Abstract: The Ag-Ge eutectic alloy system was intensively investigated with respect to its solidification characteristics at large undercoolings which were obtained by the B2O3 glass fluxing technique combined with argon protection. Grain size refinement was found in the Ag-15 wt% Ge hypoeuteciic alloy. With inereasing undercoolings the feather-like structure disappeared in the Ag-19wt% Ge eutectic alloy, and even silver slips showed up at sufficient undercoolings. Nevertheless, the fact that germanium had nucleated in preference to silver was indicated by a fine germanium line in the middle of the silver slips. The various morphologies of the germanium phase in the Ag-25 wt% Gehypereutectic alloy including the five-fold symmetry structure were explained by the joint action of high undercoolings (i.e. growth velocities) and density differences. The corpled zone of this alloy system was qualitatively estimated.

Key words: Ag-Ge alloys, nucleation, undercooling, rapid solidification