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 Mg_(17)Al_(12) decreases while that of Al_(11)(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%, Al_(11)(RE)_3 phase coarsens into rod shape and the grain size increases.The tensile properties of the AZ81 at both room temperature and 150℃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.
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