稀土铸铁定向凝固过程石墨形态的转化

本文用金相显微镜和扫描电镜对定向凝固试样中各种石墨形态的转化进行了观察分析。结果表明:随着残留稀土元素含量的下降,石墨形态会出现球墨→蠕墨→片墨的序列转化,并且,这些转变都是一个连续的过程,无需重新形核。电子探针分析结果表明:在蠕虫状石墨的生长前沿有稀土元素Ce的富集。此外,还对冷却速度和稀土元素含量对石墨形态的交互作用进行了分析。结果表明:在不出现白口的条件下,提高冷却速度(即凝固速度)与增加稀土元素含量有相似的效果。

The Morphology Transition of Graphite during the Process of Unidirection Solidification of the RE TreatedCast Iron

The transitions between the forms of the graphite in the unidirectional solidifiction specimens were observed and analysed by means of the Optical microscopy and scanning electron microscopy(SEM) .The results indicate that the graphite morphology could transform progressively from a nodular one to c/v one and then to a flake one as the retained Rare-Earth element decresing. This process is a continous one and need not renucleat-ing.The result of electron probe (WDS)analysis indicates that there is an enriched zone of Ce in the growth front of c/v graphite. Moreover, the mutual effection between RE concentration and cooling rate on the morphology was analysed.The result indicates that the raising of thecooling rate is similar to the increase of the RE concentration.