Enhancement of Strength and Fatigue Properties of Pure Titanium via Optimized ECAP Processing
| Project/Area Number |
17560620
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Structural/Functional materials
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| Research Institution | Osaka City University |
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Principal Investigator |
VINOGRADOV Alexei Osaka City University, Department of Intelligent materials Engineering, Associate professor, 大学院工学研究科, 助教授 (10283102)
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| Co-Investigator(Kenkyū-buntansha) |
KANEKO Yoshihisa Osaka City University, Department of Intelligent materials Engineering, Lecturer, 大学院工学研究科, 講師 (40283098)
HASHIMOTO Satoshi Osaka City University, Department of Intelligent materials Engineering, Professor, 大学院工学研究科, 教授 (50127122)
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| Project Period (FY) |
2005 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2006: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2005: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Keywords | severe plastic deformation / titanium / nanomaterials / fatigue / mechanical properties / structure refinement / ECAP / ナノ構造 / 引張り強度 |
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| Research Abstract |
Pure Titanium with the monotonic strength exceeding 1 GPa has been manufactured via multi-pass ECAP followed by forging and drawing. The role of processing factors such as ECAP route, number of passes and post-ECAP annealing on the structure and resultant mechanical properties and, particularly, in fatigue of metals and alloys has been investigated. The structure of ECAP-produced materials has been assessed by means of TEM and EBSD and X-ray analysis. It was shown that the structure difference between the samples produced by deifferent routes diminishes with increasing number of pressings. The processing route exerts little or no effect on both low-and high-cyclic fatigue properties, while the effect on the grain shape is very strong. Therefore, route A (no rotation of the working billet between subsequent passes) can be recommended for practical implementation. During severe plastic deformation to the effective strain of 8-30, the grain size is reduced to nanoscopic scale of 150-300 nm and the fraction of hghangle grain boundaries reaches of 65%, depending on the material, amount of imposed strain (number of ECAP pressings) and post-ECAP annealing. The improvement of fatigue properties in the high cycle regime has been demonstrated for many materials. For pure titanium the fatigue limit has reached 550 MPa after optimized severe plastic deformation processing and can be further improved by annealing. Hardening mechanisms were studied and it was shown that besides the Hall-Petch strengthening, the effect of dislocation accumulation on mechanical properties is significant. Furthermore, for precipitation hardenable materials the role of inclusion particles is important for structure stabilization and further enhancement of mechanical properties.
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Report
(3 results)
Research Products
(32 results)
