Effects of Trace Ca on Microstructure and Properties of Mg-4Ce-2Zn Alloy

The influence of trace Ca element (mass fraction 0.43%) on the microstructure and properties of Mg-4Ce-2Zn alloy after extrusion was observed and studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), nanoindentation apparatus, Vickers hardness tester, electrochemical polarization test, etc. The results show that with the addition of trace amounts of Ca cooperated with extrusion deformation process refined the grain size of Mg-4Ce-2Zn alloy, and precipitated a second phase of Ca₂Mg₆Zn₃. The mechanical properties and corrosion resistance of the alloy had been improved, with Vickers hardness, nanohardness, and elastic modulus increasing by about 12.0%, 9.98%, and 29.17%, respectively. The corrosion current density had decreased from 1.000 μA·cm^-2 to 0.015 μA·cm^-2. The improvement of mechanical properties of Mg-4Ce-2Zn alloy could be attributed to fine grain strengthening, second phase precipitation strengthening, and solid solution strengthening. The reason for the improvement of corrosion resistance is that trace Ca elements promoted the formation of a dense corrosion passivation film during the corrosion process, and the refined grains could enable the corrosion passivation film to bond with the substrate. The corrosion mode of the alloy changed from non-uniform corrosion to uniform corrosion.