Influence of Al particles as infiltration promoters on the interfacial reaction and mechanical property of a continuous SiC fiber/AZ91 composite fabricated by a low-pressure infiltration method

Highlights: • Interfacial reaction between the SiC fiber and the Mg alloy matrix was clarified. • When Al particles are used, the SiC fiber and the Mg alloy matrix do not react. • When Al particles are not used, the SiC fiber and the Mg alloy matrix react. • Interfacial reaction phase reduces the strength of MMC. -- Abstract: In this study, Mg alloy-based composites (MMC: metal matrix composite) with uniaxially oriented continuous SiC fibers were fabricated using a low-pressure infiltration method. Next, the influence of Al particles as the infiltration promoter on the interfacial reaction between the SiC fibers and the Mg alloy matrix was investigated by means of scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. In the presence of Al particles, β-Mg₁₇Al₁₂ was preferentially precipitated around the SiC fibers. The SiC fibers and the Mg alloy matrix did not react directly and remained bonded at the fracture surface. In contrast, in the absence of Al particles, whisker-like Al₄C₃ was observed around the SiC fiber, and a reaction phase consisting of MgO and Mg₂Si was observed in the circumferential part inside the SiC fiber. The detachment occurred between the SiC fibers and the Mg alloy matrix at the fracture surface.