Mechanical behavior of two-step hot-pressed ZrB_2-based composites with ZrSi_2

摘要

In this study, fully dense ZrB_2-based composites containing ZrSi_2 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 ZrSi_2 content on densification behavior and properties of the composites were assessed. The results indicated that the ZrSi_2 improved the sinterability of ZrB_2 powders. Fully dense ZrB_2-based composites with ZrSi_2 were obtained at 1550 deg C for 20-40 vol. percent ZrSi_2-conatining ZrB_2 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 ZrSi_2 content. The shear, Young's, and bulk moduli decreased with ZrSi_2 content. The range of fracture toughness values was measured to be 3.8-4.8 MPa m~(1/2). The flexural strength, which was 556MPa, was almost the constant for ZrSi_2 content of 30 vol.percent or less. For 40 vol.percent ZrSi_2, however, the strength lowered significantly to 382 MPa.