In situ reactive hot press sintering and mechanical properties of Al2O3–TiB2–B4C composites

Abstract

Dense Al2O3–TiB2–B4C composites are synthesized by in situ reactive hot press sintering of B4C with 20 wt% TiAl2 and TiAl3 at 1700 °C, respectively. The sinterability of B4C is improved by the intermetallic compounds due to the formation of Al2O3 and TiB2. The sizes of Al2O3, TiB2, and B4C grains are less than 2.5 μm. The agglomerates of Al2O3 and TiB2 particles tend to orientationally align in the direction perpendicular to the pressure axis. By incorporation of TiAl2, the flexural strength and fracture toughness reach 482 MPa and 3.6 MPa m1/2, respectively. When TiAl3 is added, the flexural strength is reduced to 408 MPa because of the thermal residual stress, while the fracture toughness is increased to 4.2 MPa·m1/2. The increase of Al2O3 in the composite can reduce the strength and enhance the toughness of the composite due to the thermal residual stress originated from the thermal expansion mismatch between B4C and Al2O3.