Published online by Cambridge University Press: 06 January 2005
The evolution toward equilibrium of the supersaturated Pb-1.5%Cd-0.15%Ag-1.25%Sn alloy has been studied by various techniques, such as hardness, optical microscopy, scanning electron microscopy and electron microprobe. The explored temperatures are 20 and 80°C. The precipitation hardening mechanisms of this alloy are similar to those of silver-free alloys. The as-quenched structure transforms toward equilibrium in a two stage process. In the first stage, called ageing, two transformations take place at the same time: a continuous hardening precipitation and a discontinuous, incomplete, softening transformation. The second stage is characterized by a discontinuous lamellar reprecipitation. The microstructure of this alloy is characterized by the presence of Ag5Cd8 precipitates and of zones corresponding to the eutectic mixture. The main effect of silver is to increase hardness by about 2 HV.