Effects of Sr

Y and compound treatment of Sr-Y on the solidification structure and mechanical properties of the Mg-9 Al-3Si alloy were investigated

and effects of different Y content on the solidification structure and mechanical properties of the alloy after compound treatment were also analyzed.The results show that the solidification structure and mechanical properties of the alloy can be improved obviously with Sr-Y composite modification

and the modification effect superior to that of one with Sr or Y alone.The size of primary Mg

2

Si phase is decreased by 40%

and the tensile strength and elongation of the alloy are increased by 31.2% and 300%

respectively

compared with those in untreated alloys.Under compound modification condition

with the increase of Y content

the size of primary Mg

2

Si phase is decreased firstly and then increased

where the turning point is0.78%.Meanwhile

the mechanical properties of the alloy are corresponded basically to the size change of primary Mg

2

Si phase.