© 2020 Elsevier Inc. Both scanning transmission electron microscopy (STEM) and atom probe tomography (APT) were exploited to study variations in chemical composition and phases that took place during thermo-mechanical processing and following slow continuous heating of Ti-10V-3Fe-3Al (wt%) alloy. For the first time for the rapid-cooled alloys, athermal ω (ωath)-assisted nucleation of α phase (≈1 nm) was revealed by high resolution STEM. No presence of ωath was detected after heating to 450 °C, which was explained by its consumption by intragranular α and dissolution. While binomial analysis of APT data after thermo-mechanical processing revealed no changes in chemical composition of ωath compared to that of β matrix, heating the sample up to 375 °C resulted in Ti–rich domains depleted in both α and β stabilisers. The results suggested the simultaneous occurrence of displacive and diffusional mechanisms for formation and growth of intragranular α.