Effects of Si-Ca alloy on the microstructure and mechanical properties of Mg-6Al-0.5Mn alloys were studied by observing the microstructure and phase composition of the alloys using OM

SEM

EDS and XRD. The results show that dispersively distributed regular polygonal Mg

2

Si particles can be formed in AM60 Mg alloy with proper Si-Ca addition. The microstructure of the AM60 Mg alloy can be improved

where semi-continuous net Mg

17 Al

12 phase becomes fine and dispersive and the grain size can be refined obviously with the increase of the Si-Ca addition

and grain size is decreased by 80 μm from 180 μm. Improvement of mechanical properties of the alloy is contributed to the formation of the enhancing phase and refinement of the microstructure

where tensile strength

elongation

and impacting toughness are increased by 13.9%

28.5% and 100%

respectively

with 1.8% Si content. It is also found that not only CaSi

2

can be acted as heterogeneous nucleation site for primary Mg

2

Si

but also Al

8

Mn

3

can do it.