Atomic scale chemistry of α₂/γ interfaces in a multi-component TiAl alloy

We report on the distribution of micro-alloying elements in a multi-component TiAl-based alloy. The specimen contains 3 at.% Nb, 1.5 at.% Cr, 0.5 at.% Mn, 0.6 at.% (W + Hf + Zr), and 0.2 at.% each of B, C, and O. The distributions of all micro-alloying elements with respect to the heterophase interface between α₂ and γ lamellae are analyzed with a three-dimensional atom-probe (3DAP) microscope. All the elements partition except boron, which resides primarily in boride precipitates. Oxygen, C, Mn, and Cr partition to the α₂-phase, whereas Nb and Zr partition to the γ-phase. Both W and Hf exhibit excess concentration values within ca. 7 nm of the lamellar interface in the α₂-phase, and their near interfacial excesses are 0.26 and 0.35 atoms nm^-2, respectively.