Densification behavior and mechanical properties of spark plasma reaction sintered ZrB2-ZrC-B4C ceramics from B4C-Zr system

The ZrB2-ZrC-B4C multiphase ceramics were produced by spark plasma reaction sintering (SPAS) from boron carbide (B4C) with different volume of zirconium (Zr). With Zr content increases, the B4C phases in the composite decreased gradually, and the zirconium carbide (ZrC) phase gradually increased. With Zr content increased to 70 vol%, the morphology of the zirconium diboride (ZrB2) changed from equiaxed crystal to platelet crystal. During the solid reaction process of Zr with B4C, carbon (C) was preferentially replaced to generate ZrB2, and then the remaining Zr reacted with C to form ZrC. With the increase of Zr content, the flexure strength and fracture toughness of the ZrB2-ZrC-B4C composite ceramics increased due to improved microstructure and more crack deflection and intergranular fracture.