Effects of C

2

Cl

6

on the as-cast microstructure and mechanical properties of AZ91 magnesium alloy have been investigated by optical microscope （OM）

X-ray diffraction analyzer （XRD） and scanning electron microscope （SEM）

and the grain size and grain area have been measured using the Imagetool Software. The results show that 0.3%

0

.8% C

2

Cl

6

addition in the AZ91 magnesium alloy can obviously refine the grain average size of α-phase from 106 μm to about 53 μm and decrease the grain area

where the best refined effects can be observed with 0.3% C

2

Cl

6

addition. In addition

C

2

Cl

6

addition can result in the dispersive distribution of fine β-Mg

17 Al

12 phase

which can greatly improve the mechanical properties of the alloy.