| Summary: | SiC fiber reinforced Si3N4 composites (SiCf/Si3N4) were prepared by chemical vapor infiltration, and the mechanical properties were optimized by tailoring the BN interphase thickness. The microstructure was characterized by transmission electron microscope and scanning electron microscope, and the evolution of mechanical properties was revealed by the finite element analysis. The results show that with the increase of BN interphase thickness from 290 to 550 nm, the flexural strength is increased from （190±39）MPa to （317±28）MPa, the fracture toughness is increased from （7.3±1.6）MPa·m1/2 to （14.7±0.5）MPa·m1/2, and the tensile strength is increased from （89±3）MPa to （176±17）MPa. The residual stress of the fiber decreases rapidly with the increase of BN interphase thickness, and the thermal mismatch is effectively alleviated， which makes the material show better mechanical properties.
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