纯铁离子渗氮扩散层中Fe_(16)N_2的透射电镜研究

TEM STUDY OF Fe_(16)N_2 NITRIDES IN THE DIFFUSION LAYER OF ION-NITRIDED IRON

利用透射电子显微镜对纯铁离子渗氮后扩散层中析出的Ｆｅ_１６Ｎ_２氮化物进行了研究.结果表明、纯铁离子渗氮后炉冷过程中，扩散层中析出的Ｆｅ_１６Ｎ_２呈非均质特征．析出形貌为长条薄片状、以α基体的｛１００｝α惯习面、长轴平行于＜０１１＞取向．实验中获得了Ｆｅ１６Ｎ２与α基体在［１００］；［１１１］，［１１０］，［０１１］，［１１３］，［３１１］，［１３３］，［３３１］．［０２１］［２１０］，［１３５］和［３５１］取向的两相电子衍射谱，二者之间的取向关系为：＜００１＞Ｆｅ_１６Ｎ_２／／＜００１＞α，｛１００｝Ｆｅ_１６Ｎ_２／／｛１００｝α。选区电子衍射表明，Ｆｅ_１６Ｎ_２的衍谢谱符合体心消光规律，未发现有符合面心消光规律的衍射谱存在．理论分析得出 Ｊａｃｋ－２（ｘ＝０２２２，ｚ＝０．３０６） 结构的 Ｆｅ_１６Ｎ_２与 Ｊａｃｋ－１（ｘ＝０．２５，ｚ＝０．３１２５）结构的

Fe_(16)N_2 nitrides in the diffusion layer of ion--nitrided iron, have been studied with transmission electron microscopy (TEM). Three sets of Fe_16N_2 do not precipitate simultaneously from the diffusion layer, which is different from the normal homogeneous precipitation in Fe-N alloys. The morphology of Fe_16N_2 is ribbon--like lamella, which precipitates from {100}α matrix plane and grows along <011>a direction. The Fe_16N_2 electron diffraction patterns of [100], [111], [110], [011], [113], [311], [133], [331], [021], [210] ,[135] and [351] zone axes, have been distinctly observed. The orientation relationship between Fe_16N_2 and or matrix is <001>Fe_16N_2 // <001>a, {100}Fe_16N_2 // {100}a. The theoretical analysis of diffracted waves shows that, all of the diffraction patterns coming from Jack-1 (x=0.25, z=0.3125) and Jack-2 (x=0.222, z=0.306) structures obey bee extinction rule.