Ordering in the sublattices of Fe3Al during the phase transformation B2 <-> D0(3)

The temperature dependence of the iron concentrations in the individual sub lattices of hyperstoichiometric binary Fe72Al28 and ternary Fe68Al28Cr4 all oys were obtained from X-ray diffraction data measured in a high temperatur e vacuum chamber during linear heating around the phase transformation B2<- >D0(3). A method for the processing of the diffraction pattern based on the splitting of the diffraction lines of the structure D0(3) into three group s is presented. Applying this method it was found that the structure B2 was not well developed in both samples. The maximum value of c(C) approximate to 0.8 gives S-B2 equal to 0.4 and 0.3 for binary and ternary alloy, respec tively. The D0(3)-order was not well developed too, because structure D0(3) arises from the structure B2. D0(3)-ordering, i.e. redistribution of atoms within the sublattices A and B, is given only by the total number of iron atoms in these sublattices before the phase transformation B2<->D0(3). (C) 1999 Elsevier Science Ltd. All rights reserved.