Effects of Ce content on the modification of MgSi phase in Mg-5Al-2Si alloy

The effect of Ce content(0–1.6 wt.%) on the modification of Mg2Si phase in the as-cast Mg-5Al-2Si alloy was investigated. The original Chinese script type Mg2Si phase was refined distinctly and transformed to dispersive block shape gradually by adding Ce element. The length of Chinese script type Mg2Si phase was reduced from 110 to 50 μm with increasing Ce content to 1.6 wt.%. The results calculated by Pandat software indicated that the added Ce element first combined with Si to form CeSi2 phase, which could serve as the heterogeneous nucleation of Mg2Si phase due to the small lattice mismatch of 7.97%. The modification of Mg2Si phase was mainly attributed to the facts that Ce changed the growth steps of Mg2Si phase and CeSi2 promoted the nucleation of Mg2Si phase. With increasing Ce content from0 wt.% to 1.6 wt.%, the YS, UTS and EL at 150 °C were improved from 67.7 MPa, 91.2 MPa and 1.6% to 84.2 MPa, 128 MPa and 7.5%,respectively.