| Project/Area Number |
18K18945
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| Research Category |
Grant-in-Aid for Challenging Research (Exploratory)
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| Allocation Type | Multi-year Fund |
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| Review Section |
Medium-sized Section 26:Materials 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) |
2018-06-29 – 2020-03-31
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| Project Status |
Completed (Fiscal Year 2019)
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| Budget Amount *help |
¥6,240,000 (Direct Cost: ¥4,800,000、Indirect Cost: ¥1,440,000)
Fiscal Year 2019: ¥3,120,000 (Direct Cost: ¥2,400,000、Indirect Cost: ¥720,000)
Fiscal Year 2018: ¥3,120,000 (Direct Cost: ¥2,400,000、Indirect Cost: ¥720,000)
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| Keywords | 六方晶 / 粒界 / プラストン / 延性 / 塑性変形 / 加工硬化 / 変形双晶 / 粒界すべり |
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| Outline of Final Research Achievements |
We have succeeded in producing bulk nanostructured pure Mg and Mg-Zn-Zr-Ca alloy having fully recrystallized ultra fine grained structures with grain sizes ranging from several hundreds nm to 100 micrometers. In the bulk nanostructured Mg-Zn-Zr-Ca alloy, <c+a> dislocations that did not operate in conventional grain sizes were nucleated from grain boundaries, and they interacted with <a> dislocations to enhance the strain hardening of the material, leading to managing both high strength and large ductility. In case of the bulk nanostructured pure Mg, it was found for the first time that grain boundary sliding happened even during room temperature deformation. We could quantitatively explain the peculiar deformation behavior of the ultra fine grained Mg and Mg alloys in terms of the concept of "platon" we had proposed, and showed a fundamental guideline for realizing HCP Mg and Mg alloys with high strength and large tensile ductility.
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| Academic Significance and Societal Importance of the Research Achievements |
Mgに代表される六方晶金属・合金は、軽量・高比強度などの優れた特性から構造材料としての応用が渇望されてきたが、乏しい遠征・加工性がその実用上の最大の障害となってきた。本研究は、プラストンという新しい概念に基づき、通常は活動しない変形モードを超微細粒Mgにおいて活性化し、強度と延性の両立を図ることが可能であることを実証したものである。本研究の成果は、構造材料の塑性変形に対する考え方を大きく転換するという学問的意味合いに加え、軽量金属として期待されつつも乏しい加工性が障害となっていた六方晶マグネシウム合金の構造材料としての応用可能性を拡大するという実用的・社会的観点からも、高い意義を有している。
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