Growth Morphology of Eutectic under Unidirectional Solidification in Al-13Si Alloys Containing Strontium and Magnesium

摘要

Effects of Sr and Mg additions on the growth morphology of Al-Si binary eutectic were investigated in a directionally-solidified Al-13%Si alloy. With an increase of Sr and Mg additions, the growth morphology of eutectic grains changes from typical planar morphology, through cellular and a mixture of cellular/columnar, to equiaxed grain structure in the nonfaceted-faceted Al-Si binary eutectic system. As a result, the amount and distribution of microporosity in the resultant microstructures is also affected. The influence of Sr and Mg on the growth morphology of Al-Si binary eutectic can be explained with the classical constitutional supercooling theory on planar interface stability of eutectic growth.