Abstract: The effect of BN addition on the grain size and rnechanical properties of Ti-34.1 wt-%Al alloy was investigated. It has been found that BN is an effective grain refiner for TiAl base alloys, The addition of a small arnount of BN to TiAl can change the coarse columnar grains of as-cast rnicrostructure into the fine equiaxed grains. It has been also determined that Ti-34.1 wt-%Al-1.0 wt-%BN alloy has better mechanical properties and microstructure