Electrical discharge machinable B4C–(Zr, Ti)B2 composites with enhanced mechanical properties

B ₄C 30 vol% (Zr _xTi _1-x)B ₂ ( x = 0.2, 0.4, 0.6 and 0.8) composites were fabricated via in-situ reaction by spark plasma sintering using B ₄C, ZrC, TiC and B powders as raw materials at 2000 °C. The effects of the Zr/Ti ratio in the (Zr _xTi _1-x)B ₂ phase on the microstructure and mechanical properties of the composites were investigated. The electrical discharge machining performance of the composites was evaluated. The formation of (Zr, Ti)B ₂ solid solutions was beneficial to fully dense composites with refined grains. The grain size of the (Zr, Ti)B ₂ phase first gradually decreased from 1.26 µm to 0.89 µm and then increased to 1.23 µm with the decreasing ZrC/TiC molar ratio. The material removal rate was slightly decreased from 6.56 mm ³/min to 5.17 mm ³/min with the decreasing ZrC/TiC molar ratio. The combined solid-solution and fine-grain strengthening has made the B ₄C 30 vol% (Zr _0.2Ti _0.8)B ₂ composite enhanced Vickers hardness, flexural strength, and fracture toughness of 28.31 GPa, 772 MPa, and 6.56 MPa·m ^1/2, respectively, with a relative density of 99.73%.