The effects of Sr on the microstructure and mechanical properties of hypereutectic Al-Mg

2

Si alloy were investigated. The results indicate that Sr has effects on both primary Mg

2

Si phase and eutectic Mg

2

Si phase in Mg

2

Si reinforced aluminum alloy. After Sr addition

the morphology of the primary Mg

2

Si phase is transformed from coarse dendritic to quadrilateral shape. Meanwhile

the morphology of eutectic Mg

2

Si phase is transformed from long rod-like to fine rod-like and granular. When Sr content is 0.1%

the modification effect is desirable

and the primary Mg

2

Si phase is tiny and evenly distributed. The tensile strength of the alloy is 121 MPa

which is increased by 55.1% compared with the unmodified alloy with slight elongation change. When the addition amount of Sr reaches 0.15%

the primary Mg

2

Si is coarsened again

and over-metamorphism occurs

resulting in the degradation of mechanical properties.