In-situ synthesis of TiC/Fe alloy composites with high strength and hardness by reactive sintering

Fe alloy composites reinforced with in-situ titanium carbide (TiC) particles were fabricated by reactive sintering using different reactant C/Ti ratios of 0.8, 0.9, 1 and 1.1 to investigate the microstructure and mechanical properties of in-situ TiC/Fe alloy composites. The microstructure showed that the in-situ synthesized TiC particles were spherical with a size of 1–3 μm, irrespective of C/Ti ratio. The stoichiometry of in-situ TiC increased from 0.85 to 0.88 with increasing C/Ti ratio from 0.8 to 0.9, but remained almost unchanged for C/Ti ratios between 0.9 and 1.1 due to the same driving force for carbon diffusion in TiC_x at the common sintering temperature. The in-situ TiC/Fe alloy composite with C/Ti = 0.9 showed improved mechanical properties compared with other C/Ti ratios because the presence of excess carbon (C/Ti = 1 and 1.1) resulted in unreacted carbon within the Fe alloy matrix, while insufficient carbon (C/Ti = 0.8) caused the depletion of carbon from the Fe alloy matrix, leading to a significant decrease in hardness. This study presents that the maximized hardness and superior strength of in-situ TiC/Fe alloy composites can be achieved by microstructure control and stoichiometric analysis of the in-situ synthesized TiC particles, while maintaining the ductility of the composites, compared to those of the unreinforced Fe alloy. Therefore, we anticipate that the in-situ synthesized TiC/Fe alloy composites with enhanced mechanical properties have great potential in cutting tool, mold and roller material applications.