On the microstructure and corrosion behavior of AZ91/SiC composites produced by rheocasting

• AZ91/SiC composites were produced using rheocasting technique.
• Microstructure and the quality of the cast components were analyzed.
• Results showed the formation of several Al carbides and intermetallics as interfacial reactions in the MMCs.
• MMCs were more prone to corrosion than the monolithic alloy.
• The poor corrosion resistance of the MMCs is carefully attributed to the SiC-induced microstructural changes.

The microstructure and atmospheric corrosion behavior of two types of SiC (10 vol%)-reinforced magnesium alloy metal matrix composites (Mg alloy AZ91D-based MMCs) produced by rheocasting (RC) were investigated and compared to the monolithic alloy. Micron-sized and nano-sized SiC particles were used for fabrication of the MMCs. Microstructural studies using a broad range of analytical techniques showed the formation Al carbides and MgO at the α-Mg/SiC interface. The higher corrosion rate of the MMCs than RC AZ91D was attributed to a lesser degree of connectivity of the β phase, the high impurity level of SiC-reinforced MMCs and also the higher fraction of casting pores in the MMCs as compared to the RC alloy.