LAUSR

Abstract The Si content of an Al alloy infiltrated into SiC matrix composites affected the microstructure and strength of SiC matrix composites. As the Si content increased from 0 to 10 wt%, the relative volume fraction of Ti 3 Si(Al)C 2 increased, and the Al 4 C 3 decreased gradually and eventually disappeared. However, as the Si content continued to increase from 10 to 20 wt%, the relative volume fraction of Ti 3 Si(Al)C 2 decreased. The phase compositions and microstructure affected the bending strength. The three-point bending strength of the infiltrated SiC ceramics was almost twice that of the original SiC. Meanwhile, the maximum three-point bending strength of SiC ceramics infiltrated with the 5 wt% Si alloy was 430 MPa due to the formation of Al 4 C 3 , while with 10 wt% Si alloy, that of the infiltrated ceramic was 433 MPa due to the formation of Ti 3 Si(Al)C 2 . However, the three-point bending strength of the samples infiltrated with 5 wt% Si alloy decreased from 430 MPa to 243 MPa after the samples were exposed to air for 30 days due to the reaction of Al 4 C 3 with H 2 O and O 2 . In contrast, the Ti 3 Si(Al)C 2 phase was stable, and the strength of the samples infiltrated with 10 wt% Si alloy almost did not change after 30 days of air exposure.