Condensation of silver–copper alloys in a solid–liquid domain of the phase diagram

An experimental study of silver–copper alloys condensation with a composition entering a liquid–solid domain of the phase diagram is presented. The vapour beams were produced by two effusion cells heated by tungsten resistors and condensed on a tilted molybdenum substrate, regulated in temperature. Condensation durations were chosen to study the successive stages of the film formation. The microstructures of the quenched condensates showed that the mechanisms were similar in the case of copper rich and silver rich domains. At the beginning, droplets of condensation formed. The surface covered with the alloy increased with time. Later on, coalescences of droplets were observed and a film was established. Both droplets and film contained solid particles whose morphology was nodular. The average nodule radius and the number density of particles in the film were determined by image analysis. It was demonstrated that the cube of the average particle radius grew with time and that the number density of crystals was inversely proportional to time. These results were in good agreement with the Ostwald ripening law.