Analysis of electron structure of γ/α2 phase boundaries in ternary TiAl intermetallics
(1.黑龙江省哈尔滨市哈尔滨工业大学材料科学与工程学院
2.School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China)
2.School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China)
Abstract: The electron structure of γ/α2 phase boundaries in lamellar colonies in Ti-47Al-2M(M=Nb, Cr, V) (mole fraction, %) alloys was theoretically investigated by Empirical Electron Theory of Solid and Molecules (EET) and the bond-length-difference (BLD) method. Average-Atom-Model was employed to calculate valence electron structure of TiAl intermetallics containing site substitution elements. 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 of γ/a2 interface is continuous(△ρ<10%). Furthermore, it is found that adding alloying elements (including Nb, Cr, and V) can improve the electron density (ρ) of γ/a2 interfaces, and decrease the electron density difference(△ρ) of γ/α2 interfaces. Adding V element decreasing △ρ is more remarkable than other site substitution elements. According to electron structure study of γ/α2 interfaces in Ti-47Al-2M alloys, the added elements improve mechanical properties of the alloy in the following order: V>Cr>Nb.
Key words: TiAl alloy; alpha phase; gamma phase; electron structure; phase boundaries; electron density