2002 Fiscal Year Final Research Report Summary
Effect of cavitation caused by superplastic deformations on thermal shock properties in ceramics
| Project/Area Number |
13650752
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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 |
Structural/Functional materials
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| Research Institution | IBARAKI UNIVERSITY |
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Principal Investigator |
MOTOHASHI Yoshinobu IBARAKI Univ., College of Engineering, Professor, 工学部, 教授 (00007783)
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| Project Period (FY) |
2001 – 2002
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| Keywords | superplasticity / ceramics / Y-TZP / cavitation / thermal shock |
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| Research Abstract |
Superplastic deformations of ceramics frequently cause various microstructural evolution such as formation and growth of cavities at grain boundaries, concurrent grain growth, variation in grain aspect ratio and so on. It has been reported that the cavities formed in 3Y-TZP owing to superplastic deformations deteriorate hardness and bending strength of the material, while they improve its fracture toughness to some extent. Another important factor to be examined must be thermal shock behavior. In this work, the effect of cavities on thermal shock resistance of the 3Y-TZP was investigated by an indentation-quenching method. Parts of the superplastically-deformed 3Y-TZP specimens were subjected to hot-isostastic-pressing (HIP) to reduce the amount of cavities to zero. The thermal shock tests were then carried out on both of the as-deformed and HIP'ed specimens to separate the effect of cavities from other factors. The main results obtained are as follows :
(1) The critical temperature difference (△T_c) is in proportion to l^<-1/2>, as is predicted from the Hasselman's equation, where l is the initial surface crack half-length.
(2) The △T_c is improved as the volume fraction of cavities (V_c) is increased. It appears that the following is responsible for this result : The apparent thermal expansion coefficient of the 3Y-TZP was probably reduced with the increase in V_c under such a condition that thermal stresses are arising upon quenching which led to the enhancement in △T_c.
(3) The △T_c, showed au upper limit at approximately 210 K within the present experimental range. It seems that this was caused by the acceleration of the degradation at the precrack up region where concentrated thermal stresses would arise with aqueous environment at around 483 K in a very beginning stage of the quenching process.
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Research Products
(2 results)
