Phase transformations in Ti–34Al–13Nb alloy

Abstract

The microstructure and orientation relationship (OR) of the α2 and ωo phases in the Ti–34Al–13Nb (at. %) alloy were investigated. The α2 segments nucleated at the ωo boundaries after aging at 900 °C for 2 h. The ORs between the two phases were studied by selected area diffraction patterns using a transmission electron microscope and interpreted by the superimposed stereographic projections. Two ORs were defined as follows: \( \left[ {1\bar{2}10} \right]\upalpha_{2} //\left[ {000\bar{1}} \right]\upomega_{o} \); \( (0002)\upalpha_{2} //\left[ {\bar{1}2\bar{1}0} \right]\upomega_{o} \) and \( \left[ {\bar{1}010} \right]\upalpha_{2} //\left[ {2\bar{4}2\bar{3}} \right]\upomega_{o} \); \( \left( {0002} \right)\upalpha_{2} //\left( {01\overline{12} } \right)\upomega_{o} \). Two α2 laths with parallel \( \left\langle {\bar{1}102} \right\rangle \) directions were observed in this alloy, which were explained by the different α2 variants nucleated at the ωo boundaries according to ORI and ORII.