First Principles Insight into L12 Precipitate Formation in Al-Zr Alloys

The nucleation of coherent L12 precipitates in aluminum alloys is investigated by first-principles supercell modeling, with density functional theory (DFT) calculations in the generalized gradient approximation, employing a plane wave basis set and pseudopotentials. Distance-resolved solute–solute interaction maps were obtained for Zr in Al, revealing a strong energetic preference for the 2nd coordination shell, consistent with the atomic arrangement in the metastable L12-Al3Zr phase. Stepwise cluster assembly shows a linear stabilization energy gain, while configurations corresponding to the equilibrium D023 structure are unfavorable at early nucleation stages. Similar 2nd-shell attraction was confirmed for Sc, Ti, and Hf, in contrast to V, Cr, and Cu, which lack strong ordering tendencies. These results provide atomistic insight into precipitate formation pathways and establish predictive criteria for identifying alloying elements with a high propensity to form thermally stable, coherent L12 phases in aluminum alloys.