Mg-7 Zn-1 Cu-0.3 Mn-xNd（x=0

0.1

0.3

0.5

%） magnesium alloys were designed. The as-cast microstructure of the alloys with different Nd contents and the evolution of semi-solid non-dendritic microstructure after isothermal heat treatment were observed by OM

XRD and SEM. The isothermal heat treatment process of Mg-7 Zn-1 Cu-0.3 Mn-0.3 Nd alloy was investigated and the evolution of semi-solid non-dendritic microstructure was analyzed. The results show that the as-cast microstructure of Mg-7 Zn-1 Cu-0.3 Mn-xNd alloy is mainly composed of α-Mg

Mg

4

Zn

7

NdCu

2

and CuMgZn phases. The desirable addition of Nd is 0.3%

where the satisfied grain refinement effect can be obtianed

and the eutectic microstructure is more dispersed. The optimal semi-solid non-dendritic microstructure of Mg-7 Zn-1 Cu-0.3 Mn-0.3 Nd alloy can be obtained after holding at 595 ℃ for 30 min. The solid fraction

shape factor and average particle size reach 57.59%

1.38 and 44.56 μm

respectively. The evolution of non-dendritic microstructure consists of the initial coarsening

structure separation

spheroidization

and final coarsening.