Zone-axis convergent-beam electron diffraction and ALCHEMI analysis of Ti-Al alloys with ternary additions

A new statistical method for atom location by channelling-enhanced microanalysis is applied to gamma-alpha(2) duplex Ti-Al based alloys containing ternary element additions of V, Cr, Mn, Ga, Y, Zr, Nb, Mo, La, Hf, Ta and W at the 1 at.% level. Incoherent channelling patterns, formed by the variation in characteristic X-ray emission as a function or orientation, are collected from a number of different zone axes from both phases. Comparisons of experimental patterns with calculated maps for various crystallographic sites indicate that the ternary atoms are incorporated substitutionally in the atomic structure of both the gamma and the alpha(2)-phases and do not occupy interstitial sites. The crystallographic site distribution of the ternary elements is determined through chi(2)-minimization techniques, together with quantitative error limits. The structure of the non-stoichiometric alpha(2)-phase is investigated by convergent-beam electron diffraction.