Quantitative characterization and prediction method for corrosion behavior of copper alloy under deep-sea static pressure

Abstract

The application relates to a quantitative characterization and prediction method for the corrosion behavior of copper alloys under deep-sea static pressure, belonging to the field of corrosion prediction. First, a thermodynamic stable structure and model of a copper alloy with surface composition segregation are obtained. On this basis, for different seawater pressures of 0.1-10 MPa, an interfacial model of copper alloy and seawater medium solvation is established by using a molecular dynamics method, the mechanical effect of seawater pressure on the alloy surface is quantitatively simulated, and an alloy evolution structure model and structure parameters under the action of different pressures are established. The copper atom vacancy formation energy barrier on the alloy surface under different pressures and the internal copper atom migration-dissolution activation energy barrier are quantitatively analyzed, and the alloy work function, corrosion rate constant and other parameters under the action of different seawater pressures are analyzed, so that the corrosion tendency and corrosion rate of the copper alloy are characterized and predicted. The corrosion result simulated by the method is compared with the actually measured corrosion rate, the trend deviation is less than 5%, and the accuracy of the prediction method is further verified.

Description

Technical Field

[0001] This invention belongs to the field of copper alloy corrosion performance research, and in particular relates to a method that simulates the effect of different seawater pressures on the microstructure of copper alloys. Starting from the microstructure evolution of the service alloy, based on the calculation of the metal migration-dissolution activation barrier and the analysis of parameters such as corrosion rate constant, it realizes the quantitative characterization and prediction of the corrosion tendency of copper alloys in deep-sea environments. This is of great significance and application value for guiding the selection of materials and the formulation of protective measures for copper alloys in service in deep-sea environments. Background Technology

[0002] With the continuous development of deep-sea resources, the performance requirements for deep-sea engineering materials are becoming increasingly stringent, especially their corrosion resistance. Copper alloys, due to their excellent physical properties and corrosion resistance, are widely used in marine engineering. However, with increasing ocean depth, the high pressure, low temperature, and high salinity conditions of the deep-sea environment pose new challenges to the corrosion resistance of copper alloys. Therefore, research on the corrosion resistance of copper alloys under deep-sea hydrostatic pressure is of great significance for ensuring the safety and economy of deep-sea engineering.

[0003] Due to the complexity of the deep-sea environment and the evolution of the microstructure of copper alloys, accurately predicting the corrosion resistance of copper alloys in deep-sea environments is challenging. In-depth research on the corrosion resistance of copper alloys under deep-sea hydrostatic pressure conditions, especially their microstructural characteristics and dynamic failure processes in such environments, is crucial for copper alloy material selection and optimizing protective measures to extend service life. Traditional experimental methods struggle to simulate complex environmental conditions and cannot obtain the microstructural evolution and failure micro-processes of copper alloys, limiting the accuracy and repeatability of experimental results. To address the shortcomings of experimental methods in characterizing and predicting copper alloy corrosion in deep-sea environments, researchers have used empirical formulas to predict complex corrosion problems based on environmental factors. However, due to the complexity and variability of environmental conditions, accurate prediction of copper alloy corrosion under high-pressure deep-sea environments is often difficult. In recent years, with the development of materials computational science, the accuracy and efficiency of simulating and predicting material failure behavior under deep-sea conditions have significantly improved. In contrast, simulation methods can start from the material itself and quantitatively analyze the material failure process at the atomic scale, gaining attention for their high accuracy and unique advantages. These advantages include: through the analysis of the inherent structure and evolution of materials, it is possible to accurately simulate corrosion processes at the microscopic level, predict the corrosion behavior of alloy materials in typical system components under different conditions, and realize simulation experiments under complex environmental conditions. Furthermore, the computational simulations exhibit high repeatability and clearly identify key influencing factors, facilitating a systematic study of the impact of different factors on corrosion behavior and providing a more reliable basis for material selection and design in deep-sea engineering. This invention aims to utilize advanced computational simulation technology to conduct in-depth research on the corrosion resistance of copper alloys in deep-sea environments, with the goal of optimizing and improving material performance.

[0004] Therefore, establishing accurate corrosion prediction models through simulation methods, which comprehensively consider the evolution of deep-sea environmental factors and the microstructure of materials, has become an important means of predicting the corrosion resistance of copper alloys in deep-sea environments. Thus, developing a new method that can comprehensively consider the influence of actual factors and accurately predict the corrosion resistance of copper alloys in deep-sea environments based on the microstructure evolution and structural instability of copper alloys under seawater hydrostatic pressure is of great significance for the selection and application of deep-sea engineering materials. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the purpose of this invention is to propose a method for predicting the corrosion resistance of copper alloys under deep-sea hydrostatic pressure by establishing a microscopic model and structural evolution of copper alloys under different seawater pressures and simulating the activation barrier of metal migration-dissolution. This method first optimizes the initial model of the Cu(111) crystal plane using DFT simulation to create a preferred orientation of the copper crystal plane. Next, based on the mass fraction ratio of alloying elements, a microscopic structure model of the solid solution alloy is designed, and the surface segregation ability of the metal is analyzed, thereby obtaining a thermodynamically stable structure of the copper alloy with surface metal atom segregation. Furthermore, by analyzing the vacancy formation energy and migration-dissolution activation barrier of surface Cu atoms during the migration-dissolution process, a stable structural model reflecting the characteristics of the copper alloy is obtained, and the failure kinetics of the alloy metal dissolution process are analyzed. Further, a copper alloy-solution interface model is established using the MD method to simulate the influence of water molecules on the migration and dissolution process of alloy surface atoms under seawater pressure. Finally, the migration and dissolution process of surface metal atoms in the alloy was analyzed under different deep-sea hydrostatic pressures, thereby obtaining the activation energy barrier and work function of the metal dissolution structure model and enabling the prediction of the corrosion resistance of copper alloys. This invention, by quantitatively simulating the influence of deep-sea hydrostatic pressure on the dissolution process of copper alloys, analyzes the corrosion resistance characteristics of copper alloys under different hydrostatic pressures, achieving an analysis of the failure kinetic mechanism of copper alloys from an atomic-scale perspective. This has significant implications and potential value for guiding the formulation of protective measures for copper alloys.

[0006] To achieve the invention's objective, the following technical solution is employed: A microstructure model of a copper alloy solid solution is designed and geometrically optimized based on the mass fraction ratio of alloying elements. On the optimized, stable segregated copper alloy model, the distance from water molecules to the alloy model surface under different deep-sea hydrostatic pressures is obtained using the MD simulation method. Water molecules are fixed directly above the Z-axis of the model, and the migration-dissolution process of surface metal atoms is simulated. Important parameters such as the vacancy formation energy barrier, migration-dissolution activation energy barrier, and work function during the surface metal dissolution process are calculated. The PBE DFT method is used for optimization. The optimized surface metal dissolution model is taken as the initial structural model, and the structure of subsurface metal atoms dissolving and migrating to the surface is taken as the final structural model. The migration-dissolution activation energy barrier of the copper alloy is calculated using the LST / QST method. The relationship between the migration-dissolution activation energy barrier and the corrosion rate is determined, and a predictive model for the copper alloy corrosion rate constant is obtained, achieving analytical analysis of parameters such as the corrosion rate constant.

[0007] A quantitative characterization and prediction method for the corrosion behavior of copper alloys under deep-sea hydrostatic pressure includes at least the following steps:

[0008] (1) Determination of the stable structural model of copper alloy surface segregation: Based on the elemental composition of copper alloy, the thermodynamically stable structural model of copper alloy with specific component segregation on the surface was obtained by calculating the formation energy of the alloy structure model. The smaller the formation energy, the less energy is required for the formation of the structural model, indicating that the thermodynamic stability of the copper alloy structure is higher. Then, the vacancy formation energy barrier of metal atoms on the alloy surface under different seawater pressures was evaluated. The higher the vacancy formation energy barrier, the slower the dissolution kinetics of metal atoms on the alloy surface, and the more difficult the corrosion process of the alloy will occur. This is used to characterize the surface structural instability and corrosion behavior of copper alloy in deep-sea environment. The final selected stable structural model of copper alloy surface segregation corresponds to the alloy structure model with the lowest formation energy and the highest vacancy formation energy barrier. The total energy E of the alloy model was calculated. total The energy E when N metal atoms in the equilibrium lattice completely replace the alloy structure slab The formation energy ΔE of the alloy structure is determined using formula (1). f :

[0009] △E f =E total -ΣNE alloy (1)

[0010] The structural model energy E after the dissolution of surface metal atoms was determined through geometric optimization. vac The energy E of a single dissolved metal atom single And the total energy E of the alloy model total The vacancy formation energy barrier ΔE of metal atoms on the alloy surface is calculated using formula (2). vac :

[0011] △E vac =E vac +E single -E total (2)

[0012] (2) Based on the segregation-stabilized structure model of the copper alloy surface obtained in step (1), an interface model for seawater solubilization of the copper alloy surface was established to quantitatively simulate the mechanical effects of different deep-sea pressures on the alloy surface: The MD method was used to establish an interface model for seawater solubilization of the copper alloy surface under different seawater pressures of 0.1-10 MPa. Based on the relationship that the greater the seawater pressure, the smaller the distance between water molecules and the alloy surface, the distance between water molecules and the alloy surface in the interface model was adjusted. Quantitatively simulate the mechanical effects of seawater pressure on alloy surfaces, analyze the chemical and mechanical effects of seawater on alloy surfaces, and at the atomic level, characterize and predict the evolution of alloy structure and corrosion behavior under different seawater pressures.

[0013] (3) Calculation of work function of copper alloy surface metal dissolution process under different deep sea hydrostatic pressure: Based on the segregation stable structure model of copper alloy surface established in step (1) and the evolution law of its structure under different seawater pressure in step (2), the work function of metal atom dissolution process is obtained by the potential of the alloy structure model under seawater pressure and the contact potential difference between it and the seawater interface. The failure and corrosion behavior of the alloy structure are quantitatively given. As the deep sea pressure increases, the work function of copper alloy gradually decreases, and electrons are more likely to escape from the alloy surface. This further illustrates that the models in steps (1) and (2) can be used as a characterization of the corrosion process of alloy accelerated by deep sea hydrostatic pressure.

[0014] Based on the contact potential difference at the metal-solution interface Given the potential value ψ of the alloy structure model under static pressure, the work function Φ required to remove surface electrons during the alloy dissolution process is calculated using formula (3):

[0015]

[0016] (4) Calculation of the migration-dissolution activation barrier of copper alloy under different deep-sea hydrostatic pressure: Based on steps (1)-(3), the LST / QST method is used to search for the transition state structure of the atomic migration-dissolution path on the alloy surface in the deep-sea environment, and the migration-dissolution activation barrier of the metal atoms inside the copper alloy is quantitatively analyzed. As the seawater pressure increases, the migration-dissolution activation barrier of the surface copper atoms gradually decreases, which further illustrates that the seawater pressure promotes the dissolution failure kinetics of the copper alloy. Combined with the analysis of parameters such as the metal migration-dissolution activation barrier, the characterization of the large amount of corrosion of copper alloy is realized, which provides a basis for predicting the corrosion resistance of copper alloy in the deep-sea environment.

[0017] By determining the energy E of a single atom in the unit cell of a metal equilibrium body alloy-b Calculate the total energy E of metal atoms N in the equilibrium lattice for the alloy model. total The effect of the pressure x was used to calculate the migration-dissolution activation barrier ΔE during the dissolution process of metal atoms under deep-sea pressure x using formula (4). a(x) :

[0018]

[0019] (5) Establishment of a prediction model for the corrosion rate constant of copper alloy under different deep-sea static pressures: Based on the transition state structure of the alloy under different seawater pressures, the migration-dissolution activation energy barrier corresponding to several discrete deep-sea pressure points is determined by formula (4), and then several corrosion rates are obtained by formula (5). The above pairs of deep-sea pressure points and corrosion rates are fitted to obtain a prediction model for the corrosion rate constant of copper alloy, and the analysis of parameters such as corrosion rate constant is realized.

[0020] Based on formula (4), the migration-dissolution activation energy barrier ΔE during the metal atom dissolution process under different deep-sea hydrostatic pressures x is obtained. a(x,T) The imaginary frequencies corresponding to the degrees of freedom of the reaction coordinates are removed from the vibrational distribution function of the transition state, and the reaction rate constant k based on the transition state theory (TST) is calculated using the thermodynamic equivalent equation.

[0021]

[0022] Where σ represents the degeneracy of the reaction pathway, which is 1; P 0 The standard pressure in the gas phase is 0.1 MPa; Δn is 0 in the unimolecular reaction; h is Planck's constant, reflecting the relationship between energy and frequency, and is 6.626 × 10⁻⁶. -34 J·s;k b is the Boltzmann constant, with a value of 1.381 × 10⁻⁶. -23 J.K. -1 R represents the universal gas constant 8.314 J·K. -1 ·mol -1 T represents room temperature 298.15K.

[0023] In a preferred embodiment of the present invention, in step (1), the method for calculating the vacancy formation energy under different deep-sea hydrostatic pressures is as follows: the distance from water molecules to the surface of the alloy model under different deep-sea hydrostatic pressures is obtained by using seawater molecular dynamics, the water molecules are fixed directly above the Z-axis of the model and the surface metal atom dissolution process is simulated, and the energy of the vacancy formed by the dissolution of surface metal atoms is calculated.

[0024] In a preferred embodiment of the present invention, in step (2), an interface model for the solvation of copper alloy and seawater medium is established based on molecular dynamics, and the method for simulating seawater pressure is as follows: A copper alloy / solution interface system was constructed in an orthogonal simulation box. The top of the model simulates a seawater environment using a 3.5% NaCl aqueous solution, consisting of 537 water molecules and 6 NaCl ions. The bottom contains a 6×12×4 copper alloy supercell structure. 28 Cu atoms in the solution... 2+ It originates from the dissolution of the alloy surface, while Cl - and OH - Used to maintain the electroneutrality of the solution. Ions in the solution relax freely within the electrolyte region. The interaction between molecules and atoms is described using the COMPASS II force field. By setting the compression distance between the seawater medium and the alloy surface under different pressures, the seawater pressures were quantitatively simulated as follows: 0.1, 4.0, 6.0, 8.0, and 10.0 MPa; the distances between water molecules in the seawater and the alloy surface were 2.8, 2.4, 2.2, and 2.0 MPa, respectively.

[0025] In a preferred embodiment of the present invention, step (3) involves calculating the work function and migration-dissolution activation barrier under different deep-sea hydrostatic pressures as follows: The minimum work required to remove surface electrons during metal atom dissolution is obtained by using the potential of the alloy structure model under seawater pressure and the contact potential difference at the seawater interface. The model is optimized using the PBE DFT method. The optimized model of surface metal dissolution is used as the initial structural model for transition state search, and the structure of subsurface metal atoms migrating and dissolving to the surface is used as the final model for transition state search. The transition state search process is then performed to obtain the migration-dissolution activation barrier of the copper alloy.

[0026] In a preferred embodiment of the present invention, in step (4), the method for determining the migration-dissolution path of metal atoms in the copper alloy is as follows: the transition states of metal atoms during the dissolution process are located and optimized by employing the linear simultaneous transfer (LST) and quadratic simultaneous transfer (QST) methods. The LST method performs a single interpolation of the maximum energy, while the QST method searches for the maximum energy under the constraint minimization condition, thereby performing a transition state search.

[0027] In a preferred embodiment of the present invention, in step (5), the calculation method for the relationship between the migration-dissolution activation energy barrier and the corrosion rate constant of the copper alloy is as follows: The transition state theory (TST) based on the partition function can be equivalent to the form based on the free energy barrier. The standard Gibbs free activation energy of the reaction is obtained by DFT calculation of the transition state, and the imaginary frequency corresponding to the degree of freedom of the reaction coordinate is excluded from the vibrational partition function of the transition state. The transition state structure at the saddle point on the potential energy surface is studied to explore the dynamic characteristics of the reaction rate. By correlating the migration-dissolution activation energy barrier with the rate constant under different seawater pressures, a prediction model for the corrosion rate constant of the copper alloy is established.

[0028] In a preferred embodiment of the present invention, the copper alloy types include manganese aluminum bronze alloy (MAB) for propellers and copper-nickel alloy (B10) for seawater pipelines, etc.

[0029] In a preferred embodiment of the present invention, a corrosion rate prediction model for MAB alloys under deep-sea hydrostatic pressure is provided.

[0030] In a preferred embodiment of the present invention, a corrosion rate prediction model for B10 alloy under deep-sea hydrostatic pressure is provided:

[0031] In a preferred embodiment of the present invention, the corrosion behavior and corrosion rate of copper alloys under deep-sea hydrostatic pressure are predicted to be consistent with the measured values, with an error of less than 5%. This has significant implications and reference value for the selection of materials and the formulation of protective measures for copper alloys in service in deep-sea environments.

[0032] Compared with existing methods for predicting the corrosion resistance of copper alloys, this invention has the following advantages:

[0033] This invention provides an efficient and accurate method for predicting the corrosion resistance of copper alloys under deep-sea hydrostatic pressure, which can alleviate the problem of in-situ testing of alloy corrosion under deep-sea conditions.

[0034] This invention can quantitatively simulate the effects of different seawater pressures on the migration-dissolution process of alloys, and realize the prediction of corrosion behavior through the migration-dissolution activation barrier, thus clarifying the corrosion resistance characteristics of copper alloys under deep-sea hydrostatic pressure.

[0035] This invention can analyze the failure kinetic mechanism of copper alloys at the atomic scale, thereby providing important guidance for the protection measures of copper alloys, and has significant significance and potential value. Attached Figure Description

[0036] The present invention will be further described below with reference to the accompanying drawings. The drawings are only for illustrative purposes and do not limit the scope of the present invention.

[0037] Figure 1 The Cu(111) flat plate model, MAB alloy solid solution model, and MAB model established in Example 1 are described. seg Alloy segregation structure model.

[0038] Figure 2 It is MAB in Example 1 seg The schematic diagram of the metal dissolution path of the structure shows the state of Cu vacancies forming on the surface, the Cu dissolution and migration transition state, and the state of forming surface and subsurface Cu vacancies.

[0039] Figure 3 It is MAB in Example 1 seg Molecular dynamics simulation snapshots of the 3.5% NaCl solution interface under deep-sea hydrostatic pressure of 0.1-10.0 MPa and H2O density distribution on the surface of the structural model.

[0040] Figure 4 Examples 1 include a schematic model simulating the effect of water molecules on the dissolution of Cu atoms on the alloy surface under different hydrostatic pressures, an energy step diagram of Cu atom dissolution in MAB alloy under deep-sea hydrostatic pressure, and the work function of the alloy model during the metal atom dissolution process.

[0041] Figure 5 This is the transition state structure diagram of the MAB metal migration-dissolution path obtained by using the LST / QST method in Example 1 under different deep-sea hydrostatic pressures.

[0042] Figure 6 This is the corrosion prediction model of MAB alloy under different deep-sea hydrostatic pressures in Example 1 and the corrosion rate after immersion for 10 hours.

[0043] Figure 7 Example 2 shows a schematic model simulating the effect of water molecules on the dissolution of Cu atoms on the alloy surface under different hydrostatic pressures, a diagram of the energy steps of Cu atom dissolution in B10 alloy under deep-sea hydrostatic pressure, and the work function value of the alloy model during the metal atom dissolution process.

[0044] Figure 8 This is the transition state structure diagram of B10 alloy metal migration-dissolution path obtained by searching the LST / QST method under different deep-sea hydrostatic pressures in Example 2.

[0045] Figure 9 This is the corrosion prediction model of B10 alloy under different deep-sea hydrostatic pressures in Example 2, and the corrosion rate after immersion for 10 hours. Detailed Implementation

[0046] The following detailed description is based on specific embodiments, but the scope of protection of the present invention is not limited to the specific implementation methods.

[0047] Example 1: High-manganese aluminum bronze (MAB) alloy for propellers

[0048] A 3×3×4 Cu(111) plate model was established using the DMol3 module of Materials Studio. The microstructure model of the copper alloy solid solution was designed according to the mass fraction ratio of the alloying elements to achieve uniform distribution of elements. The alloy model was then optimized to obtain a stable structure model of the copper alloy with surface atomic segregation.

[0049] Establish a structural model of the MAB alloy, whose lattice constant is: The alloy's elemental composition is CuAlMn, with copper, aluminum, and manganese in a ratio of 28:4:4. Geometric optimization was performed using the PBE DFT method. To prevent interaction with adjacent plates, a layer was built on top of the model. The vacuum layer. During the optimization process, the atomic coordinates of the bottom two layers of the alloy model are fixed, serving as the copper alloy matrix, while the atomic coordinates of the surface and subsurface layers are relaxed. The formation energy ΔE of the alloy structure is calculated. f The lower the formation energy, the less energy is required to form the structural model, indicating higher thermodynamic stability of the copper alloy structure. Based on this, such as Figure 1 The number of surface segregated atoms in different alloy models was statistically analyzed to obtain the manganese aluminum bronze alloy MAB with a stable surface atom segregation structure. seg Model. Constructing the metal atom dissolution-migration-dissolution process in a copper alloy model, such as... Figure 2 As shown. Based on the optimized copper alloy model with stable segregation, the dissolution process of surface metal atoms was simulated, and the vacancy formation energy barrier ΔE of the alloy surface metal atoms was calculated. vacThe higher the vacancy formation energy barrier, the slower the dissolution kinetics of metal atoms on the alloy surface, and the more difficult the corrosion process of the alloy is to occur. This can be used to characterize the surface structural instability and corrosion behavior of copper alloys in deep-sea environments.

[0050] Using the MD method in An interface model of seawater solvation on the surface of copper alloy was established in an orthogonal simulation box to quantitatively simulate the mechanical effects of different deep-sea hydrostatic pressures (0.1-10 MPa) on the alloy surface, such as... Figure 3 As shown. The top of the model simulates a seawater environment, using a 3.5% NaCl aqueous solution, and consists of 537 water molecules and 6 NaCl ions. The bottom contains a 6×12×4 copper alloy supercell structure. 28 Cu atoms in the solution... 2+ It originates from the dissolution of the alloy surface, while Cl - and OH - Used to maintain the electroneutrality of the solution. Ions in the solution are free-relaxing and randomly distributed within the electrolyte region. The interactions between molecules and atoms are described using a COMPASS II force field, and the NVT with a velocity scale thermostat maintains the simulation temperature at 298 ± 2 K. The H₂O molecular density distribution map shows that, under different deep-sea hydrostatic pressure environments, the distance between water molecules and the alloy surface increases with increasing seawater pressure. Reduce to

[0051] Based on this, simulations were performed on MAB alloys under different seawater pressures (0.1-10 MPa) by adjusting the distance between water molecules and the alloy surface in the interface model (2.8, 2.4, 2.2, 2.0, ...). ),like Figure 4 As shown, this study quantitatively simulates the mechanical effects of seawater pressure on the alloy surface, analyzes the chemical and mechanical effects of seawater on the alloy surface, and characterizes and predicts the evolution of alloy structure and corrosion behavior under different seawater pressures at the atomic level. In models under different hydrostatic pressures, the distance from water molecules to the alloy model surface is fixed to simulate the migration-dissolution process of metals in the MAB alloy, obtaining the metal migration-dissolution activation barrier steps under deep-sea hydrostatic pressures of 0.1-10 MPa. The PBE DFT method is used to optimize the model. The optimized surface metal dissolution model is used as the initial structural model for transition state search, and the structure of subsurface metal atoms dissolving and migrating to the surface is used as the final model for transition state search. The LST / QST method is used to search for the transition state structure of the alloy surface atomic migration-dissolution path in a deep-sea environment, quantitatively analyzing the migration-dissolution activation barrier ΔE during the metal atom dissolution process on the copper alloy surface. a(x,T)As seawater pressure increases, the migration-dissolution activation barrier of surface copper atoms decreases, indicating that seawater pressure promotes the dissolution failure kinetics of the copper alloy. The potential ψ of the alloy structure model under seawater pressure and the contact potential difference at the seawater interface are analyzed. The work function Φ of the metal atom dissolution process was obtained, and the alloy structure failure and corrosion behavior were quantitatively characterized. With the increase of deep-sea hydrostatic pressure, the work function of copper alloy gradually decreased, and electrons were more likely to escape from the alloy surface, which further illustrates that deep-sea hydrostatic pressure accelerates the corrosion process of MAB alloy.

[0052] The migration and surface extraction of metal atoms inside the MAB alloy under different seawater pressures are multi-step processes, with migration-dissolution activation barriers of 0.63, 0.60, 0.56, 0.55, and 0.54 eV, respectively.

[0053] The transition state search was performed on the structural model of MAB alloy under different deep-sea hydrostatic pressures to identify the pathway with the lowest reaction energy barrier during the dissolution and activation process of the subsurface metal to the surface. Figure 5 As shown. Based on the transition state structure of the alloy under different seawater pressures, the migration-dissolution activation barrier ΔE was determined. a(x,T) The relationship between the corrosion rate constant k and the corrosion rate constant was investigated, and the corrosion rate constant of the alloy under different seawater pressures was fitted to obtain a predictive model for the corrosion rate constant of copper alloys, thus achieving the analysis of parameters such as the corrosion rate constant. Through experimental verification, the corrosion mass loss and corrosion rate of MAB alloys after immersion in artificial seawater under different deep-sea hydrostatic pressures for 10 hours were calculated. When the deep-sea pressure reached 6.0 MPa, the corrosion rate increased significantly; when the pressure reached 10 MPa, the corrosion weight loss of manganese aluminum bronze reached its maximum, indicating that the corrosion resistance of manganese aluminum bronze alloys in seawater significantly weakens with increasing hydrostatic pressure. The results show that the corrosion rate constant of copper alloys obtained by the predictive model is basically consistent with the experimental corrosion rate, with a trend error of less than 5%, achieving quantitative characterization and prediction of the corrosion behavior of copper alloys in deep-sea environments. The migration-dissolution activation energy barrier ΔE of MAB alloys under different deep-sea hydrostatic pressures was determined. a(x,T) Analyze the relationship between the metal migration-dissolution activation barrier and the corrosion rate constant, such as... Figure 6 The corrosion rate prediction model for manganese aluminum bronze alloy (MAB) is shown below, with deep-sea hydrostatic pressure (x) as the abscissa and the corrosion rate constant (y) as the ordinate.

[0054] Example 2: B10 alloy for seawater pipelines

[0055] A 3×3×4 B10 alloy structure model was built using the DMol3 module of Materials Studio, with a lattice constant of . The alloy has an elemental composition of CuNi, with a copper to nickel ratio of 32:4. The geometry of the copper alloy model was optimized. To prevent interaction with adjacent plates, a layer was built on top of the model. The vacuum layer. During the optimization process, the atomic coordinates of the bottom two layers of the alloy model are fixed, serving as the copper alloy matrix, while the atomic coordinates of the surface and subsurface layers are relaxed. The formation energy of the B10 alloy structure is calculated, and the number of surface segregated atoms in different alloy models is statistically analyzed to obtain the B10 with a stable surface atomic segregation structure. seg Model. The dissolution-migration-dissolution process of metal atoms in a copper-nickel alloy model is constructed. Based on the optimized copper alloy model with stable segregation, the dissolution process of surface metal atoms is simulated to obtain the vacancy formation energy barrier of the migration-dissolution process in the copper-nickel alloy.

[0056] exist An interface model of seawater solubilization on the surface of a copper alloy was established in an orthogonal simulation box. Based on the water molecule density distribution diagrams under different deep-sea hydrostatic pressures, the distances from water molecules to the alloy model surface were simulated at seawater pressures of 0.1-10 MPa as follows: 3.0, 2.7, 2.5, 2.3, and 2.3 MPa, respectively. In models under different hydrostatic pressures, the distance between the corresponding water molecules and the surface of the alloy model is fixed as follows: Figure 7 As shown, the activation energy barrier steps of metal migration-dissolution in B10 alloy under deep-sea hydrostatic pressures of 0.1-10 MPa were obtained by simulating the migration-dissolution process. The PBE DFT method was used for optimization. The optimized surface metal dissolution model was used as the initial structural model for the transition state search, and the structure of subsurface metal atoms dissolving and migrating to the surface was used as the final structural model for the transition state search. The LST / QST method was used to search for the transition state structure of the alloy surface atom migration-dissolution path in the deep-sea environment, and the migration-dissolution activation energy barrier during the surface metal atom dissolution process of B10 alloy was quantitatively analyzed. With increasing seawater pressure, the activation energy barrier ΔE of the surface copper atoms migration-dissolution increases. a(x,T) The decrease indicates that seawater pressure promotes the dissolution failure kinetics of the copper alloy. The potential ψ of the alloy structure model under seawater pressure and the contact potential difference at the seawater interface are analyzed. The work function Φ of the metal atom dissolution process was obtained, and the structural failure and corrosion behavior of the alloy were quantitatively characterized. With the increase of deep-sea hydrostatic pressure, the work function of the copper alloy gradually decreased, and electrons were more likely to escape from the alloy surface, which further illustrates that deep-sea hydrostatic pressure accelerates the corrosion process of B10 alloy.

[0057] In a preferred embodiment of the present invention, the migration-dissolution activation barriers of B10 alloy under different seawater pressures are 0.66, 0.65, 0.61, 0.60, and 0.58 eV, respectively.

[0058] A transition state search was performed on the subsurface metal dissolution and activation process of a copper-nickel alloy structural model under different deep-sea hydrostatic pressures, selecting the path with the lowest reaction energy barrier, such as... Figure 8 As shown. Based on the transition state structure of B10 alloy under different seawater pressures, the migration-dissolution activation barrier ΔE was determined. a(x,T) The relationship between the corrosion rate constant k and the corrosion rate constant was investigated. The corrosion rate constant of the alloy under different seawater pressures was fitted to obtain a predictive model for the corrosion rate constant of copper alloys, enabling the analysis of parameters such as the corrosion rate constant. Experimental verification was conducted to obtain the corrosion rate of B10 alloy after immersion in artificial seawater under different deep-sea hydrostatic pressures for 10 hours. Experimental results show that with increasing deep-sea hydrostatic pressure, the corrosion rate of B10 alloy accelerates, and its corrosion resistance in seawater weakens. The results indicate that the corrosion rate constant of B10 alloy obtained by the predictive model is basically consistent with the experimental corrosion rate, with a trend error of less than 5%, achieving quantitative characterization and prediction of the corrosion behavior of copper alloys in deep-sea environments. The migration-dissolution activation energy barrier ΔE of B10 alloy under different deep-sea hydrostatic pressures was determined. a(x,T) Analyze the relationship between the metal migration-dissolution activation barrier and the corrosion rate constant, such as... Figure 9 The corrosion rate prediction model for copper-nickel alloy (B10) is shown below, with deep-sea hydrostatic pressure (x) as the abscissa and the corrosion rate constant (y) as the ordinate.

[0059]

[0060] Figure 1 The Cu(111) flat plate model, MAB alloy solid solution model, and MAB model established in Example 1 are described. seg Alloy segregation structure model; the stable structure of MAB alloy is an Al-rich surface segregation structure.

[0061] Figure 2 It is MAB in Example 1 seg The schematic diagram of the metal dissolution path of the structure shows the state of Cu vacancies forming on the surface, the Cu dissolution and migration transition state, and the state of forming surface and subsurface Cu vacancies.

[0062] Figure 3 It is MAB in Example 1 seg Molecular dynamics simulation snapshots and H2O density distribution on the surface of the 3.5% NaCl solution interface under deep-sea hydrostatic pressure of 0.1–10.0 MPa. With increasing seawater pressure, the distance between the characteristic density peak of H2O and the alloy surface decreases significantly, indicating that deep-sea hydrostatic pressure brings water molecules closer to the alloy surface, thereby accelerating the dissolution process of the alloy.

[0063] Figure 4This is a schematic model simulating the effect of water molecules on the dissolution of Cu atoms on the alloy surface under different deep-sea hydrostatic pressures, a diagram of the energy steps of Cu atom dissolution in MAB alloy under seawater pressure, and the work function of the alloy model during the metal atom dissolution process. The results of the energy steps diagram for Cu atom dissolution show that as the distance between water molecules and the alloy interface decreases, the work function, vacancy formation energy barrier, and migration activation energy barrier all decrease, further confirming that deep-sea hydrostatic pressure has a significant promoting effect on the dissolution process of MAB alloy.

[0064] Figure 5 This is a transition state structure diagram of the MAB metal migration-dissolution path obtained by searching the LST / QST method under different deep-sea hydrostatic pressures in Example 1. As the hydrostatic pressure increases in the range of 0.1-10.0 MPa, the metal dissolution activation energy of the MAB alloy decreases significantly; indicating that under the influence of deep-sea hydrostatic pressure, the corrosion tendency of manganese aluminum bronze is enhanced and its corrosion resistance is reduced.

[0065] Figure 6 This is a corrosion prediction model for the MAB alloy under different deep-sea hydrostatic pressures in Example 1, along with the corrosion rate after immersion for 10 hours. When the deep-sea pressure reaches 6.0 MPa, the corrosion rate increases significantly; at 10 MPa, the corrosion weight loss reaches its maximum, indicating that the corrosion resistance of the MAB alloy in seawater significantly decreases with increasing hydrostatic pressure. Comparison with the actually measured corrosion rate shows that the model can accurately and effectively predict the corrosion resistance of the MAB alloy under deep-sea hydrostatic pressure.

[0066] Figure 7 Example 2 presents a schematic model simulating the effect of water molecules on the dissolution of Cu atoms on the alloy surface under different deep-sea hydrostatic pressures, an energy step diagram of Cu atom dissolution in B10 alloy under seawater pressure, and the work function value of the alloy model during the metal atom dissolution process. The results of the energy step diagram required for surface Cu atom dissolution show that as the distance between water molecules and the alloy interface decreases, the work function, vacancy formation energy, and migration activation energy barrier all decrease, indicating that deep-sea hydrostatic pressure has a promoting effect on the migration-dissolution process of B10 alloy.

[0067] Figure 8 This is a transition state structure diagram of the B10 alloy metal migration-dissolution path obtained by searching the LST / QST method under different deep-sea hydrostatic pressures in Example 2. As the hydrostatic pressure increases in the range of 0.1-10.0 MPa, the metal dissolution activation energy of the B10 alloy gradually decreases; indicating that under the influence of deep-sea hydrostatic pressure, the corrosion tendency of the copper-nickel alloy is enhanced and its corrosion resistance is reduced.

[0068] Figure 9This is a corrosion prediction model for B10 alloy under different deep-sea hydrostatic pressures in Example 2, along with the corrosion rate after immersion for 10 hours. The results show that the corrosion rate of B10 alloy gradually increases with increasing hydrostatic pressure, indicating that increased hydrostatic pressure accelerates the corrosion process of the copper-nickel alloy. Comparison with the measured corrosion rate demonstrates that this model can accurately and effectively predict the corrosion resistance of B10 alloy under hydrostatic pressure.

[0069] The above detailed embodiments describe the basic principles and main features of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and any changes or modifications conceived without creative effort should be covered within the scope of protection of the present invention. Various changes and modifications can be made to the present invention without departing from its scope, and all such changes and modifications will fall within the scope of protection claimed.

Claims

1. A method for quantitative characterization and prediction of corrosion behavior of copper alloys under deep-sea hydrostatic pressure, characterized in that, At least the following steps are included: (1) Determination of the stable structural model of copper alloy surface segregation: Based on the elemental composition of copper alloy, the thermodynamic stable structural model of copper alloy with specific component segregation on the surface is obtained by calculating the formation energy of the alloy structure model. The smaller the formation energy, the less energy is required to form the structural model, indicating that the thermodynamic stability of the copper alloy structure is higher. Then, the vacancy formation energy barrier of metal atoms on the alloy surface under different seawater pressures is evaluated. The higher the vacancy formation energy barrier, the slower the dissolution kinetics of metal atoms on the alloy surface, and the more difficult the corrosion process of the alloy will occur. This is used to characterize the surface structure instability and corrosion behavior of copper alloy in deep-sea environment. Finally, the selected stable structural model of copper alloy surface segregation corresponds to the alloy structure model with the smallest formation energy and the highest vacancy formation energy barrier. The total energy E of the alloy model was calculated. total The energy E when N metal atoms in the equilibrium lattice completely replace the alloy structure slab The formation energy ΔE of the alloy structure is determined using formula (1). f : (1) The structural model energy E after the dissolution of surface metal atoms was determined through geometric optimization. vac The energy E of a single dissolved metal atom single And the total energy E of the alloy model total The vacancy formation energy barrier ΔE of metal atoms on the alloy surface is calculated using formula (2). vac : (2) (2) Based on the segregation stable structure model of the copper alloy obtained in step (1), an interface model of seawater solubilization on the surface of the copper alloy was established to quantitatively simulate the mechanical effects of different deep-sea pressures on the alloy surface: The MD method was used to establish an interface model of seawater solubilization on the surface of the copper alloy under different seawater pressures of 0.1-10 MPa. According to the relationship that the greater the seawater pressure, the smaller the distance between water molecules and the alloy surface, the distance between water molecules and the alloy surface in the interface model was adjusted to 2.8-1.6 Å to quantitatively simulate the mechanical effects of seawater pressure on the alloy surface. The chemical and mechanical effects of seawater medium on the alloy surface were analyzed. At the atomic level, the evolution law of alloy structure under different seawater pressures and its corrosion behavior were characterized and predicted. (3) Calculation of work function of copper alloy surface metal dissolution process under different deep sea hydrostatic pressure: Based on the segregation stable structure model of copper alloy surface established in step (1) and the evolution law of its structure under different seawater pressure in step (2), the work function of metal atom dissolution process is obtained by the potential of the alloy structure model under seawater pressure and the contact potential difference between it and the seawater interface. The failure and corrosion behavior of the alloy structure are quantitatively given. As the deep sea pressure increases, the work function of copper alloy gradually decreases, and electrons are more likely to escape from the alloy surface. This further illustrates that the models in steps (1) and (2) can be used as a characterization of the corrosion process of alloy accelerated by deep sea hydrostatic pressure. Based on the contact potential difference Δφ at the metal-solution interface m / s Given the potential value ψ of the alloy structure model under static pressure, the work function Φ required to remove surface electrons during the alloy dissolution process is calculated using formula (3): (3) (4) Calculation of the migration-dissolution activation barrier of copper alloy under different deep-sea hydrostatic pressure: Based on steps (1)-(3), the LST / QST method is used to search for the transition state structure of the atomic migration-dissolution path on the alloy surface in the deep-sea environment, and the migration-dissolution activation barrier of the metal atoms inside the copper alloy is quantitatively analyzed. As the seawater pressure increases, the migration-dissolution activation barrier of the surface copper atoms gradually decreases, which further illustrates that the seawater pressure promotes the dissolution failure kinetics of the copper alloy. Combined with the analysis of the metal migration-dissolution activation barrier parameters, the characterization of the large amount of corrosion of copper alloy is realized, which provides a basis for predicting the corrosion resistance of copper alloy in the deep-sea environment. By determining the energy E of a single atom in the unit cell of a metal equilibrium body alloy-b Calculate the total energy E of metal atoms N in the equilibrium lattice for the alloy model. total The effect of the pressure x was used to calculate the migration-dissolution activation barrier ΔE during the dissolution process of metal atoms under deep-sea pressure x using formula (4). a(x) : (4) (5) Establishment of a prediction model for the corrosion rate constant of copper alloy under different deep-sea hydrostatic pressures: Based on the transition state structure of the alloy under different seawater pressures, the migration-dissolution activation energy barrier of several discrete deep-sea pressure points is determined by formula (4). Then, according to formula (5), several corrosion rates corresponding to different seawater pressures are obtained. The migration-dissolution activation energy barrier and corrosion rate are fitted to obtain a prediction model for the corrosion rate constant of copper alloy. After that, the obtained prediction model for the corrosion rate constant of copper alloy is converted into a relationship model between deep-sea hydrostatic pressure and the corrosion rate constant of copper alloy to realize the analysis of the corrosion rate constant. Based on formula (4), the migration-dissolution activation energy barrier ΔE during the metal atom dissolution process under different deep-sea hydrostatic pressures x is obtained. a(x,T) The imaginary frequencies corresponding to the degrees of freedom of the reaction coordinates are removed from the vibrational distribution function of the transition state, and the reaction rate constant k based on the transition state theory TST is calculated using the thermodynamic equivalent equation. (5) Where σ represents the degeneracy of the reaction pathway, which is 1; P 0 The standard pressure in the gas phase is 0.1 MPa; Δn is 0 in the unimolecular reaction. h is Planck's constant, which reflects the relationship between energy and frequency, and has a value of 6.626 × 10⁻⁶. -34 J·s;k b is the Boltzmann constant, with a value of 1.381 × 10⁻⁶. -23 J.K. -1 R represents the universal gas constant 8.314 J·K. -1 ·mol -1 T represents room temperature 298.15 K.

2. The method according to claim 1, characterized in that, In step (1), the method for calculating the vacancy formation energy under different deep-sea hydrostatic pressures is as follows: the distance from water molecules to the surface of the alloy model under different deep-sea hydrostatic pressures is obtained by using seawater molecular dynamics. The water molecules are fixed directly above the Z-axis of the model and the dissolution process of surface metal atoms is simulated. The energy of the vacancy formed by the dissolution of surface metal atoms is calculated.

3. The method according to claim 1, characterized in that, In step (2), an interface model for solvation between the copper alloy and seawater medium was established based on molecular dynamics. The method for simulating seawater pressure is as follows: a copper alloy / solution interface system was established in an orthogonal simulation box of 26.56×30.67×53.10 Å; the top of the model simulates the seawater environment, using a 3.5% NaCl aqueous solution, composed of 537 water molecules and 6 NaCl ions; the bottom contains a 6×12×4 copper alloy supercell structure; 28 Cu atoms in the solution... 2+ It originates from the dissolution of the alloy surface, while Cl - and OH - Used to maintain the electroneutrality of the solution; ions in the solution relax freely in the electrolyte region; the interaction between molecules and atoms is described using the COMPASS II force field. By setting the compression distance between the seawater medium and the alloy surface under different pressures, the seawater pressures were quantitatively simulated as follows: 0.1, 4.0, 6.0, 8.0, and 10.0 MPa; the distances between water molecules in the seawater and the alloy surface were 2.8, 2.4, 2.2, 2.0, and 1.6 Å, respectively.

4. The method according to claim 1, characterized in that, In step (3), the work function and migration-dissolution activation barrier under different deep-sea hydrostatic pressures are calculated as follows: the minimum work required to remove surface electrons during metal atom dissolution is obtained by using the potential of the alloy structure model under seawater pressure and the contact potential difference with the seawater interface; the model is optimized using the PBE DFT method, and the optimized model of surface metal dissolution is used as the initial structure model for transition state search, and the structure of subsurface metal atoms migrating and dissolving to the surface is used as the final state model for transition state search. The transition state search process is then performed to obtain the migration-dissolution activation barrier of the copper alloy.

5. The method according to claim 1, characterized in that, In step (4), the method for determining the migration-dissolution path of metal atoms in the copper alloy is as follows: by using the linear simultaneous transfer (LST) and quadratic simultaneous transfer (QST) methods, the transition state of metal atoms in the dissolution process is located and optimized; the LST method performs a single interpolation of the maximum energy, while the QST method searches for the maximum energy under the constraint minimization condition, thereby performing the transition state search.

6. The method according to claim 1, characterized in that, In step (5), the calculation method for the relationship between the migration-dissolution activation energy barrier and the corrosion rate constant of the copper alloy is as follows: The transition state theory TST based on the partition function is equivalent to the form based on the free energy barrier. The standard Gibbs free activation energy of the reaction is obtained by DFT calculation of the transition state. The imaginary frequency corresponding to the degree of freedom of the reaction coordinate is excluded from the vibrational partition function of the transition state. The transition state structure at the saddle point on the potential energy surface is studied to explore the dynamic characteristics of the reaction rate. By correlating the migration-dissolution activation energy barrier with the rate constant under different seawater pressures, a prediction model for the corrosion rate constant of the copper alloy is established.

7. The method according to claim 1, characterized in that, Copper alloy types include the manganese-aluminum bronze alloy MAB for propellers and the copper-nickel alloy B10 for seawater pipelines; Corrosion rate prediction model for MAB alloys under deep-sea hydrostatic pressure: R 2 = 0.996; Corrosion rate prediction model for B10 alloy under deep-sea hydrostatic pressure: R 2 = 0.

995.

8. The method according to any one of claims 1-7, characterized in that, The geometric structure model was optimized using Materials Studio's DMol3, and the MD method was used to establish an interface model for the solubilization of copper alloy surfaces in seawater. This allowed for the quantitative characterization and prediction of the corrosion behavior of copper alloys in deep-sea environments.

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