1988 Fiscal Year Final Research Report Summary
Formation and control of solidification porosities of alloys
| Project/Area Number |
62460188
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
金属加工(含鋳造)
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
IKAWA Katuya Tohoku University Professor, 工学部, 教授 (80005199)
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| Co-Investigator(Kenkyū-buntansha) |
FUNAKUBO Tatsuya Tohoku University Assistant, 工学部, 助手 (00209149)
OHIDE Taku Tohoku University Assistant, 工学部, 助手 (70005437)
NIYAMA Eisuke Tohoku University Professor, 工学部, 教授 (50198420)
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| Project Period (FY) |
1987 – 1988
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| Keywords | solidification porosity / image analysis / Fourier transformation / X線透視法 / 画像解析 / フーリエ変換 |
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| Research Abstract |
Molten aluminum-copper alloys were first treated for controlling gas content and then poured into a preheated mold with a bottom chill for unidirectional solidification. Cooling rate, temperature gradient and solidification rate were obtained by temperature measurement.
Thin slices were cut from the casting to record Xray image of porosites, which was then processed by computer. Spacial distribution of porosities in some cylindrical castings were observed by Xray CT technique.
Porosities were scarcely observed in the copper range of 0 to 2.5 %, increased from 5 to 15 % copper and decreased again from 15 to 22.5% copper. No porosities were found above 25 % copper. Amount of porosities increased along the distance from the chill face, with a positive correlation with interdendritic tortuosity. Samples of high hydrogen contents were in the higher porosity side in the scatter band of the correlation, while low hydrogen samples were in the low porosity side.
Considering the importance of dendrite structure in porosity formation, optical microstructures of the dendrites were analyzed by Fourier transformation. The dendrite structures were described quantitatively as a periodical structure by frequency spectral analysis. The most prominent frequency thus obtained agreed with the dendrite arm spacing measured by the conventional method. In addition to that, the Fourier analysis provided other informations such as periodical structures of higher order frequencies, orientation characteristics of the structures and randomness of the orientation.
The knowledge obtained in the present study is expected to be useful in the porosity controlling techniques and also solidification structure analysis as well as more general structural analysis of the materials.
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