Site occupation of Nb, V, Mn and Cr in γ-TiAl

The lattice site occupation characteristics of Nb, Mn, vanadium, and Cr in gamma -TiAl (Al > 50 at.% Al) have been studied by channeling enhanced X-ray microanalysis in the TEM(ALCHEMI) using both the planar and axial channeling geometries. It has been found that Nb and V preferentially substitute for Ti, whereas Mn occupies the Al sublattice. Chromium showed no preferential substitution. Furthermore, both planar and axial cases gave consistent results. Although delocalization effects may restrict axial channeling for absolute quantitation if proper corrections are not incorporated, reliable quantitative site preference information could also be obtained by axial channeling analysis. Since channeling effects are enhanced in the axial geometry, this technique has potentially greater sensitivity for determinations of site occupancy when the amount of solute X is low.