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 thes e binary alloys, there is precipitation of either cadmium or tin. This stud y 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-S n alloys. The reequilibration of supersatured Pb-Cd-Sn alloys was studied b y different experimental methods: hardness measurements, optical and electr on 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 a lloys. The presence of tin has a retarding effect on the structural hardeni ng process.