The X-ray diffraction method to determine the long range order parameter in binary alloys has been extended to examine the site occupancy of third elements like V, Mn, Zr and Nb and the amount of mutually exchanged Ti and Al atoms in TiAl phase for ternary TiAl-X alloys.
In the present analysis, unknown parameters β_Al and β_X were determined by solving simultaneous equations: β_Al=P+Q×β_X with respect to different P and/Q values where β_Al or β_x represents the amounts of Al or X occupied in the Al site in the TiAl phase, P and Q are the experimentally determined values; the former depends predominantly on the ratio of integrated intensity whereas the latter only depends on the atomic scattering factors in superlattice reflections.
It was turned out that V and Mn atoms are occupied predominantly in the Al site whereas Zr and Nb atoms are occupied in the Ti site; the amount of mutually exchanged Al and Ti atoms decreases with increasing the concentration of V and Mn whereas it decreases at first and then increases for the concentration above 5 at% of Zr and Nb.