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高能离子辐照金属时形成大量的点缺陷,这些点缺陷聚集成位错环。图(a)所示是高压电镜中电子辐照铁形成的尺寸较小的位错环。为确定位错环的类型,首先要确定g·b的符号,然后确定位错环平面的倾斜方位,由于这些位错环尺寸较小,化透射电镜的实际观察中要确定位错环的倾斜方位是较困难的。作者在观察铁中的位错环时,先倾动样品获得[111]晶带轴的电子衍射花样,然后用不同的反射g观察位错象,分析观察的结果确定其柏化矢量b,再由b·B的符号确定位错环的类型。对于体心立方结构的铁,其位错的柏化矢量b为1/2<111>类型,即可能有八个方向,由于用g_1=[110]观察时位错象消失,所以g_1·b=0,再用g_2=[101]观察,位错象不消失,则g_2·b≠0,那么可以判定此位错环的柏化矢量为1/2[111]
High energy ions irradiate the metal to form a large number of point defects, these point defects aggregate into dislocation loops. Figure (a) shows the smaller size dislocation loops formed by electron-irradiated iron in a high-pressure electron microscope. In order to determine the type of dislocation loops, we first determine the sign of g · b and then determine the oblique orientation of the plane of the dislocation loops. Due to the small size of these dislocation loops, the actual observation of the TEM determines the tilt of the dislocation loops Orientation is more difficult. When observing the dislocation loops in the iron, the sample was first tilted to obtain an electron diffraction pattern of the [111] crystal axis, and then the dislocation image was observed with different reflection g to analyze the result of the observation to determine its cyromazine b and then The sign of b · B determines the type of dislocation loop. For a body-centered cubic structure of iron, the disordered bovine vector b is of the type 1/2 <111>, that is, there may be eight directions. Since the dislocation image vanishes when g_1 = [110] is observed, g_1 · b = 0, and then observed by g_2 = [101], the dislocation image does not disappear, then g_2 · b ≠ 0, then the disordered ring can be judged to be 1/2 [111]