In situ synthesis of titanium diboride composites through volume combustion

Abstract

Hard in situ synthesis of TiB₂–Fe₂B metal matrix composite (MMC) has been synthesised by volume combustion synthesis (VCS) reactions of Fe–FeTi–FeB system. VCS samples were characterised by SEM, EDX, XRD and DTA. Results show that it is possible to synthesise in situ structured MMC samples (with TiB₂ and Fe₂B phases) by VCS. Metallographic investigations show that Fe₂B and TiB₂ are found dispersed throughout the metal matrix, and other borides are present in microlevel patches dispersed in a eutectic matrix. The Fe–TiB₂ composites sintered at temperature of 1200°C consist of three different regions, i.e. α-Fe, TiB₂ and Fe₂B regions. The increase in sintering temperature to 1400°C leads to a hypereutectic microstructure of the Fe–B binary system having TiB₂ grains uniformly distributed throughout the matrix. A semiliquid phase sintering occurred by increasing eutectic phase transformation temperatures to 1400°C, which increased the efficiency of VCS. On the other hand, increasing sintering time from 1 to 3 h decreased the volume fraction of α-Fe and increased the volume fraction TiB₂ phase.