Abstract: For the as-cast Ti-55 alloy, the morphology of the alloy riser consists of coarse dendrite zone and equiaxial grain zone. The second phase particles are 2.0-25 um in diameter. Some particles appear at grain boundaries, the others precipitate within grains. The shapes of the particles are mainly ellipsoids, and a few kinds of short needle-like and block v morphologies. The Nd-rich phase particles are enriched in the liquid before the inter face and are engulfed along the solidification plane-front. Finally, bands of Nd-rich phase par-ticles form parallel to the advancing solidification plane-front.

Key words: Ti-55 alloy, Nd-rich phase, Nd