A392 alloy with P-RE mixed modification was investigated by SEM（scanning electron microscope）and XRD（X-ray diffraction）

focusing on morphology and distribution of RE element in A392 alloy as well as refinement mechanism on primary Si phase.It is revealed that the primary Si phase can be obviously refined with 0.5%

1

.5% RE and P mixed modification

in which the average grain size of primary Si phase reaches up to 19.4μm with 0.08% P and 1.1%RE mixed modification.The RE element can enrich on the growth interface of silicon crystal to restrain the diffusion of Si in alloy melt and to increase the undercooling rate

resulting in destroying the stability of growth interface

which can be responsible for the refinement effects of RE on primary Si phase.However

excessive Re element can result in generation of amounts of RE-enrichment

which can not only be detrimental to the refinement effects on primary Si phase

but also deteriorate the mechanical properties of the alloy.So

the RE content in P-RE mixed modification should be strictly controlled.