Solidification microstructure of super-α2 alloy prepared by gas atomization

Ti–25Al–10Nb–3V–1Mo alloy has been prepared by gas atomization with atomizing pressure above 8 MPa. The cooling rate of 5 × 10³ ∼ 3 × 10⁵ K s^-1 was obtained according to secondary dendritic arm spacing, as the particle size is 30 ∼ 300 μm. It is known that in the big particles two dendrite morphologies can be found, cellular dendrite and well-developed dendrite, and in small particles there exists only well-developed dendrite. The surface of particles is characteristic of solidification that is identical to the observation on the cross-sectional views. The micrographs of cross-sectional views show that the big particles, whether of cellular dendrite or well-developed dendrite, solidify by multiple nucleation events while the small particles of well-developed dendrite solidify from a single nucleation event. The microstructure of the alloy consists of single β0 phase. This revised version was published online in November 2006 with corrections to the Cover Date.