Precipitation of L12-phase nano-particles in dilute Al-Er-Zr alloys from the first-principles

Interface is fundamentally critical for understanding nano-phase precipitation in alloys. Here we present an interface-level first principles study on the formation of coherent L1(2)-phase nano-precipitates in dilute Al-Er-Zr alloys. Bulk substitution and interface energetics, including interface formation energies, coherent strain energies, and solute segregation energies, were all calculated for evaluating the nucleation and structural stabilities of various possible L1(2)-phase nano-structures in Al. The following insights were obtained. Only matrix-dissolved solutes can strongly substitute the X sublattice sites in L1(2)-Al3X. The Al3Er(L1(2))/Al3Zr(L1(2)) interface has nearly zero formation energy. Zr segregation to the Al/Al3Er(L1(2)) interface is in favor of forming a Zr-rich shell. Further analyses by combining with the classic nucleation theory revealed that ternary L1(2)-Al-3(ErxZr1-x) precipitates tend to form the Al3Er-core + Al3Zr-shell structure with a sharp core/shell interface. The effects of the Er/Zr ratio and temperature on the relative stabilities of these L1(2)-phase nano-structures in Al were also discussed.