Effects of grain boundaries and quasi-plastic deformation in shocked bi-crystal boron carbide nanopillars

Grain boundaries (GBs) significantly affect the mechanical properties of ceramics, but they are understudied. Here, we employ three bi-crystal boron carbide nanopillars to investigate the effect of GBs on the shock behaviors and deformation mechanisms of B4C, using molecular dynamics simulations with a reactive force field. The results reveal a strong correlation among the shock behaviors, interfacial energies, and grain orientations. The (11¯02)/(1¯101) model with the highest interfacial energy model shows intragranular amorphization due to the interaction between the softened GB and the unfavorable orientation of the grain, while the other two GB models experience intergranular amorphization. Furthermore, the quasi-plastic behaviors in the three models arise from GB rotation or GB sliding. The US-UP relationships of quasi-plastic waves exhibit a bilinear relationship due to the intergranular amorphization formation. Noteworthy, this bilinear behavior for the (11¯02)/(1¯101) model displays a second kink, corresponding to the formation of intragranular amorphization. This study serves as a reference for designing ceramics with superior properties.