Evolution of solid-liquid interface morphology of primary TiB₂ in non-equilibrium solidified Ti-Al-B alloys

Ti-Al-B alloys were produced by in-situ synthesis method. The phase constitutions, microstructure of these alloys and the morphology of the primary TiB₂ were investigated by XRD and SEM. The results show that these alloys are composed of TiAl and TiB₂, and the primary TiB₂ is hexagonal prism shape. Growth terraces, pyramidal protrusion, and rod shape dendrites are observed on (0001) plane of primary TiB₂. There are thin flake convexes on plane of primary TiB₂, parallel to (0001) plane of the primary TiB₂. The rod-shaped crystal orientation and thin flake convexes are parallel to primary TiB₂ where they protrude out. The solid-liquid interface morphology of primary TiB₂ during solidification was also investigated. It was indicated that the solid-liquid interface morphology of primary TiB₂ is instable and gradually develops into a complicated interface consisted of a few separated secondary interfaces. These secondary interfaces are facet with the same crystalline orientation.