Observation of the first stages of discontinuous transformation in PbCa alloys used for lead batteries

Abstract The structure of PbCa alloys undergoes progressive changes at room temperature. A study of the early stages of their aging by optical microscopy has not been accomplished because the time required to prepare the samples is too long. This article describes a preparation technique consisting of an electrolytic polishing step at a temperature of −50°C, followed by repeated chemical etching with appropriate reagents. The technique allowed us to examine the quenched structure, to pinpoint the sites of discontinuous transformation (grain boundaries, intragranular sites, and domain walls), and to follow the early stages of growth in the transformed area as well as subsequent development. Transformation areas appearing during slow cooling could be distinguished from those appearing after cooling. The results obtained using this technique corroborate evidence obtained by other methods for these transformations.