Al-Ti-Cr 합금계 L1₂기지 합금의 800℃에서의 상안정성

Abstract

Relationship between the phase stability and the composition of L1_2-based Ti-Al-Cr alloys at 800℃ was investigated. It was found that the yield strength of Al-21Ti-23Cr and Al-21Ti-15Cr alloys with Ti-lean composition after exposure at 800℃showed a relatively small increase compared with that of alloys homogenized at 1150℃. However, yield strength of al-30Ti-15Cr alloy with Ti-rich composition after exposure at 800℃ increased very remarkably. The difference in strength increment after exposure at 800℃ was due to the partial decomposition of L1_2 phase in Al-21Ti-23Cr and Al-21Ti-15Cr alloys, and the complete decomposition of L1_2 phase in al-30Ti-15Cr alloy. Therefore, alloys with Ti-lean composition were expected more suitable for light heat resistant and oxidation resistant coating material with respect to stability of L1_2 phase. It was also revealed that the phase decomposition of L1_2 phase resulted from the shift of L1_2 phase region to Al-rich corner in Al-Ti-Cr phase diagram with decreasing temperature.