A novel ceramic reinforced hierarchical metal matrix composite (Fe/Fe2B): Production and characterization

Lightweight and high strength are the common aspects of ceramic-reinforced metal matrix composites (CMMC) and wire-reinforced composites (WRC). The latter is preferred for enhanced loading response ensured by the presence of extended reinforcements in the metal matrices. Unlike the traditional Al- and Ti-matrix WRC, utilization of composite wires, instead of monolithic wires, as reinforcements for metallic WRC has multiscale engineering benefits. For example, combining the high hardness of the Fe2B and ductility of Fe can benefit tribocomponents where high temperature stability, hardness consistency and adequate toughness is required. Current study investigates the manufacturability of an Fe2B-reinforced Fe-matrix hierarchical WRC using powder metallurgy, in situ phase synthesis, and diffusion bonding. Carefully optimized boriding and diffusion bonding parameters (1100 °C, 2 h, 35 MPa, and 10–20 vol% B4C in Fe powder) assisted in manufacturing a well-bonded WRC; however, diffusion-bonded regions of the wire and sheath-core interfaces within the single-core wires developed carbon-deficient regions. Results showed that increasing fraction of the Fe2B phases within the cores minorly influenced the tensile and bending behavior of wires and WRC, respectively. The wires' tensile strength and WRC's bending fracture loads were decisively influenced by the core diameter of the single-core composite wires, acting as reinforcement. Additionally, while cores developed transverse cracks, the critical inter-wire and sheath-core interfaces preferably failed with longitudinal cracks due to the presence of carbon-deficient regions at the interfaces.