With adding 3%

9

% Si into Mg-9Al alloy

the in-situ Mg

2

Si/Mg-9Al matrix composites with10%

3

0% Mg

2

Si were fabricated successfully by induction heating.The microstructure and solidification mechanism of the composites prepared were investigated by optical microscopy（OM）

scanning electron microcopy（SEM）

X-ray energy-dispersive spectrometry（EDS）

X-ray diffraction（XRD）and differential thermal analysis（DTA）.The results indicate that the composites prepared are composed of Mg

2

Si

Mg17Al12and Mg phase.The amounts of both Mg

2

Si and Mg17Al12 phase are increased with the Si content increase.During cooling process

Mg+Mg

2

Si eutectic phase can be generated after the precipitation of primary Mg

2

Si

and the eutectic Mg

2

Si phase is grown on the primary Mg

2

Si.The Al content in the Mg-9Al matrix is increased with the Si content

which affects the solidification behavior of the Mg-9Al matrix.