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Rapid solidification of Cu-Pb monotectic alloys has been accomplished during free fall in a 3 m drop tube. Bothmacrosegregated and uniformly dispersed structures are observed in Cu-40 wt pct Pb alloy droplets, whereas dropletsof composition Cu-64 wt pct Pb exhibit only macrosegregation morphologies. The microstructures are stronglydependent on droplet size. The higher undercooling tends to facilitate liquid phase separation and results in moreextensive macrosegregation in smaller droplets. There exists a pronounced tendency for the Pb-rich liquid to occupythe surface of the droplets of both compositions, resulting from the quite lower surface tension of the Pb-rich phaseand causing a Pb-rich layer at the surface of the solidified droplet. The nucleation of monotectic cells in the Cu-40 wt pct Pb droplets with dispersed structures preferentially occurs at the droplet surface. A single nucleation eventtakes place more frequently as droplet size is reduced.