Effects of solution and multiplicity solution treatment on microstructure and mechanical properties of AZ91 magnesium alloy after aging treatment were investigated by OM（optical microscopy）

SEM（scanning electron microscopy）

XRD（X-ray diffraction）as well as hardness and tensile tests.The results indicate that the distribution of Al atoms inα-Mg is more uniform after multiplicity treatment

and the concentration difference is only 0.64 % between the grain boundary and the grain center.At the same time

the mechanical properties of AZ91 magnesium alloy after multiplicity heat treatment exhibit more satisfactory.Compared with those of the as-cast alloy

the hardness

the tensile strength and yield strength are increased by 34%

25% and by 55%

respectively

meanwhile

the decrease of elongation can be ignored

which is related with the morphology ofβ-Mg17Al12 precipitation during the aging treatment.