Boron carbide-reinforced alumnium 1100 matrix composites: Fabrication and properties

With the increasing trend in the use of light-weight functional material in emerging industrial applications, understanding the fabrication of aluminum-boron carbide (ABC) composite is becoming needful. In this context ABC composites up to 25 wt.% boron carbide (B4C) particulate reinforcement in alumnium 1100 matrix were prepared at 873 K and the resulting microstructure and physico-mechanical properties were studied. Dark-field images showed the continued existence of porosities. The density and electrical conductivity decreased from 2.52% to 1.8% and from 48% to 11% of the International Annealed Copper Standard, respectively. There was an 11-fold increase in hardness with 25 wt.% B4C addition. Although the flexure strength of the composite decreased because of transition in formation of phases at grain boundaries from ternary Al-B-C to binary Al-B, growth of Al-B and retention of boron carbides, the flexure modulus showed up to 8 times improvement with increased fraction of reinforcement. Fractographs revealed extensive damage to grain boundaries because of generated shear and particle pull-out. The tendency for brittle fracture increased with higher reinforcement fractions. The study forms the basis to commercialise ABC composites for required applications, and it is concluded that even though uncoated boroncarbide reinforcements embrittle the aluminum matrix in as-reinforced condition, improvement in other as discussed properties is significant. The study also indicates that the ductility of the metal matrix composite (MMC) may be improved by increasing the interfacial bonding and decreasing the overall porosity contents of the composite.