Abstract
Currently, an important fundamental problem of practical importance is the production of high-quality solid-phase compounds of various metals. This paper presents a theoretical model that allows one to study the diffusion process in nickel-base refractory alloys. As an example, a two-dimensional model of ternary alloy is considered to model diffusion bonding of the alloys with different compositions. The main idea is to divide the alloy components into three groups: (i) the base element Ni, (ii) the intermetallic forming elements Al and Ti and (iii) the alloying elements. This approach allows one to consider multi-component alloys as ternary alloys, which greatly simplifies the analysis. The calculations are carried out within the framework of the hard sphere model when describing interatomic interactions by pair potentials. The energy of any configuration of a given system is written in terms of order parameters and ordering energies. A vacancy diffusion model is described, which takes into account the gain/loss of potential energy due to a vacancy jump and temperature. Diffusion bonding of two dissimilar refractory alloys is modeled. The concentration profiles of the components and order parameters are analyzed at different times. The results obtained indicate that the ternary alloy model is efficient in modeling the diffusion bonding of dissimilar Ni-base refractory alloys.
Highlights
The theory and practice of diffusion welding of dissimilar metals has been actively developed over the past decades due to the undoubted importance of this process for various technologies [1,2].Some alloys can be successfully bonded without the use of an interlayer [3,4,5]
The chemical composition of VKNA-25 and EP975 alloys is shown in Table 1 in weight percent [40]
Both alloys are based on nickel, while aluminum and titanium are elements that form the intermetallic phase Ni3 Al, where aluminum atoms can be replaced by titanium atoms
Summary
The theory and practice of diffusion welding of dissimilar metals has been actively developed over the past decades due to the undoubted importance of this process for various technologies [1,2]. Various simulation methods work at different scales and they make it possible to establish ways to achieve the required alloy structure, to trace the formation of intermetallic inclusions and their distribution over the volume and to study the effect of alloying and temperature changes. The main difficulty in atomistic simulation of heat-resistant Ni-base alloys is that they include many alloying elements This prevents the use of MD modeling due to the complexity of constructing interatomic potentials. The Monte Carlo algorithm is used to simulate the diffusion process by the vacancy mechanism in a three-component metallic systems.
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