| Project/Area Number |
16560640
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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 |
Material processing/treatments
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| Research Institution | Shizuoka Institute of Science and Technology |
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Principal Investigator |
KUBOKI Isao Shizuoka Institute of Science and Technology, Faculty of Science and Technology, Associate Professor (30360225)
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| Project Period (FY) |
2004 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2006: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 2005: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2004: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Keywords | titanium / severe plastic deformation rocess / torsion processing / tensile test / hardness / surface roughness / 工業用純チタン / 高温引張試験 / チタン合金 / 硬さ試験 / 焼なまし / ねじり戻し加工 |
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| Research Abstract |
We produced specimens by applying a one-way torsion process and a cyclic back-torsion process to commercially pure titanium (CP Ti) and cold-workable β-rich (α+β) titanium alloy SP700 under various conditions. We obtained the following results from specimens by performing room-temperature and high-temperature tensile tests, hardness tests, surface roughness measurements, and structural observations:
Firstly, concerning the commercially pure titanium CP Ti :
(1) After the cyclic back-torsion process, even specimens having square cross-sections exhibited comparatively linear ridges and exhibited no great changes in appearance. The process is thus capable of restoring specimens to their original shape.
(2) The cyclic back-torsion process did not change the surface roughness greatly. This process is capable of reducing the surface roughness more than the one-way torsion process.
(3) The cyclic back-torsion process and subsequent recrystallization annealing formed a gradient structure in which
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the crystal grain size gradually decreased in the direction away from the center, whereas the hardness increased in this direction.
(4) The one-way torsion process and cyclic back-torsion process increased the tensile strength. The cyclic back-torsion process is capable of increasing the tensile strength more than the one-way torsion process since the specific angle of twist can be made greater.
(5) In the high-temperature tensile test, the cyclic back-torsion processed specimen exhibited a greater strain-rate sensitivity index m (m=0.28) at a deformation temperature of 923 K than the cold-rolled specimen. Accordingly, the total elongation of the back-torsion-processed specimen was approximately 10% to 20% greater than that of the cold-rolled specimen at any strain rate.
Concerning the titanium alloy SP700 :
(6) The cyclic back-torsion process did not greatly change the hardness of the annealed specimen, but it did increase its tensile strength. The back-torsion process caused the surface and central structures of the specimens to elongate toward the perimeter. Less
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