| Abstract |
| Interest in the L1₂ phase in the Al-Ti-Cr system has increased with respect to the demand for light weight materials at elevated temperature because of its enhanced mechanical properties that arise through the substitution of Cr for Al in Al₃Ti intermetallic compounds. Additionally, recent work has indicated that the application of L1₂- based alloys was extended to oxidation resistance coating materials for γ-based TiAl alloy because the L12 phase could form a protective Al₂O₃ scale under oxidizing environments. However, L1₂ phase decomposes partially or completely to a more brittle phase when exposed to temperatures in the range of 800~1000℃, resulting a serious degradation of the cracking resistance in L1₂-based alloys. In this study, Zr was substituted for Ti in Al-21Ti-23Cr alloys to improve the phase stability around 800℃. As a result of Zr addition in L12-based Al-Ti-Cr alloys, the fraction of L12 phase decomposition at 800℃ was decreased. Furthermore, temperature range, in which L1₂ phase was decomposed to other brittle phase, was shrunken when Zr was added in the Al-Ti-Cr alloys. These phenomena resulted from the fact that the L1₂ phase field was less shifted in the direction of the Al-rich corner at 800oC in the Al-Ti-Cr system and that atomic diffusion for the L1₂ phase decomposition was reduced. Therefore, the addition of Zr is required to increase the possibility for potential usage of L1₂-based Al-Ti-Cr alloys at elevated temperatures around 800℃ because of the improvement of phase stability. |
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| Key Words |
| L12 phase, Phase stability, Phase decomposition, Zr addition |
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