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采用稀土元素Nd对原位自生Mg2Si/Al复合材料进行变质处理;利用X射线衍射仪和金相显微镜等方法分析了变质前后合金的微观组织;并对Nd的变质机理进行了分析。结果表明:在原位自生Mg2Si/Al复合材料中添加适量的Nd对初生和共晶Mg2Si能够同时起到良好的变质作用。当Nd含量达到0.5%时,初生Mg2Si的形貌由粗大的树枝状或多角形块状转变为细小的块状,平均尺寸由47.5μm减小到13.0μm;共晶Mg2Si也由粗大的片状转变为细小的片状、纤维状或点状。其变质机理可能与Nd元素富集于Mg2Si相固-液界面降低Mg2Si相与Al液间界面张力及由富集所引起的成分过冷有关。
The rare earth element Nd was used to modify the in-situ Mg2Si / Al composites. The microstructure of the alloy before and after metamorphism was analyzed by X-ray diffraction and metallographic microscope. The mechanism of Nd metamorphism was also analyzed. The results show that proper addition of Nd to in situ Mg2Si / Al composites can play a good role in both primary and eutectic Mg2Si. When the content of Nd reaches 0.5%, the morphology of primary Mg2Si changes from coarse dendrites or polygons to lumps, and the average size decreases from 47.5μm to 13.0μm. Eutectic Mg2Si also consists of coarse flakes Into a small flake, fibrous or punctate. The metamorphic mechanism may be related to the enrichment of Nd element in the solid-liquid interface of Mg2Si phase and the decrease of the interfacial tension between Mg2Si phase and Al liquid and the overcooling of components caused by enrichment.