Abstract: A method based on electronic structure calculation is proposed to predict the substitution behavior of elements in ordered intermetallics. The electronic structure of 20 alloying elements in TiAl is calculated using the DV-Xα cluster method The bond orders between alloying elements and surrounding atoms, Bo_Ti,Bo_Al, are used as parameters. Two lines on the Bo_Ti-Bo_Al diagram separate the elements into three groups. The elements located outside of the two lines substitute either Ti or Al atom regardless of the composition of TiAl. The substitution behavior of elements between the two lines will be affected by the Ti/Al ratio and the amount of alloying elements added Substituting sequence in multi-element alloy is discussed The prediction based on this method agrees well with the experimental results.

Key words: substitution behavior, site occupancy, intermetallic compound, TiAl, electronic structure