本文用碳酸稀土直接变质共晶铝硅合金,取得了满意的效果。通过对不同变质剂加入量下共晶硅形貌的观察及特定部位的微区成份分析,探讨了稀土变质铝硅合金的机制。要使共晶硅成为密集分枝的扭曲纤维状变质形态,稀土首先要在硅相中触发足够数量的孪晶,并在生长界面前沿造就合适的稀土富集层。 In this paper, rare earth carbonated modified eutectic Al-Si alloy, and achieved satisfactory results. Through the observation of morphology of eutectic silicon and the analysis of the composition of the micro-regions in specific sites, the mechanism of rare earth modification Al-Si alloy was discussed. To make eutectic silicon become densely branched twisted fibrous state, rare earths must first trigger a sufficient number of twins in the silicon phase and create a suitable rare earth-rich layer at the front of the growth interface.