Abstract:The morphology and growth mechanism of borides in Ti-48Al+(0.2%~0.8%)B (mole fraction) alloys were investigated. The results show that TiB2phase are all flakes with width <0.5μm and aspect ratio >100 in alloys containing 0.2% and 0.5%B, respectively, but there are a few hexagonal blocky borides with habit planes of (0001) and {1010} type besides flakes in the alloy containing 0.8%B. Flake borides are the products of irregular eutectic reactions growing coupled with matrix and blocky borides are primary TiB2phases growing unconstrained in melt.

Key words: TiAl alloy; boride; morphology; growth mechanism