Methods for improving the toughness of silicon carbide ceramics

The research on enhancing the toughness and improving the density of silicon carbide ceramics has been our ongoing work. The main methods for enhancing the toughness of silicon carbide ceramics are to change the composition of the ceramic material, such as by increasing fiber/whisker toughening, second phase particle toughening, and changing the ceramic forming process to change the internal microstructure of the ceramic.

Adding carbon short fibers to silicon carbide ceramics can reduce the content of free silicon in the ceramics, form a β - SiC layer, and enhance the toughness of silicon carbide ceramics. When the volume fraction of carbon short fibers reaches 30%, the fracture toughness of silicon carbide ceramics reaches 5.1 MPa · m1/2, which is 78% higher than that of silicon carbide ceramics without carbon short fibers.

Through the study of isothermal forging technology, it was found that SiC particles were uniformly distributed in a streamline in the aluminum matrix, and the performance of the forging (chordwise sampling) was significantly improved. Rm=500 MPa Rp0.2=330 MPa、A=7%、K1C=25.0 MPa·m1/2。 

By optimizing the coarse and fine particle size distribution of silicon carbide powder, the toughness of silicon carbide is enhanced. Research has shown that the introduction of coarse powder can suppress the growth of abnormal grains in S-SiC ceramics, resulting in small equiaxed grains. As the coarse powder content increases, the toughness of S-SiC ceramics shows a pattern of first increasing and then decreasing. At a coarse powder content of 65%, the toughness of S-SiC ceramics is the highest, which is 17.1% higher than that without coarse powder, reaching (4.92 ± 0.24) MPa · m1/2.

Through the research of the above results, we have mastered the toughening preparation method of silicon carbide ceramics. Our silicon carbide ceramic products have better performance than ordinary silicon carbide ceramics, and can resist the impact of bullets. The products meet the NIJ IV bulletproof requirements.