Long range order and vacancy properties in Al-rich Fe3Al and Fe3Al(Cr) alloys

Neutron powder diffraction measurements have been carried out in situ from room temperature to about 100 degrees C in Fe28Al (28 at.% Al), Fe32.5Al (32.5 at.% Al) and Fe28Al15Cr (28 at.% Al, 5 at.% Cr) alloys. X-ray diffraction and TEM studies provided supporting information. The data were analysed to obtain information about the temperature dependence of the DO3 and B2 long range order parameters, the location of the Cr atoms and their effect on the ordering energies, and on the vacancy formation and migration properties in Fe28Al and Fe32.5Al alloys. The location of the ternary alloying addition in DO3 and B2 ordered Al-rich Fe3Al is shown to be consistent with considerations of interatomic bond energies. (C) 1998 Acta Metallurgica Inc.