2022 Fiscal Year Final Research Report
Deformation mechanism of CoCrNi medium entropy alloy with ultrafine grain microstructure
| Project/Area Number |
21K20487
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| Research Category |
Grant-in-Aid for Research Activity Start-up
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| Allocation Type | Multi-year Fund |
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| Review Section |
0401:Materials engineering, chemical engineering, and related fields
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| Research Institution | Kyoto University |
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Principal Investigator |
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| Project Period (FY) |
2021-08-30 – 2023-03-31
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| Keywords | 超微細粒金属材料 / ミディアムエントロピー合金 / 変形組織 / 電子顕微鏡 / 格子欠陥 / 転位 / 双晶 / その場回折測定 |
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| Outline of Final Research Achievements |
The present study aims to clarify the origin of the significant mechanical properties in the fully recrystallized ultrafine-grained (UFG) CoCrNi medium entropy alloy (MEA). Specimens of the UFG CoCrNi MEA were fabricated by high-pressure torsion and subsequent annealing. Tensile tests were performed at room temperature. The deformation microstructures were characterized by electron microscopy. At the yield point, widely-extended stacking faults and tangled dislocations were frequently observed. After that, deformation twins started appearing, and the density of dislocations and stacking faults increased. The extraordinary work-hardening ability of UFG CoCrNi MEA was attributed to the boundaries (such as stacking faults and deformation twins) dynamically introduced during plastic deformation as well as the increase in dislocation density.
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| Free Research Field |
金属材料学
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| Academic Significance and Societal Importance of the Research Achievements |
本研究は，UFG組織を有するCoCrNi MEAの特異な変形機構の解明を通じて，従来のUFG金属の典型的な問題点であった延性の低下を克服するために何が必要であるかを結晶粒界の拘束と変形組織発達の観点から明らかにすることができた．このようなUFG金属に特徴的な変形挙動を詳細に明らかにする研究は，これまでに世界各国で行われているUFG金属の材料科学研究の発展に大きく貢献するほか，強度と延性を両立した究極の構造材料を設計するための指針を得ることで社会・産業界の発展にも貢献できると考えられる．
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