| Project/Area Number |
06650793
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Material processing/treatments
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| Research Institution | Ibaraki University, School of Engineering |
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Principal Investigator |
MOTOHASHI Yoshinobu Ibaraki University, Department of Mechanical Enginering, Professor, 工学部, 教授 (00007783)
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| Project Period (FY) |
1994 – 1995
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1995: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1994: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | Superplasticity / Ceramics / Zirconia / Tension / Compression / Cavitation / Hardness / Fracture toughness / 機械的性質 |
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| Research Abstract |
Tension and compression tests of a yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and Y-TZP/Al_2O_3 composite were conducted in air at temperatures from 1623 to 1823K with initial strain rates from 10^<-4> to 10^<-2> sec^<-1>. The flow stress vs.strain rate relations, strain rate sensitivity exponents (m-value) and apparent activation energies were evaluated. Each specimen was pulled or compressed to pre-determined strains and microstructural evolution and density loss were measured. The deformed specimens were subjected to thermal etching and the microstructures were observed by SEM.The amounts of cavities, deformation enhanced concurrent grain growths and changes in grain aspect ratios with the tensile and compressive strains were studied as functions of the temperature, strain rate and initial grain size.
The following results were obtained. The region III in the flow stress vs.strain rate relations seemed to be not appear. The m-values observed were approximately 0.3 for both tension and compression. The flow stress under compression was larger than that under tension, whereas the activation energy evaluated for the compression was smaller than the tension, suggesting that rate contralling processes are somewhat different between the tension and compression. The amount of cavities increased with the tensile strain, while it decreased in an early stage of the compression and then it starts to increase with the compressive strain after showing a minimum value. The cavities have strong correlations with the hardness, bending strength and fracture toughness of the deformed specimens.
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