Fabrication and mechanical properties of hot-pressed TiB2-ZrB2 ceramic system

Abstract

The TiB2-ZrB2 ceramic system, which has a range of high hardnesses and electrical conductivities, was sintered by the hot-pressing method from mixed powders of TiB2 and ZrB2. The mixed powders calcined at 1450°C for 5.4 ks with compositions from 100 mol% TiB2 to 100 mol% ZrB2 (20 mol% step) were preformed at a pressure of 98 MPa, and then hot-pressed at 2000°C for 3.6 ks under a pressure of 31.2 MPa in an ambient Ar gas. The system was found to form solid solutions between TiB2 and ZrB2 crystal structures. (TiB2)0.6 (ZrB2)0.4 ceramics, for example, had a relative density of 96.5%, hardness of 30.4 GPa, flexural strength of 354 MPa, fracture toughness (KIC) of 3.87 MPa-m1/2, Young's modulus of 449 GPa, fracture energy of 16.5 J·m-2 and electrical conductivity of 6.8 MS·m-1. The ceramics is expected to be used as a ceramic mold material that can be machined by electrical discharge and as electro-conductive high-temperature structural materials.