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本文对稀土镁球墨铸铁中石墨球化的机构进行了研究.电子探针分析表明,石墨球中心存在Ce、Mg、S;氧则均匀分布在铸铁表面而不集中在球墨中心,X射线衍射分析证实球墨是以CeS和MgS为核心.计算结果表明CeS或MgS中的Ce或Mg在垂直体心对角线[111],[11(?)],……八个方向呈六方形网状结构.若与石墨的六方网重叠吋,就会有一部分Ce或Mg原子的位置和石墨的碳原子重叠,即共格.由于Ce,Mg与碳电负性差△X较大,则碳原子易被Mg或Ce原子吸引形成石墨六方网状结构堆积在Ce或Mg的六方网上,并沿上述八个方向伸展开去结晶成石墨球.

The formation of spherulites of graphite in cast iron containing Ce and Mgwas studied.X-ray pattern and electron probe showed the presence of Ce in theform of CeS of NaCl B1 type and of CeC_2 of b.c.tetragonal C11a type crystalstructures.On the basis of the lattice constants of CeS,MgS,graphite and CeC_2,the sizes of the hexagonal nets of Ce,Mg and of graphite are calculated.It isfound that certain Ce or Mg atoms in the hexagonal nets planes normal to[111],[111],…are in conformity with the C atoms of the hexagonal nets of graphite.Due to the difference of electronegativities between Ce and C or between Mg andC of graphite,the electrostatic coulombic force from Ce or Mg will attract the Catoms precipitated from the melted liquids of cast iron to deposite as hexagonallayers on layers of graphite along the eight directions[111],[111],…of CeS orMgS.The result is the formation of spherulites of graphite.The conformation theC atoms in CeC_2 with the Ce or Mg atoms in the hexagonal nets of CeS or MgSalong the directions[100],[010],…is also briefly introduced.