Effects of Zn content on microstructure, mechanical and degradation behaviors of Mg-xZn-0.2Ca-0.1Mn alloys

Abstract

In this study, the microstructure characterization, mechanical properties and degradation behaviors of the Mg-xZn-0.1Mn-0.2Ca alloys with various Zn contents were analyzed via the polarization test, electrochemical impedance spectroscopy and the static immersion measurements. Meantime, the surface film layer features and the phase constitutions of the degradation production were characterized via the confocal laser scanning microscopy (3D/CLSM) and scanning electron microscopy. The results indicated that the more secondary phases appeared and the grain sizes were remarkably refined with the further addition of Zn, such as the Ca2Mg6Zn3, Mg2Ca and Mg4Zn7. The mechanical and corrosion resistance of the Mg-xZn-0.1Mn-0.2Ca alloys both initially increased and then decreased as Zn contents increased. Besides, the special anodic phase has been detected in the interior of the matrix, where the Mg2Ca phase with the lower potentials can protect Mg matrix from dissolving in the simulated body fluids (SBF). However, the Ca2Mg6Zn3 phase with the high potentials can accelerate dissolution rate of the Mg matrix. The best mechanical properties and corrosion resistance were obtained in the Mg–1Zn-0.1Mn-0.2Ca alloys, with the corrosion rate of 6.09 mm/y, exhibiting the uniform degradation morphology.