Abstract
In this study, the modification mechanism and growth process of Al3(Sc, Zr) particles in as-cast Al-Si-Mg-Cu based alloy with addition of
Sc and Zr were systematically investigated. It was found that 0.57 wt-%Sc addition caused a significant refinement in the average grain size
of the investigated alloy, which brought about a remarkable transformation in as-cast microstructure, from thick dendritic shape to fine
equiaxed structure. A large amount of primary Al3(Sc, Zr) particles with the dimension of around 5-6 μm were also observed within the
equiaxed grain. Due to the identical orientation and similar crystal structure between primary Al3(Sc, Zr) particles and α-Al matrix, the
primary particles always served as heterogeneous nucleus for the α-Al matrix. In addition, these cusped cubic primary Al3(Sc, Zr) particles
showed triangle, star, rhomboid morphologies are generated from sectioning the particle in (111), (100) and (110) planes, respectively.
Particularly, the typical eutectic structure which contained odd number-layer (Al3(Sc, Zr)+α-Al+ +Al3(Sc, Zr)) was observed within the
investigated particles.
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