2018 Fiscal Year Final Research Report
High-Temperature Creep Mechanism of Dual-Ductile-Phase Magnesium alloy with Long-Period Stacking Ordered Phase
| Project/Area Number |
16K06707
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Physical properties of metals/Metal-base materials
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| Research Institution | Nihon University |
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Principal Investigator |
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Keywords | LPSO phase / dual-ductile-phase alloy / power-law material / indentation / creep / rule of mixture / isostrain rate condition / composite reinforcement |
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| Outline of Final Research Achievements |
The high-temperature creep mechanism in an extruded Mg alloy comprising a matrix and an LPSO phase was investigated by theoretical analyses, indentation creep tests, and FE modeling. Creep behaviors of the Mg alloy were robustly predicted using the characteristic creep parameters, volume fractions, and creep strengths of the constituent phases. The creep strength of the Mg alloy closely followed the rule of mixtures and the isostrain rate conditions. The stress exponent for creep of the alloy was expressed by the harmonic mean weighted by the effective volume fractions of the constituent phases, which strongly depended on the deformation rate. A similar trend was observed for the creep activation energy, which was expressed by the weighted arithmetic mean value. Thus, the newly derived equations of these creep parameters were shown to quantitatively capture the mechanical contribution of the reinforcing phase to the creep strength of the overall dual-ductile-phase alloy.
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| Free Research Field |
材料強度物性学
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| Academic Significance and Societal Importance of the Research Achievements |
LPSO相を含むMg合金はAl合金に代わる次世代の軽量構造材料として期待されている．各々の相が全く異なるクリープ特性をもつため，この合金のクリープ挙動は単相合金と比べて非常に複雑になる．実用合金の高温クリープ機構を解明するための筋道を見いだすことは波及効果が大きく，工業的にも重要と言える．
延性二相合金に関するクリープ理論は，未だに整備されていない状況にある．この種の二相合金のクリープ特性値（応力指数や活性化 エネルギーなど）と構成相の当該値との関係式を理論的に導き，全体のクリープ強度に及ぼす強化相の寄与の程度を理論と実験により明らかにした論文は，著者の知る限りでは見当たらない
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