Microstructure of high Nb containing TiAl alloy on large scale

Microstructure of Ti-45Al-8.5Nb-(W, B, Y) (at.%) alloy ingot on large scale melted using vacuum consumable melting followed by vacuum consumable skull melting has been studied by using optical microscopy (OP), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS). The results show that the microstructure of the ingot is near lamellar microstructure (NL) composed of finer lamellar colonies for near surface zone and coarser lamellar colonies for the majority zone and γ, β(B2) phases. For the majority zone of the ingot γ-rich zone is present, and lamellar colony size is about 75 μm with the average lamellar spacing of 700 nm. 3 phase exists either on the boundaries of the lamellar colonies in irregular morphology or within the lamellar colonies in lamellar or blocky morphology. There also exist some titanium boride ribbons and needles longer than 60 μm.