Phase studies of reactive infiltrated boron carbide-aluminium composites by quantitative XRD

Abstract

Fully dense (> 98 % of theoretical) boron carbide (B4C)-aluminium (Al) composites were produced between 985 degrees and 1370 degreesC by pressureless melt infiltration of Al alloys into porous B4C compacts under an argon (Ar) atmosphere. Wrought Al alloy blocks (2024-T3) were put on top of the porous B4C compacts and infiltrated into the substrate in an atmosphere controlled tube furnace. Quantitative phase analysis by the ratio of slopes method showed that Al3BC and AlB2 were the main phases forming in the composites. The amounts of Al3BC and AlB2 varied between 30-65 wt % and 5-15 wt %, respectively, depending on the heat treatment. At temperatures exceeding 1180 degreesC, a small amount of the boron rich AlB12C2 phase was also observed. The hygroscopic and undesired Al4C3 phase was found to form at 1370 degreesC upon prolonged exposure.