Effect of SiC whiskers on microstructure and mechanical properties of the MoSi2–SiCw composites

Abstract

In the present work, the effects of the sintering temperature and time on the microstructure and mechanical properties of the MoSi2–SiCw composites were investigated in detail. The results indicated that the relative density of the MoSi2–SiCw composites increased first and then decreased as the sintering temperature increased from 1500°C to 1750°C, and the maximum relative density of 99.7% was obtained for the MoSi2–SiCw composite sintered at 1650°C. As the sintering temperature increased from 1500°C to 1650°C, the flexural strength of MoSi2–SiCw composites increased from 428MPa to 646MPa, and then the flexural strength did not show obvious change with increasing the sintering temperature. The fracture toughness of the MoSi2–SiCw composites showed change trend similar to the change trend of the flexural strength with increasing sintering temperature and time. The maximum fracture toughness of 5.8MPam1/2 was greater than 3.3MPam1/2 of monolithic MoSi2 by 76%. The increase of fracture toughness was due to whisker bridging, whisker pull-out and crack deflection around the whiskers. The hardness of the MoSi2–SiCw composites did not show an obvious change with the change of relative density due to the bridging effect of the SiC whiskers.