phase of Ti-5Al-5Mo-5V-3Cr wt.% is formed within a heat treatment at and identified by atom probe tomography as Ti-rich/solute lean precipitates. The composition and size remain essentially constant during ageing, although the volume fraction increases to 9.5% after ageing for 8 h. This is consistent with an ongoing transformation process of athermal to isothermal . The / interface becomes enriched with oxygen. This may be of significance as oxygen strongly stabilizes the phase, and the / interface has previously been suggested as the nucleation site for subsequent formation.