Determination of parent β-phase orientation from inherited orthorhombic phase in β→O+B2 phase transformation of Ti-22Al-25Nb alloy

We propose and describe a method for determining the orientation of parent body-centred cubic (bcc) beta grains at high temperatures from the orientations of the orthorhombic variants observed at room temperature as applied to the case of high-Nb-containing Ti3Al-based alloys. The method is based on knowledge of the orientation relationship between the parent and inherited phase. By averaging, the procedure enables determination of the most probable parent orientation using an approximate orientation relationship. The beta --> O transformation in Ti3Al-based Ti-22Al-25Nb alloy is very suitable for checking the relevance and effectiveness of the method because, in this case, after certain processing, some beta-phase is retained at room temperature.