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.