Evolution of solid-liquid interface morphology of primary TiB_2 in non-equilibrium solidified Ti-Al-B alloys

摘要

Ti-Al-B alloys were produced by in-situ synthesis method. The phase constitutions, microstructure of these alloys and the morphology of the primary TiB_2 were investigated by XRD and SEM. The results show that these alloys are composed of TiAl and TiB_2, and the primary TiB_2 is hexagonal prism shape. Growth terraces, pyramidal protrusion, and rod shape dendrites are observed on (0001) plane of primary TiB_2. There are thin flake con vexes on plane of primary TiB_2, parallel to (0001) plane of the primary TiB_2. The rod-shaped crystal orientation and thin flake convexes are parallel to primary TiB_2 where they protrude out. The solid-liquid interface morphology of primary TiR_2 during solidification was also investigated. It was indicated that the solid-liquid interface morphology of primary TiB_2 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.