Mechanical response of ZrB₂-based ultra-high temperature ceramics to shock pulse loadings in a wide temperature range

The multiscale approach was used for 3D computer simulation of deformation and failure of porous nanostructured ZrB₂-B₄C composites. It was shown strong influence of ZrB₂-B₄C nanocomposites microstructure on dynamic fracture at temperatures (295-473 K). The fracture of ZrB₂-UHTC is caused by nucleation and coalescence of micro cracks. Cracks are formed near voids and in space between the strengthening particles at the mesoscale level. It was shown the transition of brittle to ductile fracture in ZrB₂-B₄C composites depends on strain rates. Thus, the strength threshold of nanostructured ZrB₂-B₄C composites depends on strain rates in temperature range (473-2200 K). The dynamic strength of ZrB₂-B₄C composites sharply decrease at temperature above 1773 K. It was shown that the dependence of normalized strength of ZrB₂-B₄C composites on the logarithm of normalized strain rates can be described by the power law. (paper)