Effects of Mo/Cr single-doping and MoCr co-doping on the TiC/steel Interface in metal matrix composites

The inadequate interface bonding strength between reinforced particles and the metal matrix in particle-reinforced steel matrix composites (PR-SMCs) is a primary factor contributing to mechanical property degradation. In this study, alloying was used to improve the interface bonding strength between TiC and matrix. First-principle calculations and experimental characterization were employed to analyze the influence of Mo/Cr single-doping and MoCr co-doping on the TiC/Fe interface bonding behavior. The results demonstrated that Mo single-doping significantly promoted interface segregation and enhanced interface bonding strength. However, excessive Mo resulted in precipitation at grain boundaries and a reduction in plasticity. Cr single-doping enhanced the mechanical properties of SMCs by increasing cementite hardness and interface stability but could not effectively reduce the interface mismatch. The synergistic effect of MoCr co-doping optimized interface bonding by suppressing excessive Mo segregation and reducing the thickness of the interface layer. The Mo1.6Cr0.4 composites exhibited the best overall mechanical properties, with a tensile strength of 1435 ± 15 MPa and an elongation of 7.3 ± 0.3 %. In contrast, excess Cr (>1.2 wt%) in MoCr co-doping SMCs promoted the formation of intermetallic compounds and acicular ferrite, which led to a reduction in mechanical properties. This study provides both a theoretical basis and novel insights into the alloying design of TiC-SMCs.