2 consisting of a 80al 5ga 5zn 5sn 5bi alloy in its as cast condition the non uniform distribution of the composition revealed by the various maps of fig1 reveals that certain alloying elements such as tin and bismuth have most noticeably exceeded their solubility limit in solid aluminum due to solid solubility limits these alloying elements have segregated during the slow air cooling of the cast process to internal surfaces boundaries such as the interdendritic spacings the non homogeneity of the composition at the microscopic level is well quantified in table 3 with ixrf eds spot analyses of the chemical compositions at selected locations of the microstructure e g aluminum grains or phases along grain boundaries for the alloy of fig1 gallium is quite uniformly distributed even at the microscopic level and that is in contrast with tin and bismuth that are nearly exclusively encountered along the internal boundaries based upon the results for this alloy in table 2 the fact that tin and bismuth did essentially not mix with aluminum as they are segregated to boundaries promoted the formation of micro galvanic cells in particular between aluminum tin and bismuth also the fact that approximately 5 to 8 percent gallium remained in solid solution in the aluminum table 3 appears to be a factor to prevent passivation or the formation of a protective layer at the surface of the composition gallium in solid solution trapped in the aluminum lattice also reduces the galvanic corrosion potential as proven by the results of table 2 for the binary aluminum gallium alloy al u2014 ga in addition to 5 to 8 percent gallium approximately 2 percent zinc.