First-principles calculations on interfacial properties and fracture behavior of the [formula omitted] interfaces

Abstract

To provide theoretical basis of the qualitative design for TiC particulate reinforced Mg matrix composite, the interfacial properties and fracture behavior of the Mg(11¯01)||TiC(11¯1) interfaces are systematically investigated by density functional theory. Five stable existing interfaces with different stacking sequences (FB, SA, SB, TC and TD interfaces) are identified after optimization. Results show that the stability order is TC> SA> SB> TD> FB interface in that TC interface with the highest work of adhesion (2.27 J/m2) and the lowest interface energy (−0.10 J/m2) after full relaxation is the steadiest. It also exhibits the greatest fracture energy of 1.76 J/m2 and the largest theoretical tensile strength of 6.690 GPa in the first-principles computational tensile tests (FPCTTs). When the separation distance is 0.05nm, the comparison of the separation energies on the five FPs (fracture plane) shows that the fracture commonly occurs on the FP-1 for FB, SB and TD interface, while FP-3 for SA and TC interface. The analyzation of charge density and density of states indicates that interfacial bonds largely come from Mg-Ti metallic/covalent mixed bonds, while the fractures mainly disrupt the Mg-Mg metallic bonds normally. The stacking sequence of TC interface can optimize the interface structure and even up the charge density, which can be the critical factors contributing to interfacial stabilization and strengthening.