Electromagnetic stirring and Sr modification in A356 alloy

The morphology of the change of primary Al phase in A356 alloy by electromagnetic stirring and Sr modification of eutectic Si was investigated. The optimum stirring current for the dendritic structure of primary Al phase to change to the globular state was above 15 A. The average size of primary Al phase with the globular shape was 54 mum. The addition of Sr more than 50 ppm was found to modify remarkably the eutectic Si with the growth of the primary Al. The growth of the Al phase is probably due to the increase of stirring time through the extended mushy zone of the alloy with Sr addition. With the same amount of Sr addition, the eutectic Si size of stirred cast alloy was smaller than that of non-stirred alloy. This is presumed to be because of the morphology change of the eutectic Si particles by the homogenized Sr modification effect through the stirring. (C) 2001 Published by Elsevier Science B.V.