Discontinuous Precipitation of Nano-Al₃Sc Particles in Al-Sc Alloy and Its Effect on Mechanical Property

Discontinuous reaction of nano-Al 3 Sc particles in Al-Sc alloys is investigated in detail, with a goal of developing high-level Sc-containing Al alloys used for aerospace and aeronautics industry. This reaction is of interest because it generally has a deleterious effect on the mechanical property of materials. Requirements for the occurrence of discontinuous precipitation in this Al-Sc alloy are distinct from the prior investigations of other Al-Sc alloys. It was found that discontinuous precipitation of nano-Al 3 Sc particles occurred widely when the alloys were aged at the intermediate temperature ranges of 300–400 ∘ C, while did not occur at relatively low (250 ∘ C) and high (500 ∘ C) temperatures. The discontinuous precipitation of nano-Al 3 Sc particles can be suppressed by continuous precipitation through controlling the heat treatment process, which helps to control the microstructures of the Al-Sc alloys. Furthermore, the effects of both continuous precipitation and discontinuous precipitation of nano-Al 3 Sc particles on the hardness of Al-Sc alloys were discussed. Finally, the morphologies of these nano-Al 3 Sc particles were also analyzed.

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