过冷对石墨生长形态的影响

采用熔炼方法，研究了Ni-石墨合金在不同冷却条件下石墨的生长形貌。结果表明：随着过冷度增大，石墨逐渐由片状形态向球状形态转变。提出石墨在生长过程中由结晶潜热引起棱面与基面的温差是影响其生长形态的重要因素。建立了石墨表面温度变化速率与过冷度及界面能之间的数学关系。计算结果表明，在没有杂质元素的影响下，过冷度越大，越利于石墨(0001)基面的生长，随着S，O等元素的增加，石墨棱面的界面能逐渐降低，有利于片状石墨的生长。球化剂Ce，Mg等元素与S，O反应后，重新使石墨棱面的界面能提高，有利于球状石墨的成长。

Influence of Undercooling on Growth Morphology of Graphite

The growing morphologies of Ni-graphite alloy under different cooling conditions were studied by melting method. The results show that with the increasing of undercooling, the morphology of graphite transite from flake-shape to spherical-shape. It was presented that the crystallization latent heat difference between (10 1 0) prismatic plane and basal plane of graphite in graphite growing procedure is an important influencing factor on the growth morphology of graphite. The mathematic relation among the change rate of graphite surface temperature, undercooling and interfacial energy is formulated. The calculation results show that without impurity element, the increment of undercooling promoted the growth of the (0001) basal plane of graphite. While with the increasing of the content of sulfur and oxygen, the interfacial energy of (10 1 0) prismatic plane of graphite decreases, which promotes the growth of the flake graphite. The (10 1 0) prismatic interfacial energy increases again due to the reaction between rare-earth nodularizer of cerium, magnesium and sulfur, oxygen, which favor the growth of spheroidal graphite.