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Vol.40, No.11, 1141 ~ 1150, 2002
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| Title |
| Effects of Si Addition on the Thermal Stability of TiAl Alloys with the Lamellar Microstructure |
| 이호년 Ho Nyun Lee , 김성웅 Seong Woong Kim , 오명훈 Myung Hoon Oh , 산구정치 Masaharu Yamaguchi , 위당문 Dang Moon Wee |
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| Abstract |
| Thermal stability of Si-doped TiAl alloys with the lamellar microstructure was investigated by partial melting in an optical floating zone(FZ) furnace to ascertain the possibility of usage as a seed material. The lamellar stability of TiAl and TiAl-X(X=Mo, Nb, W) alloys, which proved to be thermally unstable, was improved dramatically by Si addition. In the results of partial melting, it was found that there are two boundaries of Al content(low Al limit and high Al limit) which devide stable and unstable compositions. It is thought that when Al content is lower than low Al limit, recrystallization can be occurred by β-phase formation at high temperature, and when Al content is higher than high Al limit, the lamellar stability will be deteriorated by rapid variation of α/γ phase volume fraction during heating and cooling. The lamellar stability of TiAl-Si alloys can be predicted by drawing above two boundaries at TiAl-Si isothermal section. Moreover, the lamellar stability of TiAl-X-Si alloys can be also predicted by converting the compositions to TiAl-Si compositions. In addition, lamellar orientation control was successfully performed by directional solidification using the Ti-46Al-l.5Mo-1Si alloy as a seed material. |
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| Key Words |
| TiAl, Lamellar microstructure, Thermal stability, Si addition, Stable region |
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