Study of the formation reactions of silver-palladium alloys by grinding and post-milling isothermal annealing

Silver-palladium alloys in the whole composition range have been produced by mechanical alloying using, as metallic precursor, silver and palladium powders prepared in our laboratory by the polyol process. The influence of milling conditions and isothermal annealing on the Ag + Pd mixture was investigated. Two types of mixer-mill, operating either by impact or friction, were used. We established that the reaction mechanism as well as the textural features of the final alloys are strongly dependent upon both the nature of the interactions (impact or friction) and the energy of mechanical strain. Moreover, it has been observed that for high impact energy interactions, the crystalline alloy transforms into an amorphous alloy. These observations can be explained in terms of an equilibrium between the density of defects and heat recovery during the grinding process, with the friction process generating more heat than the impact process.