The compression casting experiments has been done with two different ingredients magnesium alloys in this paper. The metallurgical structure and tensile fracture pattern of the pressure castings were investigated; also the room temperature and elevated temperature mechanical properties of samples were tested. The results indicate that a little rare earth has small effect on the room temperature mechanical properties of the alloys which lied on the amount of shrinkage porosity and impurity in the matrix

but the rare earth obvious improved the elevated temperature properties of the alloys. The tensile fracture patterns of samples mainly were brittle fracture as cleavage fracture at room temperature. When 150℃

the quantity of dimple and tearing arris were visibly increased on the fractures

and the tensile fracture patterns exhibited hybrid fracture as ductile rupture.