1996 Fiscal Year Final Research Report Summary
DEVELOPMENT OF HIGH PERFORMANCE TiAl ALLOYS USING RAPIDLY SOLIDIFIED POWDER WITH MARTENSITIC STRUCTURE.
| Project/Area Number |
07555527
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 試験 |
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| Research Field |
Material processing/treatments
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| Research Institution | KUMAMOTO UNIVERSITY |
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Principal Investigator |
NISHIDA Minoru KUMAMOTO UNIVERSITY,FACULTY OF ENGINEERING,ASSOCIATE PROFESSOR, 工学部, 助教授 (90183540)
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| Co-Investigator(Kenkyū-buntansha) |
KUMAGAE Ryohei FUKUDA METAL FOIL AND POWDER CO., LTD., R&D LAB., RESEARCH SCIENTIST, 技術本部研究所, 研究員
TAKASHIMA Kazuki KUMAMOTO UNIVERSITY,FACULTY OF ENGINEERING,ASSOCIATE PROFESSOR, 工学部, 助教授 (60163193)
MIURA Hideshi KUMAMOTO UNIVERSITY,FACULTY OF ENGINEERING,PROFESSOR, 工学部, 教授 (30117254)
CHIBA Akira KUMAMOTO UNIVERSITY,FACULTY OF ENGINEERING,PROFESSOR, 工学部, 教授 (90005322)
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| Project Period (FY) |
1995 – 1996
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| Keywords | TiAl ALLOY / RAPIDLY SOLIDIFIED POWDER / PREP / MICRODUPLEX STRUCTURE / HOT PRESSING / alpha_2 MARTENSITE / SUPERPLASTIC DEFORMATION / GRAIN BOUNDERY SLIDING |
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| Research Abstract |
Effect of initial microstructure on the compactibility at elevated temperature in rapidly solidified Ti-rich TiAl alloy powders produced by the plasma rotating electrode process (PREP) has been investigated. There are two kinds of powders with respect to the microstructure. The first one has a surface relief of a martensitic phase and consists of twin related alpha_2 (Ti_3Al) lath platelets, which is referred to as M powder. The second one has a dendritic structure and consists a single phase of alpha_2 with no microstructure other than grain boundary, which is referred to as D powder. alpha_2+gamma (TiAl) microduplex and alpha_2/gamma lamellar structures are formed in M and D powders of the Ti-40 at%Al alloy by heat treatment at 1273 K,respectively. The microduplex structure consist of gamma precipitate in the twin related alpha_2 matrix with the usual orientation relationship. It is difficult to compact the D powder by hot pressing at 1273 K under 50 MPa for 14.4 ks. On the other hand, the M powder is compacted easily by hot pressing with the same condition. The twin related alpha_2 and alpha_2 boundary changes to random ones and the alpha_2 and gamma phases are lost the usual orientation relationship in the duplex structure during the hot pressing. In other words, the low energy boundaries are changed to the high energy ones suitable for grain boundary sliding. Dislocations are scarcely observed inside of both the alpha_2 and gamma crystal grains. It is concluded that the grain boundary sliding is a predominant deformation mode in the M powder during the hot pressing. D and M powders in Ti-45 and 47 at%Al alloys show the same tendency as those in Ti-40 at%Al alloy during hot pressing. From the practical viewpoint the optimization of PREP conditions is also discussed to increase the number fraction of M powder.
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