2004 Fiscal Year Final Research Report Summary
UNDERCOOLING AND HETEROGENEOUS NUCLEATION IN IRON-NIOBIUM AND NICKEL-NIOBIUM ALLOYS
| Project/Area Number |
15560637
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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 | HOKKAIDO UNIVERSITY |
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Principal Investigator |
MASAYUKI Kudoh HOKKAIDO UNIVERSITY, GRADUATE SCHOOL OF ENGINEERING, PROFESSOR, 大学院・工学研究科, 教授 (00001248)
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| Project Period (FY) |
2003 – 2004
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| Keywords | UNDERCOOLING / SUBSTRATE / IORN-NIOBIUM ALLOY / NICKEL-NIOBIUM ALLOY / CARBIDE / NUCLEATION / DENDRITE / GRAIN STRUCTURE |
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| Research Abstract |
The effects of heterogeneous substances on undercooling and solidified microstructure were investigated for Iron-niobium and Nickel-niobium binary alloys. An alumina crucible and a crucible covered with commercial glass were used in this experiment. The samples were kept for 1 hr after heating up to 1823K in the Fe-Nb alloy and 1173K in the Ni-Nb alloy and quenched at 1723K and 1673K, respectively, to keep microstructures just after solidification. The experiment on the ternary alloys made by adding 1mass% carbon to the binary alloys was also done. The results obtained are summarized as follows.
(1)The undercooling of the Fe-Nb and Ni-Nb alloys increased and reached to 15K at 2mass%Nb and 80K at 1mass%Nb, respectively. The undercooling of both alloys decreases with increasing Nb concentration. The under cooling of the Ni-Nb alloy is always larger than that of the Fe-Nb alloy. (2)When the glass covered crucible was used, the undercooling became larger and it reached to 120K in the case of Ni-Nb alloy. (3)The undercooling of the ternary alloys became lower than those of binary alloy because of carbide formation. The undercooling in the ternary alloys decreased even if glass covered crucible was used. (4)The formation process from dendrite morphology to grain structure was different from the solvent of the alloy. That is, the grain formation in the Ni-base and dendrite formation in the Fe-base alloys are easy to occur. It is concluded that crucible wall mostly acts as heterogeneous materials and subsequently the oxide or carbide formed in the melt also acts as the heterogeneous substances. In addition, the undercooling of the Ni-base alloy was always larger than that of Fe-base alloys because Fe oxide is easy to form compared with Ni oxide.
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