Degradation Behaviors Of Melt-spun Mg-based Metallic Glasses

Metallic glasses have attracted more and more interests since they were produceda few decades ago. Due to the disorder structure of atoms, metallic glasses possesssome unique properties, such as improved hardness, abrasion resistance, andcorrosion resistance. Currently a great number of different alloy systems have beendeveloped to produce metallic glasses. Comparatively, Mg based metallic glasseshave low density, outstanding biocompatibility and high recyclability, that are suitableto be applied as the function material in industry, such as aerospace, biomedicaland automobile etc. But the poor corrosion resistance of Mg based alloys hasrestricted their further wide applications. Hence, development of Mg based metallicglasses and investigation of their corrosion properties can provide the insight onMg-based metallic glasses to replace crystalline Mg alloys in applications.In this project, two kinds of melt-spun Mg67Zn28Ca5metallic glasses M1and M2are fabricated at different melt-spun spinning rate of30m/s and10m/s respectively.X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), ScanningElectron Microscopy (SEM) and Electron Dispersive X-ray spectroscopy (EDS) areemployed to characterize the obtained ribbons. The corrosion behaviors areinvestigated in Physical Sodium Solution (0.9%NaCl solution at37oC) and3.5%NaCl solution. Hydrogen gas evolution and electro chemical test are used todetermine the corrosion rate and electrochemical properties. Surface morphologiesafter immersion tests are observed under SEM. EDS and FTIR are carried out tocharacterize the surface chemical compositions, and the phases change as well ascorrosion products are studied with XRD. Based on the results obtained, both ribbons prepared at different cooling rate arein amorphous structure. And both of them show stronger corrosion resistance thancrystalline Mg. In PSS and3.5%NaCl solutions, M2shows stronger corrosionresistance than M1, indicating that higher cooling rate has adverse effect on corrosionresistance of glassy MgZnCa ribbons. Both kinds of samples possess strongercorrosion resistance in3.5%NaCl solution than that in PSS. Surface chemicalcomposition analysis demonstrates that the corrosion process is mainly caused by theloss of Mg and Ca, and the enrichment of Zn on the surface can effectively improvethe corrosion resistance. Since then, the addition of Zn can significantly improve thecorrosion resistance of Mg alloys.In summary, the higher cooling rate, the lower corrosion resistance of metallicglasses. And the component of Zn contributes more to the corrosion resistance ofMgZnCa alloys which means the addition of inert elements can improve the corrosionresistance. These principles are useful to further design of metallic glasses alloysystems that satisfy certain requirement of corrosion properties.