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 synthesised by reaction hot-press sintering with milled B4C and pure metallic Al powder at 1600 C for 1 h. XRD, SEM and TEM were used to identify the phase constituent of the milled powders and the composites. Parts of B4C and Al particles were oxidised to boron oxide (B2O3) and alumina (Al2O3) during the milling. A 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.