2006 Fiscal Year Final Research Report Summary
Better balance of room and high temperature properties by the microstructure modification for orthorhombic Ti-22A1-20Nb-2W titanium alloy.
| Project/Area Number |
16560619
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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 | National Institute for Materials Science |
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Principal Investigator |
JAGOWARA Masuo National Institute for Materials Science, Structural Metals Center, Group Leader, 新構造材料センター, グループリーダー (80354182)
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| Co-Investigator(Kenkyū-buntansha) |
EMURA Satoshi National Institute for Materials Science, Structural Metal Center, Senior Researcher, 新構造材料センター, 主任研究員 (00354184)
MAO Yong National Institute for Materials Science, Structural Metal Center, Post-Doc Researcher, 新構造材料センター, NIMSポスドク研究員
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| Project Period (FY) |
2004 – 2006
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| Keywords | Titanium intermetallic alloy / O phase / Thermo-mechanical processing / Grain size control / Lamellar microstructure / Tensile properties / Creep properties / Ductility |
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| Research Abstract |
Recently, Ti_2AlNb intermetallic phase (ordered orthorhombic phase) base alloys have received much attention for their high strength-to-weight ratio, good workability and greater fracture toughness. Especially, W-modified Ti-22Al-20Nb-2W (mol %) alloy, developed by the authors, shows superior high-temperature properties such as creep. However, this alloy exhibits poor room-temperature ductility. It would be beneficial to reduce the prior B2 (CsCl-type ordered bcc phase) phase grain size to improve its room-temperature tensile properties. This research was therefore aimed to refine the B2 grains using thermo-mechanical processing, in which HIP processed compacts of gas-atomized Ti-22Al-20Nb-2W powder were hot-rolled in the B2+α_2 (ordered hcp phase) two-phase region and subsequently annealed in the same B2+α_2 two-phase region. The distribution of spherical α_2 particles formed in the B2 matrix by this thermo-mechanical treatment was highly dependent on the annealing temperature and time, and due to the pinning effect of these α_2 particles against grain growth, B2 grain sizes ranging from 27 μm to 108 μm were finally obtained. The tensile strength and room temperature elongation of the material with B2 grain size of 108 gm were 850 MPa and 0.5 %, respectively, whereas those of the material with B2 grain size of 27 gm were 1220 MPa and 5 %, respectively. Materials with B2 grain size of 61 μm showed a better balance of room-temperature tensile strength (1050 MPa) and elongation value (3.2 %) without sacrificing high-temperature creep properties (steady-state creep rate : 1.0 x 10^<-9> s^<-1>.
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Research Products
(4 results)
