Mechanical properties of C-SiC composite materials fabricated by the Si-Cr alloy melt-infiltration method

Abstract

Although carbon fiber-reinforced silicon carbide matrix composites fabricated using the liquid silicon infiltration method exhibit high thermal and oxidation resistances, their physical characteristics are limited because of the presence of unreacted, free Si within the materials. To resolve this problem, ingots prepared by alloying Cr with Si in ratios of 0, 5, 10, 25, and 50at% were melted and made to infiltrate the composite, resulting in the formation of CrSi2 in the unreacted, free Si region without degrading the composite's properties. The CrSi2 in the composite material reduced the amount of free Si and caused minimal variation in the flexural strength while significantly improving the fracture toughness of the composite. The results of scanning electron microscopy and transmission electron microscopy analyses indicated that the improvement in the fracture toughness was due to the presence of an amorphous interlayer between the Si and CrSi2 phases, as well as because of a stress field surrounding the CrSi2 phase.