Microstructure and Corrosion Behavior of Laser Surface Alloyed Magnesium Alloys with TiO2-CeO2

Resumo

TiO₂–CeO₂ ceramic oxides were prepared on magnesium alloys by laser surface alloying for corrosion protection. The microstructure and composition of laser modified surfaces were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), optical microscope (OM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The corrosion behavior was analyzed by electrochemical and salt spray tests. The effect of relative proportion between the two ceramic components on corrosion resistance of laser alloyed magnesium alloys was investigated. Results showed that there was a margin improvement in corrosion resistance after laser surface alloying with TiO₂ and CeO₂ at the ratio of 4 : 1 (wt %) due to the protection effect of oxides. When the content of CeO₂ increased, and the ratio of TiO₂ and CeO₂ was 1 : 4 (wt %), defects were introduced for the poor compatibility between CeO₂ and Mg matrix. The defects speed up the failure of the layer, and the corrosion resistance was even decreased compared with the as-received magnesium alloy.