Ordering in the sublattices of Fe3Al during the phase transformation B2⇆D03

The temperature dependence of the iron concentrations in the individual sublattices of hyperstoichiometric binary Fe72Al28 and ternary Fe68Al28Cr4 alloys were obtained from X-ray diffraction data measured in a high temperature 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 groups 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, respectively. 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.