研究者詳細 - 仲村　龍介

論文 - 仲村　龍介

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放射性トレーサーを用いた低拡散係数の高精度測定査読

Iijima Y., Nitta H., Nakamura R., Takasawa K., Inoue A., Takemoto S., Yamazaki Y.

日本金属学会誌 69 ( 4 ) 321 - 331 2005年4月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：日本金属学会参加形態：共同（副担当）

Experimental techniques for precise determination of low tracer diffusion coefficients in solid metals and alloys using radioisotopes are reviewed. Sputter-microsectioning method is most useful to measure submicron diffusion profiles at low temperatures. Measurements of tracer diffusivity along grain boundaries and dislocations in iron and stainless steels from the analysis of type C kinetics as well as type B kinetics are discussed. © 2005 The Japan Institute of Metals.

DOI： 10.2320/jinstmet.69.321

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Self-diffusion of cobalt in B2 type intermetallic compound CoAl 査読国際誌

Nakamura R., Iijima Y.

Intermetallics 13 ( 2 ) 163 - 167 2005年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Intermetallics 参加形態：共同（主担当）

The self-diffusion coefficient of 57Co in B2 type intermetallic compound CoAl at the concentrations of 42, 46, 50 and 52 at.% Al has been determined in the temperature range between 1250 and 1630 K by use of the serial radio-frequency sputter-microsectioning technique. The diffusion coefficient of cobalt, D*Co, decreases with increase in Al concentration from the Co-rich composition to the stoichiometry, while D*Co in Al-rich Co-52 at.% Al alloy is almost equal to that at the stoichiometry. At higher temperature region above 0.8 Tm (T m: melting temperature of alloys), D*Co deviates upward largely from the Arrhenius line, suggesting that the diffusion mechanism changes with increasing temperature from the monovacancy to the divacancy mechanism. © 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.intermet.2004.07.040

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Activation volume for interdiffusion in B2 type intermetallic compounds NiAl and FeAl 査読国際誌

Nakamura R., Lijima Y.

Defect and Diffusion Forum 237-240 ( PART 1 ) 364 - 369 2005年1月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）参加形態：共同（主担当）

Activation volume for interdiffusion, ΔṼ, in B2 type intermetallic compounds NiAl (40 ∼ 49 at%Al) and FeAl (40 ∼ 50 at%Al) has been obtained above 0.75 Tm (Tm: melting temperature of alloys) by measuring the interdiffusion coefficient under the pressure from 0.1 MPa to 5 GPa. ΔṼ in NiA1 shows almost constant value of 1.0 V0 (V0 : molar volume of alloys), suggesting that the divacancy mechanism is dominant at higher temperature region. On the other hand, ΔṼ in FeA1 increases from 0.6 to 0.8∼0.9 V0 with increasing temperature, showing that the contribution of divacancies to diffusion increases with increasing temperature. Diffusion mechanisms in NiAl and FeAl have been discussed with the help of our experimental data on intrinsic diffusion in them.

DOI： 10.4028/www.scientific.net/ddf.237-240.364

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Substructure development in rapidly solidified B2-type TiCo ribbons 査読

Yoshimi K., Sung M., Tsurekawa S., Yamauchi A., Nakamura R., Hanada S., Kawahara K., Watanabe T.

Materials Science Forum 475-479 ( I ) 849 - 852 2005年1月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）参加形態：共同（副担当）

Substructure development through aging and annealing treatments was studied for rapidly solidified TiCo ribbons using TEM. In as-spun ribbons, equiaxed grain structure was developed and its crystal structure was B2-ordered immediately after melt-spinning, while a small amount of fine precipitates existed as second phase. Some grains were dislocation-free but others contained a certain amount of curved or helical dislocations and loops. The dislocation density in the ribbons annealed at 700°C for 24 h was obviously higher than those in the as-spun ribbons and the ribbons aged at 200°C for 100 h. The increase of the dislocation density in the annealed ribbons would result from the absorption of excess vacancies. Therefore, the obtained results indicated that a large amount of supersaturated thermal vacancies were retained in TiCo as-spun ribbons by the rapid solidification. © 2005 Trans Tech Publications, Switzerland.

DOI： 10.4028/0-87849-960-1.849

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Interdiffusion in Fe/Pt bulk diffusion couples 査読国際誌

Lee C.G., Nakamura R., Shimozaki T., Okino T.

Defect and Diffusion Forum 237-240 ( PART 1 ) 426 - 431 2005年1月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）参加形態：共同（副担当）

Interdiffusion in Fe/Pt multi-phase diffusion couples has been investigated in the range from 1173 to 1473 K. Interdiffusion coefficients, D were determined by the Boltzmann-Matano analysis. At 1473 K. The values of interdiffusion coefficients in Pt3Fe and FePt phases coincide well with those determined from single-phase diffusion couples. The extrapolated value of the interdiffusion coefficients at NFe=0 coincides with the impurity diffusion coefficient of Fe in Pt at 1473 K. However, the extrapolated values of interdiffusion coefficients at NFe=l is much smaller than the impurity diffusion coefficient of Pt in Fe. On the other hand, the interdiffusion coefficients obtained in both Pt3Fe and FePt at lower temperatures are much larger than those determined by single-phase diffusion couples. It is supposed that the interface reaction or short circuit diffusion such grain boundary diffusion in multi-phase diffusion couple predominated.

DOI： 10.4028/www.scientific.net/ddf.237-240.426

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Activation volume for interdiffusion in bcc ordered and disordered phases of the Fe-Al system 査読国際誌

Nakamura R., Iijima Y.

Philosophical Magazine 84 ( 19 ) 1907 - 1926 2004年7月

記述言語：英語掲載種別：研究論文（学術雑誌）参加形態：共同（主担当）

The activation volume ΔṼ for interdiffusion in bcc ordered and disordered phases of the Fe-Al system has been determined in the temperature range from 1173 to 1473 K by measuring the pressure dependence of the interdiffusion coefficient. ΔṼ in the concentration range from 10 to 20 at.% Al of the bcc disordered phase is found to have an almost constant value of (0.40-0.45) V0 (V0 is the molar volume of the alloys) against temperature, which corresponds to the lower limit for the monovacancy mechanism in bcc pure metals or random alloys. On the other hand, the value of ΔṼ in the B2 FeAl phase increases with increasing temperature from 0.60V0, the upper limit for the monovacancy mechanism, to (0.80-0.90)V0, suggesting that divacancies contribute substantially to the diffusion at higher temperatures and in the off-stoichiometric region.

DOI： 10.1080/14786430410001664492

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Diffusion mechanisms in B2 NiAl phase studied by experiments on Kirkendall effect and interdiffusion under high pressures 査読国際誌

Nakamura R., Fujita K., Iijima Y., Okada M.

Acta Materialia 51 ( 13 ) 3861 - 3870 2003年8月

記述言語：英語掲載種別：研究論文（学術雑誌）参加形態：共同（主担当）

The intrinsic diffusivities of both components and the activation volume for interdiffusion in the B2 type NiAl phase have been measured in the high temperature region from 1473-1773 K. The activation volume for interdiffusion in 40-49 at% Al is found to be almost constant value of 1.0 V0 (V0: molar volume of alloys) at 1473-1773 K, suggesting that divacancies contribute to the diffusion. Near 43 at% Al, the diffusion mechanism for Al atoms is most likely the triple defect mechanism with the activation energy of 320 kJmol-1, while that of Ni atoms is probably the anti-structure bridge mechanism with the smaller activation energy of 240 kJmol-1. However, at 50.5 at% Al, Al atoms diffuse by the nearest neighbor mechanism with the smaller activation energy (260 kJmol-1), whereas Ni atoms diffuse probably by the next nearest neighbor jump related to the triple defect with the larger activation energy (360 kJmol-1). © 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S1359-6454(03)00210-6

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Self-diffusion of aluminium in the intermetallic compound Fe-48at.%Al 査読国際誌

Nakamura R., Iijima Y.

Philosophical Magazine 83 ( 4 ) 477 - 483 2003年2月

記述言語：英語掲載種別：研究論文（学術雑誌）参加形態：共同（主担当）

The self-diffusion coefficient of Aluminium in the B2-type intermetallic compound Fe-48 at.% Al was determined. The self-diffusion coefficient of Al in Fe-48 at.% Al was estimated to be a factor of about 0.6 smaller than that of Fe. The activation energy for the self-diffusion of Al was found to be 280 kJ mol-1, which is a little larger than the value of 262 kJ mol -1 for the self-diffusion of Fe.

DOI： 10.1080/0141861021000055655

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Interdiffusion in B2 type intermetallic compound FeAl under high pressures 査読国際誌

Nakamura R., Yamazaki Y., Iijima Y.

Materials Transactions 44 ( 1 ) 78 - 82 2003年1月

記述言語：英語掲載種別：研究論文（学術雑誌）参加形態：共同（主担当）

Interdiffusion coefficient in the B2 FeAl phase at 46-50 at%Al has been measured in the temperature range from 1173 to 1473 K under the pressure from 0.1 MPa to 5 GPa. The activation volume for interdiffusion, ΔV̄, derived from the pressure dependence of interdiffusion coefficient is found to be 0.58-0.90Vm (Vm: molar volume of alloys), which is comparable to or larger than 0.4-0.6Vm for the monovacancy mechanism in bcc pure metals or random alloys. The value of ΔV̄ increases with increasing temperature and also with deviating from stoichiometry, suggesting that divacancy contributes to the diffusion in higher temperatures and in the region of off-stoichiometry.

DOI： 10.2320/matertrans.44.78

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Single-phase interdiffusion in the B2 type intermetallic compounds NiAl, CoAl and FeAl 査読国際誌

Nakamura R., Takasawa K., Yamazaki Y., Iijima Y.

Intermetallics 10 ( 2 ) 195 - 204 2002年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Intermetallics 参加形態：共同（主担当）

Interdiffusion coefficients, D̃, in the B2 type NiAl, CoAl and FeAl phases have been determined by single phase diffusion couples over a wide temperature range from 1073 to 1773 K. The value of D̃ in the NiAl and CoAl phases shows a minimum at about 47 at.% Al deviating slightly from the stoichiometric composition, while the value of D̃ in the FeAl phase has a weak minimum at about 41 at.% Al. The value of the activation energy, Q̃, for interdiffusion in the NiAl and CoAl phases shows a maximum at about 47 at.% Al, where the value of Q̃ in the CoAl phase is much higher than that in the NiAl phase, while the value of Q̃ in the FeAl phase is nearly constant and much lower than those in the other two phases. It is observed that the larger the lattice constant of the compounds becomes, the lower the activation energy for diffusion in the compounds becomes. Thus, the magnitude of activation energy for diffusion in the B2 type NiAl, CoAl and FeAl is probably related to the lattice constant of the compounds. Using the interdiffusion coefficient and the tracer diffusion coefficients of Ni and Fe with the help of Darken's relation, the diffusion coefficient of Al in the NiAl and FeAl phases has been estimated. © 2002 Published by Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0966-9795(01)00125-X

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