００時間の機械的合金化処理を行った。機械的合金化処理時の雰囲気は１５０ｍｍＨｇの減圧アルゴンガス雰囲気とし、粉末とボールの重量比が約１：２７になるようにした。容器と１０ｍｍ径の粉砕球にはクロム鋼を用いた。得られた材料は数マイクロメートル程度の粉末であった。
【００１９】
鉄粉末、テルビウム粉末、ディスプロシウム粉末とクロム粉末を機械的に合金化した混合粉末６ｇを５×３０ｍｍの黒鉛製の型に入れ、約１ｍｍＨｇの真空中で通電加熱による固化成形を行った。焼結は、４２０ｋｇｆ／ｃｍ2 の加圧下にて１０００℃で５分間保持した。得られた成形体は５×５×３０ｍｍの角柱状になった。
【００２０】
得られた焼結体を管状炉内に静置し、アルゴンガスを炉内に環流させた状態で熱処理を行った。熱処理は９００℃で３時間保持した。熱処理によってより緻密化し、結晶粒が若干成長した。
【００２１】
得られた成形体は、超磁歪特性を示す、鉄−テルビウム、鉄−ディスプロシウム化合物からなっており、クロムが微細に分散していた。成形体の磁歪特性はクロムがない場合と比較して同程度以上となった。また、クロムの添加により酸化による重量増加が約１／９となり、耐酸化性が改善された。
【００２２】
【発明の効果】
以上詳述した通り、本発明は、超磁歪合金を構成する元素のうち、鉄の一部をクロムで置き換え、機械的合金化によって合金を合成し、得られた合金粉末を焼結して固化成形し、更に熱処理することにより超磁歪合金を製造する方法及びその製品に係るものであり、本発明により、１）超磁歪特性を損なうことなく、耐酸化性に優れた超磁歪合金を得ることができる、２）この超磁歪合金は、耐酸化性の改善により、種々の分野の磁歪材料として利用可能である、３）この磁性材料は、例えば、ディーゼルエンジンの燃料インジェクター、宇宙開発分野で要求される超精密流量制御バルブ、医学分野における生体内で用いられるマイクロマシン、コードレスで制御可能なアクチュエーターなどへ応用可能である、という効果が奏される。
【図面の簡単な説明】
【図１】Ｃｒ無添加及びＣｒ添加試料の加熱中の試料の重量増加を示す説明図である。
【図２】耐酸化性評価に使用した試料と同じ試料の磁歪特性を示す説明図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a giant magnetostrictive alloy having excellent oxidation resistance and a method for producing the same. More specifically, the present invention relates to an alloy of iron powder, chromium powder, terbium powder, and dysprosium powder by a mechanical alloying method. The present invention relates to a method for producing a giant magnetostrictive alloy having improved oxidation resistance and an obtained giant magnetostrictive alloy. The present invention makes it possible to produce and provide a giant magnetostrictive alloy excellent in oxidation resistance by mixing chromium with an element constituting the giant magnetostrictive alloy.
[0002]
[Prior art]
Since the amount of displacement of a giant magnetostrictive alloy can be precisely controlled by a magnetic field generated by an electric current, various improvements in its giant magnetostrictive element and magnetostrictive characteristics have been studied. Among them, an alloy composed of iron, terbium, and dysprosium has a large dimensional change due to a magnetic field, and is attracting attention as a giant magnetostrictive element. The giant magnetostrictive element has been developed so that the dimensional change becomes larger and a large change can be obtained with a smaller magnetic field. By the way, paying attention to the environment where the use of the giant magnetostrictive element is assumed, the environment is often a severe environment for the material such as the engine room, the space environment or the inside of the living body. In order to use the giant magnetostrictive element stably in such an environment for a long period of time, it is indispensable to develop an element having excellent oxidation resistance without impairing the giant magnetostrictive characteristics. However, so far, no giant magnetostrictive alloy having excellent oxidation resistance has been developed.
[0003]
[Problems to be solved by the invention]
Under such circumstances, the present inventors have intensively studied to solve the above problems, and as a result, have found the following results and have completed the present invention.
First, chromium powder is added to iron powder, terbium powder, and dysprosium powder, which are constituent elements of a giant magnetostrictive alloy, and an alloy is synthesized by a mechanical alloying method. In that case, in order not to impair the giant magnetostrictive characteristics, chromium is mixed in a form replacing iron, and the total ratio of iron and chromium is made to be 64 atomic% to 69 atomic%. Furthermore, the ratio of chromium is set to 6 atom% to 20 atom%. The remainder is blended so that terbium and dysprosium are in an arbitrary ratio. It has been found that by sintering the obtained powder, a giant magnetostrictive alloy excellent in oxidation resistance can be obtained without impairing giant magnetostrictive properties.
An object of the present invention is to produce and provide a giant magnetostrictive alloy having improved oxidation resistance without impairing the giant magnetostrictive characteristics by mixing chromium with the elements constituting the giant magnetostrictive alloy.
[0004]
[Means for Solving the Problems]
The present invention for solving the above-described problems comprises the following technical means.
(1) without impairing the super magnetostrictive characteristics, a method for producing a super magnetostrictive alloy imparts oxidation resistance, 1) iron powder as a constituent element of the super magnetostrictive alloy, Te Rubiumu powder, and dysprosium powder The alloy is synthesized by treating the chromium powder and its inevitable metal element by a mechanical alloying method. 2) In that case, chromium is mixed in the form of replacing iron, and iron and chromium are combined to make a total of 64 to 69. and atomic%, and the proportion of chromium and 6-20 atomic%, blending the remaining whole as terbium and dysprosium is arbitrary ratio, 3) by sintering an alloy powder obtained 4) By the above 1) to 3), an oxidation resistance characterized by producing a giant magnetostrictive alloy with improved oxidation resistance without impairing the giant magnetostrictive characteristics was imparted. method of manufacturing a super-magnetostrictive alloy.
(2) The above- described super magnetostrictive alloy imparted with oxidation resistance according to the above (1), wherein the alloy powder is molded while being pressed to produce a sintered body, which is heat-treated to be densified. Production method.
(3) A giant magnetostrictive alloy imparted with oxidation resistance without impairing the giant magnetostrictive characteristics, the following steps: 1) iron powder, terbium powder, dysprosium powder, which are constituent elements of the giant magnetostrictive alloy, Chromium powder and its inevitable metal elements are processed by mechanical alloying to synthesize the alloy. 2) In that case, chromium is mixed in the form of replacing iron, and iron and chromium are combined to make a total of 64 to 69 atoms. %, And the ratio of chromium is 6 to 20 atomic%, and the remainder is blended so that terbium and dysprosium are in an arbitrary ratio. 3) Sintering and sintering the obtained alloy powder 4) Oxidation resistance, characterized in that it was produced by 4) producing a giant magnetostrictive alloy with improved oxidation resistance without damaging the giant magnetostriction characteristics according to 1) to 3) above. Giant magnetostrictive alloy.
(4) The super magnetostrictive alloy imparted with oxidation resistance according to (3) above, wherein the alloy powder is molded while being pressed to produce a sintered body, which is heat-treated to be densified.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in more detail.
Commercially available iron powder, chromium powder, terbium powder, and dysprosium powder can be used for the material used in the present invention. The size of the powder is not particularly specified, but generally a powder of several tens of microns to several millimeters can be used. The mixing ratio of each powder is from 64 atomic% to 69 atomic% of the total of iron and chromium, and the ratio of chromium is 6 atomic% to 20 atomic%. The rest of the total is terbium and dysprosium. Is blended so as to have an arbitrary ratio. The reason why iron and chromium are 64 to 69 atomic% is that when the amount is less than 64 atomic% or more than 69 atomic%, a crystal phase showing magnetostriction is not formed, and the ratio of chromium is 6 to 20 atomic%. The reason for this is that if the amount is less than 6 atomic%, the effect of improving the oxidation resistance is not observed, and if the amount is more than 20 atomic%, the magnetostrictive characteristics are deteriorated.
[0006]
A dry pulverizer can be used for the mechanical alloying treatment, and preferably a vibration type ball mill, a planetary ball mill, a rolling ball mill, an attritor, or the like can be used. The atmosphere during the mechanical alloying treatment is preferably an inert gas atmosphere or a reduced pressure atmosphere in order to prevent oxidation of the powder. Also, a milling aid added so that the metal powder does not adhere to the container or ball during the mechanical alloying treatment should not be used because carbon is mixed into the alloy powder and the alloy powder burns during recovery.
[0007]
The time for the mechanical alloying is not particularly specified, but is preferably 50 to 150 hours. If it is shorter than 50 hours, the mixed state of each element is insufficient, and alloying may not be achieved. On the other hand, if it exceeds 150 hours, oxidation or nitridation of the powder increases during the mechanical alloying treatment, and oxides and nitrides that cause performance deterioration of the giant magnetostrictive alloy are generated. Furthermore, as a pressure transmission medium at the time of mechanical alloying, general pulverized balls such as steel balls, ceramic balls, and hard balls can be used.
[0008]
A powder obtained by alloying a powder of an element mixed in a predetermined composition by a mechanical alloying process is a fine powder of several micrometers or less, and its inside is composed of fine crystals or amorphous.
[0009]
The atmosphere for solidifying the obtained powder is preferably an inert gas atmosphere, a reduced pressure or a vacuum atmosphere in order to prevent oxidation of the powder. Preferably, argon, helium, or the like is used as the inert gas. The decompression condition is preferably 150 mmHg to 500 mmHg, and the vacuum condition is preferably 0.1 mmHg or less. Although the heating method is not particularly specified, a method of reaching the target temperature in a short time is preferable. For example, an electric heating, an infrared image furnace, a high-frequency heating furnace, or the like can be used. The sintering temperature condition is preferably 900 ° C. to 1100 ° C. Moreover, in order to improve a moldability at the time of a heating, you must pressurize. Although the pressurizing method is not particularly specified, generally, uniaxial pressurization using hydraulic pressure or pneumatic pressure, or isotropic pressurization using gas pressure is used. Preferably, from 400 kgf / cm 2 pressure of 500 kgf / cm 2 is used as the pressure.
[0010]
The atmosphere for heat-treating the obtained sintered body is preferably an inert gas atmosphere, a reduced pressure or a vacuum atmosphere in order to prevent oxidation of the sintered body. Preferably, the conditions include an argon gas or helium gas atmosphere of about 150 mmHg to 500 mmHg, or a vacuum atmosphere of 0.1 mmHg or less. Although the heating method is not particularly specified, a method having a large soaking zone is preferable, and for example, a tubular furnace or an infrared image furnace can be used. The heat treatment temperature is preferably 800 ° C. to 1000 ° C.
[0011]
By using the production method of the present invention, a giant magnetostrictive alloy having excellent oxidation resistance can be obtained without impairing the giant magnetostrictive characteristics. The magnetostrictive alloy can control the amount of displacement by a magnetic field generated by an electric current, so that a quick operation and precise positioning can be performed. In addition, when the acid resistance is further improved, for example, by using a fuel injector of a diesel engine or the like, the fuel injection amount can be strictly controlled, and environmental pollutants contained in the exhaust gas can be reduced. Furthermore, it is expected to be applied to ultra-precise flow control valves that will be required in future space development. Also, if the viewpoint is shifted to the medical field, it can be applied to micromachines that are active in the body. Since the inside of a living body is complicated, a magnetostrictive material is attracting attention as an actuator that can be controlled cordlessly. However, since the living body is a corrosive environment, it is considered that stable activity of the free material is difficult. Since the oxidation resistance is improved by using the method of the present invention, it can be applied in such a field. As described above, the present invention is expected to contribute to development in various industrial fields.
[0012]
【Example】
Hereinafter, the present invention will be described in more detail based on examples. However, the following examples show preferred examples of the present invention, and the present invention is not limited to the examples. .
Example 1
Iron powder (special grade of Wako Pure Chemical reagent) 5.1g, Terbium powder (special grade of rare metal reagent) 4.6g, dysprosium powder (special grade of rare metal reagent) 4.7g, chromium powder (special grade of Nacalai Tesque reagent) 0.6g And a mechanical alloying treatment for 100 hours was performed in a planetary ball mill. The atmosphere during the mechanical alloying treatment was a reduced pressure argon gas atmosphere of 150 mmHg so that the weight ratio of the powder to the ball was about 1:27. Chrome steel was used for the vessel and the 10 mm diameter grinding sphere. The obtained material was a powder of about several micrometers.
[0013]
6 g of a mixed powder obtained by mechanically alloying iron powder, terbium powder, dysprosium powder and chromium powder was put into a 5 × 30 mm graphite mold, and solidified by electric heating in a vacuum of about 1 mmHg. Sintering was held at 1000 ° C. for 5 minutes under a pressure of 420 kgf / cm 2 . The obtained molded body became a prismatic shape of 5 × 5 × 30 mm.
[0014]
The obtained molded body was composed of an iron-terbium or iron-dysprosium compound exhibiting giant magnetostriction characteristics, and chromium was finely dispersed. The magnetostriction characteristics of the molded body were comparable to the case without chromium. Further, the addition of chromium reduced the weight increase due to oxidation to about 1/7 and improved the oxidation resistance. FIG. 1 shows the weight increase of the sample during heating. FIG. 2 shows the magnetostriction characteristics of the same sample used for the oxidation resistance evaluation. From FIG. 1, it can be seen that the sample without addition of Cr has a large weight increase due to oxidation (bonding with oxygen), and when Cr is added, the oxidation is suppressed and the weight increase is small. Moreover, it turns out that the dependence by the presence or absence of Cr addition is not seen from FIG.
[0015]
Example 2
Iron powder (special grade of Wako Pure Chemical reagent) 5.2g, Terbium powder (special grade of rare metal reagent) 5.2g, dysprosium powder (special grade of rare metal reagent) 0.9g, chromium powder (special grade of Nacalai Tesque reagent) 0.6g And a mechanical alloying treatment for 100 hours was performed in a planetary ball mill. The atmosphere during the mechanical alloying treatment was a reduced pressure argon gas atmosphere of 500 mmHg so that the weight ratio of the powder to the ball was about 1:27. Chrome steel was used for the vessel and the 10 mm diameter grinding sphere. The obtained material was a powder of about several micrometers.
[0016]
11 g of a mixed powder obtained by mechanically alloying iron powder, terbium powder, dysprosium powder and chromium powder was placed in a 9 × 30 mm graphite mold, and solidified by electric heating in a vacuum of about 1 mmHg. Sintering was held at 1000 ° C. for 5 minutes under a pressure of 420 kgf / cm 2 . The obtained molded body became a prismatic shape of 5 × 9 × 30 mm.
[0017]
The obtained molded body was composed of an iron-terbium or iron-dysprosium compound exhibiting giant magnetostriction characteristics, and chromium was finely dispersed. The magnetostriction characteristics of the molded body were comparable to the case without chromium. Further, the addition of chromium reduced the weight increase due to oxidation to about 1/7 and improved the oxidation resistance.
[0018]
Example 3
Iron powder (special grade of Wako Pure Chemical reagent) 4.6g, terbium powder (special grade of rare metal reagent) 2.7g, dysprosium powder (special grade of rare metal reagent) 6.5g, chromium powder (special grade of Nacalai Tesque reagent) 1.1g And a mechanical alloying treatment for 100 hours was performed in a planetary ball mill. The atmosphere during the mechanical alloying treatment was a reduced pressure argon gas atmosphere of 150 mmHg so that the weight ratio of the powder to the ball was about 1:27. Chrome steel was used for the vessel and the 10 mm diameter grinding sphere. The obtained material was a powder of about several micrometers.
[0019]
6 g of a mixed powder obtained by mechanically alloying iron powder, terbium powder, dysprosium powder and chromium powder was put into a 5 × 30 mm graphite mold, and solidified by electric heating in a vacuum of about 1 mmHg. Sintering was held at 1000 ° C. for 5 minutes under a pressure of 420 kgf / cm 2 . The obtained molded body became a prismatic shape of 5 × 5 × 30 mm.
[0020]
The obtained sintered body was left in a tubular furnace, and heat treatment was performed in a state where argon gas was circulated in the furnace. The heat treatment was held at 900 ° C. for 3 hours. It became denser by the heat treatment, and crystal grains grew slightly.
[0021]
The obtained molded body was composed of iron-terbium and iron-dysprosium compounds exhibiting giant magnetostrictive properties, and chromium was finely dispersed. The magnetostriction characteristic of the molded body was the same or higher than that of the case without chromium. Further, the addition of chromium reduced the weight increase by oxidation to about 1/9 and improved the oxidation resistance.
[0022]
【The invention's effect】
As described in detail above, the present invention replaces a part of iron among the elements constituting the giant magnetostrictive alloy with chromium, synthesizes the alloy by mechanical alloying, and sinters and solidifies the obtained alloy powder. The present invention relates to a method for producing a giant magnetostrictive alloy by molding and further heat treatment and the product thereof. According to the present invention, 1) a giant magnetostrictive alloy having excellent oxidation resistance is obtained without impairing the giant magnetostrictive properties. 2) This super-magnetostrictive alloy can be used as a magnetostrictive material in various fields by improving oxidation resistance. 3) This magnetic material is required in, for example, a fuel injector for a diesel engine and a space development field. It can be applied to ultra-precise flow control valves, micromachines used in vivo in the medical field, actuators that can be controlled cordlessly, and the like.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an increase in the weight of a sample during heating of a Cr-free sample and a Cr-added sample.
FIG. 2 is an explanatory diagram showing magnetostriction characteristics of the same sample as that used for evaluation of oxidation resistance.
Claims (4)
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