Spherical indentation with multiple partial unloading for assessing the mechanical properties of ZrB2–SiC composites

In this research, spherical instrumented micro-indentation tests with multiple partial unloading were performed to determine the mechanical properties of the ZrB2–SiC composites reinforced with and without the mixture of boron nitride nanotubes (BNNTs) and boron nitride nanoplatelets (BNNPs), the indentation stress–strain curves of these ZrB2–SiC composites were also reconstructed. Results showed that strain-hardening exponents of the sintered ZrB2–SiC composites are in the range of ~0.50 to ~0.52, and the added mixture of BNNTs–BNNPs has little effect on the indentation yield strength of the composites. Synergetic influences of the Orowan-type strengthening effect and the capability of large plastic deformation associated with the added BNNPs might be ascribed to the neglectable changes in the strain-hardening exponent and the indentation yield strength of the (BNNT–BNNP)/(ZrB2–SiC) composites. This research is expected to facilitate a better understanding of the microscopic plastic deformation behavior of ZrB2 and its composites.