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 ele ctronic theory of alloys in pseudopotential approximation in order to predict impurity effects on DO3 double-line arrow pointing left and ri ght B2 phase transition temperature and the characteristics of atomic short-range order in Fe3Al-type intermetallics. Impurity elements in F e3(Al, Me) Me-Cr, Si, Ge, Cu, Mn, Zn, V, Nb, Ta, Mo, W, Zr or Hf are c onsidered (up to 1 at.% concentration). The study shows, in agreement with experimental observations in literature, that all impurity elemen ts raise the DO3 double-line arrow pointing left and right B2 transiti on temperature relative to that of the binary alloy. It is further fou nd that impurities of Nb, Ta, Mo, W, Zr or Hf substitute mainly Fe sit es in the Fe3Al (DO3) superstructure and are more effective in increas ing the transition temperature.