Structural and compositional evolution of Al₃(Zr,Y) precipitates in Al-Zr-Y alloy

Structural and compositional evolution of Al₃(Zr,Y) precipitates in aged Al-Zr-Y alloy was investigated through atom probe tomography (APT) and transmission electron microscope (TEM) analysis and first principles calculations. The results show that short-bar-shaped D0₁₉-Al₃Y with some Zr atoms dissolved in precipitated at the very beginning of decomposition and worked as heterogeneous nuclei for L1₂-Al₃Zr with spherical morphology after being aged at 400 °C for 2 h. Quasi-static coarsening happened as the aging treatment lasted from 2 h to 200 h. However, distribution of Zr and Y atoms in Al₃(Zr,Y) is nearly uniform and Al₃(Zr,Y) do not have the typical "Al₃RE core-Al₃Zr shell" structure which observed in other RE containing Al-Zr-RE alloys with L1₂-Al₃RE as nuclei. First principles calculations revealed that binding energy between Y and Zr is strong during the growth of Al₃(Zr,Y), which led to the co-precipitation of Y and Zr atoms and attribute to the evolution of Al₃(Zr,Y). - Highlights: •Al₃Y precipitated firstly and then became nuclei for Al₃Zr during aging of Al-Zr-Y. •Al₃(Zr,Y) precipitates do not have the typical "Al₃Y core-Al₃Zr shell" structure. •Strong binding between Y and Zr led to the co-precipitation of Y and Zr atoms.