The microstructure evolutions of Al-Mg-Si alloy with elements La, Ce, and Er were studied by optical microscopy, scanning electron microscopy, and transmission electron microscopy. The conductivity and mechanical properties of the Al-Mg-Si alloy were tested. The results showed that after adding the rare-earth elements La, Ce, and Er, the amount of precipitation phases within the grains of the Al-Mg-Si alloy decreased, and the precipitation phases migrated towards to the grain boundaries, resulting in coarsening of the grain boundaries. Moreover, rare-earth elements reacted with Si and Fe to form intermetallic compounds precipitated from the matrix, which greatly reduced the presence of Si elemental. The addition of rare-earth elements La, Ce, and Er could improve the conductivity and mechanical properties of the Al-Mg-Si alloy in some degree.
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