Morphology and formation mechanism of primary TiB₂ in TiAlB alloys

Microstructure and phase constitution of Ti-53Al-xB alloys produced by an in-situ growing method were investigated by X-ray diffraction and scanning electron microscope respectively. The results show that these alloys are composed of TiAl and TiB₂ phase, while the primary hexagonal prism TiB₂ exhibits pyramidal protrusion or rod shape dendrites on its basal facets. The protrusions or rods exhibit facets which parallel to that of the primary TiB₂. The solid-liquid interface stability of primary TiB₂ was discussed and the formation mechanism of the morphology of primary TiB₂ was investigated.