The structure of nitrogen-supersaturated ferrite produced by ball milling
The structure of nitrogen-supersaturated ferrite produced by ball milling
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DOI：
10.1080/14786430802322198
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发表时间：
2008-04
影响因子：
1.6
通讯作者：
J. Aufrecht;A. Leineweber;J. Foct;E. J. Mittemeijer;E. J. Mittemeijer
中科院分区：
文献类型：
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作者：
J. Aufrecht;A. Leineweber;J. Foct;E. J. Mittemeijer;E. J. Mittemeijer
通过球磨α-Fe和ε-Fe 3 N1. 08的各种粉末混合物制备了氮在铁素体（bcc）中的高度过饱和固溶体。采用X射线粉末衍射、高分辨电子显微镜和穆斯堡尔谱仪研究了产物相的微观结构和晶体结构随氮含量的变化。研究发现，随着氮含量的增加，晶粒尺寸减小。观察到过饱和N-铁氧体的X-射线粉末衍射图中的反射的意外位移，这取决于反射的hkl值和氮含量。这些位移不能用体心立方晶胞的四方畸变来解释，但它们与体心立方{211}面上某种类型的堆垛层错的出现是一致的。这一结果，连同一些孤立的面心立方晶体的观察（通过高分辨率电子显微镜）和高氮含量的微应变下降，表明非常规的变形机制在这些材料中低于一定的晶粒尺寸是有效的，导致故障的经典霍尔-佩奇关系机械强化。
Highly supersaturated solid solutions of nitrogen in ferrite (bcc) were produced by ball milling of various powder mixtures of α-iron and ε-Fe3N1.08. The microstructure and the crystal structure of the product phases were examined as a function of nitrogen content using X-ray powder diffraction, high-resolution electron microscopy and Mössbauer spectroscopy. It was found that the grain size decreases with increasing nitrogen content. Unexpected shifts of the reflections in the X-ray powder diffraction patterns of the supersaturated N-ferrites, depending on the hkl values of the reflections and nitrogen content, were observed. These shifts cannot be explained by tetragonal distortion of the bcc unit cell, but they are in accordance with the occurrence of a certain type of stacking faults on bcc {211} planes. This result, together with the observation of some isolated fcc crystals (by high-resolution electron microscopy) and a drop in microstrain for high nitrogen contents, demonstrates that unconventional deformation mechanisms are operative in these materials below a certain grain size, leading to a breakdown of the classical Hall–Petch relation for mechanical strengthening.