The effects of scandium heterogeneous distribution on the precipitation behavior of Al3(Sc, Zr) in aluminum alloys

Sc-containing Al alloys have excellent mechanical properties, which provide the foundation for their applications. The precipitation of the Al3Sc/Al-3(Sc, Zr) is generally considered to be a key factor for the performance boost. However, the performances of the alloy in different production batches often exhibit unstable and fluctuation, which may be related to the heterogeneous of scandium. Herein, we investigated the precipitation behaviors of Al3Sc/Al-3(Sc, Zr) phases in the Al-0.5Sc and Al-0.5Sc-0.25Zr alloys at 340 degrees C. Results shown that the high scandium-zirconium ratio not only lead to the discontinuous precipitation, but also contribute to the abnormal continuous Al-3(Sc, Zr) precipitation in Al-0.5Sc-0.25Zr alloy. The morphology of abnormal Al-3(Sc, Zr) is similar to the common secondary Al-3(Sc, Zr) phase with a coffee-bean like morphology. With the aid of ThreeDimensional Atomic Probe (3DAP), the core-shell structures of Al-3(Sc, Zr) phases are quantitatively analyzed. In the shell layer of abnormal Al-3(Sc, Zr) phase, the atomic concentration ratio of Sc to Zr is much higher than the common continuous precipitated Al-3(Sc, Zr) phase. The abnormal Al-3(Sc, Zr) phase may be one of the key factors for the structure heredity of Sc-containing Al alloys.

Automated summary

Sc-containing Al alloys with Al3Sc/Al-3(Sc, Zr) precipitation have excellent mechanical properties. An abnormal continuous precipitation of Al-3(Sc, Zr) phase can be caused by a high scandium-zirconium ratio in some cases, and it may be a key factor for the structural heredity of Sc-containing Al alloys.