Effects of Cu addition on the solidification structure of Zn-27Al alloy were investigated.The phase transition and the microstructure distribution of the alloy with different Cu addition were analyzed through observing microstructure and dendrite morphologies using X-ray diffraction

Electro-probe microanalyzer and scanning electron microscope.The results show that the Cu-enrichment phase ε with dispersedly distribution in the microstructure is gradually converted into CuZn4 phase which is enriched on dendritic arm of α-Al phase with the increase of Cu addition.And the microstructure in Zn-27Al alloy is gradually transformed from the coarse equiaxed grains into developed dendrites

and to the columnar dendrites with big length-diameter ratio

and then to the dendrites with the developed secondary branches and relatively short primary arm.