2023 Fiscal Year Final Research Report
Microstructure formation in high-Strength ductility high oxygen concentration additively manufactured Ti alloys
| Project/Area Number |
20K05155
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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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| Review Section |
Basic Section 26050:Material processing and microstructure control-related
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| Research Institution | Osaka University |
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Principal Investigator |
Umeda Junko 大阪大学, 接合科学研究所, 教授 (50345162)
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| Project Period (FY) |
2020-04-01 – 2024-03-31
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| Keywords | チタン / 積層造形体 |
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| Outline of Final Research Achievements |
Focusing on oxygen as a stabilizing element of the α-phase, which was considered to be a negative material factor, it was clarified that a small amount of oxygen contributes to the formation of a specific crystal structure through microscopic structural analysis of the behavior of oxygen atoms during the layer fabrication process. The dissociated oxygen atoms after decomposition of TiO2 particles, which are the source of oxygen, were found to solid-solubilize into α-Ti grains, and the transformation from coarse columnar grains to fine needle-like martensite phase was observed.
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| Free Research Field |
粉末冶金
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| Academic Significance and Societal Importance of the Research Achievements |
チタン材料では，酸素成分の粒界偏析に起因した脆化現象が報告されており，特に規格上限値を超える高濃度では，伸び値が激減する．しかし，酸素は本当に負の因子であるのか？と問い，レアメタルの代替物質として酸素に着目した．積層造形時の溶融・超急冷凝固過程での酸素原子の振舞いを理解し，チタン材の延性低下を招く結晶粒界近傍での酸素濃化による化合物相の形成を抑制し，酸素元素をα-Ti内に均一固溶することで結晶粒径や集合組織を制御することで，高強度と高延性の同時発現が可能であることを明らかにした．その結果，チタン合金の高強度化に必須であるレアメタル使用撤廃の可能性を示したことは学術的な意義であると考える．
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