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Vol.42, No.8, 648 ~ 656, 2004

Title

Thermal Stability and Mechanical Properties of TiAl-Nb Alloys Containing Si and C

김정환 J. H. Kim , 김성웅 S. W Kim , 이호년 H. N. Lee , 김민철 M. C. Kim , 오명훈 M. H. Oh , 위당문 D. M. Wee

Abstract

Thermal stability of the lamellar microstructure in TiAI-Nb alloys containing Si and C was investigated by partial melting experiments. The proper compositions which have enough thermal stability to be used as a seed material were found for TiAl-Nb-Si-C alloy system. The lamellar microstructure of the Ti-44.5A1-3Nb-0.6Si-0.2C and Ti-45Al-2Nb-0.6Si-0.2C alloys was successfully aligned parallel to the growth direction by directional solidification using Ti-44.5A1-3Nb-0.6Si-0.2C alloy as a seed material. The DS ingots of these alloys exhibited a excellent combination of room-temperature ductility (8.5%) and high-temperature yield strength (700 MPa at 800℃). Nb was not an effective element to improve the lamellar stability. However, adding a small amount of Si and C to the TiAl-Nb system was very effective to improve the thermal stability of the lamellar microstructure.

Key Words

TiAl, Seeding technique, Directional solidification, Lamellar orientation, Thermal stability

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