On the High Elastic Modulus Mechanism of Iron Matrix Composites

High modulus steels are characterized by high specific strength and specific stiffness, which can be attributed to the presence of hard reinforced particles. This paper investigates two common iron matrix composites, namely Fe/TiB2 and Fe/TiC, prepared through in situ reaction, focusing on their structures and properties. The results show that both types of reinforced particles in the high modulus steels consist of coarse primary particles and fine eutectic particles. In comparison to Fe/TiC composites, Fe/TiB2 composites exhibit larger elastic modulus (210 GPa). The reasons for the phenomenon that the experimentally measured values of the modulus of elasticity are lower than the calculated values at equilibrium are discussed. It was found that microporous defects left over from the casting process are often present inside the coarse primary particles, which can be the source of microcracks or fractures. In addition, matrix/particle interface stability calculations revealed that TiB2 possesses a distinctive hexagonal structure, resulting in a smaller interfacial distance (d0 = 1.375 Å) with the ferrite matrix phase. The high interfacial work of adhesion (Wad = 3.992 J/m2) further confirms the stronger interfacial stability of the Fe/TiB2 composite in comparison to the Fe/TiC composite.