Structural hardening of lead-cadmium-tin alloys for battery's grids.

It is known that lead-cadmium alloys are very well hardened by a continuous precipitation and a discontinuous transformation, whereas lead-tin alloys present a discontinuous precipitation with a weak hardening effect. In these binary alloys, there is precipitation of either cadmium or tin. This study is focused on the type of precipitation, the nature and the morphology of the precipitated phases, and the intensity of hardening in ternary Pb-Cd-Sn alloys. The reequilibration of supersatured Pb-Cd-Sn alloys was studied by different experimental methods: hardness measurements, optical and electron microscopy, electron microprobe. Two structural states were considered: as-cast alloy, rehomogenised alloy. The alloys contain 1.5 wt% Cd and 0.25, 0.5 or 1.25wt% Sn. The explored temperatures were 20, 80 and 100 degrees C. The corresponding aging and overaging are similar to those of the Pb-Cd alloys. The presence of tin has a retarding effect on the structural hardening process.