Elemental preference and atomic scale site recognition in a Co-Al-W-base superalloy.

Using state-of-the-art atomic scale super energy dispersive X-ray spectroscopy and high angle annular dark field imaging this study reveals the elemental partitioning preference between the γ' and γ phases in a Co-Al-W-Ti-Ta superalloy and the site preference of its alloying elements in the ordered L12 γ' phase. A semi-quantitative analysis of atomic column compositions in the ordered L12 γ' structure is provided. Co atoms were found to occupy the {1/2, 1/2, 0} face-center positions whereas Al, W, Ti and Ta atoms prefer to occupy the {0, 0, 0} cube corner positions in the L12 γ phase. These findings agree well with predictions from first principles simulations in the literature.