Abstract: The valence electron structure ofγ/α2 phase boundaries in lamellar colonies in Ti-47Al-2M (M=Nb, Cr, V) (at. pct) was investigated by empirical electron theory of solid and molecules (EET) and its bond-length-difference (BLD) method. On this basis, the boundary condition of electron movement was employed in the improved Thomas-Fermi-Dirac (TFD) theory to decide the continuity of the electron density of the lamellar colonies interface and it is found that ofγ/α2 interface is continuous. Furthermore, it is found that adding alloying elements (including Nb, Cr, and V) can improve the electron density ( ρ ) ofγ/α2 interface, decrease △ρ ofγ/α2 interface. With the electron structure analysis together with properties analysis, the effect mechanism of alloying elements (Nb, Cr, V) improving mechanical properties was explained.

Key words: TiAl based alloy, Valence electron structure, Phase boundaries, Site occupancy