Mechanical properties of the low-temperature reactive melt infiltrated ZrB2–ZrC based composites

Zirconium diboride–zirconium carbide based composites were fabricated by reactive melt infiltration with boron carbide and Zr2Cu at 1200 °C. Mechanical properties of the composites before and after high temperature treatments were investigated. The presence of elongated ZrB2 grains and amorphous residual alloy provided the composites with an excellent fracture toughness of 12.1 MPa m1/2. High temperature treatments could improve the density of sintered composite and increase the bonding strength between ZrB2 and ZrC grains. This resulted in a flexural strength of 469.7 MPa and an excellent fracture toughness of 13.6 MPa m1/2 was obtained after a treatment at 1600 °C in argon. The evaporation of copper at 1600 °C in vacuum during heat treatment caused degradation in the mechanical properties. However, at a higher temperature of 1800 °C, the composite showed the highest flexural strength of 484.1 MPa and the highest flexural modulus of 282.2 GPa, apparently counterbalanced the Cu-loss effect.

► The ZrB2–ZrC based composites had an excellent toughness of 12.1 MPa m1/2.
► The 1600 °C treatment in argon could improve the mechanical properties.
► The composites treated at 1800 °C had the best flexural strength and modulus.