Method for evaluating and predicting copper alloy failure under coupling action of seawater pressure and flow velocity in deep sea environment

Abstract

The invention discloses a copper alloy failure evaluation and prediction method under the seawater pressure and flow velocity coupling effect in a deep sea environment, and belongs to the technical field of deep sea flowing copper alloy corrosion. Firstly, an XRD spectrum under the coupling action of deep sea pressure and seawater flow velocity is analyzed, and the micro-strain level is quantified. Secondly, a copper alloy / seawater solvation interface model is established, and the evolution process of the copper alloy microstructure in the dynamic deep sea environment is simulated; and in combination with the actually measured micro-strain level, atomic-scale axial strain is applied, and a copper alloy microstructure model under the seawater pressure and flow velocity coupling effect is constructed. And analyzing the quantitative relationship between the activation energy barrier and the dissolution rate under the action of different seawater and flow rates. And establishing a corrosion rate prediction model comprehensively considering seawater pressure and flow velocity. By establishing a corrosion rate prediction model, the influence of the seawater pressure and flow velocity coupling effect on the alloy surface microstructure is accurately evaluated, and an effective means is provided for evaluating the failure tendency of the copper alloy in the deep sea environment.

Description

Technical Field

[0001] The present invention belongs to the field of copper alloy corrosion and protection technology in deep-sea flow environment, and in particular, it involves simulating the influence of seawater pressure and flow rate on the microstructure of copper alloy, and accurately predicting the corrosion rate of copper alloy in deep-sea dynamic and complex environment by analyzing key corrosion kinetic parameters such as partial wave state density, work function and dissolution potential. The invention has important engineering application value for optimizing the protection measures of typical system components in deep-sea systems and improving equipment durability and operating efficiency. Background Art

[0002] The corrosion problem in the deep-sea environment poses a severe challenge to the long-term safety and durability of marine engineering equipment, especially in typical system components such as propellers, seawater piping systems and deep-sea submersibles. Copper alloys are widely used in the manufacture of these deep-sea equipment due to their excellent corrosion resistance and mechanical properties. However, the complex fluid dynamics factors in the deep-sea environment, such as high pressure, strong flow rate and turbulence, have a significant impact on the corrosion behavior of the alloy surface. At present, the prediction method for the corrosion rate of copper alloys in the deep-sea dynamic environment mainly relies on experimental data and empirical formulas, but due to the complexity of the deep-sea environment, the existing methods often lack an accurate description of the flow rate, pressure and alloy microstructure changes, resulting in large uncertainties in the corrosion rate prediction results. Therefore, accurately predicting the corrosion rate of copper alloys in the deep-sea dynamic environment has become a key issue to improve the operating safety of deep-sea equipment and extend its service life.

[0003] The significance of studying the corrosion failure process of alloys in deep-sea dynamic environments is that it not only affects the long-term reliability of the equipment, but also the economic benefits of the entire marine engineering project. In recent years, the research on the corrosion behavior of alloys in deep-sea environments has gradually deepened, covering the effects of multiple factors such as pressure, flow rate, and temperature. However, most studies are still limited to static or quasi-static experimental conditions, and lack systematic theoretical and experimental support for simulating the corrosion process under the coupling of pressure and flow rate in dynamic deep-sea environments. In addition, the microstructural changes of alloys and their interactions with the environment are often not fully considered. This makes it difficult to accurately predict the corrosion rate and failure mechanism of copper alloys under different deep-sea environmental conditions, affecting the formulation of protection strategies for deep-sea system components and the improvement of equipment operation efficiency.

[0004] In order to solve the problem of corrosion rate prediction in deep-sea dynamic environment, the method combining experiments and numerical simulations has shown significant advantages. Numerical simulation can accurately control parameters such as pressure, flow rate and microstructural changes. At the same time, experimental verification can provide corrosion behavior data in real environment to calibrate and optimize simulation results. Through the combination of experiments and numerical simulations, not only can the corrosion mechanism of copper alloys in deep-sea dynamic environment be accurately analyzed, but also a high-precision corrosion rate prediction model can be established. This method helps to improve the accuracy of corrosion rate prediction, reduce prediction errors, and provide a reliable basis for the design and protection of typical system components in marine engineering, promoting the optimization design of deep-sea equipment and the development of long-term protection strategies. Summary of the invention

[0005] In order to solve the limitations of the prior art, the present invention aims to combine experiments with numerical simulations to study the corrosion behavior of copper alloys under the action of coupled mechanics in a deep-sea dynamic environment, and develop a method for evaluating the failure tendency of copper alloys and predicting the corrosion rate based on coupled mechanics in a deep-sea dynamic environment. The method first analyzes the XRD spectrum under the coupled action of deep-sea pressure and seawater flow rate to quantify the microstrain level of copper alloys under different coupled mechanics conditions. Secondly, a copper alloy / seawater solvation interface model is established to simulate the evolution of the microstructure of the copper alloy under different seawater pressure conditions. On this basis, combined with the quantitative relationship of the measured alloy surface microstrain under the action of coupled mechanics, atomic-level axial strain is applied to the copper alloy (111) crystal plane, and a copper alloy microstructure model under the coupled action of seawater pressure and flow rate is further constructed. Based on the analysis of corrosion kinetic parameters such as partial wave state density, work function and dissolution potential, the corrosion tendency of copper alloys in a deep-sea dynamic environment is predicted. In addition, the present invention quantitatively analyzes the influence of different flow rates on the surface atomic migration and dissolution activation energy barrier of copper alloys under the same deep-sea pressure, and obtains the quantitative relationship between the activation energy barrier and the dissolution rate. Combined with the intrinsic diffusion coefficient of copper atoms, a corrosion rate prediction model that comprehensively considers seawater pressure and flow rate was established. By establishing a corrosion rate prediction model, the present invention accurately evaluates the influence of the coupling effect of seawater pressure and flow rate on the alloy surface microstructure, providing an effective means for evaluating the failure tendency of copper alloys in deep-sea environments.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical scheme: the microstrain of the copper alloy under the action of coupled mechanics is determined by analyzing the diffraction peak shape and peak width by XRD. The molecular dynamics (MD) method is used to establish a copper alloy / seawater solvation interface model under different seawater pressures of 0.1-10Mpa, and the mechanical effect of seawater pressure on the alloy surface is quantitatively simulated by regulating the distance between the water molecules and the copper alloy surface in the interface model. Density functional theory (DFT) is used, based on the determined copper alloy / seawater solvation interface model, by precisely controlling the lattice constant of the copper alloy in the deep-sea flow environment, microstrain is applied along the (111) crystal plane direction, and a copper alloy microstructure model under the action of coupled mechanics is constructed. The PBE-GGA method is used to optimize the geometric structure model of the alloy, calculate the work function and dissolution potential of the copper alloy under the action of coupled mechanics, and use the DFT semi-nuclear pseudopotential (DSPP) method to introduce relativistic effects to deal with nuclear electrons. The linear simultaneous transfer (LST) and quadratic simultaneous transfer (QST) transition state search methods were used to quantitatively analyze the activation energy barrier of copper alloy atoms under the combined effects of seawater flow rate and pressure, and the quantitative relationship between the activation energy barrier and the dissolution rate was obtained. Combined with the intrinsic diffusion coefficient of copper atoms, a corrosion rate prediction model that comprehensively considers seawater pressure and flow rate was established.

[0007] A method for evaluating and predicting copper alloy failure under the coupling of seawater pressure and flow velocity in a deep sea environment, characterized in that the method comprises the following steps:

[0008] (1) Microstrain analysis of copper alloy under coupled mechanics: Based on the X-ray diffraction (XRD) test results of copper alloy after corrosion under the coupled conditions of seawater pressure and flow velocity, the microstrain value is determined by analyzing the diffraction peak shape and using peak broadening to obtain the strain level of the alloy's internal lattice;

[0009] The microstrain level ε of the alloy under the action of coupled mechanics is calculated according to formula (1) by using the half-height width β of the diffraction peak and the Bragg angle θ (ε obtained by coupling different seawater pressures and different flow velocities may be different):

[0010]

[0011] This method shows that under the same seawater pressure conditions, the microstrain of copper alloy increases significantly with the increase of flow velocity. Combined with the analysis of corrosion morphology, it confirms the accelerated corrosion process of copper alloy under the coupling of deep-sea pressure and flow velocity.

[0012] (2) The copper alloy / seawater solvation interface model based on molecular dynamics is used to simulate the mechanical effect of seawater pressure on the copper alloy surface. The copper alloy / seawater solvation interface model under different seawater pressures of 0.1-10 MPa is established by molecular dynamics method. The mechanical effect of seawater pressure on the alloy surface is quantitatively simulated by regulating the distance between water molecules and the copper alloy surface in the interface model. As the seawater pressure increases, the distance between water molecules and the copper alloy surface decreases, and the interaction between copper atoms and water molecules increases, indicating that seawater pressure accelerates the dissolution process of copper atoms in the alloy.

[0013] (3) A density functional theory-based alloy structure model under coupled mechanics is used to simulate the corrosion behavior of the copper alloy surface under the combined action of seawater pressure and flow rate: Based on the copper alloy / seawater solvation interface model determined in step (2), the microstrain level ε of the copper alloy under coupled mechanics is obtained in combination with the XRD analysis in step (1). By precisely controlling the lattice constant of the copper alloy model in the deep-sea flow environment, microstrain is applied along the (111) crystal plane direction to construct a copper alloy microstructure model under the coupled mechanics of seawater pressure and flow rate;

[0014] When the copper alloy / seawater solvation interface model of step (2) is used, the corresponding seawater pressure is first determined, and then the corresponding microstrain level ε at different flow rates is simulated; then the different seawater pressures are changed and the microstrain level ε at different flow rates of the different seawater pressures is simulated, and so on, traversing all seawater pressures;

[0015] This method shows that there is a significant interaction between the metal d orbital and the Op orbital. The coupled mechanical effect causes the peak of water molecules adsorbed on the alloy surface to shift negatively, the adsorption capacity of water molecules is enhanced, and the corrosion tendency of the copper alloy is accelerated.

[0016] (4) Calculation of the work function of copper alloy under the coupled mechanics of deep-sea dynamic environment: Based on the alloy structure model under the coupled mechanics established in step (3), the potential of the alloy model under the combined action of seawater pressure and flow rate, i.e., the potential value and the contact potential difference between the alloy model and the seawater interface, are calculated to obtain the dissolution work function of copper atoms, thereby characterizing the failure process and corrosion behavior of the alloy;

[0017] Based on the contact potential difference between the copper alloy and the solution interface and the potential value ψ of the alloy structure under the action of coupled mechanics, the work function Φ for removing surface electrons during alloy dissolution is calculated by formula (3):

[0018]

[0019] The work function Φ for removing surface electrons is different with different seawater pressures and seawater flow rates. Under the same deep-sea pressure conditions, as the seawater flow rate increases, the work function of the copper alloy decreases significantly, and electrons are more likely to escape from the alloy surface, indicating that the coupled mechanical effect significantly accelerates the corrosion process of the alloy.

[0020] (5) Calculation of the dissolution potential of copper alloy under the coupled mechanics of deep-sea dynamic environment: Based on the alloy structure model under the coupled mechanics established in step (3), calculate the deviation of the metal dissolution electrode potential under the same seawater pressure and different seawater flow rates;

[0021] The energy E of the alloy model without axial tensile strain is determined by alloy and the energy of the alloy model under axial tensile strain and the energy E of the alloy vacancy model without axial tensile strain alloy-vac and the energy of the alloy vacancy model under axial tensile strain According to formula (3), the deviation of the metal dissolution electrode potential caused by the introduction of microstrain in copper alloy is calculated:

[0022]

[0023] Change the seawater pressure to a different level and recalculate the offset of the metal dissolution electrode potential under different seawater flow rates. The offset of the alloy metal dissolution electrode potential is different when the seawater pressure is different. Generally, as the dissolution potential of the copper alloy shifts negatively, its corrosion resistance decreases.

[0024] This method shows that under fixed deep-sea pressure, as the seawater flow rate increases, the dissolution potential of the copper alloy shifts negatively, indicating that its corrosion resistance decreases.

[0025] (6) Calculation of activation energy barrier and dissolution rate of copper alloy under the action of coupled mechanics in deep-sea dynamic environment: Using LST / QST transition state search method, quantitatively analyze the activation energy barrier of copper alloy atoms under the combined action of seawater velocity and pressure, and then calculate the dissolution rate;

[0026] Through transition state search, the activation energy barrier ΔE(t) of alloy dissolution under the coupling of different seawater flow rates and a certain fixed seawater pressure is obtained, where σ is the degeneracy of the reaction path and takes the value of 1, P 0 is the standard gas pressure of 0.1 MPa, Δn is 0, and h is Planck's constant of 6.626×10 -34 J.s,k b The Boltzmann constant is 1.381×10 -23 J.K. -1 , R is the universal gas constant 8.314 J·K -1·mol -1 According to formula (4), the dissolution rate k under the coupled mechanics of deep-sea dynamic environment is calculated. TST :

[0027]

[0028] k TST The unit is s -1 , t is the temperature corresponding to the seawater pressure; for example, the present invention is applicable to a seawater depth of 0 to 1000 m (the corresponding pressure is 0.1 to 10 Mpa seawater pressure, and the corresponding seawater temperature after conversion is 25 to 5° C., which is well known in the art, for example, a seawater pressure of 10 Mpa corresponding to a seawater depth of 1000 m corresponds to 5° C.); different seawater pressures correspond to different k TST .

[0029] The dissolution activation barrier ΔE(t) of the alloy is the activation energy related to the seawater flow rate at the corresponding temperature t. This method shows that under specified deep-sea pressure conditions, as the seawater flow rate increases, the dissolution activation barrier decreases significantly and the dissolution rate of the alloy increases. This method can accurately evaluate the effect of the coupling of pressure and flow rate on the corrosion kinetics of the alloy and realize the tendency assessment of copper alloy corrosion failure in complex marine environments.

[0030] (7) Establishment of a prediction model for the corrosion rate of copper alloys under the coupled mechanical action of deep-sea dynamic environment: Based on the coupled mechanical model of copper alloys under seawater pressure and different seawater flow rates in steps (1)-(3), and the quantitative relationship between the dissolution rate and the activation energy barrier established in step (6), the dissolution rate of copper alloys under different seawater pressures and different seawater flow rates is obtained. Combined with parameters such as the intrinsic diffusion coefficient of copper atoms, the different seawater flow rate variables under a certain seawater pressure are fitted to the dissolution rate, and the dissolution rate spectrum is converted into a relationship model between the seawater flow rate and the corrosion rate y under the action of coupled mechanics. The unit is mm / a (millimeter / year), where k is the correction coefficient, D is the intrinsic diffusion coefficient, T is the time conversion factor, α is the fitting coefficient, and C is a parameter related to the alloy and seawater pressure. It can be obtained by fitting the dissolution rate under the seawater flow rate x and the corresponding seawater pressure to achieve accurate prediction of the corrosion rate of copper alloys in complex seawater environments. The model relationship of the corrosion rate y corresponding to different seawater pressures is different, that is, k is the correction coefficient, α is the fitting coefficient, and C is different.

[0031] Comparison with the measured values ​​shows that the model can accurately predict the corrosion rate of copper alloys in deep-sea dynamic environments.

[0032] In a preferred embodiment of the present invention, in step (1), the seawater pressure range of the MAB propeller is 0.1-10 MPa, and the seawater flow rate of 0-12 m / s includes 2, 4, 6, 8, and 12 m / s.

[0033] In a preferred embodiment of the present invention, in step (1), the seawater pressure of the B10 seawater pipeline ranges from 0.1 to 4 MPa, and the seawater flow rate of 0-4 m / s includes 1, 2, 3, and 4 m / s.

[0034] In a preferred embodiment of the present invention, in step (2), the molecular dynamics method is used to simulate the mechanical effect of seawater pressure on the alloy surface. The top of the copper alloy / seawater solvation interface model uses a 3.5% NaCl solution to simulate the seawater environment, and the bottom contains a supercell structure of the copper alloy. The ions in the solution relax freely in the electrolyte region, wherein Cl - and OH - It is used to maintain the electrical neutrality of the solution. The COMPASS II force field is used to describe the interaction between water molecules and copper atoms. By analyzing the density distribution of water molecules on the alloy surface under different pressures, the numerical simulation distance between the seawater medium and the alloy surface is obtained.

[0035] In a preferred embodiment of the present invention, in step (3), density functional theory is used to simulate the corrosion behavior of the copper alloy under the combined action of seawater pressure and flow rate. Based on the determined copper alloy / seawater solvation interface model, the application of different seawater pressures is achieved by regulating the distance between the seawater medium and the alloy surface. At the same time, the microstrain level of the copper alloy under the coupled mechanics is obtained in combination with XRD analysis. By precisely controlling the lattice constant of the alloy in a deep-sea flow environment, quantitative microstrain is applied along the (111) crystal plane direction, and a microstructure model of the copper alloy under the coupled mechanics of seawater pressure and flow rate is constructed.

[0036] In a preferred embodiment of the present invention, in steps (4)-(5), the PBE-GGA method is used to optimize the geometric structure model of the alloy, the work function and dissolution potential of the copper alloy under the action of coupled mechanics are calculated, the DFT semi-nuclear pseudopotential (DSPP) method is used to introduce the relativistic effect to treat nuclear electrons, the basis set is double numerical plus polarization (DNP), and the convergence criterion of the self-consistent field (SCF) is 2.72×10 per atom. -3 eV, the Brillouin zone of the alloy surface was sampled on a (2×2×1) k-point grid using the Monkhorst-Pack method, and the lattice constant of face-centered cubic Cu is This is consistent with the previous DFT calculation results. In order to prevent the interaction with the adjacent plates, a The vacuum layer releases the top two layers of atoms as the surface layer and fixes the other layers of atoms as the alloy matrix.

[0037] In a preferred embodiment of the present invention, in steps (6)-(7), the transition state search method of linear simultaneous transfer (LST) and quadratic simultaneous transfer (QST) is used to quantitatively analyze the activation energy barrier for dissolution of copper alloy atoms under the combined action of seawater flow rate and pressure, and the dissolution rate is calculated based on the method of Sobereva. By establishing a quantitative relationship between the dissolution rate and the activation energy barrier, the dissolution rate of the copper alloy under different seawater flow rates under specified seawater pressure conditions is obtained (the dissolution rate of the copper alloy under different seawater flow rates under one set of pressures may be different from the dissolution rate expression of the copper alloy under different seawater flow rates under another set of pressures, that is, the pressure difference also has an impact). Combined with parameters such as the intrinsic diffusion coefficient of copper atoms, the seawater flow rate variable and the dissolution rate are fitted, and the dissolution rate spectrum is converted into a model of seawater flow rate and corrosion rate under the action of coupled mechanics, thereby realizing the prediction of the corrosion rate of copper alloys in complex deep-sea dynamic environments.

[0038] 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.

[0039] In a preferred embodiment of the present invention, the corrosion rate prediction model of MAB alloy under the coupling of seawater pressure and flow velocity in deep sea dynamic environment is: R 2 =0.993(correction coefficient k1=-8.38×10 -7 , the intrinsic diffusion coefficient of copper atoms D = 1.06 × 10 -7 , time conversion factor T = 3.15 × 10 7 , α=87.56).

[0040] In a preferred embodiment of the present invention, the corrosion rate prediction model of B10 alloy under the coupling of seawater pressure and flow velocity in a deep sea dynamic environment is: R 2 =0.992(correction coefficient k2=-4.83×10 -8 , the intrinsic diffusion coefficient of copper atoms D = 1.06 × 10 -7 , time conversion factor T = 3.15 × 10 7 , β=0.29).

[0041] In a preferred embodiment of the present invention, it is used to predict the corrosion behavior of copper alloys under the coupled mechanics of deep-sea dynamic environment. The simulated predicted corrosion rate is consistent with the trend of the measured value, and the prediction accuracy deviation is less than 13%, which provides an effective method for evaluating the failure tendency of copper alloys in deep-sea environment.

[0042] Compared with the existing copper alloy corrosion rate prediction method, the present invention has the following advantages:

[0043] By combining experiments and numerical simulations, the present invention can accurately control key parameters such as pressure, flow rate and microstructural changes, and reflect the actual corrosion behavior of copper alloys in deep-sea environments more comprehensively than traditional methods.

[0044] The present invention utilizes methods such as molecular dynamics (MD) and density functional theory (DFT) to deeply analyze corrosion kinetic parameters, such as activation energy barrier and work function, and can improve the accuracy of copper alloy corrosion rate prediction.

[0045] The present invention reduces prediction errors by effectively combining experimental verification with simulation results, provides a reliable scientific basis for the design and protection of deep-sea equipment, and improves the long-term safety and durability of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention will be further described below in conjunction with the accompanying drawings. The accompanying drawings are only used to schematically illustrate and explain the present invention and do not limit the scope of the present invention.

[0047] Figure 1 This is the SEM spectrum of the MAB alloy after corrosion in Example 1 at a seawater pressure of 10 MPa and a seawater flow rate of 2-12 m / s.

[0048] Figure 2 It is the XRD spectrum and microstrain analysis of the MAB alloy after corrosion in Example 1 at a seawater pressure of 10 MPa and a seawater flow rate of 2-12 m / s.

[0049] Figure 3 It is a snapshot of the molecular dynamics simulation of the MAB alloy in Example 1 under a seawater pressure of 10.0 MPa and the seawater density distribution on the alloy surface.

[0050] Figure 4 It is the structural model of the MAB alloy in Example 1 under the coupling effect of seawater pressure and flow velocity and the partial wave state density diagram of the alloy under different flow velocity conditions.

[0051] Figure 5 is the work function and dissolution potential of the MAB alloy under the action of coupled mechanics in Example 1.

[0052] Figure 6 It is the activation energy barrier and dissolution rate of the MAB alloy under the coupled mechanical action in Example 1.

[0053] Figure 7 It is a prediction model for the weight loss rate and corrosion rate of the MAB alloy under coupled mechanics in Example 1.

[0054] Figure 8 This is a graph showing the corrosion rate of the MAB alloy under coupled mechanics in Example 1.

[0055] Fig. 9 This is the SEM spectrum of the B10 alloy after corrosion in Example 2 at a seawater pressure of 4 MPa and a seawater flow rate of 1-4 m / s.

[0056] Fig.10 It is the activation energy barrier and dissolution rate of B10 alloy under the coupled mechanical action in Example 2.

[0057] Fig.11 It is the prediction model of the weight loss rate and corrosion rate of B10 alloy under the action of coupled mechanics in Example 2. DETAILED DESCRIPTION

[0058] The present invention is described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited by the specific embodiments.

[0059] Example 1: High manganese aluminum bronze alloy (MAB) for propeller

[0060] The corrosion behavior of the alloy was studied by corrosion weight loss experiment when the seawater pressure was 10MPa and the seawater flow rate was 2-12m / s. The morphological characteristics of the alloy corrosion surface were analyzed by SEM. Figure 1 As shown in the figure, at 2-4 m / s, the corrosion product morphology is pitted and relatively evenly covers the alloy surface. When the flow rate is greater than 4 m / s, the corrosion situation intensifies. At a flow rate of 12 m / s, concave corrosion pits with corrosion product accumulation appear on the alloy surface along the flow direction of seawater. GSAS-Ⅱ software was used to analyze the XRD diffraction peaks of MAB alloy under coupled mechanics, as shown in the figure. Figure 2 As shown. The microstrain was determined by peak broadening, and the axial tensile strain and dislocation density of the alloy's internal lattice were obtained. When the seawater pressure was fixed, it was found that the axial strain of the copper alloy increased significantly with the increase of the seawater flow rate of 2-12m / s. Figure 3 As shown in the figure, the molecular dynamics method was used to establish the MAB alloy / seawater solvation interface model under 10Mpa seawater pressure, and the mechanical effect of seawater pressure on the alloy surface was quantitatively simulated by adjusting the distance between water molecules and the copper alloy surface in the interface model. When the pressure is 10Mpa, the corresponding distance between water molecules and the alloy surface is The results show that as the seawater pressure increases, the distance between water molecules and the surface of the copper alloy decreases, and the interaction between copper atoms and water molecules increases, indicating that the seawater pressure accelerates the dissolution process of copper atoms in the alloy.

[0061] Based on the MAB alloy / seawater solvation interface model determined by molecular dynamics method, combined with XRD analysis, the microstrain level of copper alloy under coupled mechanics was obtained, such as Figure 4 As shown, the DMol3 module of Materials Studio is used to establish a 3×3×4 MAB alloy model with a lattice constant of By precisely controlling the lattice constant of copper alloy in the deep-sea flow environment, microstrain is applied along the (111) crystal plane direction, and a copper alloy model under the coupled mechanics of seawater pressure and flow velocity is constructed. This method shows that there is a significant interaction between the metal d orbital and the Op orbital. The coupled mechanics causes the peak of water molecules adsorbed on the alloy surface to shift negatively, enhancing the adsorption capacity of water molecules and accelerating the corrosion process of the copper alloy.

[0062] The DFT calculation results show that by calculating the potential of the alloy model under the combined action of seawater pressure and flow rate and the contact potential difference between the alloy model and the seawater interface, the dissolution work function of the copper atom can be obtained, thereby characterizing the failure process and corrosion behavior of the alloy. Figure 5 As shown in the figure, under the same deep-sea pressure conditions, the work function of the copper alloy decreases significantly with the increase of seawater flow rate, which indicates that electrons can escape from the alloy surface more easily. The chemical activation energy of the alloy under the action of coupled mechanics and the absolute potential in the equilibrium state are calculated. The dissolution potential of the alloy shifts negatively, which further illustrates that the coupled mechanics leads to a decrease in the corrosion resistance of the copper alloy.

[0063] The LST / QST transition state search method is used to quantitatively analyze the activation energy barrier of MAB alloy dissolution under the combined effects of seawater flow rate and pressure. Figure 6 As shown in the figure, the results show that under the specified deep-sea pressure conditions, with the increase of seawater flow rate, the dissolution activation barrier significantly decreases and the dissolution rate of the alloy increases. Based on the dissolution activation barrier of copper atoms, under a pressure of 10Mpa, the dissolution rate of copper alloys under different seawater flow rates was calculated according to the formula. With the increase of flow rate, the dissolution rate constant of copper alloy becomes larger and the corrosion kinetics process accelerates, which verifies the promotion effect of deep-sea dynamic environment coupled mechanical action on the corrosion behavior of alloys.

[0064] Combined with parameters such as the intrinsic diffusion coefficient D of copper atoms, different seawater flow rate variables and dissolution rates are fitted, and the dissolution rate map is converted into a relationship model between seawater flow rate and corrosion rate under coupled mechanics, thereby achieving accurate prediction of the corrosion rate of copper alloys in deep-sea dynamic environments. Through experimental verification, corrosion weight loss experiments were carried out in artificial seawater, and the corrosion weight loss rates of MAB alloys at different flow rates of 10Mpa were determined. The results show that the predicted corrosion rate of MAB alloys under the coupled mechanics of deep-sea dynamic environments is basically consistent with the experimental value, and the prediction accuracy deviation is less than 13%, which basically achieves accurate prediction of the corrosion rate of copper alloys in complex seawater environments. Figure 7 As shown, the corrosion rate prediction model of MAB alloy in deep sea dynamic environment was finally obtained by fitting: R 2 =0.993(correction coefficient k1=-8.38×10 -7 , the intrinsic diffusion coefficient of copper atoms D = 1.06 × 10 -7, time conversion factor T = 3.15 × 10 7 , α=87.56). Figure 8 As shown, the corrosion rate prediction cloud map of MAB alloy under the combined action of seawater pressure and flow rate was obtained.

[0065] Example 2: B10 alloy for seawater pipelines

[0066] The corrosion behavior of B10 alloy was studied based on the corrosion weight loss experiment when the seawater pressure was 4MPa and the seawater flow rate was 1-4m / s. The morphological characteristics of the alloy corrosion surface were analyzed by SEM. Fig. 9 As shown in the figure, under the action of flowing seawater, a relatively stable and dense corrosion product film is formed on the surface of B10 alloy along the flow direction. As the flow rate increases, the corrosion product film becomes rough, some corrosion products fall off, and the corrosion of the alloy surface intensifies.

[0067] The LST / QST transition state search method is also used to quantitatively analyze the dissolution activation energy barrier of B10 alloy under the combined action of seawater flow rate and pressure, such as Fig.10 As shown in the figure, the results show that under the seawater pressure of 4Mpa, as the seawater flow rate increases, the dissolution activation barrier decreases significantly and the dissolution rate of the alloy increases. Based on the dissolution activation barrier of copper atoms, the dissolution rate of B10 alloy when the seawater flow rate is 1-4m / s is calculated according to the formula under seawater pressure. As the flow rate increases, the dissolution rate constant of B10 alloy increases and the corrosion kinetics process accelerates.

[0068] The dissolution rate constant is converted into a model of seawater flow rate and corrosion rate under coupled mechanics, thereby achieving an accurate prediction of the corrosion rate of B10 alloy in deep-sea dynamic environment. Through experimental verification, corrosion weight loss experiments were carried out in artificial seawater, and the corrosion weight loss rate of B10 alloy at different flow rates of 4Mpa was measured. The results show that the predicted corrosion rate of MAB alloy under the coupled mechanics of deep-sea dynamic environment is basically consistent with the experimental value, indicating that the model is accurate in predicting the corrosion rate of copper alloys. Fig.11 As shown in the figure, the corrosion rate prediction model of B10 alloy in deep sea dynamic environment is finally obtained by fitting: R 2 =0.992(correction coefficient k2=-4.83×10 -8 , the intrinsic diffusion coefficient of copper atoms D = 1.06 × 10 -7 , time conversion factor T = 3.15 × 10 7 , β=0.29).

[0069] Figure 1This is the SEM spectrum of the MAB alloy after corrosion in Example 1 at a seawater pressure of 10Mpa and a seawater flow rate of 2-12m / s. At 2-4m / s, the corrosion product morphology is pitted and relatively evenly covers the alloy surface. When the flow rate is greater than 4m / s, the corrosion situation intensifies. At a flow rate of 12m / s, concave corrosion pits with corrosion product accumulation appear on the alloy surface along the flow direction of seawater.

[0070] Figure 2 The XRD spectrum and microstrain analysis of the MAB alloy after corrosion in Example 1 at a seawater pressure of 10 MPa and a seawater flow rate of 2-12 m / s. Under the same seawater pressure conditions, the microstrain of the copper alloy increases significantly with the increase of the flow rate. Combined with the analysis of the corrosion morphology, the accelerated corrosion process of the copper alloy under the coupling of deep sea pressure and flow rate is confirmed.

[0071] Figure 3 It is a snapshot of the molecular dynamics simulation of the MAB alloy under 10.0 MPa seawater pressure and the seawater density distribution on the alloy surface in Example 1. The seawater pressure causes the distance between the water molecules and the alloy surface to decrease, and the interaction between the copper atoms and the water molecules to increase, indicating that the seawater pressure accelerates the dissolution process of copper atoms in the MAB alloy.

[0072] Figure 4 The structure model of the MAB alloy under the coupling effect of seawater pressure and flow velocity in Example 1 and the partial wave state density diagram of the alloy under different flow velocity conditions are shown. The results show that there is a significant interaction between the metal d orbital and the Op orbital. The coupling mechanics causes the peak of water molecules adsorbed on the alloy surface to shift negatively, and the water molecule adsorption capacity is enhanced, which accelerates the corrosion tendency of the copper alloy.

[0073] Figure 5 is the work function and dissolution potential of the MAB alloy under the coupled mechanics in Example 1. As the seawater flow rate increases, the work function of the copper alloy decreases significantly, and electrons are more likely to escape from the alloy surface. At the same time, the dissolution potential of the MAB alloy shifts negatively, indicating that its corrosion resistance decreases, which shows that the coupled mechanics significantly accelerates the corrosion process of the alloy.

[0074] Figure 6 It is the activation energy barrier and dissolution rate of the MAB alloy under the coupled mechanics in Example 1. Under a deep sea pressure of 10 MPa, as the seawater flow rate increases, the dissolution activation energy barrier decreases significantly and the dissolution rate increases. This method can accurately evaluate the effect of pressure and flow rate coupling on the corrosion kinetics of the MAB alloy.

[0075] Figure 7It is the prediction model of weight loss rate and corrosion rate of MAB alloy under coupled mechanics in Example 1. The results show that under 10Mpa seawater pressure, the corrosion rate of MAB alloy increases significantly with the increase of seawater flow rate. Compared with the measured corrosion rate, it shows that the model can effectively predict the corrosion behavior of MAB alloy under coupled mechanics in deep sea dynamic environment.

[0076] Figure 8 It is a graph of the corrosion rate of the MAB alloy under the action of coupled mechanics in Example 1. Under the deep sea pressure of 0.1-10 MPa, as the seawater flow rate increases, the corrosion rate significantly accelerates.

[0077] Fig. 9 This is the SEM spectrum of the B10 alloy after corrosion at a seawater pressure of 4 MPa and a seawater flow rate of 1-4 m / s in Example 2. Under the action of flowing seawater, a relatively stable and dense corrosion product film is formed on the surface of the B10 alloy along the flow direction. As the flow rate increases, the corrosion product film becomes rough and some corrosion products fall off, and the corrosion of the alloy surface intensifies.

[0078] Fig.10 It is the activation energy barrier and dissolution rate of B10 alloy under the coupled mechanical action in Example 2. Under 4Mpa seawater pressure, with the increase of flow rate, the dissolution activation energy barrier is significantly reduced and the dissolution rate is increased. This method can accurately evaluate the effect of coupled mechanical action on the corrosion behavior of B10 alloy.

[0079] Fig.11 It is the weight loss rate and corrosion rate prediction model of B10 alloy under coupled mechanics in Example 2. The results show that under 4Mpa seawater pressure, as the seawater flow rate increases, the corrosion rate of B10 alloy increases significantly, further verifying the accuracy and reliability of the corrosion prediction model.

[0080] The above specific embodiments describe the basic principles and main features of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments, and any changes or modifications that are not thought of through creative work should be included in the protection scope of the present invention. Without departing from the scope of the present invention, the present invention will also have various changes and improvements, and these changes and improvements will fall within the scope of protection required.

Claims

1. A method for evaluating copper alloy failure under the coupling of seawater pressure and flow velocity in a deep sea environment, characterized in that: The method comprises the following steps: (1) Microstrain analysis of copper alloy under coupled mechanics: Based on the X-ray diffraction (XRD) test results of copper alloy after corrosion under the coupled conditions of seawater pressure and flow velocity, the microstrain value is determined by analyzing the diffraction peak shape and using peak broadening to obtain the strain level of the alloy's internal lattice; The microstrain level ε of the alloy under the action of coupled mechanics is calculated according to formula (1) by using the half-width of the diffraction peak β and the Bragg angle θ. The ε obtained by coupling different seawater pressures and different flow velocities may be different: Under the same seawater pressure conditions, as the flow rate increases, the microstrain of the copper alloy increases significantly. Combined with the analysis of the corrosion morphology, the accelerated corrosion process of the copper alloy under the coupling of deep sea pressure and flow rate is shown; (2) A copper alloy / seawater solvation interface model based on molecular dynamics is used to simulate the mechanical effect of seawater pressure on the copper alloy surface. The molecular dynamics method is used to establish a copper alloy / seawater solvation interface model under different seawater pressures of 0.1-10 MPa. By regulating the distance between water molecules and the copper alloy surface in the interface model, the mechanical effect of seawater pressure on the alloy surface is quantitatively simulated. As the seawater pressure increases, the distance between water molecules and the copper alloy surface decreases, and the interaction between copper atoms and water molecules increases. The seawater pressure accelerates the dissolution process of copper atoms in the alloy. (3) A density functional theory-based alloy structure model under coupled mechanics is used to simulate the corrosion behavior of the copper alloy surface under the combined action of seawater pressure and flow rate: Based on the copper alloy / seawater solvation interface model determined in step (2), the microstrain level ε of the copper alloy under coupled mechanics is obtained in combination with the XRD analysis in step (1). By precisely controlling the lattice constant of the copper alloy model in the deep-sea flow environment, microstrain is applied along the (111) crystal plane direction to construct a copper alloy microstructure model under the coupled mechanics of seawater pressure and flow rate; When the copper alloy / seawater solvation interface model of step (2) is used, the corresponding seawater pressure is first determined, and then the corresponding microstrain level ε at different flow rates is simulated; then the different seawater pressures are changed and the microstrain level ε at different flow rates of the different seawater pressures is simulated, and so on, traversing all seawater pressures; There is a significant interaction between the metal d orbital and the Op orbital. The coupled mechanical effect causes the peak of water molecules adsorbed on the alloy surface to shift negatively, and the water molecule adsorption capacity is enhanced, which accelerates the corrosion tendency of the copper alloy. (4) Calculation of the work function of copper alloy under the coupled mechanics of deep-sea dynamic environment: Based on the alloy structure model under the coupled mechanics established in step (3), the potential of the alloy model under the combined action of seawater pressure and flow rate, i.e., the potential value and the contact potential difference between the alloy model and the seawater interface, are calculated to obtain the dissolution work function of copper atoms, thereby characterizing the failure process and corrosion behavior of the alloy; Based on the contact potential difference between the copper alloy and the solution interface and the potential value ψ of the alloy structure under the action of coupled mechanics, the work function Φ for removing surface electrons during alloy dissolution is calculated by formula (3): The work function Φ for removing surface electrons varies with different seawater pressures and seawater flow rates. Under the same deep-sea pressure conditions, as the seawater flow rate increases, the work function of the copper alloy decreases significantly, and electrons are more likely to escape from the alloy surface, indicating that the coupled mechanics significantly accelerates the corrosion process of the alloy. (5) Calculation of the dissolution potential of copper alloy under the coupled mechanics of deep-sea dynamic environment: Based on the alloy structure model under the coupled mechanics established in step (3), calculate the deviation of the metal dissolution electrode potential under the same seawater pressure and different seawater flow rates; The energy E of the alloy model without axial tensile strain is determined by alloy and the energy of the alloy model under axial tensile strain and the energy E of the alloy vacancy model without axial tensile strain alloy-vac and the energy of the alloy vacancy model under axial tensile strain According to formula (3), the shift of metal dissolution electrode potential caused by the introduction of microstrain in copper alloy is calculated as -eΔV Change the seawater pressure to a different level and recalculate the offset of the metal dissolution electrode potential under different seawater flow rates. The offset of the alloy metal dissolution electrode potential is different when the seawater pressure is different. Generally, as the dissolution potential of the copper alloy shifts negatively, its corrosion resistance decreases. It is shown that under fixed deep-sea pressure, as the seawater velocity increases, the dissolution potential of the copper alloy shifts negatively, indicating that its corrosion resistance decreases; (6) Calculation of activation energy barrier and dissolution rate of copper alloy under the action of coupled mechanics in deep-sea dynamic environment: Using LST / QST transition state search method, quantitatively analyze the activation energy barrier of copper alloy atoms under the combined action of seawater velocity and pressure, and then calculate the dissolution rate; Through transition state search, the activation energy barrier ΔE(t) of alloy dissolution under the coupling of different seawater flow rates at a fixed seawater pressure is obtained, where σ is the degeneracy of the reaction path and takes the value of 1, P 0 is the standard gas pressure of 0.1 MPa, Δn is 0, and h is Planck's constant of 6.626×10 -34 J.s,k b The Boltzmann constant is 1.381×10 -23 J.K. -1 , R is the universal gas constant 8.314 J·K -1 ·mol -1 According to formula (4), the dissolution rate k under the coupled mechanics of deep-sea dynamic environment is calculated. TST : k TST The unit is s -1 , t is the temperature corresponding to the seawater pressure, for example, the seawater temperature corresponding to the seawater depth of 0 to 1000m (seawater pressure of 0.1 to 10Mpa) is 25 to 5°C; different seawater pressures correspond to different k TST ; The activation energy barrier ΔE(t) of alloy dissolution is the activation energy related to the seawater velocity at the corresponding temperature t; Under specified deep-sea pressure conditions, as the seawater flow rate increases, the dissolution activation energy barrier decreases significantly and the dissolution rate of the alloy increases. This can accurately evaluate the impact of the coupling effect of pressure and flow rate on the alloy corrosion kinetics process and realize the tendency assessment of copper alloy corrosion failure in complex marine environments.

2. A method for evaluating copper alloy failure under the coupling of seawater pressure and flow velocity in a deep sea environment according to claim 1, characterized in that: In step (1), the copper alloy types include manganese aluminum bronze alloy (MAB) for propellers and copper nickel alloy (B10) for seawater pipelines, etc. The seawater pressure range of the MAB propeller is 0.1 to 10 MPa, and the seawater flow rate is 0-12 m / s; The seawater pressure range of the B10 seawater pipeline is 0.1~4Mpa, and the seawater flow rate is 0-4m / s.

3. A method for evaluating copper alloy failure under the coupling of seawater pressure and flow velocity in a deep sea environment according to claim 1, characterized in that: In step (2), the molecular dynamics method is used to simulate the mechanical effect of seawater pressure on the alloy surface. The top of the copper alloy / seawater solvation interface model uses a 3.5% NaCl solution to simulate the seawater environment, and the bottom contains a supercell structure of the copper alloy. The ions in the solution relax freely in the electrolyte region, where Cl - and OH - Used to maintain the electrical neutrality of the solution; the COMPASS II force field is used to describe the interaction between water molecules and copper atoms. By analyzing the density distribution of water molecules on the alloy surface under different pressures, the numerical simulation distance between the seawater medium and the alloy surface is obtained.

4. A method for evaluating copper alloy failure under the coupling of seawater pressure and flow velocity in a deep sea environment according to claim 1, characterized in that: In step (3), density functional theory is used to simulate the corrosion behavior of the copper alloy under the combined action of seawater pressure and flow rate. Based on the determined copper alloy / seawater solvation interface model, the application of different seawater pressures is achieved by regulating the distance between the seawater medium and the alloy surface. At the same time, the microstrain level of the copper alloy under the coupled mechanics is obtained in combination with XRD analysis. By precisely controlling the lattice constant of the alloy in the deep sea flow environment, quantitative microstrain is applied along the (111) crystal plane direction, and a microstructure model of the copper alloy under the coupled mechanics of seawater pressure and flow rate is constructed.

5. A method for evaluating copper alloy failure under the coupling of seawater pressure and flow velocity in a deep sea environment according to claim 1, characterized in that: In steps (4)-(5), the PBE-GGA method is used to optimize the geometric structure model of the alloy, and the work function and dissolution potential of the copper alloy under the action of coupled mechanics are calculated. The DFT semi-nuclear pseudopotential (DSPP) method is used to introduce relativistic effects to deal with nuclear electrons. The basis set is double numerical plus polarization (DNP), and the convergence criterion of the self-consistent field (SCF) is 2.72×10 per atom. -3 eV, the Brillouin zone of the alloy surface was sampled on a (2×2×1) k-point grid using the Monkhorst-Pack method, and the lattice constant of the face-centered cubic structure Cu is This is consistent with the previous DFT calculation results. In order to prevent the interaction with the adjacent plates, a The vacuum layer releases the top two layers of atoms as the surface layer and fixes the other layers of atoms as the alloy matrix.

6. A method for evaluating copper alloy failure under the coupling of seawater pressure and flow velocity in a deep sea environment according to claim 1, characterized in that: In step (6), the transition state search method of linear simultaneous transfer (LST) and quadratic simultaneous transfer (QST) is used to quantitatively analyze the dissolution activation energy barrier of copper alloy atoms under the combined action of seawater flow rate and pressure, and the dissolution rate is calculated based on Sobereva's method. By establishing a quantitative relationship between the dissolution rate and the activation energy barrier, the dissolution rate of the copper alloy under different seawater flow rates under specified seawater pressure conditions is obtained.

7. A method for establishing a prediction model for copper alloy corrosion rate under the action of deep-sea dynamic environment coupled mechanics, characterized in that: Based on the coupled mechanical model of copper alloy under seawater pressure and different seawater flow rates in steps (1)-(3) of claim 1, and the quantitative relationship between the dissolution rate and the activation energy barrier established by step (6), the dissolution rate of the copper alloy under different seawater pressures and different seawater flow rates is obtained, and the different seawater flow rate variables under a certain seawater pressure are fitted with the dissolution rate in combination with parameters such as the intrinsic diffusion coefficient of copper atoms, and the dissolution rate is converted into a relationship model between the seawater flow rate and the corrosion rate y under the action of coupled mechanics. The unit is mm / a (millimeter / year), where k is the correction coefficient, D is the intrinsic diffusion coefficient, T is the time conversion factor, α is the fitting coefficient, and C is a parameter related to the alloy and seawater pressure. It can be obtained by fitting the seawater flow rate x with the dissolution rate under the corresponding seawater pressure to achieve accurate prediction of the corrosion rate of copper alloys in complex seawater environments; the model relationship of the corrosion rate y corresponding to different seawater pressures is different, that is, k is the correction coefficient, α is the fitting coefficient, and C is different.

8. The method according to claim 7, characterized in that: Corrosion rate prediction model of MAB alloy under the coupling of seawater pressure and flow velocity in deep sea dynamic environment: R 2 =0.993, correction coefficient k1 = -8.38 × 10 -7 , the intrinsic diffusion coefficient of copper atoms D = 1.06 × 10 -7 , time conversion factor T = 3.15 × 10 7 , α=87.56; Corrosion rate prediction model of B10 alloy under the coupling of seawater pressure and flow velocity in deep sea dynamic environment: R 2 =0.992; correction coefficient k2 = -4.83 × 10 -8 , the intrinsic diffusion coefficient of copper atoms D = 1.06 × 10 -7 , time conversion factor T = 3.15 × 10 7 , β=0.29.

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