Abstract: According to the E E T, the valence electron structures of the various phases in Ti-Al-Nb alloys are calculated. Effect of Nb on embrittlement of Ti3A1 is analysed in view of uniform deforming factor a, cleave enery Gc and dislocation movement. Analysis shows that Nb makes α2 partly disordered and novel phase toughened, and then a and Gc bigger. Ti-Ti bond weakened and dislocation slip increased in basis plane. As a result, embrittlement of Ti3A1 alloyed with Nb is naturally improved.

Key words: Embrittlement, Ti3Al Ti3Al-Nb, Valence electron structure