Site Determination of Third Elements in TiAl Compound by X-ray Diffractometry

Abstract

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 (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 TiAl-phase, and P and Q are experimentally determined; the former depends predominantly on the ratio of integrated intensity whereas the latter only depends on the atomic scattering factors in superlattice reflections.
It turned out that V and Mn atoms occupy predominantly the Al site whereas Zr and Nb atoms occupy the Ti site; the amount of mutually exchanged Al and Ti atoms decreases with increasing concentration of V and Mn, whereas it decreases at first and then increases for the concentration above 5 at% of Zr and Nb.