Reactive melt infiltration of carbon fibre reinforced ZrB2/B composites with Zr2Cu

The microstructure and mechanical properties of carbon fibre reinforced ZrB2 composites produced by slurry infiltration and consolidated by reactive melt infiltration were investigated. Fibres were preliminary infiltrated with ZrB2/B slurries with varying ZrB2/B ratios. Then the composites were infiltrated with Zr2Cu melt at 1200 °C under vacuum. Boron was chosen as the reactant phase, while raw ZrB2 was added as a filler to prevent excessive swelling. With increase of boron content the infiltration becomes more difficult due to the reaction of alloy and boron. The boron is completely converted to nano ZrB2 grains. Some ZrC is produced from the side reaction between Zr2Cu and the carbon fibre, resulting in reduction of fibre diameter. The flexural strength increased from 360 to 560 MPa with the increase of boron content, while KIc amounted to 10 MPa⋅m0.5 but was affected by large scatter. The mechanical behaviour was mostly dominated by matrix properties.