Mechanical behavior of two-step hot-pressed ZrB2-based composites with ZrSi2

In this study, fully dense ZrB2-based composites containing ZrSi2 were sintered using a two-step hot pressing process. The elastic moduli, fracture toughness and flexural strength of the hot-pressed composites were determined. The effects of ZrSi2 content on densification behavior and properties of the composites were assessed. The results indicated that the ZrSi2 improved the sinterability of ZrB2 powders. Fully dense ZrB2-based composites with ZrSi2 were obtained at 1550 °C for 20–40 vol.% ZrSi2-conatining ZrB2 powders. The microstructure of the resulting composites was fine and homogeneous. The elastic moduli, fracture toughness and flexural strength of the obtained composites depended on ZrSi2 content. The shear, Young's, and bulk moduli decreased with ZrSi2 content. The range of fracture toughness values was measured to be 3.8–4.8 MPa m1/2. The flexural strength, which was 556 MPa, was almost the constant for ZrSi2 content of 30 vol.% or less. For 40 vol.% ZrSi2, however, the strength lowered significantly to 382 MPa.