Precipitation behavior of ωo phase in Ti-37.5Al-12.5Nb alloy

Abstract

Mutual transformation between α2 and ωo phases has been an interesting topic in recent years. In this study, martensitic α2 was obtained by air-cooling from 1250 °C in Ti-37.5Al-12.5Nb (at%) alloy while four ωo variants formed in the βo phase matrix during the cooling process. Nonetheless, only one ωo variant was observed at the periphery of the α2 plates in the βo phase and the orientation relationship between these two phases was [0001] α2//[1210] ωo; (1120) α2//(0002) ωo. Thin γ plates precipitated within the α2 phase and were thought to be related to the appearance of ωo phase. The redistribution of the compositions during the phase transformations was studied by energy dispersive X-ray spectroscopy analysis. The corresponding mechanisms of the phase transformations mentioned above are discussed.