The modification effect of rare earth Gd on primary Mg2 Si in hypereutectic Mg-5Si alloy was analyzed

meanwhile

effects of Gd on microstructure and mechanical properties of the alloy were presented

and modification mechanism was described.The results reveal that Gd exhibits desirable modification effects on primary Mg2 Si phase in the hypereutectic Mg-5Si alloy

especially 2.0% Mg-30 Gd addition.The average size of primary Mg2 Si phase can be decreased to less than 25μm

and the morphology of primary Mg2 Si phase is transformed from the coarse dendrite into fine polyhedron particle with more uniform distribution.The tensile strength and elongation of the alloy reach 105 MPa and 3.1%

respectively.However

with the Mg-30 Gd content more than 3.0%

the primary Mg2 Si phase in the hypereutectic Mg-5Si alloy is coarsen again.The refinement of Gd is mainly associated with the enrichment of Gd on the growth facets of the primary Mg2 Si crystals to depress the preferred crystal growth.In addition

intermetallic compound GdxSiycan be taken as heterogeneous nuclei of the primary Mg2 Si phase growth.