Residual stress effects on toughening of ultrafine-grained B4C-SiC ceramics

The attainment of both enhanced toughness and super hardness is crucial for B4C ceramics. Refining grains to the nanoscale is known to be an effective strategy to address the above issue, but remains a great challenge. In this work, B4C and SiC nanoparticles were synthesized and used for the preparation of ultrafine-grained B4C-SiC ceramics. The grain size effect on the mechanical properties of composites was systematically investigated. It is found that, contrary to the conventional view that there is almost no residual thermal stress in the B4C-SiC interface, residual stress arises as B4C grains reach a nanostructured state, and the toughness can be considerably improved to 5.13 MPa m1/2. The B4C-SiC composite also demonstrates excellent hardness of 36.6 GPa, even superior to that of monolithic B4C ceramics. This study has important implications for the development of toughening mechanisms for B4C-SiC ceramics and presents a new strategy for producing high-performance ceramics.