1998 Fiscal Year Final Research Report Summary
Kinetic Measurement of the Martensitic Transformation in Y-TZP Samll Particles
| Project/Area Number |
09650718
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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 Univ., Faculty of Engineering, Professor, 工学部, 教授 (60093621)
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| Co-Investigator(Kenkyū-buntansha) |
ONDA Tetsuhiko Tottori Univ., Faculty of Engineering, Research Associate, 工学部, 助手 (80273879)
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| Project Period (FY) |
1997 – 1998
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| Keywords | tetragonal zirconia polycrystals / yttria doped / spherical particles / agglomcration in oil / martensitic transformation / isothermal martensite / kinetics measurement / micro-dilatometer |
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| Research Abstract |
Kinetics of the martensitic transformation of yttria doped zirconia was studied on small spherical specimens of 500 mum size prepared by the agglomeration method in oil. The main results obtained are as follows :
1. Small spherical specimens allowed to study the transformation kinetics by rapid cooling and heating treatments. Rapid quenching resulted in a highly metastable tetragonal phase at room temperature for the zirconia containing small amount of yttria which normally transform during the usual cooling rate for a bulk specimen. The fact suggested that the martensitic transformation involves a thermally activated process.
2. The metastable t-phase underwent isothermal transformation when held at an intermediate temperature. The kinetics was described by a C-curve in the TTT diagram with an upper limit at 450ﾟC and a nose at 350ﾟC.
3. The metastable t-phase undergoes a burst transformation during subzero-cooling. The Ms temperature was located at-1 18+-6ﾟC.
4. From the above observation, it was verified that the metastable t-phase undergoes both isothermal and athermal transformations depending on the heat treatment. Such phenomenon cannot be explained by the existing theories of the nucleation of martensite.
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