JP3600350B2

JP3600350B2 - Functionally graded material and method for producing the same

Info

Publication number: JP3600350B2
Application number: JP05021696A
Authority: JP
Inventors: 孝浩奥畑; 斉青山; 雅士高橋
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 1996-03-07
Filing date: 1996-03-07
Publication date: 2004-12-15
Anticipated expiration: 2016-03-07
Also published as: JPH09241705A

Description

【０００１】
【発明の属する技術分野】
本発明は、傾斜機能材料及びその製造方法に係り、特に、タングステンと銅からなる傾斜機能材料に関する。
【０００２】
【従来の技術】
核融合炉に使用されるダイバ−タ板、ビ−ムダンプ、カロリ−メ−タ−等の部材は、プラズマにさらされ、高熱負荷及び高粒子負荷を受けるという極めて苛酷な環境の下で使用される。かかる部材を構成する材料として、近年、タングステン（Ｗ）のような耐熱性を有する高融点材料と、銅（Ｃｕ）のような熱伝導性の高い低融点材料とを接合し、両者の組成を積層方向に変化させて熱応力の緩和を図った傾斜機能材料が提案されている。
【０００３】
このＷ／Ｃｕ傾斜機能材料は、例えば焼結溶浸法と呼ばれる方法により製造される。焼結溶浸法によるＷ／Ｃｕ傾斜機能材料の製造は、次のようにして行われる。即ち、まずＷ粉末を粒径を変えて順次積層し、プレス成型し、焼結して密度が積層方向に変化したＷ焼結体を形成する。この場合、粒径が小さい層は密度が高く、粒径が大きい層は密度が低くなる。次いで、Ｗ焼結体にオ−プンＨＩＰ（熱間等方圧加圧）処理を施し、Ｗ焼結体中の閉気孔を潰し、開気孔のみを残す。最後にＷ焼結体の開気孔中にＣｕを溶浸する。
このようにして得た傾斜機能材料は、密度の高い、Ｃｕの溶浸量の少ないＷ層から、密度の低い、溶浸量の多いＷ層まで変化する傾斜組成を示す。
【０００４】
【発明が解決しようとする課題】
しかし、以上説明した焼結溶浸法による傾斜機能材料の製造には、以下のような種々の問題がある。
（１）Ｗ／Ｃｕ傾斜機能材料は、Ｃｕの溶浸後、Ｃｕの凝固過程において熱収縮を生ずるが、傾斜機能材料のＷの密度の高い層は、Ｃｕの溶浸量が少ないか、全く溶浸されないため、熱応力に耐えることが出来ず、クラックが生じてしまう。
【０００５】
（２）Ｗ粉末の粒径が積層方向において異なるため、焼結後の収縮の割合が積層方向で大きく異なり、Ｗ焼結体に反りが生じたり、クラックが発生する。
（３）粒径の大きな低密度のＷ粉末層では、成型時に成型不良となり、成型体を移動する際にカケたり、焼結後にクラックが発生したりする。
【０００６】
（４）粒径の異なるＷ粉末層では、焼結開始温度が異なるため、従来の５℃／分程度の昇温速度で焼結すると、各層のＷ粉末の粒径が異なるため、各層の焼結開始温度が異なる。したがって、低温で長時間保持されると、粒径が小さい層のみ焼結が進み、粒径が大きい層では焼結が進まないため、層間でクラックが生じてしまう。
【０００７】
本発明は、上記の問題点に鑑みてなされ、焼結溶浸法における、密度が積層方向に変化した高融点材料への低融点材料の溶浸後の溶浸材料である低融点材料の凝固収縮の際の熱応力に耐える傾斜機能材料を提供することを目的とする。
【０００８】
本発明の他の目的は、密度が積層方向に変化した高融点材料に反りが生じたり、クラックが発生することのない傾斜機能材料の製造方法を提供することにある。
【０００９】
【課題を解決するための手段】
上記課題を解決するため、本発明は、小粒径高融点材料粉末層の上下に、それぞれ上下で粒径が対称となるように順次粒径を増大させて、１層又は２層以上の大粒径高融点材料粉末層を積層し、成形する工程と、成形された積層体を焼結する工程と、得られた焼結体の前記小粒径高融点材料粉末層に対応する層の相対密度が９０％以上の場合には、前記小粒径高融点材料粉末層に対応する層のほぼ中心において焼結体を切断し、得られた焼結体の前記小粒径高融点材料粉末層に対応する層の相対密度が９０％未満の場合には切断することなく、前記焼結体に熱伝導性の高い低融点材料を溶浸させ、その後前記小粒径高融点材料粉末層に対応する層のほぼ中心において焼結体を切断し、低融点材料に対する高融点材料の相対密度が連続的又は段階的に変化している傾斜機能材料を得る工程を具備する傾斜機能材料の製造方法を提供する。
【００１０】
本発明において、前記低融点材料がＣｕ、Ａｇ及びそれらの合金から選ばれた１種以上、前記高融点材料が、Ｗ、Ｍｏ、それらの合金及びセラミックから選ばれた１種以上とすることが出来る。
【００１２】
また、本発明（請求項２）は、大粒径高融点材料粉末層の上下に、それぞれ小粒径高融点材料粉末層を積層し、成形する工程と、成形された積層体を焼結する工程と、得られた焼結体の前記小粒径高融点材料粉末層の一方を除去する工程と、前記焼結体に熱伝導性の高い低融点材料を溶浸させ、小粒径高融点材料粉末層側から大粒径高融点材料粉末層側に低融点材料に対する高融点材料の相対密度が連続的又は段階的に変化している傾斜機能材料を得る工程を具備する傾斜機能材料の製造方法を提供する。
【００１３】
更に、本発明（請求項３）は、粒径の異なる複数の高融点材料粉末層を積層し、成形する工程と、成形された積層体を、０．１７〜０．３３℃／ｓの温度勾配で焼結温度まで昇温する工程と、焼結温度で焼結する工程と、得られた焼結体に熱伝導性の高い低融点材料を溶浸させ、小粒径高融点材料粉末層側から大粒径高融点材料粉末層側に低融点材料に対する高融点材料の相対密度が連続的又は段階的に変化している傾斜機能材料を得る工程を具備する傾斜機能材料の製造方法を提供する。
【００１４】
以下、本発明について、より詳細に説明する。
第１の発明は、高融点材料層の高相対密度側が、高い延性を有する高融点金属又は合金により構成されていることを特徴とする。
【００１５】
この場合、低融点材料としては、Ｃｕ、Ａｇ又はそれらの合金、高融点材料としては、Ｗ、Ｍｏ又はそれらの合金を用いることが出来る。
Ｗ、Ｍｏの合金の具体的なものとしては、Ｒｅ−Ｗ合金、Ｒｅ−Ｍｏ合金、Ｗ−Ｍｏ合金などの各種合金、前記金属同士の合金に限らず、Ｙ_２Ｏ_３などのＹを含む希土類の酸化物が分散したＭｏ又はＷ等、さらには各種セラミックス材料など各種材料があげられる。
【００１６】
また、本発明でいう延性を有する高融点金属としては、Ｗ、Ｍｏ及びその合金から選ばれた１種以上を用いることが出来る。Ｗ及びＭｏの合金の具体的なものとしては、Ｒｅ−Ｗ合金、Ｒｅ−Ｍｏ合金、Ｗ−Ｍｏ合金などの各種合金などの各種材料があげられる。
【００１７】
なお、本発明においては、前記高融点材料と高融点金属は、同一の材料を使用してもよい。
各Ｍｏ又はＷの合金の具体的組成及び組成限定理由は、下記の通りである。
【００１８】
（１）Ｒｅ−Ｗ合金
この合金中のＲｅ含量は、１〜５０重量％であるのが好ましい。Ｒｅ含量が１重量％未満では、Ｒｅの添加による合金の延性、強度の向上効果が認められず、一方、５０重量％を越えると、合金中におけるＲｅの分散性の悪化や密度の低下がより顕著となり、望ましくない。
【００１９】
（２）Ｒｅ−Ｍｏ合金
この合金中のＲｅ含量は、１〜５０重量％であるのが好ましい。Ｒｅ含量が１重量％未満では、Ｒｅの添加による合金の延性、強度の向上効果が認められず、一方、５０重量％を越えると、合金中におけるＲｅの分散性の悪化や密度の低下がより顕著となり、望ましくない。なお、より好ましいＲｅ含量は、３〜３０重量％である。
【００２０】
（３）Ｗ−Ｍｏ合金
この合金中のＭｏ含量は、１０〜７０重量％であるのが好ましい。Ｍｏ含量が１０重量％未満では、Ｍｏの添加による合金の延性の向上効果が認められず、一方、７０重量％を越えると、耐熱性が低下し、望ましくない。
【００２１】
（４）Ｙ_２Ｏ_３ −Ｗ合金
この合金中のＹ_２Ｏ_３の割合は、５〜５０体積％であるのが好ましく、７．５〜１５体積％であるのがより好ましい。Ｙ_２Ｏ_３の割合が５体積％未満では、Ｙ_２Ｏ_３の焼結助剤としての効果を発揮することが困難となり、一方、５０体積％を越えると、得られた傾斜機能材料の機械的強度が劣化してしまうとともに、二次加工する際の加工性が乏しくなる。Ｗ粉末の平均粒径は、０．５〜４μｍが好ましく、２〜３μｍがより好ましい。
【００２２】
なお、Ｙ_２Ｏ_３の添加の効果は、次の通りである。
ａ．Ｙ_２Ｏ_３を添加することにより、Ｗの強度が改善され、低融点材料の溶浸後の熱収縮に充分耐え得るようになる。
【００２３】
ｂ．Ｙ_２Ｏ_３のピン止め効果により、焼結時の結晶の粗大化による強度低下を抑えることが出来る。
ｃ．従来のプロセスよりも粉末成型、焼結の条件を広い範囲で設定できるようになる。
【００２４】
（５）Ｙ_２Ｏ_３ −Ｍｏ合金
この合金中のＹ_２Ｏ_３の割合は、５〜５０体積％であるのが好ましく、７．５〜１５体積％であるのがより好ましい。Ｙ_２Ｏ_３の割合が５体積％未満では、Ｙ_２Ｏ_３の焼結助剤としての効果を発揮することが困難となり、一方、５０体積％を越えると、得られた傾斜機能材料の機械的強度が劣化してしまうとともに、二次加工する際の加工性が乏しくなる。Ｍｏ粉末の平均粒径は、０．５〜４μｍが好ましく、２〜３μｍがより好ましい。
【００２５】
Ｙ_２Ｏ_３の添加による効果は、Ｙ_２Ｏ_３ −Ｗ合金の場合と同様である。
以上挙げた合金は、各成分の混合粉末を用いることにより、得ることが出来る。
【００２６】
第１の発明に係る傾斜機能材料は、次のようにして得ることが出来る。まず、粒径の小さい高融点金属粉末又は高融点合金用混合粉末、及び、それより順次粒径を大きくした１層又はそれ以上の高融点材料粉末層を順次積層し、４９〜１９６ＭＰａの圧力で成形する。次いで、水素雰囲気で、１８７３〜２４７３Ｋの焼結温度で、１４．４〜８６．４ｋｓ焼結する。
【００２７】
次に、９８〜１９６ＭＰａの圧力、１８７３〜２２７３Ｋの焼結温度の下で、７．２〜２８．８ｋｓ、カプセルフリ−ＨＩＰ処理を行う。その結果、密度が高融点金属又は合金層から順次減少した焼結体が得られる。
【００２８】
その後、この焼結体に熱伝導性の高い低融点材料の溶浸キャニングＨＩＰ処理を行う。処理条件は、４９〜２９４ＭＰａの圧力、１３２３〜１５７３Ｋの焼結温度の下で、３．６〜１８ｋｓである。最後に、仕上げ加工を行い、第１の発明に係る傾斜機能材料を得ることが出来る。
【００２９】
このようにして得た傾斜機能材料は、溶浸された低融点材料の凝固収縮による熱応力に充分に耐え、クラックが生ずることがない。
第２の発明は、小粒径高融点材料粉末層の上下に、それぞれ粒径が対称となるように順次粒径を増大させて、１層又は２層以上の大粒径高融点材料粉末層を積層して、成形、焼結等を行うことを特徴とする。
【００３０】
この第２の発明では、積層体の成形、焼結、カプセルフリ−ＨＩＰ、低融点材料の溶浸キャニングＨＩＰ処理は、第１の発明と同様であるが、小粒径高融点材料層の密度が９０％以上の高密度である場合に、低融点材料の溶浸処理前に、小粒径高融点材料層の中心において、積層面に平行に切断する工程が行われる。その後の溶浸処理及び仕上げ加工は、第１の発明と同様である。小粒径高融点材料層の密度が９０％未満の場合には、小粒径高融点材料層にも低融点材料の溶浸が支障なく行われるため、低融点材料の溶浸処理前にではなく、溶浸処理後に切断が行われる。
【００３１】
このようにして得た傾斜機能材料は、粒径の分布が上下で対称の形で成形、焼結が行われたため、反りが生じたり、小粒径高融点材料層にクラックが発生したりすることがない。
【００３２】
なお、高融点材料及び低融点材料は、第１の発明と同様のものを使用可能である。
第３の発明は、大粒径高融点材料粉末層を２層の小粒径高融点材料粉末層により挟んで成形し、焼結することを特徴とする。即ち、成形の困難な大粒径高融点材料粉末層を２層の小粒径高融点材料粉末層により挟むことにより、大粒径高融点材料粉末層にスプリングバックによりクラックが発生することを防止するものである。
【００３３】
得られた焼結体について、２層の小粒径高融点材料粉末層のうちの一部を除去した後、熱伝導性の高い低融点材料の溶浸キャニングＨＩＰ処理を行う。なお、高融点材料及び低融点材料は、第１の発明と同様のものを使用可能である。
【００３４】
第４の発明は、粒径の異なる複数の高融点材料粉末層の成形された積層体を、０．１７〜０．３３℃／ｓの温度勾配で焼結温度まで昇温することを特徴とする。即ち、昇温速度を従来よりも速めることにより、各層の焼結開始温度の相違による影響を少なくすることが出来、各層間におけるクラックの発生を防止することが出来る。
【００３５】
なお、温度勾配が０．１７℃／ｓ未満では、成形体が徐々に常温から高温になるため、各層の焼結温度の相違の影響が顕著に表れ、各層間でクラックが発生してしまう。一方、温度勾配が０．３３℃／ｓを越えると、主として成形体の中心部のガスが抜けきらないため、各層の密度が充分に得られなかったり、均一な焼結が行われないという問題が生ずる。好ましい温度勾配は、０．２２〜０．２８℃／ｓである。
高融点材料及び低融点材料は、第１の発明と同様のものを使用可能である。
【００３６】
【発明の実施の形態】
以下、本発明の種々の実施例を示し、本発明をより具体的に説明する。
実施例１
この実施例は、第１の発明に係る実施例である。
【００３７】
図１に示すように、小粒径高融点金属又は合金粉末層１として、下記表１に示す５種の材料を用い、これに更に３．０μｍの粒径のＷ粉末層２、９．０μｍの粒径のＷ粉末層３を積層し、これを１４７ＭＰａの圧力で成形した。この成形体を水素雰囲気で２０７３Ｋで２８．８ｋｓ、焼結した。次いで、１７６ＭＰａの圧力、２０７３Ｋで１４．４ｋｓ、カプセルフリ−ＨＩＰ処理を行った。その結果、小粒径高融点材料層１の相対密度は、表１に示す値であり、Ｗ層２の相対密度は８０±２％、Ｗ層３の相対密度は６０±２％であった。
【００３８】
次に、９８ＭＰａの圧力、１３７３Ｋで７．２ｋｓ、Ｃｕ溶浸キャニングＨＩＰ処理を行った。最後に、仕上げ加工を行い、６０ｍｍ四方、２ｍｍの厚さの層が３層積層された６種の傾斜機能材料が得られた。
これら傾斜機能材料を研磨し、クラックの発生の有無を染色浸透探傷により調べたところ、下記表１に示す結果を得た。
【００３９】
【表１】

【００４０】
上記表１から明らかなように、小粒径高融点材料として延性の良好な金属又は合金を用いた場合には、いずれもクラックの発生が皆無であるのに対し、純Ｗを用いた場合には、クラックの発生が認められた。
【００４１】
実施例２
この実施例は、第２の発明に係る実施例である。
図２に示すように、平均粒径９μｍのＷ粉末層１１、平均粒径３μｍのＷ粉末層１２、平均粒径２μｍのＷ粉末層１３、平均粒径３μｍのＷ粉末層１４、平均粒径９μｍのＷ粉末層１５を積層し、これを１４７ＭＰａの圧力で成形した。この成形体を水素雰囲気で２０７３Ｋで２８．８ｋｓ、焼結した。次いで、１７６ＭＰａの圧力、２０７３Ｋで１４．４ｋｓ、カプセルフリ−ＨＩＰ処理を行った。その結果、それぞれの相対密度は、Ｗ粉末層１１，１５が６０％、Ｗ粉末層１２，１２が８０％、Ｗ粉末層１３が８８％であった。なお、それぞれの層の厚さは、Ｗ粉末層１１，１２、１４、１５が２ｍｍ、Ｗ粉末層１３が６ｍｍであり、全体の大きさは、３０ｍｍ四方、１４ｍｍの厚さであった。
【００４２】
次に、大気圧下、水素雰囲気中、１３７３Ｋで１４．４ｋｓ、Ｃｕ溶浸処理を行った。最後に、仕上げ加工を行い、１０種の傾斜機能材料が得られた。
これら傾斜機能材料を研磨し、クラックの発生の有無を染色浸透探傷により調べたところ、クラック発生率（クラック数／試作数）は０ｐ／１０ｐであり、クラックは全く観察されなかった。
【００４３】
実施例３
この実施例もまた、第２の発明に係る実施例である。
図２に示すＷ粉末層１３として、平均粒径１μｍのＷ粉末を用いることにより、カプセルフリ−ＨＩＰ処理後のＷ粉末層１３の相対密度を９７％とし、かつカプセルフリ−ＨＩＰ処理後の焼結体を中心で切断し、各層２ｍｍになるように仕上げたことをことを除いて、実施例２と同様にして、１０種の傾斜機能材料を作成した。
【００４４】
これら傾斜機能材料のクラックの発生の有無を染色浸透探傷により調べたところ、クラック発生率（クラック数／試作数）は０ｐ／１０ｐであり、クラックは全く観察されなかった。
【００４５】
比較例１
この比較例は、第２の発明に対する比較例である。
図２に示すＷ粉末層１３として、平均粒径１μｍのＷ粉末を用いることにより、カプセルフリ−ＨＩＰ処理後のＷ粉末層１３の相対密度を９７％としたことをことを除いて、実施例２と同様にして、１０種の傾斜機能材料を作成した。
【００４６】
これら傾斜機能材料のクラックの発生の有無を染色浸透探傷により調べたところ、クラック発生率（クラック数／試作数）は１０ｐ／１０ｐであり、すべての試料にクラックの発生が認められた。
【００４７】
以上の実施例２、実施例３、及び比較例１から、中心層の相対密度が９０％以上の高密度である場合には、カプセルフリ−ＨＩＰ処理後の焼結体を中心で切断して、Ｃｕ溶浸処理を行う必要があることがわかる。
【００４８】
実施例４
この実施例は、第３の発明に係るものである。
図３に示すように、平均粒径３μｍのＷ粉末層２１、平均粒径９μｍのＷ粉末層２２、平均粒径３μｍのＷ粉末層２３、平均粒径１μｍのＷ粉末層２４、平均粒径３μｍのＷ粉末層２５、平均粒径９μｍのＷ粉末層２６、平均粒径３μｍのＷ粉末層２７を積層し、これを１４７ＭＰａの圧力で成形した。得られた成形体の大粒径のＷ粉末層２２、２６には、１０個の試料につき、クラックや割れは全く認められなかった。
【００４９】
この成形体を水素雰囲気で２０７３Ｋで２８．８ｋｓ、焼結した。次いで、１７６ＭＰａの圧力、２０７３Ｋで１４．４ｋｓ、カプセルフリ−ＨＩＰ処理を行った。
【００５０】
次に、Ｗ粉末層２４の中心で切断し、更にＷ粉末層２１とＷ粉末層２２との間、Ｗ粉末層２６とＷ粉末層２７との間でそれぞれ切断し、研磨した。
その後、９８ＭＰａの圧力、１３７３Ｋで７．２ｋｓ、Ｃｕ溶浸キャニングＨＩＰ処理を行った。最後に、仕上げ加工を行い、６０ｍｍ四方、２ｍｍの厚さの層が３層積層され、Ｗ粉末層２２及び２６に対応する層の側にＣｕ層が設けられた傾斜機能材料が得られた。
【００５１】
なお、３層の相対密度は、高密度側から順に、９７％、８０％、６０％であった。
比較例２
この比較例は、第３の発明に対するものである。
【００５２】
図４に示すように、平均粒径９μｍのＷ粉末層３１、平均粒径３μｍのＷ粉末層３２、平均粒径１μｍのＷ粉末層３３、平均粒径３μｍのＷ粉末層３３、平均粒径９μｍのＷ粉末層３４を積層し、これを１４７ＭＰａの圧力で成形した。得られた成形体の大粒径のＷ粉末層３１、３６には、５個の試料につき、割れが認められた。
【００５３】
この成形体を水素雰囲気で２０７３Ｋで２８．８ｋｓ、焼結した。次いで、１７６ＭＰａの圧力、２０７３Ｋで１４．４ｋｓ、カプセルフリ−ＨＩＰ処理を行った。
【００５４】
次に、Ｗ粉末層３３の中心で切断し、研磨した。その後、９８ＭＰａの圧力、１３７３Ｋで７．２ｋｓ、Ｃｕ溶浸キャニングＨＩＰ処理を行った。最後に、仕上げ加工を行い、６０ｍｍ四方、２ｍｍの厚さの層が３層積層され、Ｗ粉末層３１及び３５に対応する層の側にＣｕ層が設けられた傾斜機能材料が得られた。
【００５５】
なお、３層の相対密度は、高密度側から順に、９７％、８０％、６０％であった。
実施例４及び比較例２から、大粒径のＷ粉末層をそれより粒径の小さいＷ粉末層で挟むことにより、成形後の割れやクラックを防止することが出来ることがわかる。
【００５６】
実施例５
この実施例は、第４の発明に係るものである。
図５に示すように、平均粒径３μｍのＷ粉末層４１、平均粒径９μｍのＷ粉末層４２、平均粒径３μｍのＷ粉末層４３、平均粒径１μｍのＷ粉末層４４、平均粒径３μｍのＷ粉末層４５、平均粒径９μｍのＷ粉末層４６、平均粒径３μｍのＷ粉末層４７を積層し、これを１４７ＭＰａの圧力で成形した。
【００５７】
この成形体を水素雰囲気で２０７３Ｋで２８．８ｋｓ、焼結し、６０ｍｍ×１１０ｍｍ×厚さ１６ｍｍの焼結体を得た。焼結は、昇温の温度勾配を、０．０５℃／ｓ、０．０８℃／ｓ、０．１２℃／ｓ、０．１７℃／ｓ、０．２２℃／ｓ、０．２８℃／ｓ、０．３３℃／ｓ、０．３８℃／ｓ、０．４２℃／ｓと変化させて行った。焼結後の各層間のクラックの発生を顕微鏡により観察したところ、下記表２に示す結果を得た。
【００５８】
【表２】

【００５９】
上記表から明らかなように、０．１７〜０．３３℃／ｓの温度勾配では、焼結後の各層間にクラックの発生が認められないのに対し、この範囲外の温度勾配では、いずれも各層間でクラックの発生が観察された。
【００６０】
【発明の効果】
以上説明したように、第１の発明によると、高密度側に延性を有する高融点金属又は合金層が設けられているため、傾斜機能材料は、溶浸された低融点材料の凝固収縮による熱応力に充分に耐え、クラックが生ずることがない。また、第２の発明によると、粒径の分布が上下で対称の形で成形、焼結が行われているため、傾斜機能材料に反りが生じたり、小粒径高融点材料層にクラックが発生したりすることがない。更に、第３の発明によると、成形の困難な大粒径高融点材料粉末層を２層の小粒径高融点材料粉末層により挟むことにより、大粒径高融点材料粉末層にスプリングバックによりクラックが発生することが防止される。更にまた、第４の発明によると、焼結温度への昇温速度を従来よりも速めることにより、各層の焼結開始温度の相違による影響を少なくすることが出来、各層間におけるクラックの発生を防止することが出来る。
【００６１】
以上のように、本発明によると、溶浸材料の凝固収縮の際の熱応力に耐える傾斜機能材料、及び焼結体に反りが生じたり、クラックが発生することがない傾斜機能材料の製造方法が提供される。
【図面の簡単な説明】
【図１】実施例１で用いた積層成形体の構成を示す図。
【図２】実施例２で用いた積層成形体の構成を示す図。
【図３】実施例４で用いた積層成形体の構成を示す図。
【図４】比較例２で用いた積層成形体の構成を示す図。
【図５】実施例５で用いた積層成形体の構成を示す図。
【符号の説明】
１…小粒径高融点金属又は合金粉末層
２，３，１１，１２，１３，１４，１５，２１，２２，２３，２４，２５，２６，３１，３２，３３，３４，３５，４１，４２，４３，４４，４５，４６，４７…Ｗ粉末層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a functionally graded material and a method of manufacturing the same, and more particularly, to a functionally graded material composed of tungsten and copper.
[0002]
[Prior art]
Divertor plates, beam dumps, calorimeters, and other components used in fusion reactors are used in extremely harsh environments exposed to plasma and subjected to high heat loads and high particle loads. You. In recent years, as a material constituting such a member, a high melting point material having heat resistance such as tungsten (W) and a low melting point material having high thermal conductivity such as copper (Cu) have been joined, and the composition of both materials has been changed. There has been proposed a functionally graded material in which the thermal stress is reduced by changing the direction in the stacking direction.
[0003]
This W / Cu functionally graded material is manufactured, for example, by a method called a sintering infiltration method. The production of the W / Cu functionally gradient material by the sintering infiltration method is performed as follows. That is, first, W powders are sequentially laminated with varying particle diameters, press-molded, and sintered to form a W sintered body whose density changes in the laminating direction. In this case, a layer having a small particle size has a high density, and a layer having a large particle size has a low density. Next, open WIP (hot isostatic pressing) treatment is performed on the W sintered body to crush closed pores in the W sintered body, leaving only open pores. Finally, Cu is infiltrated into the open pores of the W sintered body.
The functionally graded material thus obtained exhibits a gradient composition that varies from a high-density W layer with a low Cu infiltration amount to a low-density W layer with a high infiltration amount.
[0004]
[Problems to be solved by the invention]
However, the production of the functionally gradient material by the sintering and infiltration method described above has various problems as follows.
(1) Although the W / Cu functionally graded material undergoes thermal contraction during the solidification process of Cu after infiltration of Cu, a layer with a high density of W of the functionally graded material has a small or no Cu infiltration amount. Since it is not infiltrated, it cannot withstand thermal stress and cracks occur.
[0005]
(2) Since the particle size of the W powder is different in the laminating direction, the shrinkage ratio after sintering is largely different in the laminating direction, and the W sintered body is warped or cracked.
(3) In the case of a low-density W powder layer having a large particle diameter, molding failure occurs during molding, and chipping occurs when the molded body moves, and cracks occur after sintering.
[0006]
(4) Since the sintering start temperature is different in the W powder layers having different particle diameters, sintering at a conventional heating rate of about 5 ° C./min results in a difference in the particle diameter of the W powder in each layer. The setting start temperature is different. Therefore, if the layer is kept at a low temperature for a long time, sintering proceeds only in the layer having a small particle diameter, and sintering does not proceed in the layer having a large particle diameter, so that cracks occur between the layers.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in the sintering infiltration method, solidification of a low melting point material which is an infiltration material after infiltration of a low melting point material into a high melting point material whose density has changed in a laminating direction. It is an object of the present invention to provide a functionally graded material that can withstand thermal stress during shrinkage.
[0008]
Another object of the present invention is to provide a method for producing a functionally graded material in which a high-melting-point material whose density has changed in the laminating direction does not warp or crack.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention is to increase the size of one or two or more layers by sequentially increasing the particle size above and below the small-particle-size high-melting-point material powder layer so that the particle size is symmetrical above and below. Laminating and shaping the particle size high melting point material powder layer, sintering the formed laminate, and relative to the layer corresponding to the small particle size high melting point material powder layer of the obtained sintered body. When the density is 90% or more, the sintered body is cut at substantially the center of the layer corresponding to the small particle size high melting point material powder layer, and the small particle size high melting point material powder layer of the obtained sintered body is obtained. When the relative density of the layer corresponding to the above is less than 90%, the sintered body is infiltrated with a low-melting material having high thermal conductivity without cutting, and then the small-grain high-melting material powder layer is formed. The sintered body is cut at approximately the center of the layer to be heated, and the relative density of the high melting To provide a method of manufacturing a gradient function material comprising the step of obtaining the varying to have FGM.
[0010]
In the present invention, the low melting point material is Cu, at least one selected from Ag and their alloys, the refractory material, W, Mo, be one or more selected from these alloys and ceramics I can do it.
[0012]
Further, the present invention (claim 2) provides a step of laminating and molding small particle size high melting point material powder layers above and below a large particle size high melting point material powder layer, respectively, and sintering the molded laminate. A step of removing one of the small-grain high-melting point material powder layers of the obtained sintered body; and Production of a functionally graded material including a step of obtaining a functionally graded material in which the relative density of the high melting point material relative to the low melting point material changes continuously or stepwise from the material powder layer side to the large particle size high melting point material powder layer side Provide a method.
[0013]
Further, the present invention (Claim 3) provides a step of laminating and molding a plurality of high melting point material powder layers having different particle diameters, and forming the molded laminate at a temperature of 0.17 to 0.33 ° C./s. A step of raising the temperature to the sintering temperature with a gradient, a step of sintering at the sintering temperature, and a step of infiltrating the obtained sintered body with a low-melting-point material having high thermal conductivity to form a small-particle-size high-melting-point material powder layer A method for producing a functionally graded material comprising a step of obtaining a functionally graded material in which the relative density of a high melting point material relative to a low melting point material changes continuously or stepwise from a side to a large particle size high melting point material powder layer side I do.
[0014]
Hereinafter, the present invention will be described in more detail.
The first invention is characterized in that the high relative density side of the high melting point material layer is made of a high melting point metal or alloy having high ductility.
[0015]
In this case, Cu, Ag or an alloy thereof can be used as the low melting point material, and W, Mo or an alloy thereof can be used as the high melting point material.
W, as the ones specifically of Mo alloy, Re-W alloy, Re-Mo alloy, various alloys such as W-Mo alloy, not only the alloy of the metal to each _other, including Y, such as Y 2 _{O 3} Various materials such as Mo or W in which a rare earth oxide is dispersed, and various ceramic materials are also used.
[0016]
Further, as the high melting point metal having ductility referred to in the present invention, one or more selected from W, Mo and alloys thereof can be used. Specific examples of the alloy of W and Mo include various materials such as various alloys such as Re-W alloy, Re-Mo alloy, and W-Mo alloy.
[0017]
In the present invention, the same material may be used for the high melting point material and the high melting point metal.
The specific composition of each Mo or W alloy and the reasons for limiting the composition are as follows.
[0018]
(1) Re-W alloy The Re content in this alloy is preferably 1 to 50% by weight. When the Re content is less than 1% by weight, the effect of adding Re does not improve the ductility and strength of the alloy. On the other hand, when the content exceeds 50% by weight, the dispersibility of Re in the alloy and the decrease in density are more reduced. Becomes noticeable and undesirable.
[0019]
(2) Re-Mo alloy The Re content in this alloy is preferably 1 to 50% by weight. When the Re content is less than 1% by weight, the effect of adding Re does not improve the ductility and strength of the alloy. On the other hand, when the content exceeds 50% by weight, the dispersibility of Re in the alloy and the decrease in density are more reduced. Becomes noticeable and undesirable. In addition, a more preferable Re content is 3 to 30% by weight.
[0020]
(3) W-Mo alloy The Mo content in this alloy is preferably from 10 to 70% by weight. When the Mo content is less than 10% by weight, the effect of improving the ductility of the alloy by the addition of Mo is not recognized. On the other hand, when it exceeds 70% by weight, the heat resistance decreases, which is not desirable.
[0021]
₍₄₎ Y _{2 O} 3 -W alloy ratio of _Y 2 _{O 3} in the alloy is preferably from 5 to 50 vol%, and more preferably 7.5 to 15% by volume. If the proportion of Y ₂ O ₃ is less than 5% by volume, it will be difficult to exert the effect of Y ₂ O _{3 as} a sintering aid, while if it exceeds 50% by volume, the obtained mechanically-graded material of the functionally graded material will be difficult. The target strength is deteriorated, and the workability at the time of secondary processing is poor. The average particle size of the W powder is preferably 0.5 to 4 μm, more preferably 2 to 3 μm.
[0022]
The effect of the addition of Y ₂ O ₃ is as follows.
a. By adding Y ₂ O ₃ , the strength of W is improved and it becomes possible to sufficiently withstand the heat shrinkage after infiltration of the low melting point material.
[0023]
b. Due to the pinning effect of Y ₂ O _3, a decrease in strength due to coarsening of crystals during sintering can be suppressed.
c. The conditions for powder molding and sintering can be set in a wider range than in the conventional process.
[0024]
₍₅₎ _{Y 2} O 3 -Mo alloy ratio of _Y 2 _{O 3} in the alloy is preferably from 5 to 50 vol%, and more preferably 7.5 to 15% by volume. If the proportion of Y ₂ O ₃ is less than 5% by volume, it will be difficult to exert the effect of Y ₂ O _{3 as} a sintering aid, while if it exceeds 50% by volume, the obtained mechanically-graded material of the functionally graded material will be difficult. The target strength is deteriorated, and the workability at the time of secondary processing is poor. The average particle size of the Mo powder is preferably 0.5 to 4 μm, more preferably 2 to 3 μm.
[0025]
Effect of the addition of Y ₂ O ₃ _is the same as in the case of Y _{2 O} 3 -W alloy.
The above-mentioned alloys can be obtained by using a mixed powder of each component.
[0026]
The functionally gradient material according to the first invention can be obtained as follows. First, a high melting point metal powder or a mixed powder for a high melting point alloy having a small particle diameter, and one or more high melting point material powder layers whose particle diameters are sequentially increased are sequentially laminated, and a pressure of 49 to 196 MPa is applied. Mold. Next, sintering is performed for 14.4 to 86.4 ks in a hydrogen atmosphere at a sintering temperature of 1873 to 2473 K.
[0027]
Next, capsule free HIP processing is performed at a pressure of 98 to 196 MPa and a sintering temperature of 1873 to 2273 K for 7.2 to 28.8 ks. As a result, a sintered body whose density is gradually reduced from the high melting point metal or alloy layer is obtained.
[0028]
Thereafter, the sintered body is subjected to infiltration canning HIP processing of a low-melting-point material having high thermal conductivity. The processing conditions are 3.6-18ks under a pressure of 49-294MPa and a sintering temperature of 1323-1573K. Finally, finishing is performed to obtain the functionally graded material according to the first invention.
[0029]
The functionally graded material thus obtained sufficiently withstands thermal stress due to solidification shrinkage of the infiltrated low-melting-point material, and cracks do not occur.
According to a second aspect of the present invention, one or two or more large-particle high-melting-point material powder layers are sequentially increased in size above and below the small-particle-size high-melting-point material powder layer so that the particle diameters are symmetrical. Are laminated, and molding, sintering and the like are performed.
[0030]
In the second invention, the molding, sintering, capsule-free HIP, and infiltration canning HIP treatment of the low-melting material are the same as those of the first invention, but the density of the small-grain high-melting material layer is reduced. Is high density of 90% or more, before the infiltration treatment of the low-melting-point material, a step of cutting in the center of the small-diameter high-melting-point material layer in parallel with the lamination surface is performed. Subsequent infiltration and finishing are the same as in the first invention. When the density of the small particle size high melting point material layer is less than 90%, the small particle size high melting point material layer is infiltrated with the low melting point material without any trouble. Instead, cutting is performed after the infiltration treatment.
[0031]
Since the functionally graded material obtained in this manner is formed and sintered in a form in which the particle size distribution is vertically symmetric, warpage occurs or cracks occur in the small particle size high melting point material layer. Nothing.
[0032]
The high melting point material and the low melting point material may be the same as those in the first invention.
The third invention is characterized in that a large-diameter high-melting-point material powder layer is sandwiched between two small-diameter high-melting-point material powder layers, molded and sintered. That is, by sandwiching a large-diameter high-melting-point material powder layer that is difficult to mold between two small-diameter high-melting-point material powder layers, cracks are prevented from occurring in the large-diameter high-melting-point material powder layer due to springback. Is what you do.
[0033]
Obtained with the sintered body, after removing the part of the two-layer small diameter high melting point material powder layer, performing infiltration canning HIP treatment of high thermal conductivity low melting point material. The high melting point material and the low melting point material may be the same as those in the first invention.
[0034]
A fourth invention is characterized in that a molded body of a plurality of high melting point material powder layers having different particle sizes is heated to a sintering temperature at a temperature gradient of 0.17 to 0.33 ° C./s. I do. That is, by increasing the heating rate faster than before, the influence of the difference in the sintering start temperature of each layer can be reduced, and the occurrence of cracks between the layers can be prevented.
[0035]
If the temperature gradient is less than 0.17 ° C./s, the temperature of the molded body gradually increases from room temperature to a high temperature, so that the influence of the difference in the sintering temperature of each layer is remarkable, and cracks occur between the layers. On the other hand, if the temperature gradient exceeds 0.33 ° C./s, the gas in the central part of the molded body cannot be completely removed, so that the density of each layer cannot be sufficiently obtained and uniform sintering cannot be performed. Occurs. A preferred temperature gradient is between 0.22 and 0.28 ° C / s.
As the high melting point material and the low melting point material, the same materials as those in the first invention can be used.
[0036]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, various examples of the present invention will be described, and the present invention will be described more specifically.
Example 1
This embodiment is an embodiment according to the first invention.
[0037]
As shown in FIG. 1, five kinds of materials shown in the following Table 1 were used as the small-particle-size high-melting-point metal or alloy powder layer 1, and a W powder layer 2 having a particle diameter of 3.0 μm and 9.0 μm were further added thereto. A W powder layer 3 having a particle size of 3 was laminated, and was formed under a pressure of 147 MPa. The compact was sintered at 2073 K for 28.8 ks in a hydrogen atmosphere. Next, capsule-free HIP processing was performed at a pressure of 176 MPa and 2073 K for 14.4 ks. As a result, the relative density of the small particle size high melting point material layer 1 was a value shown in Table 1, the relative density of the W layer 2 was 80 ± 2%, and the relative density of the W layer 3 was 60 ± 2%. .
[0038]
Next, Cu infiltration canning HIP treatment was performed at a pressure of 98 MPa and 1373 K for 7.2 ks. Finally, finishing was performed to obtain six types of functionally graded materials in which three layers each having a thickness of 60 mm square and 2 mm were laminated.
These functionally graded materials were polished, and the presence or absence of cracks was examined by dye penetrant inspection. The results shown in Table 1 below were obtained.
[0039]
[Table 1]

[0040]
As is clear from Table 1, when a metal or an alloy having good ductility is used as the small-particle-size high-melting point material, no crack is generated in any case. For, cracks were observed.
[0041]
Example 2
This embodiment is an embodiment according to the second invention.
As shown in FIG. 2, a W powder layer 11 having an average particle size of 9 μm, a W powder layer 12 having an average particle size of 3 μm, a W powder layer 13 having an average particle size of 2 μm, a W powder layer 14 having an average particle size of 3 μm, and an average particle size A 9 μm W powder layer 15 was laminated and molded at a pressure of 147 MPa. The compact was sintered at 2073 K for 28.8 ks in a hydrogen atmosphere. Next, capsule-free HIP processing was performed at a pressure of 176 MPa and 2073 K for 14.4 ks. As a result, the relative density of each of the W powder layers 11 and 15 was 60%, that of the W powder layers 12 and 12 was 80%, and that of the W powder layer 13 was 88%. The thickness of each layer was 2 mm for the W powder layers 11, 12, 14, and 15 and 6 mm for the W powder layer 13, and the overall size was 30 mm square and 14 mm thick.
[0042]
Next, Cu infiltration treatment was performed at 1373 K for 14.4 ks in a hydrogen atmosphere under atmospheric pressure. Finally, finishing was performed, and ten types of functionally graded materials were obtained.
These functionally graded materials were polished, and the presence or absence of cracks was examined by dye penetrant flaw detection. The crack occurrence rate (the number of cracks / the number of prototypes) was 0p / 10p, and no cracks were observed.
[0043]
Example 3
This embodiment is also an embodiment according to the second invention.
By using W powder having an average particle diameter of 1 μm as the W powder layer 13 shown in FIG. 2, the relative density of the W powder layer 13 after the capsule-free HIP processing is set to 97%, and the firing after the capsule-free HIP processing is performed. Ten kinds of functionally graded materials were produced in the same manner as in Example 2 except that the binder was cut at the center and finished to be 2 mm in each layer.
[0044]
When the presence or absence of cracks in these functionally graded materials was examined by dye penetrant inspection, the crack occurrence rate (the number of cracks / the number of prototypes) was 0p / 10p, and no cracks were observed.
[0045]
Comparative Example 1
This comparative example is a comparative example for the second invention.
Except that the relative density of the W powder layer 13 after the capsule-free HIP treatment was 97% by using W powder having an average particle diameter of 1 μm as the W powder layer 13 shown in FIG. In the same manner as in Example 2, ten kinds of functionally gradient materials were produced.
[0046]
When the presence or absence of cracks of these functionally graded materials was examined by dye penetrant inspection, the crack occurrence rate (the number of cracks / the number of prototypes) was 10p / 10p, and cracks were observed in all samples.
[0047]
From the above Examples 2, 3 and Comparative Example 1, when the relative density of the central layer is higher than 90%, the sintered body after the capsule-free HIP treatment is cut at the center. , It is necessary to perform Cu infiltration treatment.
[0048]
Example 4
This embodiment relates to the third invention.
As shown in FIG. 3, a W powder layer 21 having an average particle diameter of 3 μm, a W powder layer 22 having an average particle diameter of 9 μm, a W powder layer 23 having an average particle diameter of 3 μm, a W powder layer 24 having an average particle diameter of 1 μm, and an average particle diameter A 3 μm W powder layer 25, a W powder layer 26 having an average particle diameter of 9 μm, and a W powder layer 27 having an average particle diameter of 3 μm were laminated, and were formed under a pressure of 147 MPa. In the W powder layers 22 and 26 having a large particle diameter of the obtained molded body, no crack or crack was observed at all for 10 samples.
[0049]
The compact was sintered at 2073 K for 28.8 ks in a hydrogen atmosphere. Next, capsule-free HIP processing was performed at a pressure of 176 MPa and 2073 K for 14.4 ks.
[0050]
Next, cutting was performed at the center of the W powder layer 24, and further, between the W powder layer 21 and the W powder layer 22, and between the W powder layer 26 and the W powder layer 27, and polished.
Then, Cu infiltration canning HIP processing was performed at a pressure of 98 MPa and 1373 K for 7.2 ks. Finally, finishing was performed to obtain a functionally graded material in which three layers each having a thickness of 60 mm square and 2 mm were laminated, and a Cu layer was provided on the side of the layer corresponding to the W powder layers 22 and 26.
[0051]
The relative densities of the three layers were 97%, 80%, and 60% in order from the high density side.
Comparative Example 2
This comparative example is for the third invention.
[0052]
As shown in FIG. 4, a W powder layer 31 having an average particle diameter of 9 μm, a W powder layer 32 having an average particle diameter of 3 μm, a W powder layer 33 having an average particle diameter of 1 μm, a W powder layer 33 having an average particle diameter of 3 μm, and an average particle diameter A 9 μm W powder layer 34 was laminated and molded at a pressure of 147 MPa. In the W powder layers 31 and 36 having a large particle diameter of the obtained molded body, cracks were observed in five samples.
[0053]
The compact was sintered at 2073 K for 28.8 ks in a hydrogen atmosphere. Next, capsule-free HIP processing was performed at a pressure of 176 MPa and 2073 K for 14.4 ks.
[0054]
Next, it was cut at the center of the W powder layer 33 and polished. Then, Cu infiltration canning HIP processing was performed at a pressure of 98 MPa and 1373 K for 7.2 ks. Finally, finishing was performed to obtain a functionally graded material in which three layers each having a thickness of 60 mm square and 2 mm were laminated, and a Cu layer was provided on the side of the layer corresponding to the W powder layers 31 and 35.
[0055]
The relative densities of the three layers were 97%, 80%, and 60% in order from the high density side.
From Example 4 and Comparative Example 2, it is understood that cracks and cracks after molding can be prevented by sandwiching a W powder layer having a large particle diameter with a W powder layer having a smaller particle diameter.
[0056]
Example 5
This embodiment relates to the fourth invention.
As shown in FIG. 5, a W powder layer 41 having an average particle diameter of 3 μm, a W powder layer 42 having an average particle diameter of 9 μm, a W powder layer 43 having an average particle diameter of 3 μm, a W powder layer 44 having an average particle diameter of 1 μm, and an average particle diameter A 3 μm W powder layer 45, a W powder layer 46 having an average particle diameter of 9 μm, and a W powder layer 47 having an average particle diameter of 3 μm were laminated and formed at a pressure of 147 MPa.
[0057]
This compact was sintered in a hydrogen atmosphere at 2073 K for 28.8 ks to obtain a 60 mm × 110 mm × 16 mm thick sintered body. In sintering, the temperature gradient of the temperature rise was set to 0.05 ° C./s, 0.08 ° C./s, 0.12 ° C./s, 0.17 ° C./s, 0.22 ° C./s, 0.28 ° C. / S, 0.33 ° C / s, 0.38 ° C / s, and 0.42 ° C / s. The occurrence of cracks between the layers after sintering was observed with a microscope, and the results shown in Table 2 below were obtained.
[0058]
[Table 2]

[0059]
As is clear from the above table, cracks are not observed between the layers after sintering at a temperature gradient of 0.17 to 0.33 ° C./s, but at a temperature gradient outside this range, Also, cracks were observed between the layers.
[0060]
【The invention's effect】
As described above, according to the first invention, since the high-melting-point metal or alloy layer having ductility is provided on the high-density side, the functionally-graded material is heated by solidification shrinkage of the infiltrated low-melting-point material. Resists stress sufficiently and does not crack. According to the second aspect of the invention, since the molding and sintering are performed in such a manner that the particle size distribution is vertically symmetrical, warpage occurs in the functionally graded material, and cracks are formed in the small particle size high melting point material layer. It does not occur. Further, according to the third invention, the large-diameter high-melting-point material powder layer which is difficult to mold is sandwiched between two small-diameter high-melting-point material powder layers, so that the large-diameter high-melting-point material powder layer is spring-backed. Cracks are prevented from occurring. Still further, according to the fourth aspect, by increasing the rate of temperature rise to the sintering temperature as compared with the related art, the influence of the difference in the sintering start temperature of each layer can be reduced, and the occurrence of cracks between the layers can be reduced. Can be prevented.
[0061]
INDUSTRIAL APPLICABILITY As described above, according to the present invention, a method for producing a functionally graded material that withstands thermal stress during solidification and contraction of an infiltration material, and a method for producing a functionally graded material that does not cause warpage or cracks in a sintered body Is provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a laminated molded article used in Example 1.
FIG. 2 is a view showing a configuration of a laminated molded article used in Example 2.
FIG. 3 is a diagram showing a configuration of a laminated molded product used in Example 4.
FIG. 4 is a view showing a configuration of a laminated molded product used in Comparative Example 2.
FIG. 5 is a diagram showing a configuration of a laminated molded product used in Example 5.
[Explanation of symbols]
1 ... small particle size high melting point metal or

alloy powder layer

2, 3, 11, 12, 13, 14, 15, 21, 22, 23, 24, 25, 26, 31, 32, 33, 34, 35, 41, 42, 43, 44, 45, 46, 47 ... W powder layer

Claims

Above and below the small particle size high melting point material powder layer, the particle size is sequentially increased so that the particle size is symmetrical above and below, and one or two or more large particle size high melting point material powder layers are laminated, Forming, sintering the formed laminate, and, when the relative density of the layer corresponding to the small-grain high-melting point material powder layer of the obtained sintered body is 90% or more, The sintered body is cut substantially at the center of the layer corresponding to the small-grained high-melting point material powder layer, and the relative density of the layer corresponding to the small-grained high-melting point material powder layer of the obtained sintered body is less than 90%. In the case of the above, without cutting, the sintered body is infiltrated with a low melting point material having high thermal conductivity, and then the sintered body is cut at substantially the center of the layer corresponding to the small particle size high melting point material powder layer. to give the FGM relative density of the refractory material for the low-melting-point material is changed continuously or stepwise Method of manufacturing a gradient function material comprising the step.

A step of laminating a small particle size high melting point material powder layer above and below the large particle size high melting point material powder layer, forming, and sintering the formed laminate, and the step of sintering the obtained sintered body. A step of removing one of the small-grain high-melting-point material powder layers, and infiltrating a low-melting-point material with high thermal conductivity into the sintered body; A method for producing a functionally graded material, comprising a step of obtaining, on the powder layer side, a functionally graded material in which the relative density of a high melting point material relative to a low melting point material changes continuously or stepwise.

Laminating and molding a plurality of high melting point material powder layers having different particle diameters, and heating the molded laminate to a sintering temperature at a temperature gradient of 0.17 to 0.33 ° C./s. Sintering at the sintering temperature, and infiltrating the obtained sintered body with a low-melting-point material with high thermal conductivity, from the small-particle-size high-melting-point material powder layer side to the large-particle-size high-melting-point material powder layer side A step of obtaining a functionally gradient material in which the relative density of the high melting point material relative to the low melting point material changes continuously or stepwise.