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 α2phase, 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.