Deformation behavior and mechanical anisotropy in ZrB2-based ceramic

The deformation behavior and mechanical properties of ZBHOx ceramic (ZrB2 based ceramics with different amounts of (HfO2 + 2vol.% CaO), x = 10 - 25vol.%) have been investigated. The results demonstrated that the flow stress of ZBHOx ceramic decreased with an increase in the (HfO2+2vol.% CaO) addition at the same strain rate. The flow stress decreased from ∼178 MPa for ZBHO10 to ∼13 MPa for ZBHO20 at 1700 °C and a strain rate of 2×10−4 s−1, representing a reduction of an order of magnitude. The intergranular deformation twinning and the amorphous phase contribute to the grain boundary sliding and grain rotation of the boride matrix grains, resulting in a significant reduction in flow stress. The matrix grains orientations on the P face (the face perpendicular to the extrusion direction) primarily tend to be along the {0001} plane, while that on the V face (the face parallel to the extrusion direction) tend to be along the {-12-10} plane or {01–10} plane. The textured ZBHOx ceramics exhibit distinct mechanical anisotropy because of the significant orientation difference in the microstructure. The hardness of textured ZBHOx ceramics on V face is higher than that on P face. And the fracture toughness of ZBHOx ceramics exhibits anisotropy on the V face, the fracture toughness in the V-o direction (the direction perpendicular to the P face) is higher than that in V-p direction (the direction parallel to the P face) of ZBHOx ceramics.