钼晶体中的位错线蚀象的研究

实验结果表明,应用甲醇、硫酸、盐酸的混合液为电解浸蚀剂,可以在钼晶体的{100},{111}及{110}面上显示位错蚀斑,而在{111}面及{110}面上同时可以显示出排列成平行线或六方网络的蚀线,这些蚀线被证明为位错线的蚀象。根据观测结果,总结出解释位错线蚀象的经验规律:观测到的蚀象相当于一定深度内位错线在观察面的投影;蚀象的宽度决定于位错线段到原始表面的距离,距离愈远,宽度愈细,类似于一种夸张的光学透视效应,因而根据蚀象就可以直接推出位错线在空间的位置,采用多次浸蚀的方法,对于一些位错空间排列组态的实

A STUDY OF ETCH-FIGURES OF DISLOCATION LINES IN MOLYBDENUM CRYSTALS

Experimental results about dislocation etch-pits on {100}, {111}, and {110} surfaces of electron beam floating zone-melted molybdenum single crystals are described. Electrolytic etching reagents used in this work are mixtures of methyl alcohol, sulphuric acid, and chloric acid. Besides, etch-lines arranged in parallel sets and hexagonal networks are observed on {111} and {110} surfaces, these are interpreted as etch-figures of dislocation lines.An empirical rule for the interpretation of etch-figures of dislocation lines is deduced from observations. Observed etch-figures are projections on observation plane of dislocation lines in the etched layer, its widths depend on the distance between dislocation line-elements and original surface, so that an exaggerated perspective effect is obtained. Hence the arrangements of dislocation lines in space may be deduced directly from observed etch-figures. By means of multiple etching technique, some examples of dislocation arrangements in space are presented.Correspondance between etch-pits and sites of dislocation lines intersecting original surface has been studied. In general, such correspondance is observed by means of an etching-polishing-reetching technique. However, experimental results show that such correspondance may be violated in some cases. For instance, when the angle between a dislocation line and observation plane is less than a critical value (15°-24°), no etch-pit is observed. On the other hand, nodes of dislocation networks after prolonged etching, may be revealed as arrays of etch-pits. The significances of these results on the interpretation of etch-pits figures are discussed.The etch-figure method has been compared with other methods of direct observation of dislocation lines, its merits and demerits are discussed, and it is concluded that the etch-figure methods is superior to all other existing methods in the study of dislocations in metal crystals when the dislocation density is within the range from 10⁴ to 10⁸ cm^-2.