Interfacial characterization and its influence on the corrosion behavior of Mg-SiO2 nanocomposites

In this work, the corrosion behavior of Mg-SiO2 nanocomposites, fabricated by powder metallurgy coupled with hybrid microwave sintering and subsequent hot extrusion, was investigated using electrochemical, hydrogen evolution and weight loss measurements. Localized intergranular corrosion behavior was analyzed based on microstructural characteristics, which were characterized by scanning electron microscopy, energy-dispersive x-ray spectroscopy, and high-resolution transmission electron microscopy (HRTEM). In particular, copious numbers of Mg/MgO misfit dislocations were identified at the interface between the matrix Mg and SiO2 nanoparticles; indeed, first principles calculations revealed that the MgO/Mg interfaces were relatively weakly bonded as compared to the close-packed interfacial Mg(0001)//MgO(111) structure. Using geometrical phase analysis of the HRTEM images to determine the lattice strains in the Mg/MgO interfacial area, we conclude that the highly strained and weakly bonded Mg/MgO interfaces act to promote significant localized dissolution and thus play a dominant role in intensifying intergranular corrosion in these nanocomposites.