Modification of Mg2Si Phase Morphology in Mg-4Si Alloy by Sb and Nd Additions

We reported the effects of compound modification with Nd and Sb on the microstructure evolution and mechanical properties of Mg-4Si alloys. The characterization results showed that adding 1.0 wt.% Sb and 1.0 wt.% Nd to the alloy can effectively change the morphology of Mg2Si particles. The primary Mg2Si particles changed from coarse dendrites to regular polygons, and the average particle size decreased from 78.3 to 6.5 μm. Meanwhile, the Chinese eutectic Mg2Si became small short fiber. The experimental results showed that the Nd4Sb3 phase could be formed after adding 1.0 wt.% Sb and 1.0 wt.% Nd to the alloy. The Nd4Sb3 phase could act as the heterogeneous nucleation core of Mg2Si phase, which increased the nucleation rate of Mg2Si and improved the morphology of Mg2Si particles. The mechanical properties test found that the tensile properties and Brinell hardness of the alloy were improved with Sb and Nd alloyed. After adding 1.0 wt.% Sb and 1.0 wt.% Nd to the alloy, the ultimate tensile strength increased from 113 to 184 MPa, the elongation increased from 2.23 to 4.61%, and the Brinell hardness increased from 65.45 to 87.32 HB.