Abstract
The light-figure phenomena have been observed with chemically etched single crystals of nickel-iron alloys containing 30∼81.5 percent nickel, and the suitability of the observed light figures for determining crystal orientations and the crystal planes developed by etching have been examined. All of the etchants tested, namely, aqua regia plus water (1:1), saturated aqueous solution of ferric chloride at boiling and room temperatures, saturated aqueous solution of ferric chloride plus concentrated hydrochloric acid (95:5), and saturated aqueous solution of ammonium persulphate at boiling temperature, produced distinct light figures, suitable for the orientation determination, for all of alloy crystals, among which boiling saturated aqueous solution of ferric chloride was found most suitable. It has been found that the most close-packed {111} faces, their vicinal faces, and high-index crystal faces inclined 10∼15° to {100} and {110} planes are developed by etching.
