Development and characterization of magnesium composites containing nano-sized silicon carbide and carbon nanotubes as hybrid reinforcements

Magnesium based hybrid composites containing nano-sized silicon carbide and carbon nanotubes reinforcements with minimal porosity were successfully fabricated using powder metallurgy technique with microwave sintering and hot extrusion. It was found that the addition of nanosized silicon carbide and carbon nanotubes reinforcements lowered the coefficient of thermal expansion of magnesium. Moreover, increasing presence of silicon carbide particles led to a progressive reduction in coefficient of thermal expansion for a constant overall amount of reinforcements indicating that carbon nanotubes lowered the coefficient of thermal expansion to a lesser extent when compared to silicon carbide. Micro-hardness, 0.2% YS and UTS (except for Mg+1%CNT) showed improvement, while failure strain decreased when nano-sized silicon carbide and carbon nanotubes were added to magnesium. The failure mode of magnesium and magnesium composites was predominantly brittle exhibiting the presence of cleavage steps.