On the microsegregation of Ti–45Al–(8–9)Nb–(W, B, Y) alloy

The morphology, distribution and origin of microsegregation of an as-cast high Nb containing TiAl alloy and the effect of the microsegregation on as-forged and heat-treated microstructures had been investigated. The results showed that there were three kinds of microsegregations, designated as L-segregation, β-segregation and α-segregation, existing on boundaries of primary β grains, on triple junctions of lamellar colonies, within lamellar colonies, respectively. The segregations were formed during solidification and phase transformation of the alloy due to high cooling rate and low atom diffusion rate. After forging in (α + γ) region β-segregation and α-segregation could be eliminated after, but L-segregation could not be eliminated. L-segregation was detrimental to heat treatment of the as-forged material.