Effect of Ce-rich misch metal addition on squeeze cast microstructure and mechanical properties of AZ81 alloy

The effect of cerium-rich misch metal addition on the microstructure and properties of squeeze cast magnesium alloys AZ81 was empirically investigated. The results indicate that the addition of cerium-rich misch metal modifies the microstructure gradually. With the increase of the RE addition, the amount of Mg17Al12 decreases while that of Al11(RE)3 increases, accompanied by grain refinement. When the addition reaches 1.5%, the grain refinement becomes obvious. However, when the addition exceeds 2.0%, Al11(RE)3 phase coarsens into rod shape and the grain size increases. The tensile properties of the AZ81 at both room temperature and 150°C increase with the addition, and reach their optimal values with the addition of 1.5%. Further increase of the addition to above 2.0% decreases the tensile properties considerably. The tensile fracture of the alloy is characterized by the cleavage of the brittle second phases and ductile dimples of the matrix.