Grant amount：\3770000 （ Direct Cost: \2900000 、 Indirect Cost：\870000 ）

Small crystalline particles are often formed comprising near-polyhedral shapes with round edges. When near-polyhedral shapes are analyzed and discussed, it is convenient if these shapes can be expressed by equations with simple parameters. Pseudo-polyhedra are solids expressing various shapes between those of polyhedra and spheres. The pseudo-polyhedral-shape approximation is used in this study to consider the morphology of small crystalline particles. Various near-polyhedral shapes composed of crystallographically low-index planes are described using a simple equation with shape-related parameters. Cubic crystal structure particles are treated in the present study. It is shown that the pseudo-polyhedral-shape approximation is a useful geometrical tool for evaluating the morphology of small crystalline particles.

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Grant amount：\4550000 （ Direct Cost: \3500000 、 Indirect Cost：\1050000 ）

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Grant amount：\4550000 （ Direct Cost: \3500000 、 Indirect Cost：\1050000 ）

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Grant amount：\1600000 （ Direct Cost: \1600000 ）

磁気駆動型超磁歪材料などの新規形状記憶合金、非磁性材料も含めた金属材料の再結晶集合組織制御、結晶配向制御、異方性組織制御、凝固組織の微細化など、磁場による材料組織制御の可能性が見出されている。その一方で、材料組織を形成する拡散変態、無拡散変態における磁気効果について、その理解は非常に限られている。そこで、以下のような項目について、研究内容の把握、研究動向調査、研究連携の可能性について調査を行った。
(1-1)核生成における磁気効果
(1-2)成長における磁気効果
(2-1)結晶配向における磁気効果
(2-2)磁化を利用した定量測定手法の開発と磁気効果解明への応用
研究内容、動向の調査は、日本金属学会、応用物理学会、日本磁気科学会、日本鉄鋼協会などの年次講演大会ならびに、日本鉄鋼協会の交流強磁場・環境プロセス研究会、低温工学協会新規磁場応用に関する調査研究会などの研究会、5th International symposium on electromagnetic processing of materials 2006(H18.10、仙台)に参加し、議論を重ねた。
さらに、企画調査のとりまとめとして、平成19年1月27日に大阪大学大学院工学研究科において、磁気効果を利用した機能性組織制御の原理と応用に関する研究会を開催し、磁気効果を利用した材料プロセス分野の発展、材料組織制御プロセスへの応用に必要となる磁場下での相変態・組織形成の学術基盤について議論した。これらの成果の一部は、ISIJ International誌のレビューとして受理され、2007.4に出版される予定である。

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Grant amount：\3700000 （ Direct Cost: \3700000 ）

A double cylindrical bicrystal is a bicrystal consisting of a cylindrical inside grain with a second grain wrapped around its curved side surface. Using a double cylindrical bicrystal of a Cu-SiO_2 alloy, tensile tests were performed at 800K under 2×10^<-4>/s. Three specimens cut from the same bicrystal were deformed to three different strains. Preferential formation of grain-boundary cracks around the cylindrical inside grain was observed after the tensile tests. In addition to the occurrence of grain-boundary sliding, the misfit of slip deformation at the grain boundary affects the formation of the grain-boundary cracks.

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Grant amount：\2900000 （ Direct Cost: \2900000 ）

Crystallography and morphology of precipitate particles in Cu-Fe-Co, Cu-Co-Cr and Cu-Ni-Si alloys were investigated. From experiments using Cu-Fe-Co alloys, it has been found that fcc Fe-Co particles transform into bcc particles by applying magnetic field. Transformability of the particles strongly depends on the particle size, cooling rate and the composition of the particles. It has been found that the magnetic field is useful to control microstructures without any deformation of a specimen.
Through extensive investigation using Cu-Ni-Si alloys, it has been found that the crystallographic orientation relationship between Ni_2Si precipitate particles and a Cu matrix, (110)_<Cu>//(001)_<Ni2Si>, [001]_<Cu>//[010] _<Ni2Si>, is satisfied. The Ni_2Si particles tend to grow along the invariant-line direction. The strength is strongly affected by not only the size but also the shape of particles. The elongated shape of the particles results in retarding the peak aging time. We concluded that we are able to obtain the optimum aging condition for the maximum strength with precise consideration of the shape of particles.

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Grant amount：\3400000 （ Direct Cost: \3400000 ）

We have made the following studies to understand the change of mechanical properties of materials caused by dispersion of doughnut-like second phase.
Cu-Si alloys are internally oxidized at various of Si atoms with oxygen, film-like SiO_2 precipitates formed on grain boundaries (GBs) is observed. After the reaction of Si atoms with oxygen, film-like SiO_2 precipitates with holes which expose GB of Cu are initially formed. At temperatures used for the internal oxidation, the holes rapidly grow and the morphology of the film-like SiO_2 evolves to a particulate equilibrium shape through formation of two-dimensional SiO_2 network.
Theoretical calculations to understand effects of doughnut-like inclusions on the mechanical properties of materials are made. The averaged Eshelby tensors that relate uniform eigenstrains and average total strains in doughnut-like inclusions are obtained. These are compared with the Eshelby tensors of oblate spheroidal and rod-like inclusions. We show that the averaged Eshelby tensors of the doughnut-like inclusions on a plane are almost the same as the average of the Eshelby tensors of randomly oriented rod-like inclusions on the same plane. This is satisfied for both "thin" doughnut-like inclusions. The strain field caused by uniform and purely dilatational eigenstrains is also discussed for a doughnut-like inclusion. Near the doughnut-like inclusion, there are two points where all components of the strains are null. Using the results results obtained, we have discussed the effects of the doughnut-like inclusions on the mechanical properties of materials.

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Grant amount：\14800000 （ Direct Cost: \14800000 ）

Strain-controlled cyclic deformation tests for pure Cu, Cu alloys, A1 and A1 alloys (mostly single crystals) were conducted. Although the crystal structure of these metals and alloys are all fcc, the fatigue behavior was quite different. For example, pure Cu showed cyclic hardening to saturation, whereas pure Al showed hardening followed by distinct softening. Observation of dislocation microstructure has revealed that the PSB ladder structure develops in Cu and it is absent in Al. Through extensive investigation, it has been found that the differences in both the fatigue behavior and microstructure can be explained by the relative feasibility of cross slip that is determined by the magnitude of stacking fault energy. Furthermore, from experiments using a Cu-Fe alloy with dispersed small Fe precipitate particles in Cu, it has been found that the Fe particles are effective in preventing the development of fatigue dislocation structure. With this knowledge, dislocation structure diagrams that indicate fatigue dislocation structure as a function of size and distribution of second-phase particles were successfully constructed.
Dislocation structures developed during fatigue tests are found to be much more stable (both thermally and mechanically) compared with those developed after cold rolling. Owing to the to-and-fro motion during cyclic deformation, dislocations arrange themselves into an energetically stable configuration resulting in the formation of characteristic fatigue microstructures that eventually lead to fatigue failure.
In conclusion, we could obtain various new results and findings, most of which are very valuable for life assessment of structural materials.

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Grant amount：\2200000 （ Direct Cost: \2200000 ）

平成14年度では,平成13年度中の研究によって開発したCu-Co-Cr合金において,強度と導電性に加え磁気的性質にも注目し,磁化のCo/Cr組成比依存,熱処理温度依存,熱処理時間依存を調べた.Coに対するCrの相対濃度が増すにつれ,合金の飽和磁化は急激に減少することがわかった.Co-Cr粒子中のCr濃度が20%をこえると,合金は磁化を示さなくなる.また,飽和磁化を最大にする最適の時効温度が約600℃であることを見いだした.500℃の時効では,磁化の時効時間依存性が現れ,ナノサイズのCo-Cr粒子の超常磁性的振る舞いによるものと理解できた.Cu-1.94vol%Co-0.24vol%Cr合金単結晶から得た結晶磁気異方性定数は,約-15000J/m^3であり,fcc Coの1/5程度の大きさであることがわかった.さらに,時効後の合金を組成変形させると,Co-Cr粒子の一部が相変態し,同時に形状変化を伴うことにより,形状磁気異方性発現することがわかった.
Cu-Cr合金を用いて行った転位上優先析出に関する研究では,転位が析出粒子の優先核生成サイトとなり得ることに加えて,優先析出するCr粒子バリアントが転位の性質に大きく依存することを明らかにした.転位の周りの応力場と析出粒子が持つミスフィットひずみの弾性相互作用エネルギーを求めることにより,優先析出しやすいバリアントを予測することが可能であることを示した.

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Grant amount：\3400000 （ Direct Cost: \3400000 ）

When a misfit precipitate generates in a material, it causes two changes of the free energy of the material. One is the change in the precipitate/matrix interface energy and the other is that in the elastic strain energy. Both of the changes depend on the precipitate shape and the equilibrium shape of the precipitate is determined by the sum of the interface energy and the elastic strain energy. The interface energy and the elastic strain energy are proportional to the surface area and the volume of the precipitate, respectively, Hence the interface energy and the elastic strain energy are dominant for smaller and larger precipitates, respectively.
In some alloys with coherent precipitates, shape transitions of the precipitates from spherical to cuboidal are observed with increasing the precipitate size. The energy analysis on the change of the equilibrium shape becomes straightforward if its possible shapes can be described geometrically. The shape transitions can be geometrically approximated with variations of shapes of superspheres. In the present study, the elasticォenergy caused by super ellipsoidal precipitates embedded in cubic materials is discussed. The equilibrium shape of the precipitates is obtained as the shape that causes the minimum of sum total of the elastic strain energy and interface energy. It is shown that the present analysis reasonably explains experimental results on the shape change of the precipitates in Ni-Ni3AI and Cu-Cr-Co alloys.

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Grant amount：\1100000 （ Direct Cost: \1100000 ）

1.Siの(100),(110)および(111)単結晶基板上にAlとCuをそれぞれ真空蒸着し、形成されたエピタキシャル方位関係を調べた。なお、今回の設備備品費で購入した試料固定治具は、真空蒸着の際Si基板を固定するために用いた。
2.AlもCuもともにSi基板上でエピタキシャル成長するものの、CuとSiの間で形成されるエピタキシャル方位関係は、AlとSiの間で形成されるものと異なっていた。AlとSiの間のエピタキシャル方位関係は、ZurとMcCillが提唱した超格子対応を用いた幾何学的考え方でうまく実験結果を説明できる。しかし、CuとSiの間で形成されるエピタキシャル方位関係の優先性やCuとAlの違いを説明することはできない。そこで、本研究では、格子対応の選択として、O格子理論を基に、基本格子対応を用い、これまでの幾何学的クライテリアを修正した。この新たな幾何学的クライテリアを用いれば、Al、Cuのそれぞれの実験結果を合理的に説明することができ、2つの金属で形成されるエピタキシャル方位関係が異なる理由も理解できた。
本研究で考案した幾何学的クライテリアは、Al、Cuに限らず、格子定数が大きく異なる物質同士のエピタキシャル方位関係にも適用できる汎用性を持つものである。
本研究で得られた研究成果はすでに国際会議で発表を終え、会議録が平成9年中に出版されることになっている。

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Grant amount：\7500000 （ Direct Cost: \7500000 ）

The main purpose of this research is to understand the role of diffusional relaxation on high-temperature deformation of dispersion-hardened alloys. High-temperature tensile tests were conducted using Cu-SiO_2, Cu-GeO_2 and Cu-Fe alloy single crystals and bicrystals and various stress-strain curves were obtained. In addition, intergranular brittle fracture was found to be very sensitive to the nature of grain boundaries. To quantitatively discuss these experimental results, it was necessary to obtain information on the shape change of dispersed particles that occurs during the deformation. Misorientation-dependent grain-boundary energy must also be characterized. Therefore, basic data on these quantities were also obtained.
As theoretical studies, diffusional relaxation around dispersed particles was analyzed by combining mechanics, thermodynamics and kinetics and the rate equations for the relaxation process could be obtained sucessfully. Furthermore, stable shape of dispersed particles and precipitates under a given set of conditions was quantitatively analyzed using micromechanics.
In comparison with the high-temperature deformation tests, low-cycle fatigue of Cu-Fe alloy single crystals were performed to reveal the effect of dispersed particles on the development of stable dislocation structure. The similarities and differences in the dislocation structure between high-temperature deformation and cyclic deformation were found very clearly.
It is true that this research project has been successfully completed in a sense that it has greatly improved our understanding. What is more important, however, is that this project resulted in the discovery of various new research areas that are essential to understand the high-temperature deformation of dispersion-hardened alloys.

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Grant amount：\900000 （ Direct Cost: \900000 ）

本研究では、Cu単結晶母相中に析出したfcc構造をもつ強磁性Co粒子の形状に及ぼす外部磁場効果を明らかにする目的で、磁気異方性測定と透過電子顕微鏡観察の2つの方法により、磁場中時効によるCo粒子の形状変化を調べた。
(110)を板面とするCu-2.7mass%Co合金単結晶板を作製し、1273Kで4h溶体化処理の後、直径10mmの円板試料を切り出した。この試料を、973Kで種々の時間、1.25MA/mの強磁場中で時効した。磁場印加方向は、[001]方向とした。また、比較のために無磁場での時効も行った。時効を終えた各々の試料の室温における磁気トルクを測定した。磁気異方性測定に用いた試料と同一の熱処理を施した試料を用いて、透過電子顕微鏡観察した。
得られた磁気トルク曲線を、Co粒子の結晶磁気異方性と形状磁気異方性の観点から、理論的に解析し、透過電子顕微鏡観察結果と比較検討した結果、以下の結論を得た。(1)無磁場時効により析出するCo粒子の形状は、球状であるが、[001]方向の磁場中で時効すると、Co粒子は磁場印加方向に伸びた楕円体状になる。(2)これより、強い外部磁場は、強磁性体粒子に対し、磁場印加方向への成長促進効果を持つといえる。(3)磁場中時効においても、無磁場時効と同様に、fccCo粒子は非整合化し、{111}面からなる八面体形状へと変化する。
本研究成果は、すでに本年度の第115回日本金属学会秋期大会において口頭発表されている。今後、研究成果をまとめた論文を日本金属学会誌に投稿する予定である。

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