Distribution of the transition metals V, Nb, Cr and their influence on thecomposition of the gamma-phase of TiAl base alloys

Two-phase alpha(2)/gamma TiAl alloys without and with additions of the tran sition metals Cr, Nb and V were investigated:by atom-probe field ion micros copy (APFIM). Cr and V atoms are more homogeneously distributed in the gamm a-phase than Nb atoms. These preferentially occupy the Ti sublattice and te nd to form a superlattice structure. No similar lattice formation was obser ved in gamma titanium aluminides with Cr and V additions. In comparison to a binary TiAl alloy the concentration ratio c(Al)/c(Ti) in the gamma-phase is only slightly changed by V and Cr additions, but remarkably increased by Nb additions. The gamma-phase of the TiAlNb alloy revealed more brittle th an those of the conventional binary alloy and TiAl based alloys with additi on of Cr and V.