Grain refinement effect of La2(CO3)3 on AZ91 magnesium alloy

The La-2(CO3)(3) addition makes the grain of AZ91 alloy be refined obviously. The average primary dendrite size of the alloy decreases from 150 to 50 mu m. The microstructure of typical dendrite turns into the equal-axed grain with the addition of 2.5 wt. % La-2(CO3)(3) refiner. The mechanical properties tests indicate that the tensile strength and especially elongation of the alloys are improved with the addition of La-2(CO3)(3) and their maximum enhancing rates based on the La-2 (CO3)(3)-free AZ91 alloy are 26% and 5.2 times at 2.5 wt. % Lag (CO3)(3) refiner respectively.