A STUDY OF IMPURITY EFFECT ON ORDERING CHARACTERISTICS OF FE3AL INTERMETALLICS

A study is carried out into energetical and structural characteristics of atomic ordering processes in Fe3Al. The statistico-thermodynamical theory of ordering by a quasichemical method is combined with the electronic theory of alloys in pseudopotential approximation in order to predict impurity effects on DO3 double-line arrow pointing left and right B2 phase transition temperature and the characteristics of atomic short-range order in Fe3Al-type intermetallics. Impurity elements in Fe3(Al, Me) Me-Cr, Si, Ge, Cu, Mn, Zn, V, Nb, Ta, Mo, W, Zr or Hf are considered (up to 1 at.% concentration). The study shows, in agreement with experimental observations in literature, that all impurity elements raise the DO3 double-line arrow pointing left and right B2 transition temperature relative to that of the binary alloy. It is further found that impurities of Nb, Ta, Mo, W, Zr or Hf substitute mainly Fe sites in the Fe3Al (DO3) superstructure and are more effective in increasing the transition temperature