Abstract
The ωo phase transformation within βo areas in high Nb-containing TiAl alloys has been a popular research topic in recent years. However, a single ωo phase alloy is difficult to prepare because of the difficulty in reaching the equilibrium state at lower temperatures and the ambiguous position of the ωo phase in the phase diagram. In this study, a Ti–34Al–13Nb alloy based on the composition of the βo areas in high Nb-containing TiAl alloys is prepared. The phase transformation behaviors in the Ti–34Al–13Nb alloy during annealing are examined by electron microscopy. The results show that the α2 phase in different variants precipitates during annealing at 900 °C and follows the orientation relationship [112¯0]α2//[0001]ωo; (0001)α2//(112¯0)ωo with the ωo phase. The interfaces between different α2 variants are examined by high-resolution transmission electron microscopy (HRTEM). A unique twin-like interface between α2 grains is observed. The formation mechanism of this interface is considered to be related to the growth of two [112¯0]/60° α2 variants after self-accommodation. A stereographic projection analysis is also applied to explain the corresponding mechanisms.
Published Version
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