An in situ Al-matrix TiB particle (10-50 mu m size, similar to 10 vol %) composite was formed by stir casting at 900 degrees C a slurry containing liquid aluminium (2024), TiO2, KBF4 and Na3AlF6 in the weight ratio 13.5:4:1:4. The reactions among these ingredients resulted in TiB, together with small amounts of TiB2 and TiAl3. The composite (after T-6 heat treatment, but no secondary processing) exhibited tensile strength 270 MPa, modulus 91 GPa and ductility 8%.