Erbium　(Er)　has　attracted　considerable　attention　as　a　substitute　to　scandium　(Sc)　for　microalloying.　The　solid　solution　of　Er　and　Zr　decomposes　to　form　a　dispersion　of　secondary　Al-3(ZrxEr1-x)　during　annealing.　This　secondary　Al-3(ZrxEr1-x)　precipitates　improve　strength,　especially　the　elevated　temperature　strength.　In　the　present　paper　we　investigate　the　evolution　of　Al-3(ZrxEr1-x)　precipitate　during　annealing　by　transmission　electron　microscopy　(TEM).　The　Al-3(ZrxEr1-x)　precipitates　nucleate　homogeneously　at　lower　temperatures　(280　degrees　C　and　470　degrees　C).　The　transition　from　homogeneous　to　heterogeneous　nucleation　at　higher　aging　temperature　(510　degrees　C)　is　a　natural　consequence　of　the　reduced　driving　force　for　nucleus　formation　as　the　temperature　increases　and　the　Er　supersaturation　in　the　alpha-Al　matrix　decreases.　The　change　in　morphology　of　the　Al-3(ZrxEr1-x)　precipitates　from　faceted　to　approximately　spheroidal　is　associated　with　a　change　in　the　value　of　interfacial　free　energies.　The　diameter　and　the　ratio　of　Zr/Er　increase　with　increasing　aging　time　at　constant　temperature.　The　coarsening　of　Al-3(ZrxEr1-x)　is　dependent　on　the　diffusivity　of　Er,　Zr　in　alpha-Al.