Construction Of N-Body Potentials And Study On Alloying Mechanisms Of Binary Immiscible Metal Systems

Laminated composite materials based on the binary immiscible metal systems have broad application prospects in the industrial fields of nuclear fusion engineering,electronic packaging,aerospace and military industry due to their excellent comprehensive properties.However,because of the positive heat of formation and the great differences in chemical and physical properties between the two components,it is difficult to realize the direct metallurgical combination of immiscible metals system through traditional process.In the previous studies of our research,it was found that direct alloying of immiscible metal systems could be achieved through high-temperature structure induced alloying and irradiation damage alloying methods,however it was difficult to study the alloying mechanism.In order to investigate the atomic diffusion mechanism during the direct alloying process,the W-Cu layered composites were taken as the research object in this study,and the W-Cu direct alloying process induced by high-temperature structure at the interface was analyzed through molecular dynamics simulation.Since the existing W-Cu potentials have large deviations in calculating the physical properties of W and Cu at high temperature,and cannot effectively describe the interaction between W and Cu atoms,the construction process of n-body potential was proposed in this study.And a new interatomic potential suitable for W-Cu system was constructed.Meanwhile,based on the above process,the potentials of immiscible metal systems such as W-Ag,Mo-Ag,Mo-Cu and Nb-Cu were constructed to verify the universality of this research.The main results of this paper are as follows:（1）The W-Cu n-body potential was constructed by combining F-S potential with extended F-S potential.Then the physical properties of B2 and L1₂ virtual solid solutions were obtained through the first principle method.Based on the calculation results,the parameters of W-Cu potential were obtained by iterative method and least square method.Through the above process,the interatomic potential suitable for W-Cu binary immiscible metal system was successfully constructed.The molecular dynamics simulation results showed that the potential can accurately calculate the physical properties of W and Cu.（2）Based on the constructed W-Cu n-body potential,the alloying mechanism in the direct alloying process of W-Cu binary immiscible system was studied by molecular dynamics simulation.The results showed that the alloying temperature has an important effect on the direct alloying process,and the diffusion layer can be formed between W and Cu within the temperature range of 0.67-0.96 T_mCu(T_mCu is the melting point of Cu),and the alloying was realized.These results were in good agreement with the experimental results,which showed that the potential constructed in this study is reasonable.The disordered amorphous phase structure was found in the interface characterization results of high-angle annular dark-field scanning transmission electron microscopy（HAADF-STEM）,which also verified the rationality of the potential constructed and the calculation results in this study.（3）The interatomic potentials of W-Ag,Mo-Cu,Mo-Ag and Nb-Cu binary immiscible systems were obtained by using the same n-body potential construction method.The physical properties of each metal and alloy in these binary systems were calculated based on the potentials obtained to verify the validity and reliability of the obtained n-body potentials.It is proved that they can reasonably describe the physical properties of these systems in equilibrium and non-equilibrium states.These results also show that the n-body potential construction method presented in this study is universal for immiscible metal systems.