Widmannstätten laths in Ti48Al2Cr2Nb alloy by undercooled solidification

Widmannstätten laths in Ti48Al2Cr2Nb alloy were obtained by containerless electromagnetic levitation during undercooled solidification rather than heat treatments in most cases. The nucleation of γ_{Widmannstätten} is confirmed by the thermal history of the second recalescence behaviour. High dislocation density, stacking faults and dislocation slip are observed by transmission electron microscopy. By quantitative analysis of the transformation energy, the driving force for γ_{Widmannstätten} in the solid state phase transformation is calculated, compared with that of heat treatments. Meanwhile, the proper undercoolings (ΔT = 257-300 K), post-solidification cooling rates (11.1-29.1 K/s), the fine lamellar colony sizes (306-467 μm) and proper undercoolings in the solid state phase transformation are in favour of promoting the formation of Widmannstätten laths at moderate undercoolings.