Formation and Relative Stabilities of Core-Shelled L1₂-Phase Nano-structures in Dilute Al–Sc–Er Alloys

Chaomin Zhang^1,2，Yong Jiang²，Xiuhua Guo^1,3,4，Kexing Song^1,3,5

1. School of Materials Science and Engineering ,Henan University of Science and Technology2. School of Materials Science and Engineering ,Central South University3. Henan Province Key Laboratory of Nonferrous Metal Material Science and Processing Technology4. Collaborative Innovation Center of Nonferrous Metals5. Provincial and Ministerial Co-construction of Collaborative Innovation Center for Non-ferrous Metal New Materials and Advanced Processing Technology

摘 要：First-principles thermodynamic calculations were carried out at the interface level for understanding the precipitation of coherent L1₂-phase nano-structures in dilute Al–Sc–Er alloys. All energetics, relevant to bulk substitution, interface formation,interfacial coherent strain and segregation, were calculated and used to evaluate the nucleation and relative stabilities of various possible L1₂ nano-structures. Only matrix-dissolved solute Er（or Sc） can substitute Sc（or Er） in L1₂-Al₃Sc（or Al₃Er）. The inter-substitution between L1₂-Al₃Sc and Al₃Er is not energy feasible. Ternary L1₂-Al₃（Er x Sc 1. x） precipitates tend to form the Al₃Er-core and Al₃Sc-shell structure with a sharp core/shell interface. Three possible formation mechanisms were proposed and examined. The eff ects of Er/Sc ratio and aging temperature on the relative stabilities of L1₂-phase nanostructures in Al were also discussed.

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