Effect of micro-alloying of Ca and Gd on microstructure and mechanical properties of Mg-Zn-Al alloy

Mg-2Zn-1Al alloy was used as the matrix, and 0.2wt% Ca, 0.2wt% Gd, and 0.2wt% Ca+0.2wt% Gd were added into it. The target alloys with four components were extruded at 200℃ and extruded bars with good surface quality were obtained. Optical microscope (OM), scanning electron microscope (SEM), X-ray (XRD) and tensile mechanics experiment were adopted to analyze the effect of trace Ca and Gd on the microstructure and mechanical properties of Mg-2Zn-1Al alloy. It is found that the grain size of the as-cast matrix alloy can be refined by adding Ca and Gd, and the effect of grain refinement was the superposition of the two effects added separately. This is due to the heterogeneous nucleation of Al2Ca and the segregation of Gd in front of the solid-liquid interface leads to the inhibition of grain growth. Furthermore, the addition of Ca and Gd can make the extruded micro-structure fine and uniform, which can weak the texture to improve the mechanical properties of the alloy. And the composite addition has the best refinement effect and texture weakening effect. Therefore, the alloy with the composite addition of the two showed the best mechanical properties.