The NaCl-Induced Atmospheric Corrosion Performance of Magnesium-Based Metal Matrix Composites

Abstract

Magnesium alloys-based metal matrix composites (Mg alloys-based MMCs) are emerging as light structural materials for variety of new applications. They exhibit superior properties such as low specific weight, improved tensile strength and high wear resistance. However, composite technology is a difficult application for these class of metallic materials due to the fact that Mg is the least noble engineering metal. Hence, Mg alloys-based MMCs are very prone to environmental degradation. In this research, the occurrence of micro-galvanic corrosion cells in cast Mg alloys-based MMCs are evaluated. The relationships between the microstructure and atmospheric corrosion performance of SiC (10 vol.%)-reinforced Mg alloy AZ91D-based composites are studied. Microstructural studies are performed using various types of analytical techniques including electron energy loss spectroscopy (EELS) in the transmission electron microscope (TEM) revealed the formation Al carbides, Mg-hydride (MgH2), and MgO at the a-Mg/SiC interfaces. The corrosion rates of the MMCs are compared with those of the monolithic alloys. The higher corrosion rate of the AZ91D-based MMCs than the alloy AZ91D is shown to be linked to a less degree of the connectivity of the β phase (Mg17Al12 intermetallic particles) and also higher fraction of casting pores in the MMCs as compared to the monolithic alloys. We show that the corrosion resistance of MMCs can be significantly enhanced by controlling the casting process. The current advances and challenges in the field of Mg-based composites are also discussed. Figure 1