蠕虫状石墨铸铁的结构

本文对蠕墨铸铁进行深腐蚀和热氧腐蚀，并用扫描电子显微镜进行观察研究，揭示了蠕虫状石墨的三维立体形貌和内部晶面取向特征。通过共晶团腐蚀，观察了这种铸铁的共晶团数量和结构特点。结果表明，用各种含有稀土元素的变质剂处理均可得到蠕虫状石墨，其端部具有球状石墨的生长特征，在同一共晶团内部，各蠕虫石墨片间互相联系，这又类似于片状石墨。热氧腐蚀试验表明，蠕虫状石墨端部（0001）面沿圆周方向分布，呈年轮状排列。在枝干分部，则（0001）面沿着枝干方向分布，但其方向变化频繁，呈多晶体。据此，作者提出了蠕虫状石墨晶面取向的模型。蠕墨铸铁的共晶团数量介于灰铸铁和球墨铸铁之间，共晶团的结构也兼有片状石墨和球状石墨两者共晶团的特征。为此，作者也提出了相应的模型。

MICROSCOPIC STRUCTURE OF VERMICULAR GRAPHITF CAST IRON

It has been observed that specimens was treated with deep-etching and thermal-oxidation etching processes to make use of scanning electron microscope. So that the three demensional stereo morphology and orientation of crystal of vermicular graphite may be revealed. The number and structure of the eutectic cells in ver micular graphite cast iron were observed also with both optical microscope and scanning electron microscope.It was demonstrated that vermicular graphite may be obtained in cast iron treated with modifying agent in which the rare earth elements were involved; the growth at the end of it was similar to the spheroidal graphites It was also similar to flake graphite because it was connected each other in same eutectic cell. With the thermal oxidation process it was revealed that the (0001) plane was arranged along to thecircumference at the end of vermicular graphite. So that there are annual ring structure at it. The (0001) plane at the branches was a anged along to the longitudinal: and the orientation of it changed freguently So that the vermicular graphite was polycrystalline. As mentioned abore the model of the crystal plane orientation of vermicular graphite was drown by authors.Both the size and the number of the eutectic cell in vermicular graphite iron was intermediate between the flake and spheroidal. And the structure of it has common characteristic both of flake and of spheroidal also. As stated above the corresponding model was drown by authors.It may be concluded that the properties of vermicular graphite cast iron was entirely consistant with the characteristic on the microscopic structure of it.