2022 Fiscal Year Annual Research Report
Explication of the degradation mechanism of the strength of heat-resistant alloys under random loading at elevated temperatures and the establishment of the prediction method of their lifetime
| Project/Area Number |
21F50350
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| Research Institution | Tohoku University |
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Principal Investigator |
三浦 英生 東北大学, 工学研究科, 教授 (90361112)
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| Co-Investigator(Kenkyū-buntansha) |
WANG RUNZI 東北大学, 工学(系)研究科(研究院), 外国人特別研究員
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| Project Period (FY) |
2021-11-18 – 2023-03-31
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| Keywords | 高温強度 / 粒界割れ / クリープ疲労損傷 / 結晶品質 / 電子線後方散乱回折 |
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| Outline of Annual Research Achievements |
The main objectives of this research are 1) Clarification of the acceleration mechanism of the degradation of materials under creep-fatigue loading at elevated temperatures, and 2) Establishment of the quantitative evaluation method of the damage of the materials under random load conditions. Original small dumbbell-shape specimens were manufactured for both the observation of the degradation process under the distribution of the applied load and the direct observation of the change of the local crystallinity of the alloy in a scanning electron microscope. The degradation process of the crystallinity of the representative heat-resistant alloy, Ni-base superalloy, under creep-fatigue loading at elevated temperatures was monitored continuously by using our original intermittent micro tensile test method with electron microscopy. The degradation process of the crystallinity and strength of the material was continuously observed, and it was explicated by applying the modified Arrhenius equation by considering the effect of mechanical stress on the local decrease in the activation energy of atomic diffusion. it was also found that the accumulation of vacancies and dislocations was accelerated only around grain boundaries and thus, the initiation time of intergranular cracking became shorter when the strain rate during loading and unloading became faster. The main reason for the acceleration was found to be the activation of viscoelasticity of the alloy at the elevated temperature.
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| Research Progress Status |
令和4年度が最終年度であるため、記入しない。
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| Strategy for Future Research Activity |
令和4年度が最終年度であるため、記入しない。
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