Microstructure and mechanical properties of SiC fiber/Si-CoSi2 matrix composites fabricated by carbon chemical vapor infiltration and Si alloy melt infiltration process

Abstract

For this study, orthogonal three dimensional (3D) woven silicon carbide (SiC) fiber (Hi-Nicalon, Hi-Nicalon Type S) -reinforced Si-CoSi2 matrix composites (SiC fiber/Si-CoSi2 composites) were fabricated and the microstructures and mechanical properties were characterized. The SiC fibers (28% fiber volume fraction) woven into orthogonal 3D fabrics and used as reinforcement were coated with chemical vapor infiltration (CVI)-carbon to control the fiber–matrix interface. The composite material infiltrated with Si-CoSi2 was produced using a melt-infiltration process. Four-point bending tests conducted at room temperature showed bending strength exceeding 300 MPa and tensile fracture strain exceeding 0.7%. Furthermore, bending strength greater than 400 MPa was found from a high-temperature four-point bending test under an Ar atmosphere. The failure mode was quasi-ductile. Fiber pull-out and fiber cross-linking were observed clearly. Melt infiltration of the Si-Co alloy caused little damage to the SiC fibers, confirming CVI-C layer protection of the fibers during melt infiltration and confirming that the layer can control mechanical properties at the fiber–matrix interface.