‘Sub-Grains’ and Etch Figures in Lead

Abstract

IN the course of a recent investigation into the ageing characteristics of lead–antimony alloys¹, microscopical examinations of a range of aged specimens were carried out and recrystallized areas were observed in a number of the specimens which had been strained prior to ageing. The specimens had been prepared by the normal metallographic techniques of grinding and polishing and had been etched in Worner and Worner's reagent² to disclose the extent of precipitation. In a number of the specimens the precipitated antimony was cleared from the surface by a brief immersion in concentrated nitric acid (s.g. 1.42) and subsequent examinations showed the recrystallized areas to be covered with networks of fine lines producing an appearance of sub-grains, similar to that due to polygonization, which had been absent from the specimens prior to the nitric acid treatment.