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).