Microstructure evolution of Ti-46Al-6Nb-(Si,B) alloys during heat treatment with W addition

The cast ingots of Ti-46Al-6Nb-0.25Si-0.2B and Ti-46Al-6Nb-0.5W-0.25Si-0.2B (at%) were made by induction skull melting (ISM) technique. A series of heat treatments (HTs) were conducted to research the microstructure evolution of both alloys. Microstructure and tensile property were examined by scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscope (TEM), and tensile testing machine. The results show that microsegregation (liquid segregation and solid segregation) is exacerbated by the addition of 0.5 at% W; the addition of Nb, W in TiAl alloy makes the phase transition difficultly take place; then, the microstructures and tensile properties of both alloys are improved after certain HT processes; finally, the thicknesses of the gamma/alpha(2) lamellae after a certain HT process are significantly affected by the number of residual gamma phases before the furnace-cooling moment.