Effect of trace Ce on microstructure, mechanical properties and corrosion behavior of Mg-14Gd-xCe-0.5Zr alloy

The effects of Ce addition on the microstructure, corrosion behavior and mechanical properties of as-cast Mg14Gd-xCe-0.5Zr (x = 0, 0.3, 0.6, 1 wt%) alloys were investigated in this work. The results show that the introduction of trace Ce promoted the refinement of the alloy grains and achieved a high degree of homogenization of the eutectic phase distribution. The number of cathodic corrosion potentials in the alloy increased significantly, showing more severe micro-galvanic corrosion. Notably, the addition of 0.3Ce reduces the hydrogen evolution rate of the alloy, and increases the weight loss volume and weight loss rate. This is due to the large amount of dissolution of the eutectic phase, and the oxides/hydroxides of Gd and Ce are attached to the magnesium matrix. The weight loss rate of 0.6Ce alloy is only 7.35 mg center dot cm- 2 center dot d- 1, showing the best corrosion resistance. Precipitates are enriched on the surface of 1Ce alloy, and the thicker or aggregated film leads to lower anode utilization. In addition, the introduction of low content of Ce enhances the grain boundary strength, thereby enhancing the mechanical properties. The UTS, YS and EL of 0.6Ce alloy reach 254 MPa, 220 MPa and 4.63 %, respectively. However, with the introduction of excessive Ce, more brittle Mg12Ce phases are accumulated at the grain boundaries, resulting in weakened mechanical properties.