To investigate the effect of yttrium(Y)on microstructure refinement and mechanical properties of aluminum alloy A356.2,the different trace contents of Y(0 wt％,0.025 wt％,0.050 wt％,0.075 wt％,or 0.100 wt％)were introduced into the liquid alloy.The alloys were fabricated in a preheated permanent mold,and subse-quently treated by a T6 heat treatment.The results of tensile testing indicate that the yield strength(YS),the ultimate tensile strength(UTS)and the elongation(El)of the A356.2 alloy are improved by the Y additions.The YS dependence on grain size for the test alloys follows the Hall-Petch equation,which gives YS=-354.1+2875.2d-1/2 with a correlation of R2=0.83.As 0.050 wt％Y is added,the optimum values of the YS,UTS and El are achieved after T6 heat treatment.The secondary phases were identified by X-ray diffraction(XRD)which mainly consisted as Si,Mg2Si and A13Y.The scanning electron microscope(SEM)and energy-dispersive spectrometer(EDS)analyses reveal the presence of the nano-sized A13Y particles on the surface of the Si phase.The A356.2 alloy with the Y addition is strengthened by the dendritic refinement,and the presence of the micron-and nano-sized A13Y precipitates.