The effect of continuous heating on microstructure development in thermo-mechanically processed Ti-10V-3Fe-3Al alloy produced by powder metallurgy

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.