Effects of SiC Particle Size and Process Parameters on the Microstructure and Hardness of AZ91/SiC Composite Layer Fabricated by FSP

In this study, friction stir processing (FSP) was employed to develop a composite layer on the surface of as-cast AZ91 magnesium alloy using SiC particles (5 μm and 30 nm). The effects of the rotational and traverse speeds and the FSP pass number on the microstructure and microhardness of the friction stir processed (FSPed) layer with and without SiC particles were investigated. Optical microscopy and scanning electron microscopy (SEM) were employed for microstructural analysis. FSP produces a homogeneous microstructure by eliminating the precipitates near the grain boundaries. The analyses showed that the effects of the rotational and traverse speeds on the microstructure of specimens produced without nano-sized SiC particles are considerable; however, they are negligible in the specimens with particles. While the second FSP pass enhances the microstructure and microhardness of the samples with SiC particles, it has no significant effect on such properties in the samples without SiC particles.