The Inversion Of Metal/Transition Metal Carbide Interfacial Potential And The Theoretical Study Of Interfacial Stability

Transitional metal carbides (TMC) have always been used in materials engineering for the high melting point, high hardness, wear and corrosion resistance, and chemical stability. For example, the group IV and V transition metal carbides are very important compounds as reinforced materials in the bulk metal and various stable coating on the surfaces. The unique properties of Fe/TMC composites have been attracting increasingly theoretical and experimental studies. The interfacial features have an important effect on the desirable performances of the engineering materials and coating fail when inherent defects appear between iron-based matrix and TMC particle. So, it is essential to investigate the interfacial structures and mechanical behaviors of metal/TMC composites.In the present paper, we supposed three ideal atomic structural models of bcc[110]/B1[100],bcc[100]/B1[100] and fcc[100]/B1[100] interfaces, and it’s a first time to systematically employ the Chen-Mobius inversion method to extract the effectively interfacial potentials form the interfacial adhesive energy curves based on the first-principle calculation. Then we get these interfacial potentials of Fe[110]/TMC[100] and Fe[100]/TMC[100](M=Ti、Zr、Hf、V、Nb and Ta) interfacial systems, as well as Cu[100]/TMC[100](M=Ti、Zr、Hf、V and Nb) interfacial systems.The purpose of this thesis is to employ the interfacial potentials of Fe/TMC and Cu/TMC systems to investigate the interfacial stability. Firstly, based on semi-coherent interfacial model, the different sizes of the (m, n) misfit dislocation models are employed to compare the interfacial energy and atomic structure of the dislocation, and the formation energy and force of the dislocation cores are used to quaitatively analysis the effect of dislocations. Then, the crystal particulate boundary models are employed to describe the toughening effect of TMC in metal materials, and due to the external force, the fracture and compressiong progresses are simulated by energy minimization method. Theoretical cohesive strength σmax, the surface energy of cleavage plane γs, interfacial breaking force F and Young’s modulus values ε are used to indicated that the tensile stress required for crack propagation. In compareing σ-x curves, the changed trend can indicate anti-compression ability of interfacial system during the compression process. Then, the stabilities of different interfacial systems are detailedly discussed based on interface energy, fracture and compression processes. Finally, the tensile fracture mechanism of these interfaces is suggested based on the analysis of evolution of interfacial structure during the fracture processes.According to simulate the stretch and compression processes of Fe/TMC and Cu/TMC interfaces, NbC and HfC may extremely develop the anti-stretch and anti-compression ability of Fe/TMC interfacial system. However, ZrC and HfC can be used to excellent strengthen Cu matrix. Via the comparison of atomic structures in the different interfacial fracture processes, the dislocation climbs provide the relative space to promote the atomic motions. The possible fracture mechanism is that the extended interfacial damages are derived from the cracks between the dislocation cores on the stress.