稀土元素对过共晶铸铁中石墨一次结晶的作用及其机理

从过共晶铸铁中石墨形态的考察入手,用液淬和热解石墨生长的方法,研究了稀土元素对过共晶铸铁石墨一次结晶的作用。结果指出,不论初生或共晶石墨都可蠕化,而石墨蠕化是稀土元素作用的结果,奥氏体的作用是次要的。但石墨发生弯曲的主要原因是奥氏体而不是稀土元素。首次提出了光滑界面晶体生长时,螺旋台阶增殖的观点,并给出了两个基本增殖模型,据此解释了石墨结晶形貌问题。

EFFECTS OF RARE EARTH ELEMENTS ON PRIMARY CRYSTALIZATION OF GRAPHITE AND ITS MECHANISM IN HYPERUTECTIC CAST IRON

Starting with examination of the particular morphology of intermediate graphite in hypereutectic cast iron, the effect of rare earth alloys on crystalization of graphite in hypereutectic cast iron was investigated with the technique of liquid quenching and pyrolytic graphite seed growth in cast iron melt saturated with carbon. It was found that both hypereutectic and eutectic graphite can be vermiculated by adding rare earth alloys, whereas the action of austentite is not necessary. However the bending of graphite is primarily due to the action of austenite, the rare earth elements are less important. A new viewpoint was first suggested that multiplication of spiral steps would take place in process of smoth interfaced crystal growth, and two basic models were given. Based on two models the crystal morphology of graphite was explained.