Micromorphology and distribution characteristics of IIR needles in TIB/Ti-Al composites

The microstructure and phase constituent of TiB₂Ti-Al composites prepared by XD^TM were investigated by XRD, SEM and TEM. It was found that there exists a flake convex facets with 0.2 μm a lower than thickness whose length reached up to 4 μm on the surface in {101̄0} facets perpendicular to [0001] orientation of TiB₂ needles, and the orientation of the convex facets is parallel to that of TiB₂ needles. TiB₂ needles, which exists in cruciate or radicalized form, were dispersed at α₂/γ lamellar matrix. The Al-rich and Ti-rich layers and heterogeneity in supersaturation solution at solid-liquid interface resulted from non-equilibrium solidification may keep solid-liquid interface stable to result in the formation of the structure characteristic of the TiB₂ needles.