| Project/Area Number |
05452284
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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 |
Structural/Functional materials
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| Research Institution | Tohoku University |
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Principal Investigator |
ABIKO Kenji Tohoku Univ.IMR Assoc.Prof., 金属材料研究所, 助教授 (80005959)
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| Co-Investigator(Kenkyū-buntansha) |
LIU Chun-Ming Tohoku Univ.IMR Res.Associate, 金属材料研究所, 助手 (00241571)
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| Project Period (FY) |
1993 – 1994
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| Project Status |
Completed (Fiscal Year 1994)
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| Budget Amount *help |
¥7,300,000 (Direct Cost: ¥7,300,000)
Fiscal Year 1994: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1993: ¥6,200,000 (Direct Cost: ¥6,200,000)
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| Keywords | High purity iron alloys / Impurity element / Tensile test / Hot ductility / Intergranular fracture / Segregation at grain boundary / Cavitation / Mechanical property / 高温変形 |
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| Research Abstract |
We have succeeded in the development of a ultra-high vacuum chamber for high temperature tensile test. The vacuum during testing is better than 10<@D1-7@>D1 torr ; the specimen can be quickly heated to a given temperature up to 1000ﾟC ; the accuracy of load can be controlled in (]SY.+-。[)50g.
High purity Fe-S and Fe-P alloys with the compositions controlled in one ppm have been prepared to clarify the effects of sulphur and phosphorus on the hot ductility of high purity iron. Tensile test was performed at temperatures ranging from room temperature to 900ﾟC.The observations of microstructure and fracture surface, and the AES analysis of grain boundaries and void surfaces were also carried out to clarify the mechanism of the intrinsic effects. The main results obtained in the present study can be summarized as follows :
1. High purity iron shows an excellent hot ductility, that is, reduction in area (RA) larger than 90%, at the test temperatures.
2. Soluble sulphur of only 5 ppm causes a significant hot ductility drop of high purity iron near 650ﾟC.Increasing the soluble sulphur content further decreases the hot ductility and widens the temperature range of embrittlement. The embrittlement occurs by growth and coalescence of cavities nucleated at the grain boundaries with sulphur segregation. The segregated sulfur at grain boundaries facilitates the nucleation of cavities and the more segregation of sulphur on the cavity surfaces enhances the growth of cavities.
3. The addition of phosphorus to high purity iron remarkably increases the elongation of iron to fracture at test temperatures above 500ﾟC.The phenomenon has been shown to be related with the effect of phosphorus on the dynamic recovery and recrystallization of iron.
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