Fe_3Al合金B2有序化过程的场离子显微镜观察

FIM OBSERVATION ON B2 ORDERING IN Fe_3Al ALLOY

对不同有序度下的Ｂ２结构Ｆｅ_３Ａｌ进行了场离子显微镜（ＦＩＭ）研究．不论是否达到最大Ｂ２有序度，ＦＩＭ像的总体规则程度均很差，难以由常规方法得到有序度的信息．但是，ＦＩＭ像中的局部区域，也即〈１００〉极的场蒸发过程却提供了Ｂ２有序度的信息，通过对其连续观察发现，Ｆｅ_３Ａｌ的Ｂ２有序化进程在纳米尺度范围是不均匀的．从〈１２０〉极上得到的结果与〈１００〉极一致．这种一致性再一次证实了“Ａｌ成像，Ｆｅ不可见”的观点是正确的．

Fe_3Al alloys in B2 structure with different order degree are studied by means of field-ion microscope (FIM). Whether or not the maximum B2 order degree got, the total regularity of the FIM image is so poor that it is even difficult to know the B2 order degree qualitatively. However, the local evaporation characters of the〈100〉pole contain the information of B2 ordering. By successive examination, it is discovered that the evolution of B2 ordering is not homogeneous in nano-scale. The result got from the〈120〉pole is the similar to that from the〈100〉pole. This consistence confirms once more the conclusion'only the Al atoms contribute to the image while the Fe atoms are invisible' .Correspondent: ZHI Rentao, professor, Deportment of Materials Physics, University of Science and Technology Beijing, Beijing 100083