As-cast microstructure and phase constituent of AZ91 magnesium alloy containing 2.5% RE （RE presents Nd or Ce only or mixed Nd and Ce ） were observed by means of SEM （scanning electron microscope） and XRD （X-ray diffraction）

and ambient mechanical properties of the alloy were measured. The results indicate that bulk Al2Nd phase and acicular Al11Ce3 phase can be created in the AZ91 magnesium alloy with Nd addition only and one with Ce addition only

respectively. Meanwhile

both the bulk Al2Nd phase and acicular Al11Ce3 phase can be generated in the AZ91 alloy with mixed addition of Nd and Ce

in which relative content is positively related to the relative concentration of Nd and Ce

in which a part of Nd atom in the Al2Nd phase is substituted by Ce atom and a part of Ce atom in the Al11Ce3 phase is substituted by Nd. Mechanical properties of AZ91 magnesium alloy can be acceptably improved with addition of Nd and Ce

which is attributed to the depletion of Al in matrix by RE phase and the refinement of grain as well as dispersion strengthening

and the tensile strength and elongation of as-cast alloy are 240MPa and 11%

respectively

with 1.0% Nd and 1%Ce mixed addition

exhibiting desirable mechanical properties.