Studies on Chemical and Ion Etchings of Polycrystalline Metals

The specimen surfaces bombarded with Ar+ ions prepared from OFHC, Nb base super-conducting alloy ingots and multi-layered magnetic alloys plated on thin wire of Cu-3wt % Ag alloy were observed mainly with optical and electron microscopes, interference microscope and differential interference microscope to discuss the distinction between chemical and ion etchings. The results of experiments were as follows: (1) In both of chemical and ion etchings of OFHC specimen, a clear step was observed between two neighboring crystal grains having different crystal orientations. In the chemical etching, no change was seen in the height of step with the lapse of time. (2) In the chemical etching, marks of slip lines, having been produced by plastic deformation, were too indistinct to be observed. While, in the ion etching the marks, having be lessened by electropolishing, reappeared. (3) Typical nodular structures were observed by chemical etching of Nb-base super-conducting alloy ingots. While, the nodular structures disappeared by ion etching, showing preferential removing of Zr and Ti from the alloy. (4) The multi-layered structure, mainly consisting of magnetic alloys, could not be clearly observed by the conventional chemical etching; but, it could be clearly observed by application of the ion etching.