First-principles Calculation Of Structure And Interface Of NiAlV Alloy System

Nickel-based superalloys usually have the characteristics of heat resistance,oxidation resistance,and excellent high-temperature mechanical properties.Because of their good structural stability after alloying,they are commonly used in aerospace,nuclear reactors,and energy conversion fields.NiAlV medium-entropy alloy has a high potential for application due to its certain lattice distortion,delayed diffusion and cocktail effect.Ni₃Al and Ni₃V in the NiAlV system play a key role in the performance of the alloy.Therefore,this paper uses the first-principles calculation method to study the properties of the mid-entropy alloy and the law between the intermetallic compounds and matrix.The dependence of the macroscopic physical properties of the alloy system on the microstructure is explained from the electron-atomic scale.In this paper,the first-principles calculation method based on density functional theory is used to study the stability,thermodynamic properties,elastic mechanical properties and electronic structure of NiAlV medium-entropy alloys with disordered solid solution structure,the lattice mismatch and stability of the Ni?Ni₃Al and Ni?Ni₃V two-phase interface in the NiAlV alloy system are investigated,The interface energy,fracture performance and electronic structure characteristics of the Ni?Ni₃V?Ni₃Al three-phase composite interface structure were studied.The results obtained are as follows:(1)A special quasi-random structure generation algorithm based on Monte Carlo is used to obtain the disordered solid solution structure of NiAlV.The calculation results of the formation enthalpy of the structure show that the structure has excellent stability,and the thermodynamic calculation results show that the alloy system is sensitive to pressure and temperature.Elasticity mechanics calculation results show that the alloy has strong toughness,and the distribution of electrons above the Fermi level in the density of states diagram also indicates the characteristics of the metal bond between atoms in the alloy system,It is shown that the essence of thermodynamics and elasticity of alloys is the interaction of the metal bonds between atoms.(2)After the surface convergence test,the optimal Ni?Ni₃Al and Ni?Ni₃V two-phase interface structures are obtained.The calculation of the lattice mismatch degree reflects the characteristics of the lattice distortion at the interface.The calculation results of the interface energy show that due to the DO₂₂ structural characteristics of Ni₃V,there is a strong directional dependence in the Ni?Ni₃V interface system.The calculation results of the adhesion work also reflect this,and the stress concentration in the interface area will also lead to the preferentially initiation and propagation of cracks in this region.(3)Ni?Ni₃V?Ni₃Al three-phase composite structures are established based on the characteristics of Ni3V precipitation between the matrix Ni and the strengthening phase Ni3Al.The calculation results of the interface energy show that the structure is in a metastable state,which indicates that Ni,Ni3V and Ni3Al phase do not spontaneously form a coherent interface structure in the equilibrium state.With the gradual increase of pressure,the stability of the interface structure has been enhanced to a certain extent.The interface structure and the fracture resistance calculations of the three pure members of Ni,Ni₃V and Ni₃Al show that the interface structure will be separated before other regions under the action of external force.The calculations of the density of states and the differential charge density of the interface show that the electrons around the Ni atom contribute to the metal bond in the interface area during the formation of the interface,and at the same time,the interaction with the V atom is formed,which increases the stability of the interface structure.