2000 Fiscal Year Final Research Report Summary
Faceted Peritecric Growth Mechanism of Superconductive RE-Oxides
| Project/Area Number |
11650766
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Metal making engineering
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
MORI Nobuyuki Kyushu University, Materials Sci.& Eng., Ass.Prof., 大学院・工学研究院, 助教授 (20108666)
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| Co-Investigator(Kenkyū-buntansha) |
OGI Keisaku Kyushu University, Materials Sci.& Eng., Prof., 大学院・工学研究院, 教授 (40038005)
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| Project Period (FY) |
1999 – 2000
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| Keywords | YBa2Cu3O7-X / superconductor / peritectic / nucleation / facet / solidification / simulation / superconducting oxide |
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| Research Abstract |
To clarify the solidification mechanism of unidirectionally solidified superconductive YBCO oxides, numerical and analytical studies were performed on solidification process of faceted 123 (YBa_2Cu_3O_<7-X>) crystals from liquid + 211 phases. Firstly, to clarify the effects of growth conditions and morphologies on the microstructures of 123 crystals, two-dimensional numerical simulation of faceted peritectic growth of 123 crystal was made by evaluating a series of primitive processes ; the faceted growth of 123 crystal, the melting of 211 particles in the liquid and the solute diffusion in the liquid. Solute distributions in the liquid during the 123 growth were calculated by FDM, and the distributions of residual 211 particles and liquid pools in the faceted 123 crystals were calculated from the experimentally obtained log-normal distributions of 211 particles in the liquid of YBCO.The calculated results well agreed with the experimental ones for various growth modes and conditions. Secondary, the transition of macrostructures from columnar to equiaxed 123 crystals in zone-melted or unidirectionally solidified YBCO was also studied analytically. Critical conditions for columnar-equiaxed transition (relations of growth rate (R) and temperature gradient (G) ) were calculated by equating the undercooling(ΔTc) for the columnar growth of faceted 123 cells and that (ΔTt) for the nucleation and growth of new crystals to a fraction of solid : fs (=10^<-10>, or 0.01). To assess the ΔTt, the CCT-curve was determined from TTT-curve, which was obtained by applying a modified Johnson-Mehl-Avrami equation, evaluating the incubation time (tinc) for nucleation in the effective sample volume. Calculated results agreed well with experimental results also for wide ranges of temperature gradient (G).
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