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 similar to 0.50 to similar 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. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.