Solidification processes of ZAlSi7Mg-xY （0.1

0.3

0.5wt.%） alloys were investigated by thermal analysis. The microstructures were observed by using optical microscopy and scanning electron microscopy. Effects of different concentrations of Y on tensile performance both as cast and T6 heat treated were studied at room temperature respectively. The results shown that: with increased concentration of Y

little changes happened in liquidus while it result in an obvious depression of solidus curve and eutectic arrest temperature in the solidification process

so the solidification interval increased significantly. The optimization of microstructure and performance was obtained when concentration of Yttrium is 0.1wt.% .With an increment of Yttrium

more large flakelike compound of yttrium gathered in grain boundaries

the performance especially the elongation of the alloy decrease remarkably.