Effect of silicon on grain refinement of aluminum produced by electrolysis

The influence of various silicon contents on the grain refinement and crystal morphology of pure aluminum and the Al-based alloy with low titanium content produced by electrolysis is comparatively investigated. The nucleation behavior and crystal morphology are studied with SEM and the nucleants are detected by EDS. The Al-based alloy shows better grain refinement response to silicon content, especially to high silicon content. The alpha-Al crystal morphology remains fine equi-axed structure even though silicon content of the Al-based alloy increases to 5%. This better grain refinement should be attributed to the potential nucleants. All the nucleants might be in the type of TiAl3 or Ti(Al1-X, Si-X)(3), but the atomic fraction of silicon, X, might increase with increase in silicon content of the alloy. The increases of macro-grain grade and micro-grain size with silicon content might be attributed more to the change of phase structure than to the change of alpha-Al crystal morphology.