稀土在Al-Si合金中的分布及其对变质过程的影响

Distribution of Rare Earths in Al-Si Alloys and Their Influence on Modification Process

通过俄歇微探针定点成分分析和X射线粉末照像方法 ,分别对稀土在初生Si颗粒和共晶组织两相中的存在和分布特点进行了研究。结果表明 :稀土变质剂使初生Si颗粒由开花状板片变成多面体颗粒状。产生这种变化的原因是与稀土吸附并阻碍Si相沿孪晶凹坑的生长有关 ;在Al Si合金中 ,微量稀土主要存在于Si相 ,在Si相中分布较均匀 ,未发现选择性吸附和明显的浓度偏聚 ;微量稀土变质剂没有明显的形成化合物 ,不形成Si相的异质核心。

The presence and distribution behavior of rare earths in primary silicon particles and the eutectic structure are studied by means of AES and X-ray powder diffraction with result that,owing to the effect of the RE modifying agent,the shape of the Si particles changes from“petals”into“polyhedrons”.This change has much to do with the fact that rare earths are adsorbed on the silicon particles and prevent them from growing along the concave twin-grain slots.Besides,it is unveiled that trace RE are only present in the silicon phase of the alloy,so uniformly that no obvious selective adsorption and segregation can be formed and therefore no obvious formation of compound between Si and RE and heterogeneous cores can be observed.