| Project/Area Number |
12650660
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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 |
Physical properties of metals
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| Research Institution | Tottori University |
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Principal Investigator |
HAYAKAWA Motozo Tottori University, Mechanical Eng., Professor, 工学部, 教授 (60093621)
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| Co-Investigator(Kenkyū-buntansha) |
AKAO Takahiro Tottori University, Mechanical Eng., Research Associate, 工学部, 助手 (70335503)
ONDA Tetsuhiko Tottori University, Mechanical Eng., Assistant Professor, 工学部, 講師 (80273879)
WANG Lei Tottori University, Mechanical Eng., Associate Professor, 工学部, 助教授 (00293762)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2001: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2000: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Keywords | zirconia / yttria doped / martensitic transformation / isothermal martensite / athermal martensite / transformation start time / composition dependence / grain size dependence / 組成依存性 / バースト変態 / サブゼロ冷却 / 変態開始温度 / 微細球状試料 |
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| Research Abstract |
Zirconia doped with a small amount of yttria exhibits both isothermal and athermal burst type transformation depending on being heated at around 300 ℃ or subzero cooled. In this work, the effect of yttria content, grain size and the specimen size were quantitatively measured for both modes of transformation to look insight into the nucleation of martensite. Small spherical specimens of 0.3〜0.8 mm diameter containing 1.4〜1.6 mol%Y_2O_3 and the range of grain size 0.5〜1.0 μm were prepared. The isothermal transformation kinetics was studied by micro-dilatometer during isothermal holding and Mb temperature was measured by video recording the burst transformation together with temperature while the specimens were continuously cooled.
Isothermal transformation started after some incubation time and followed a sigmoidal curve until its completion in a relatively short time. A transformation start time exhibited a typical C-curve in a TTT diagram. The C-curve shifted toward short time side with decreasing yttria content and with increasing grain size. The effect of aging during the incubation period was found cumulative, suggesting a continuous growth of nucleation during the incubation period. The Mb temperature was also significantly increased with decreasing yttria content and with increasing grain size, suggesting a significant destabilizing effect of the reduction of yttria content and grain growth. On the other hand, Mb temperature decreased only slightly with decreasing specimen size. The Weibull modulus for Mb was 80, which was considerably higher than that for the fracture strength of a similar material (m〜6). This suggests that the embryos of the martensite have an essentially different distribution from those defects responsible for the fracture.
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