Microstructure and mechanical properties of multi-carbides/(Al, Si) composites derived from porous B4C preforms by reactive melt infiltration

Multi-carbides/(Al, Si) composites were prepared by a spontaneous reactive melt infiltration technique. B4C and B4C with extra carbon (B4C/C) preforms were infiltrated with Al–Si alloys with Si contents ranging from 36 to 80 wt.%. The infiltration was conducted at temperatures 200 °C above the liquidus of the Al–Si alloys. Influence of the composition of the Al–Si alloys on the structure and the correlation of the structure and the mechanical properties of the composites have been studied. The alloys show good infiltration ability to the B4C and B4C/C preforms. The Al–Si alloys reacted with B4C, forming new carbides. Composites composed of carbides of SiC, B4C, AlB12C2, Al3B48C2 and residual Si and Al are obtained. The typical upper values of Vickers hardness and flexure strength are 17 ± 3 GPa and 328 ± 8 MPa, respectively, which are provided by the infiltration couple of B4C/Al–55 wt.% Si. The fracture mechanism of the composites has also been discussed.