Phase identification of Al–B4C ceramic composites synthesized by reaction hot-press sintering

A series of boron carbide (B4C) matrix composites with different contents of Al, were synthesized by reaction hot-press sintering with milled B4C and pure metallic Al powder at 1600 °C for 1 h. X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM) were used to identify the phase constituent of the milled powders and the composites. The results have shown that parts of B4C and Al particles were oxidized to boron oxide (B2O3) and alumina (Al2O3) during the milling. Thermit reaction occurred and B2O3 was reverted during hot-press sintering. A ternary phase of Al boron carbide (Al8B4C7) was found in the composites, and the B4C transformed to a rich boron phase (B6.5C) because of the superfluous boron in the system.