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

Abstract

Discontinuous reaction of nano-Al3Sc 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-Al3Sc 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-Al3Sc 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-Al3Sc particles on the hardness of Al-Sc alloys were discussed. Finally, the morphologies of these nano-Al3Sc particles were also analyzed.