Abstract
The multiple microalloying influences of Si & Sc on the aging behavior and thermal stability of Al-4Cu-0.5Mg alloy were systematically studied. The result revealed that precipitation evolution of Al-4.0Cu-0.5Mg alloy was closely relevant to the content of Si. Si enhanced formation of the Q′ phases serving as nucleation sites for the θ′-Al2Cu phases, resulting in a refined distribution of θ′ phases. Al-4.0Cu-0.5Mg-0.40Si-0.1Sc alloy is a combination of high strength and outstanding heat resistance because of the finer and denser Q' & θ′ as well as the segregational structure of Mg, Si and Sc. Especially, the Sc-segregation at the interfaces of θ'/Al is essential to stabilize the microstructure of θ′ precipitates at high temperatures. The solute segregation of Sc atoms in θ′ phases inhibits their coarsening rate. The high-temperature strength of Al-Cu-Mg-Si-Sc alloy are increased dramatically compared with that of typical heat resistant 2618 aluminum alloy.
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