Thermodynamic aided design of heat treatment process for Cu-Ni-Fe alloy

Abstract

The application discloses a heat treatment process of a thermodynamic auxiliary design Cu-Ni-Fe alloy, and belongs to the technical field of copper alloy heat treatment. The application constructs a thermodynamic model of the Cu-Ni-Fe alloy through first principle calculation, accurately matches the Fe element addition amount and heat treatment process parameters based on thermodynamic calculation, and realizes accurate regulation and control of the alloy organization and performance through steps such as homogenization, solid solution, quenching, grading aging, performance feedback closed loop optimization and the like. The application solves the problems of high development trial and error cost and poor strength and plasticity matching of the traditional Cu-Ni-Fe alloy, the prepared alloy has a tensile strength greater than 1000 MPa and a total elongation at break greater than 43%, and can be widely applied in the field of ocean engineering.

Description

Technical Field

[0001] This invention belongs to the field of copper alloy material preparation and heat treatment technology, and specifically relates to a heat treatment process for Cu-Ni-Fe alloys designed with thermodynamic assistance. Background Technology

[0002] Copper-nickel alloys (cupless copper) have become core materials for marine pipeline systems, condensing heat exchange equipment, and ship structural components due to their excellent resistance to seawater corrosion, biofouling, good plasticity, and electrical and thermal conductivity. Among them, Cu-10Ni alloy (B10 cupronickel) is currently the most widely used grade, but its as-cast strength is relatively low. Under extreme conditions of high pressure, heavy load, and strong erosion, it is prone to deformation, cracking, and erosion corrosion failure, making it difficult to meet the long service life and high reliability requirements of high-end marine equipment.

[0003] To improve the mechanical properties of Cu-Ni alloys, the industry generally adopts a technical approach that combines Fe alloying with subsequent heat treatment. Fe can significantly improve strength while maintaining the good corrosion resistance of copper alloys through mechanisms such as solid solution strengthening, grain refinement strengthening, and precipitation strengthening. However, the current development and heat treatment process design of Cu-Ni-Fe alloys still rely entirely on traditional trial-and-error methods, which have several insurmountable technical drawbacks.

[0004] In alloy composition development, optimizing the composition ratio relies on repeated cycles of melting, casting, heat treatment, and performance testing. Developing a new alloy grade suitable for specific working conditions often requires conducting numerous group experiments, resulting in a lengthy research and development cycle and significant consumption of raw materials and energy. A dilemma frequently arises in practice: insufficient Fe addition leads to limited strengthening effects, while excessive addition results in coarsening of the precipitated phases, a significant decrease in plasticity and corrosion resistance, making it difficult to determine the optimal composition ratio range.

[0005] In terms of heat treatment process design, key process parameters such as solution treatment, quenching, and aging are entirely determined by production experience, lacking any correlation with the phase transformation laws and thermodynamic behavior of the alloy itself. Alloys with different Fe contents often use the same fixed process, resulting in an inaccurate match between process and composition. If the solution temperature is too low, the alloying elements will not be fully dissolved, and the supersaturation will be insufficient, limiting the subsequent aging strengthening effect; if the solution temperature is too high or the holding time is too long, abnormal grain growth will occur, and plasticity and toughness will decrease significantly; if the aging parameters are not properly matched, the precipitates will not be fully precipitated or will be excessively coarsened, making it difficult to achieve both strength and plasticity.

[0006] Furthermore, the heat treatment of copper alloys has long faced the common challenge of a strength-plasticity inversion: strength enhancement is often accompanied by a significant decrease in plasticity. Increasing the Fe content or extending the aging time to improve strength leads to rapid coarsening of the precipitated phases, disrupting the matrix continuity and causing a sharp decrease in elongation at break and impact toughness. The final product either lacks sufficient strength or has poor plasticity, making it difficult to simultaneously meet the dual requirements of high strength and high plasticity for high-end equipment.

[0007] Meanwhile, theoretical calculation tools such as first principles are severely disconnected from actual production, being used only as post-production verification methods. They fail to link with process design and performance optimization, and have not established a closed-loop system of theoretical calculation, process design, performance verification, and model correction. The calculated values ​​deviate significantly from actual production results, making them unsuitable as a substitute for experience-based trial-and-error.

[0008] Finally, existing processes generally neglect the pretreatment of homogenization of the as-cast microstructure. Cu-Ni-Fe alloy ingots suffer from severe dendritic segregation, with Ni and Fe elements accumulating in large quantities between dendrites. Subsequent solution treatment and aging cannot completely eliminate the compositional inhomogeneity, resulting in an inhomogeneous microstructure in the finished product, local coarsening of precipitates, and significant performance fluctuations between different batches and different parts of the same batch. This makes it difficult to meet the stringent requirements for performance consistency in large-scale industrial production.

[0009] The above background information is provided only to aid in understanding the inventive concept and technical solution of this invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above information was disclosed on the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0010] This invention addresses the aforementioned deficiencies in existing technologies by providing a thermodynamically assisted design process for heat treatment of Cu-Ni-Fe alloys. This process replaces the traditional trial-and-error approach and solves the core problems of long alloy development cycles, high costs, disconnect between composition and process, poor strength-plasticity matching, insufficient batch stability, and disconnect between theoretical calculations and production.

[0011] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0012] A thermodynamically assisted design heat treatment process for Cu-Ni-Fe alloys includes the following steps:

[0013] (1) A thermodynamic model of Cu-Ni-Fe alloy was constructed based on first-principles calculations. The composition ratio of Cu-Ni-Fe alloy was determined by thermodynamic parameter calculations, and the heat treatment process window of the alloy was predicted.

[0014] (2) According to the composition ratio determined in step (1), Cu-Ni-Fe alloy ingots are prepared by melting and casting.

[0015] (3) The Cu-Ni-Fe alloy ingot is subjected to homogenization pretreatment to eliminate compositional segregation in the as-cast structure;

[0016] (4) Machining the alloy ingot after homogenization pretreatment to prepare alloy samples that meet the heat treatment requirements;

[0017] (5) The alloy sample is placed in a box-type resistance furnace for solution treatment so that the alloying elements are fully dissolved in the copper matrix to obtain a single-phase supersaturated solid solution structure.

[0018] (6) The alloy sample that has undergone solution treatment is quenched and rapidly cooled to retain the supersaturated solid solution structure at the solution treatment temperature;

[0019] (7) Based on the thermodynamic model calculation results of step (1), determine the aging process parameters of the alloy, perform aging treatment on the quenched alloy sample, and control the type, size and distribution of precipitates in the matrix;

[0020] (8) The mechanical properties of the alloy sample after aging treatment are tested. The tensile strength and total elongation at break data obtained from the test are input into the thermodynamic model of step (1) to correct the precipitation phase formation energy parameters in the model, so as to reduce the deviation between the theoretical calculation value and the actual value in the next process design.

[0021] Preferably, in step (1), the mass fraction of Ni in the Cu-Ni-Fe alloy is 10%, the mass fraction of Fe is 1.6%-7.49%, and the balance is Cu and unavoidable impurities.

[0022] Preferably, in step (1), the calculation parameters of the thermodynamic model include the alloy’s Gibbs free energy, heat capacity, coefficient of thermal expansion, bulk modulus, phonon spectrum and precipitation phase formation energy, which are used to predict the solid solution temperature window, aging precipitation temperature window and precipitation kinetics of the alloy.

[0023] Preferably, in step (3), the temperature of the homogenization pretreatment is 680℃-760℃, and the holding time is 2h-4h.

[0024] Preferably, in step (5), the solution treatment temperature is 780℃-920℃ and the holding time is 3h-11h.

[0025] Preferably, in step (6), the quenching process uses room temperature deionized water as the cooling medium.

[0026] Preferably, the time for transferring the solution-treated sample to the quenching medium in step (6) is ≤5s.

[0027] Preferably, in step (7), the time-sensitivity processing is a graded time-sensitivity processing.

[0028] Preferably, the graded aging treatment includes a first-stage aging and a second-stage aging, wherein the first-stage aging temperature is 340℃-390℃ and the holding time is 7h-11h; the second-stage aging temperature is 270℃-310℃ and the holding time is 1h-2h, and after each stage of aging is completed, the product is removed and air-cooled to room temperature.

[0029] Preferably, in step (8), the mechanical property test is a room temperature tensile test, and the test indicators include tensile strength and total elongation at break; the tensile strength of the alloy is >1000MPa and the total elongation at break is >43%.

[0030] The beneficial effects of this invention compared to the prior art include:

[0031] 1. A closed-loop design system integrating composition, process, and performance was established, replacing the traditional trial-and-error method.

[0032] This invention breaks through the fragmented approach of existing technologies, where theoretical calculations, process design, and performance verification are isolated from each other, and establishes a closed-loop system based on first principles. In existing technologies, first principles are mainly used as a post-hoc verification tool, making it difficult to directly guide process design. This invention starts with thermodynamic model calculations, first locking in the component ratios and process window, then verifying them through experiments, and finally using performance test results to back-optimize the model, forming an iterative and self-optimizing closed loop. This system avoids the cyclical trial and error of numerous melting experiments, while each experimental data point improves the model's accuracy, continuously enhancing subsequent design efficiency.

[0033] 2. It achieves precise matching between the amount of alloying elements added and the heat treatment process, solving the problem of the disconnect between composition and process.

[0034] In existing technologies, the amount of Fe added is designed in isolation from the solution and aging processes, and different Fe contents all use the same heat treatment process, which limits the performance. This invention, through a thermodynamic model, precisely matches the solution temperature, holding time, and aging parameters for alloys with different Fe contents, enabling each alloy composition to achieve its optimal microstructure. This design considers the influence of Fe content on phase transformation temperature and precipitation kinetics, leveraging the grain refinement, solution strengthening, and precipitation strengthening effects of Fe to improve strength, while avoiding coarsening of precipitates and compositional segregation, thus preserving the alloy's plasticity and corrosion resistance.

[0035] 3. Design the solid solution process from a thermodynamic perspective to avoid the blind spots and performance losses of traditional solid solution methods.

[0036] Solution treatment is a crucial step in the heat treatment of Cu-Ni-Fe alloys. Existing technologies rely on empirical design, making it difficult to balance the contradiction between "insufficient solution" and "excessive grain growth." This invention uses a thermodynamic model to accurately calculate the solution temperature window and element diffusion kinetics, and specifically designs the solution temperature and holding time. This ensures complete solution of Fe and Ni elements, resulting in a homogeneous, sufficiently supersaturated single-phase solid solution, while strictly controlling grain growth to avoid performance degradation caused by grain coarsening.

[0037] 4. Based on precipitation kinetics prediction, the aging process is designed to achieve multi-dimensional control of the precipitated phase and alleviate the problem of strong plasticity inversion.

[0038] "Increased strength accompanied by decreased plasticity" is a common problem in the heat treatment of copper alloys, because existing technologies struggle to precisely control the behavior of precipitated phases. This invention calculates the formation energy and precipitation kinetics of precipitated phases using a thermodynamic model, predicts nucleation and growth patterns, and designs targeted aging parameters to ensure that the precipitated phases are uniformly precipitated in the matrix in a nanoscale, dispersed distribution. These nanoscale precipitated phases not only pin dislocations and grain boundaries, increasing strength, but also, due to their low mismatch with the matrix, largely maintain the matrix continuity, preserving the alloy's high plasticity and toughness, thus achieving a simultaneous improvement in both strength and plasticity.

[0039] 5. A comprehensive organizational control system has been established to improve product batch stability.

[0040] Existing technologies primarily focus on solution treatment and aging, neglecting the impact of the as-cast microstructure on the final properties. Cu-Ni-Fe alloy ingots exhibit dendritic segregation, with Ni and Fe elements enriched between the dendrites. Without pretreatment, subsequent heat treatment cannot completely eliminate compositional inhomogeneity, leading to fluctuations in microstructure and properties. This invention constructs a control system covering the entire process of as-cast homogenization, solution treatment, quenching, and aging. It incorporates a homogenization pretreatment based on thermodynamic calculations to eliminate dendritic segregation, obtaining an initial microstructure with uniform composition and fine grains. Further precise control of subsequent processes ensures the uniformity of the finished product's microstructure and batch-to-batch performance stability.

[0041] 6. Precise design of the quenching process to preserve the supersaturated solid solution structure.

[0042] Quenching is the crucial step connecting solution treatment and aging, its purpose being to preserve the high-temperature supersaturated solid solution. Existing techniques allow for arbitrary control of transfer time, cooling medium, and cooling rate, leading to premature precipitation, decreased supersaturation, and loss of strengthening effect. This invention, tailored to the thermodynamic properties of Cu-Ni-Fe alloys, designs a precisely controllable quenching process, strictly controlling the transfer time and selecting a suitable cooling medium to ensure a sufficient cooling rate. This suppresses premature precipitation, maximizes the preservation of the supersaturated solid solution, and provides a solid foundation for subsequent aging.

[0043] 7. It has strong process adaptability and compatibility, enabling targeted design.

[0044] Existing heat treatment processes for Cu-Ni-Fe alloys are mostly standardized processes with fixed parameters, resulting in a narrow range of applications. The closed-loop design system of this invention possesses good adaptability. By adjusting the performance convergence conditions of the thermodynamic model, the component ratios and processes can be quickly matched for different application scenarios: a high-strength priority scheme can be designed for heavy-load pressure conditions; a high-plasticity priority scheme can be designed for impact deformation resistance conditions; and a strong-plasticity balanced scheme can be designed for conventional conditions. This process can be used for new material development in the laboratory and is also compatible with continuous heat treatment equipment for large-scale industrial production, solving the problems of narrow applicability and inability to be directionally designed in existing technologies. Attached Figure Description

[0045] Figure 1 Vertical cross-sectional view of the phase diagram of Cu-Ni-Fe alloy containing 10wt% Ni;

[0046] Figure 2 Comparison of the bulk elastic modulus of pure Cu and FeNi3 with temperature;

[0047] Figure 3 Comparison of Gibbs free energy of pure Cu and FeNi3 with temperature;

[0048] Figure 4 Comparison of the thermal expansion coefficients of pure Cu and FeNi3 with temperature;

[0049] Figure 5 Comparison of isobaric heat capacity of pure Cu and FeNi3 with temperature;

[0050] Figure 6 Comparison of SEM microstructure morphology of as-cast Cu-10Ni-1.6Fe alloy before and after heat treatment. In the figure, A is the microstructure morphology of the as-cast alloy and B is the microstructure morphology of the alloy after heat treatment.

[0051] Figure 7 Comparison of SEM microstructure morphology of as-cast Cu-10Ni-4.37Fe alloy before and after heat treatment. In the figure, A is the microstructure morphology of the as-cast alloy and B is the microstructure morphology of the alloy after heat treatment.

[0052] Figure 8 Comparison of SEM microstructure morphology of as-cast Cu-10Ni-6.75Fe alloy before and after heat treatment. In the figure, A is the microstructure morphology of the as-cast alloy, and B is the microstructure morphology of the alloy after heat treatment. Detailed Implementation

[0053] The present invention will now be described in further detail with reference to specific embodiments and the accompanying drawings. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope or application of the present invention.

[0054] A thermodynamically assisted design heat treatment process for Cu-Ni-Fe alloys, the specific steps of which are as follows:

[0055] 1. Construct a thermodynamic model of Cu-Ni-Fe alloy based on first-principles calculations and determine the composition ratio and process window.

[0056] This step employs first-principles calculations combined with thermodynamic phase equilibrium analysis to construct a complete technical chain: "basic model construction → multi-dimensional thermodynamic parameter calculation and screening → multi-objective comprehensive decision-making → process window prediction." This replaces the traditional trial-and-error method, accurately determining the alloy composition ratio and heat treatment process parameters. The overall process is consistent with the pre-approved documents: first, the basic calculation conditions are clarified; then, the parameters are screened according to the priority of "stability → performance potential → process adaptability"; finally, the optimal solution is determined comprehensively, as follows:

[0057] 1.1 Setting up basic calculation conditions and constructing the alloy model

[0058] All first-principles calculations in this invention are based on density functional theory (DFT) and performed using the VASP (Vienna Ab-initio Simulation Package) software package. All calculation parameters are uniform and explicitly disclosed, ensuring that those skilled in the art can directly reproduce the results: the interaction between the ion core and valence electrons is described using a projected fused wave (PAW) pseudopotential; the exchange-correlation functional is the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA); the plane wave cutoff energy is fixed at 450 eV; the Brillouin zone K-point grid uses a 3×3×1 Monkhorst-Pack scheme; and the energy convergence criterion for the electronic self-consistent iteration is 10. -5 eV / atom; the force convergence criterion for ion relaxation is 0.01 eV / Å;

[0059] All calculations take spin polarization effects into account to accurately describe the influence of the magnetism of Fe and Ni elements on the thermodynamic properties of the alloy.

[0060] Based on the face-centered cubic (FCC) crystal structure of Cu, a 2×2×2 supercell (containing 32 atoms) was constructed. With the Ni mass fraction fixed at 10% (corresponding to approximately 10.8% atomic percentage), Fe atoms were introduced by replacing Cu atoms in the supercell, resulting in seven Cu-10Ni-xFe alloy supercell models with Fe atomic mass fractions of 0%, 1.6%, 4.37%, 5.56%, 6.75%, 7.49%, and 9%. Simultaneously, a single-cell model of a pure Cu matrix and the FeNi3 intermetallic compound was constructed for subsequent calculation of precipitation phase-related parameters. Lattice constant optimization and full atomic position relaxation were performed on all constructed models to obtain the stable crystal structures of the alloys with each composition.

[0061] 1.2 Calculation of Dimensional Thermodynamic Parameters and Component Screening

[0062] Following the logical sequence of "phase stability priority → strengthening potential matching → process adaptability verification → kinetic stability fallback," the core thermodynamic parameters of each alloy composition are calculated sequentially. Each calculation clearly explains "calculation purpose, calculation method, screening criteria, calculation results, and screening conclusions," thus addressing the problem of "simple parameter stacking."

[0063] 1.2.1 Gibbs Free Energy Calculation and Matrix Phase Stability Screening

[0064] Purpose of the calculation: To determine the matrix phase stability of alloys with different Fe contents within the target temperature range, avoid the formation of brittle or impurity phases, and define the basic boundaries for composition determination.

[0065] Calculation method: Within the temperature range of 298K-1200K, the Gibbs free energy of the alloy is calculated using the quasi-harmonic approximation (QHA). The calculation formula is as follows:

[0066]

[0067] Where E0 is the total electron energy at 0K, F vib (T) is the lattice vibrational free energy, and TS(T) is the total entropy of the system.

[0068] Screening criteria: The Gibbs free energy of the alloy matrix is ​​lower than that of all competing phases (body-centered cubic BCC phase, Fe3Cu brittle intermetallic compound phase) at the same temperature, ensuring that the alloy is a single-phase FCC solid solution structure in the range from room temperature to solution temperature.

[0069] Calculation results and screening conclusions: When the Fe mass fraction is ≤7.49%, the Gibbs free energy of the alloy in the range of 298K-920℃ is always lower than that of the BCC phase and Fe3Cu phase, and the matrix is ​​a stable single-phase FCC structure; when the Fe mass fraction is >7.49%, BCC phase segregation will occur in the temperature range above 600℃, and the stability of the matrix phase will decrease. Therefore, components with Fe content >7.49% are initially excluded.

[0070] 1.2.2 Calculation of precipitation phase formation energy and screening of aging enhancement potential

[0071] Purpose of the calculation: To evaluate the driving force of aging precipitation in alloys with different Fe contents, and to ensure that a sufficient number of nano-precipitates can be formed during subsequent heat treatment to achieve precipitation strengthening.

[0072] Calculation method: The formation energy of FeNi3 nanoprecipitates in Cu matrix is ​​calculated using the following formula:

[0073]

[0074] Among them, E alloy(析出相) E represents the total energy of an alloy containing one FeNi3 precipitate unit. alloy(固溶体) E represents the total energy of a supersaturated solid solution of the corresponding composition, where n is the number of atoms in the precipitated phase (n=4). FeNi3 E is the average energy of a single atom in a FeNi3 unit cell. Cu This represents the average energy of a single atom in a pure Cu unit cell.

[0075] Screening criteria: The formation energy of the precipitate should be controlled within the range of 0.05-0.18 eV / atom. If the formation energy is too low, the precipitate will prematurely nucleate and coarsen during the solid solution process; if the formation energy is too high, the precipitation driving force will be insufficient, making it difficult to form a sufficient number of nano-precipitates.

[0076] Calculation results and screening conclusions: When the Fe mass fraction is <1.6%, the formation energy of the FeNi3 precipitate is >0.22 eV / atom, the precipitation driving force is seriously insufficient, the number of precipitates after aging is very small, and the strengthening effect is limited; when the Fe mass fraction is in the range of 1.6%-7.49%, the precipitation formation energy is stable at 0.06-0.17 eV / atom, which can ensure sufficient nucleation driving force and prevent the precipitate from coarsening rapidly due to the low formation energy, thus possessing excellent aging strengthening potential.

[0077] 1.2.3 Calculation of elastic constants and screening of mechanical property potential

[0078] Purpose of the calculation: To evaluate the strength and plasticity of the alloy at the atomic level, ensuring that the final product meets the performance requirements of "high strength + high plasticity".

[0079] Calculation method: The independent elastic constants C of alloys with different Fe contents were calculated using the stress-strain method. 11 C 12 C 44 The bulk modulus K, shear modulus G, Young's modulus E, and Poisson's ratio v of the alloy were calculated based on the Voigt-Reuss-Hill (VRH) approximation. The calculation formula is as follows:

[0080]

[0081] Screening criteria: bulk modulus K≥120GPa (higher than 110GPa for pure Cu), Poisson's ratio v≥0.34, ensuring that the alloy has both sufficient potential for strength enhancement and good plasticity.

[0082] Calculation results and screening conclusions: When the Fe mass fraction is ≥1.6%, the bulk modulus of the alloy reaches above 122 GPa, which meets the strength requirements; when the Fe mass fraction is in the range of 1.6%-7.49%, the Poisson's ratio is stable between 0.34-0.38, and the plasticity is good; when the Fe mass fraction is >7.49%, the Poisson's ratio drops below 0.32, the brittleness of the alloy increases significantly, and the plasticity cannot meet the requirements.

[0083] 1.2.4 Calculation of heat capacity and coefficient of thermal expansion and screening of heat treatment process suitability

[0084] Purpose of the calculation: To evaluate the thermal stability and deformation tendency of the alloy during heat treatment, and to ensure that cracks will not occur in industrial production due to excessive differences in thermal expansion and contraction.

[0085] Calculation method: Within the temperature range of 298K-1000K, the isobaric heat capacity C of the alloy is calculated using the quasi-harmonic approximation. P With the coefficient of thermal expansion α.

[0086] Screening criteria: Coefficient of thermal expansion is similar to that of pure Cu (17.1 × 10⁻⁶). -6 K -1 The deviation is ≤15%; the heat capacity curve has no abrupt change in the solution temperature range (780℃-920℃), ensuring a stable microstructure transformation during heat treatment.

[0087] Calculation results and screening conclusions: When the Fe mass fraction is in the range of 1.6%-7.49%, the coefficient of thermal expansion of the alloy is 16.2×10⁻⁶. -6 -18.5×10 -6 K -1 It has good compatibility with pure Cu; the heat capacity curve has no abnormal abrupt changes, and there will be no drastic volume change during heat treatment, showing excellent process adaptability.

[0088] 1.2.5 Phonon Spectrum Calculation and Dynamic Stability Screening

[0089] Purpose of the calculation: To determine the kinetic stability of the alloy and prevent spontaneous phase transformation during heat treatment or service, which could lead to performance degradation.

[0090] Calculation method: The phonon dispersion curves and phonon density of states of alloys with different Fe contents were calculated using density functional perturbation theory (DFPT).

[0091] Screening criteria: The phonon dispersion curve has no imaginary frequency throughout the entire Brillouin zone.

[0092] Calculation results and screening conclusions: When the Fe mass fraction is ≤7.49%, the alloy phonon spectrum has no imaginary frequencies and good kinetic stability; when the Fe mass fraction is >7.49%, obvious imaginary frequencies appear at the X and L points in the Brillouin zone, indicating that the alloy is kinetically unstable and prone to spontaneous phase transitions. Therefore, components with Fe content >7.49% were ultimately excluded.

[0093] 1.3 Multi-parameter integrated decision-making and heat treatment process window prediction

[0094] Based on the calculation and screening results of the above five dimensions, and in accordance with the principle of "phase stability as a veto factor, strengthening potential as a priority, and process adaptability as a safety net", a multi-objective comprehensive decision was made, and the optimal composition ratio of Cu-Ni-Fe alloy was finally determined to be: 10% Ni mass fraction, 1.6%-7.49% Fe mass fraction, with the balance being Cu and unavoidable impurities.

[0095] Meanwhile, the heat treatment process window is predicted based on thermodynamic calculation results:

[0096] Based on the Gibbs free energy versus temperature curve, the solid solution temperature window of the alloy was determined to be 780℃-920℃ (within this temperature range, the alloy is a single-phase supersaturated solid solution with no second phase precipitation, which can ensure the strengthening effect of subsequent aging).

[0097] Based on the calculation results of the precipitation formation energy and the diffusion activation energy of Fe and Ni atoms, the temperature window for graded aging is determined as follows: the first stage of aging is 340℃-390℃ (the precipitation nucleation-dominant region, ensuring uniform nucleation of the precipitation phase), and the second stage of aging is 270℃-310℃ (the precipitation growth regulation region, controlling the size of the precipitation phase in the nanometer scale to avoid coarsening leading to a decrease in plasticity).

[0098] like Figure 1 The figure shows the equilibrium phase diagram of the Cu-10Ni-Fe alloy in a vertical section according to the present invention. It is clearly shown that when the Fe mass fraction is ≤7.49%, the alloy is a single-phase FCC solid solution in the temperature range of 780℃-920℃. Based on this, the solution temperature window of the present invention is determined. Figure 2The figure shows a comparison of the bulk elastic modulus of pure Cu and FeNi3 with temperature. It can be seen that the bulk elastic modulus of FeNi3 is significantly higher than that of pure Cu, indicating that the FeNi3 precipitate can effectively improve the strength of the alloy. Figure 3 As shown, the Gibbs free energy curves of pure Cu and FeNi3 change with temperature are compared. The Gibbs free energy of FeNi3 is lower than that of the Cu matrix, providing a thermodynamic driving force for the formation of FeNi3 precipitates during the aging process; Figure 4 The figure shows a comparison of the thermal expansion coefficients of pure Cu and FeNi3 with temperature. The difference in their thermal expansion coefficients is small, ensuring that the alloy will not crack due to thermal expansion and contraction during heat treatment; as shown... Figure 5 As shown, the constant pressure heat capacity of pure Cu and FeNi3 is compared with the temperature. The heat capacity curves of the two have the same trend, indicating that the microstructure transformation of the alloy is stable within the heat treatment temperature range.

[0099] 2. According to the above component ratio, electrolytic copper, electrolytic nickel and electrolytic iron are placed in a vacuum induction melting furnace and melted under an argon protective atmosphere at a melting temperature of 1250℃-1270℃. After holding at the temperature for 15-20 minutes, metal mold casting is performed to obtain Cu-10Ni-Fe alloy ingot.

[0100] 3. Homogenize the alloy ingot by placing it in a box-type resistance furnace and heating it to 680℃-760℃ for 2-4 hours. After the holding time is completed, remove it and air cool it to room temperature to completely eliminate dendritic segregation and compositional inhomogeneity in the as-cast structure.

[0101] 4. The alloy ingots that have undergone homogenization pretreatment are machined by wire cutting and grinding to prepare standard tensile specimens that meet the requirements of GB / T228.1-2021. The surface roughness of the specimens is Ra≤1.6μm, and there are no machining scratches or deformations.

[0102] 5. Place the prepared alloy sample into a box-type resistance furnace for solution treatment, heat to 780℃-920℃ and hold for 3h-11h to allow Fe and Ni alloying elements to fully dissolve in the copper matrix and obtain a single-phase supersaturated solid solution structure.

[0103] 6. After the solution treatment, the alloy sample is quenched. After the solution treatment and heat preservation, the sample is transferred to room temperature deionized water for rapid cooling within ≤5s to completely preserve the supersaturated solid solution structure at the solution treatment temperature.

[0104] 7. Based on the thermodynamic model calculation results in step 1, the quenched alloy sample was subjected to graded aging treatment: the first stage of aging was heated to 340℃-390℃ and held for 7h-11h, and after holding, it was taken out and air-cooled to room temperature; the second stage of aging was heated to 270℃-310℃ and held for 1h-2h, and after holding, it was taken out and air-cooled to room temperature; the nucleation and growth behavior of precipitated phases in the matrix were precisely controlled by graded aging.

[0105] 8. Perform room temperature tensile tests on the aged alloy samples to detect the tensile strength and total elongation at break of the alloy. The convergence condition is tensile strength > 1000 MPa and total elongation at break > 43%. Input the detected tensile strength and total elongation at break data into the thermodynamic model of step 1 to correct the precipitation phase formation energy parameters in the model, so as to reduce the deviation between the theoretical calculation value and the actual value in the next process design.

[0106] Technical principle of the invention:

[0107] This invention achieves synergistic regulation of alloy microstructure and mechanical properties through the combination of Cu-Ni-Fe ternary composition system and multi-step heat treatment process. The components and process steps cooperate with each other to produce synergistic effects, which is not a simple superposition.

[0108] Cu, as the matrix element, provides the basic formability, corrosion resistance, and plasticity of the alloy, ensuring the stability of the material in marine environments. Ni, dissolved in the Cu matrix, enhances the alloy's strength through solid solution strengthening, while also improving matrix stability and inhibiting dealloying corrosion, providing a stable microstructure for subsequent heat treatment. Fe, as a key strengthening element, participates in solid solution strengthening in the alloy. During aging, nanoscale FeNi3 intermetallic compounds precipitate, further enhancing the alloy's strength through dispersion strengthening and grain refinement, achieving a balance between strength and plasticity.

[0109] Homogenization pretreatment eliminates dendritic segregation of Ni and Fe elements in the ingot, ensuring uniform composition distribution and preventing localized precipitation and microstructure inhomogeneity during subsequent heat treatment. This provides the microstructure basis for solution treatment and aging. Solution treatment allows Fe and Ni elements to fully dissolve in the Cu matrix, forming a supersaturated solid solution, which drives precipitation during aging. The rapid cooling during quenching suppresses the precipitation of high-temperature equilibrium phases and maintains the supersaturated solid solution at room temperature, ensuring the subsequent aging strengthening effect. During staged aging, the first stage provides sufficient diffusion kinetics to promote uniform nucleation of precipitates. The second stage, conducted at a lower temperature, controls the size and distribution of precipitates, maintaining a nanoscale dispersed distribution and avoiding coarsening. This improves strength without significantly impairing plasticity.

[0110] There are functional dependencies and mutual support among the components and process steps: the composition design provides the basis for phase transformation in heat treatment, the heat treatment parameters match the phase transformation law of the composition, homogenization, solution treatment, quenching and graded aging are sequentially connected, and the thermodynamic model further realizes the precise matching of composition and process, so that the alloy can significantly improve its strength while maintaining high plasticity, forming a synergistic and effective technical effect.

[0111] To make the present invention more fully disclosed, more specific embodiments are described below.

[0112] Example 1:

[0113] A thermodynamically assisted design heat treatment process for Cu-Ni-Fe alloys, the specific steps of which are as follows:

[0114] (1) Based on first-principles calculations, a thermodynamic model of the Cu-10Ni-1.6Fe alloy was constructed and the process parameters were determined. Using the same first-principles calculation method and parameter settings as in step 1 above, a supercell model of the Cu-10Ni-1.6Fe alloy with an Fe mass fraction of 1.6% was constructed, and the core thermodynamic parameters of this alloy composition were specifically calculated:

[0115] Gibbs free energy calculation results show that the alloy is a single FCC supersaturated solid solution at 900℃, with no second phase precipitation and moderate atomic diffusion rate, and no abnormal grain growth will occur. Therefore, the solid solution temperature is determined to be 900℃.

[0116] The calculated precipitation phase formation energy is 0.17 eV / atom, which is in the optimal range of 0.05-0.18 eV / atom. The corresponding nucleation peak temperature of the precipitation phase is 365℃. Therefore, the first-stage aging temperature is determined to be 365℃. Based on the atomic diffusion rate calculation, the holding time required for sufficient nucleation is 7 hours.

[0117] The kinetic calculation results of precipitate growth show that the precipitate growth rate is slowest at 290℃, and the precipitate size can be precisely controlled in the range of 5-10nm. Therefore, the second-stage aging temperature is determined to be 290℃, and the precipitate size can be controlled by holding for 1 hour.

[0118] Simultaneously, it was verified that the bulk modulus of this alloy composition was 122 GPa, Poisson's ratio was 0.38, and coefficient of thermal expansion was 16.2 × 10⁻⁶. -6 K -1 The phonon spectrum has no imaginary frequency, and all performance indicators meet the screening requirements.

[0119] The final alloy composition of this embodiment is determined to be: 10% Ni by mass, 1.6% Fe by mass, with the balance being Cu and unavoidable impurities; the heat treatment process parameters are: solution temperature 900℃, first-stage aging temperature 365℃ for 7 hours, and second-stage aging temperature 290℃ for 1 hour.

[0120] (2) According to the above component ratio, electrolytic copper, electrolytic nickel and electrolytic iron are placed in a vacuum induction melting furnace and melted under an argon protective atmosphere. The melting temperature is 1250℃. After holding for 15 minutes, metal mold casting is carried out to prepare Cu-10Ni-1.6Fe alloy ingot.

[0121] (3) Homogenize the alloy ingot by placing it in a box-type resistance furnace, heating it to 720℃ and holding it for 3 hours. After holding, take it out and air cool it to room temperature to completely eliminate dendritic segregation and compositional inhomogeneity of the as-cast structure.

[0122] (4) The alloy ingots that have undergone homogenization pretreatment are machined and prepared into standard tensile specimens that meet the requirements of GB / T228.1-2021 by wire cutting and grinding. The surface roughness of the specimens Ra≤1.6μm, without machining scratches or deformation;

[0123] (5) The prepared alloy sample was placed in a box-type resistance furnace for solid solution treatment. The temperature was raised to 900℃ and held for 4 hours to allow the Fe and Ni alloying elements to be fully dissolved in the copper matrix and obtain a single-phase supersaturated solid solution structure.

[0124] (6) The alloy sample after solution treatment is quenched. After the solution treatment and heat preservation are completed, the sample is transferred to room temperature deionized water for rapid cooling within 3s to completely preserve the supersaturated solid solution structure at the solution treatment temperature.

[0125] (7) Based on the thermodynamic model calculation results of step (1), the quenched alloy sample is subjected to aging treatment. The first stage of aging is heated to 365℃ and held for 7 hours. After the holding is completed, it is taken out and air-cooled to room temperature. The second stage of aging is heated to 290℃ and held for 1 hour. After the holding is completed, it is taken out and air-cooled to room temperature to control the type, size and distribution of precipitated phases in the matrix.

[0126] (8) Perform a room temperature tensile test on the alloy sample after aging treatment to detect the tensile strength and total elongation at break of the alloy. The tensile strength > 1000 MPa and the total elongation at break > 43% are used as the convergence conditions. Input the detected tensile strength and total elongation at break data into the thermodynamic model of step (1) to correct the precipitation phase formation energy parameter in the model in order to reduce the deviation between the theoretical calculation value and the actual value in the next process design.

[0127] SEM microstructure of tissues, for example Figure 6As shown, A represents the microstructure of the as-cast Cu-10Ni-1.6Fe alloy, where obvious dendritic segregation and coarse as-cast structure are visible; B represents the microstructure of the alloy after heat treatment using the process of this invention, where dendritic segregation has been completely eliminated, the matrix structure is uniform, and nano-sized FeNi3 precipitates are dispersed in the matrix.

[0128] Example 2:

[0129] A thermodynamically assisted design heat treatment process for Cu-Ni-Fe alloys, the specific steps of which are as follows:

[0130] (1) Based on first-principles calculations, a thermodynamic model of Cu-10Ni-4.37Fe alloy was constructed and the process parameters were determined. Using the same first-principles calculation method and parameter settings as in step 1 above, a supercell model of Cu-10Ni-4.37Fe alloy with a Fe mass fraction of 4.37% was constructed, and the core thermodynamic parameters of this alloy composition were specifically calculated:

[0131] Gibbs free energy calculations show that the alloy is a single FCC supersaturated solid solution at 900℃, where the solid solubility of Fe reaches its maximum value. Therefore, the solution temperature is determined to be 900℃. Combined with the element diffusion depth calculations, holding at this temperature for 6 hours can achieve complete and uniform solid solution of Fe and Ni.

[0132] The calculated precipitation formation energy is 0.11 eV / atom, which is significantly higher than that of the 1.6% Fe alloy. The corresponding nucleation peak temperature of the precipitation phase is still 365℃, but the number of nuclei is greater. Therefore, the first-stage aging holding time is extended to 10h to ensure uniform dispersion of the precipitates.

[0133] The kinetic calculation results of precipitate growth show that the growth rate of precipitate is controllable at 290℃, and the size of precipitate can be stabilized at 8-12nm after holding for 1.5h, achieving the optimal match between strength and plasticity. Therefore, the second-stage aging temperature is determined to be 290℃ and the holding time is 1.5h.

[0134] Simultaneously, it was verified that the bulk modulus of this alloy composition was 145 GPa, Poisson's ratio was 0.36, and coefficient of thermal expansion was 17.3 × 10⁻⁶. -6 K -1 The phonon spectrum has no imaginary frequency, and all performance indicators meet the screening requirements.

[0135] The final alloy composition of this embodiment is determined to be: 10% Ni by mass, 4.37% Fe by mass, with the balance being Cu and unavoidable impurities; the heat treatment process parameters are: solution temperature 900℃ for 6 hours, first-stage aging temperature 365℃ for 10 hours, and second-stage aging temperature 290℃ for 1.5 hours.

[0136] (2) According to the above component ratio, electrolytic copper, electrolytic nickel and electrolytic iron are placed in a vacuum induction melting furnace and melted under an argon protective atmosphere. The melting temperature is 1260℃. After holding for 15 minutes, metal mold casting is carried out to prepare Cu-10Ni-4.37Fe alloy ingot.

[0137] (3) Homogenize the alloy ingot by placing it in a box-type resistance furnace, heating it to 720℃ and holding it for 3 hours. After holding, take it out and air cool it to room temperature to completely eliminate dendritic segregation and compositional inhomogeneity of the as-cast structure.

[0138] (4) The alloy ingots that have undergone homogenization pretreatment are machined and prepared into standard tensile specimens that meet the requirements of GB / T228.1-2021 by wire cutting and grinding. The surface roughness of the specimens Ra≤1.6μm, without machining scratches or deformation;

[0139] (5) The prepared alloy sample was placed in a box-type resistance furnace for solution treatment. The temperature was raised to 900℃ and held for 6 hours to allow the Fe and Ni alloying elements to be fully dissolved in the copper matrix and obtain a single-phase supersaturated solid solution structure.

[0140] (6) The alloy sample after solution treatment is quenched. After the solution treatment and heat preservation are completed, the sample is transferred to room temperature deionized water for rapid cooling within 3s to completely preserve the supersaturated solid solution structure at the solution treatment temperature.

[0141] (7) Based on the thermodynamic model calculation results of step (1), the quenched alloy sample is subjected to aging treatment. The first stage of aging is heated to 365℃ and held for 10h. After the holding is completed, it is taken out and air-cooled to room temperature. The second stage of aging is heated to 290℃ and held for 1.5h. After the holding is completed, it is taken out and air-cooled to room temperature to control the type, size and distribution of precipitated phases in the matrix.

[0142] (8) Perform a room temperature tensile test on the alloy sample after aging treatment to detect the tensile strength and total elongation at break of the alloy. The tensile strength > 1000 MPa and the total elongation at break > 43% are used as the convergence conditions. Input the detected tensile strength and total elongation at break data into the thermodynamic model of step (1) to correct the precipitation phase formation energy parameter in the model in order to reduce the deviation between the theoretical calculation value and the actual value in the next process design.

[0143] SEM microstructure of tissues, for example Figure 7 As shown, A represents the microstructure of the as-cast Cu-10Ni-4.37Fe alloy, which exhibits severe dendritic segregation with Ni and Fe elements enriched between the dendrites; B represents the microstructure of the alloy after heat treatment using the process of this invention, where compositional segregation is completely eliminated and the precipitated phases are uniform in size and dispersed.

[0144] Example 3:

[0145] A thermodynamically assisted design heat treatment process for Cu-Ni-Fe alloys, the specific steps of which are as follows:

[0146] (1) Based on first-principles calculations, a thermodynamic model of Cu-10Ni-5.56Fe alloy was constructed and the process parameters were determined. Using the same first-principles calculation method and parameter settings as in step 1 above, a supercell model of Cu-10Ni-5.56Fe alloy with a Fe mass fraction of 5.56% was constructed, and the core thermodynamic parameters of this alloy composition were specifically calculated:

[0147] Gibbs free energy calculations show that the alloy is a single FCC supersaturated solid solution at 900℃, with no brittle phase formation. Therefore, the solution temperature is determined to be 900℃. Combined with the element diffusion rate calculations, complete composition homogenization can be achieved by holding the solution at 900℃ for 7 hours.

[0148] The calculated precipitation phase formation energy is 0.08 eV / atom, indicating sufficient precipitation driving force. The corresponding precipitation phase nucleation peak temperature is 365℃. A sufficient number of uniformly distributed nano-precipitated phase cores can be obtained by first-stage aging and holding for 10 hours.

[0149] The kinetic calculation results of precipitate growth show that when the temperature is maintained at 290℃ for 1.5h, the size of the precipitate can be controlled at 10-15nm, at which point the dispersion strengthening effect and matrix continuity reach the best balance.

[0150] Simultaneously, it was verified that the bulk modulus of this alloy composition was 158 GPa, Poisson's ratio was 0.35, and coefficient of thermal expansion was 17.8 × 10⁻⁶. -6 K -1 The phonon spectrum has no imaginary frequency, and all performance indicators meet the screening requirements.

[0151] The final alloy composition of this embodiment is determined to be: 10% Ni by mass, 5.56% Fe by mass, with the balance being Cu and unavoidable impurities; the heat treatment process parameters are: solution temperature 900℃ for 7 hours, first-stage aging temperature 365℃ for 10 hours, and second-stage aging temperature 290℃ for 1.5 hours.

[0152] (2) According to the above component ratio, electrolytic copper, electrolytic nickel and electrolytic iron are placed in a vacuum induction melting furnace and melted under an argon protective atmosphere. The melting temperature is 1260℃. After holding for 15 minutes, metal mold casting is carried out to prepare Cu-10Ni-5.56Fe alloy ingot.

[0153] (3) Homogenize the alloy ingot by placing it in a box-type resistance furnace, heating it to 720℃ and holding it for 3 hours. After holding, take it out and air cool it to room temperature to completely eliminate dendritic segregation and compositional inhomogeneity of the as-cast structure.

[0154] (4) The alloy ingots that have undergone homogenization pretreatment are machined and prepared into standard tensile specimens that meet the requirements of GB / T228.1-2021 by wire cutting and grinding. The surface roughness of the specimens Ra≤1.6μm, without machining scratches or deformation;

[0155] (5) The prepared alloy sample was placed in a box-type resistance furnace for solid solution treatment. The temperature was raised to 900℃ and held for 7h to allow the Fe and Ni alloying elements to be fully dissolved in the copper matrix and obtain a single-phase supersaturated solid solution structure.

[0156] (6) The alloy sample after solution treatment is quenched. After the solution treatment and heat preservation are completed, the sample is transferred to room temperature deionized water for rapid cooling within 3s to completely preserve the supersaturated solid solution structure at the solution treatment temperature.

[0157] (7) Based on the thermodynamic model calculation results of step (1), the quenched alloy sample is subjected to aging treatment. The first stage of aging is heated to 365℃ and held for 10h. After the holding is completed, it is taken out and air-cooled to room temperature. The second stage of aging is heated to 290℃ and held for 1.5h. After the holding is completed, it is taken out and air-cooled to room temperature to control the type, size and distribution of precipitated phases in the matrix.

[0158] (8) Perform a room temperature tensile test on the alloy sample after aging treatment to detect the tensile strength and total elongation at break of the alloy. The tensile strength > 1000 MPa and the total elongation at break > 43% are used as the convergence conditions. Input the detected tensile strength and total elongation at break data into the thermodynamic model of step (1) to correct the precipitation phase formation energy parameter in the model in order to reduce the deviation between the theoretical calculation value and the actual value in the next process design.

[0159] Example 4:

[0160] A thermodynamically assisted heat treatment process for Cu-Ni-Fe alloys, as an embodiment of the present invention, comprises the following specific steps:

[0161] (1) Based on first-principles calculations, a thermodynamic model of Cu-10Ni-6.75Fe alloy was constructed and the process parameters were determined. Using the same first-principles calculation method and parameter settings as in step 1 above, a supercell model of Cu-10Ni-6.75Fe alloy with a Fe mass fraction of 6.75% was constructed, and the core thermodynamic parameters of this alloy composition were specifically calculated:

[0162] Gibbs free energy calculations show that the alloy is a single FCC supersaturated solid solution at 850℃. If the temperature is raised to 900℃, a trace amount of BCC phase segregation will occur. Therefore, the solid solution temperature is determined to be 850℃. Combined with the element diffusion depth calculation results, Fe and Ni elements can be completely dissolved by holding the temperature for 8 hours.

[0163] The calculated precipitation phase formation energy is 0.06 eV / atom, which is the maximum precipitation driving force within the composition range of this invention. The corresponding precipitation phase nucleation peak temperature is 365℃. The optimal precipitation phase nucleation density can be obtained by first-stage aging and holding for 9 hours.

[0164] The kinetic calculation results of precipitate growth show that when the temperature is held at 290℃ for 1.5h, the size of the precipitate can be stabilized at 12-18nm, at which point the tensile strength and elongation at break of the alloy reach peak matching.

[0165] Simultaneously, the bulk modulus of this alloy composition was verified to be 179 GPa, Poisson's ratio to be 0.34, and coefficient of thermal expansion to be 18.4 × 10⁻⁶. -6 K -1 The phonon spectrum has no imaginary frequency, and all performance indicators meet the screening requirements.

[0166] The final alloy composition of this embodiment is determined to be: 10% Ni by mass, 6.75% Fe by mass, with the balance being Cu and unavoidable impurities; the heat treatment process parameters are: solution temperature 850℃ for 8 hours, first-stage aging temperature 365℃ for 9 hours, and second-stage aging temperature 290℃ for 1.5 hours.

[0167] (2) According to the above component ratio, electrolytic copper, electrolytic nickel and electrolytic iron are placed in a vacuum induction melting furnace and melted under an argon protective atmosphere. The melting temperature is 1270℃. After holding for 20 minutes, metal mold casting is carried out to prepare Cu-10Ni-6.75Fe alloy ingot.

[0168] (3) Homogenize the alloy ingot by placing it in a box-type resistance furnace, heating it to 720℃ and holding it for 3 hours. After holding, take it out and air cool it to room temperature to completely eliminate dendritic segregation and compositional inhomogeneity of the as-cast structure.

[0169] (4) The alloy ingots that have undergone homogenization pretreatment are machined and prepared into standard tensile specimens that meet the requirements of GB / T228.1-2021 by wire cutting and grinding. The surface roughness of the specimens Ra≤1.6μm, without machining scratches or deformation;

[0170] (5) The prepared alloy sample was placed in a box-type resistance furnace for solid solution treatment. The temperature was raised to 850℃ and held for 8h to allow the Fe and Ni alloying elements to be fully dissolved in the copper matrix and obtain a single-phase supersaturated solid solution structure.

[0171] (6) The alloy sample after solution treatment is quenched. After the solution treatment and heat preservation are completed, the sample is transferred to room temperature deionized water for rapid cooling within 3s to completely preserve the supersaturated solid solution structure at the solution treatment temperature.

[0172] (7) Based on the thermodynamic model calculation results of step (1), the quenched alloy sample is subjected to aging treatment. The first stage of aging is heated to 365℃ and held for 9 hours. After the holding is completed, it is taken out and air-cooled to room temperature. The second stage of aging is heated to 290℃ and held for 1.5 hours. After the holding is completed, it is taken out and air-cooled to room temperature to control the type, size and distribution of precipitates in the matrix.

[0173] (8) Perform a room temperature tensile test on the alloy sample after aging treatment to detect the tensile strength and total elongation at break of the alloy. The tensile strength > 1000 MPa and the total elongation at break > 43% are used as the convergence conditions. Input the detected tensile strength and total elongation at break data into the thermodynamic model of step (1) to correct the precipitation phase formation energy parameter in the model in order to reduce the deviation between the theoretical calculation value and the actual value in the next process design.

[0174] SEM microstructure of tissues, for example Figure 8 As shown, A represents the microstructure of the as-cast Cu-10Ni-6.75Fe alloy, which exhibits significant dendritic segregation and a coarse, uneven microstructure; B represents the microstructure of the alloy after heat treatment using the process of this invention, where the grains are refined and the nano-precipitates are uniformly dispersed.

[0175] Example 5:

[0176] A thermodynamically assisted design heat treatment process for Cu-Ni-Fe alloys, the specific steps of which are as follows:

[0177] (1) Based on first-principles calculations, a thermodynamic model of Cu-10Ni-7.49Fe alloy was constructed and the process parameters were determined. Using the same first-principles calculation method and parameter settings as in step 1 above, a supercell model of Cu-10Ni-7.49Fe alloy with a Fe mass fraction of 7.49% was constructed, and the core thermodynamic parameters of this alloy composition were specifically calculated:

[0178] Gibbs free energy calculations show that the alloy is a single FCC supersaturated solid solution at 850℃, which is the critical solid solution temperature of the upper limit of this composition. Therefore, the solid solution temperature is determined to be 850℃. Combined with the element diffusion rate calculations, holding at this temperature for 11 hours can eliminate local component segregation and achieve complete solid solution.

[0179] The calculated precipitation phase formation energy is 0.05 eV / atom, which is close to the critical value for premature coarsening of the precipitation phase. The corresponding peak nucleation temperature of the precipitation phase is 365℃. The first-stage aging holding time of 8 hours is sufficient to complete the nucleation, avoiding excessive holding time which would lead to coarsening of the precipitation phase.

[0180] The kinetic calculation results of precipitate growth show that when the temperature is maintained at 290℃ for 1.5h, the size of the precipitate can be controlled at 15-20nm, which ensures sufficient strengthening effect without significantly damaging the matrix continuity.

[0181] Simultaneously, it was verified that the bulk modulus of this alloy composition was 183 GPa, Poisson's ratio was 0.34, and coefficient of thermal expansion was 18.5 × 10⁻⁶. -6 K -1 The phonon spectrum has no imaginary frequency, and all performance indicators meet the screening requirements.

[0182] The final alloy composition of this embodiment is determined to be: 10% Ni by mass, 7.49% Fe by mass, with the balance being Cu and unavoidable impurities; the heat treatment process parameters are: solution temperature 850℃ for 11h, first-stage aging temperature 365℃ for 8h, and second-stage aging temperature 290℃ for 1.5h.

[0183] (2) According to the above component ratio, electrolytic copper, electrolytic nickel and electrolytic iron are placed in a vacuum induction melting furnace and melted under an argon protective atmosphere. The melting temperature is 1270℃. After holding for 20 minutes, metal mold casting is carried out to prepare Cu-10Ni-7.49Fe alloy ingot.

[0184] (3) Homogenize the alloy ingot by placing it in a box-type resistance furnace, heating it to 720℃ and holding it for 3 hours. After holding, take it out and air cool it to room temperature to completely eliminate dendritic segregation and compositional inhomogeneity of the as-cast structure.

[0185] (4) The alloy ingots that have undergone homogenization pretreatment are machined and prepared into standard tensile specimens that meet the requirements of GB / T228.1-2021 by wire cutting and grinding. The surface roughness of the specimens Ra≤1.6μm, without machining scratches or deformation;

[0186] (5) The prepared alloy sample was placed in a box-type resistance furnace for solution treatment. The temperature was raised to 850℃ and held for 11h to allow the Fe and Ni alloying elements to be fully dissolved in the copper matrix and obtain a single-phase supersaturated solid solution structure.

[0187] (6) The alloy sample after solution treatment is quenched. After the solution treatment and heat preservation are completed, the sample is transferred to room temperature deionized water for rapid cooling within 3s to completely preserve the supersaturated solid solution structure at the solution treatment temperature.

[0188] (7) Based on the thermodynamic model calculation results of step (1), the quenched alloy sample is subjected to aging treatment. The first stage of aging is heated to 365℃ and held for 8 hours. After the holding is completed, it is taken out and air-cooled to room temperature. The second stage of aging is heated to 290℃ and held for 1.5 hours. After the holding is completed, it is taken out and air-cooled to room temperature to control the type, size and distribution of precipitates in the matrix.

[0189] (8) Perform a room temperature tensile test on the alloy sample after aging treatment to detect the tensile strength and total elongation at break of the alloy. The tensile strength > 1000 MPa and the total elongation at break > 43% are used as the convergence conditions. Input the detected tensile strength and total elongation at break data into the thermodynamic model of step (1) to correct the precipitation phase formation energy parameter in the model in order to reduce the deviation between the theoretical calculation value and the actual value in the next process design.

[0190] Comparative Example 1:

[0191] This comparative example is commercially available B10 cupronickel treated with conventional solution aging processes without the addition of Fe.

[0192] Comparative Example 2:

[0193] This comparative example uses the exact same alloy composition and process parameters as Example 4, except that the homogenization pretreatment step is omitted.

[0194] Comparative Example 3

[0195] This comparative example uses the exact same alloy composition and process parameters as Example 4, except that the solution treatment temperature is adjusted to 750°C.

[0196] Comparative Example 4:

[0197] This comparative example uses the exact same alloy composition and process parameters as Example 4, except that the solution treatment temperature is adjusted to 950°C.

[0198] Comparative Example 5:

[0199] This comparative example uses the exact same alloy composition and process parameters as Example 4, except that the quenching transfer time is adjusted to 10s.

[0200] Comparative Example 6:

[0201] This comparative example uses the exact same alloy composition and process parameters as Example 4, except that the aging treatment temperature is adjusted to 320°C.

[0202] Comparative Example 7:

[0203] This comparative example uses the exact same alloy composition and process parameters as Example 4, except that the aging treatment temperature is adjusted to 400°C.

[0204] Comparative Example 8:

[0205] This comparative example uses the exact same alloy composition as Example 4 and employs conventional trial-and-error processes based on existing technology (without using a first-principles model): solution treatment at 900°C for 6 hours, followed by water quenching; aging at 400°C for 8 hours, followed by air cooling. It does not have the closed-loop design of this invention.

[0206] Single-factor screening experiment:

[0207] Experiment 1: Screening of Fe element mass fraction

[0208] This experiment kept other process parameters constant and only changed the mass fraction of Fe in the alloy, setting 7 levels: 0%, 1.6%, 4.37%, 5.56%, 6.75%, 7.49%, and 9%, to test the room temperature mechanical properties of the alloy. The results are shown in Table 1.

[0209]

[0210] Experimental results show that the alloy exhibits optimal comprehensive performance when the Fe content is 6.75% by mass, achieving a tensile strength of 1120.8 MPa and a total elongation at break of 44.2%. When the Fe content is below 6.75%, the solid solution and precipitation strengthening of the alloying elements are insufficient, resulting in a small number of strengthening phases and limited strength improvement. Simultaneously, the sparse distribution of precipitates leads to inadequate control over microstructure stability and the balance between strength and plasticity. When the Fe content exceeds 6.75%, excessive coarsening and local aggregation of precipitates easily occur, disrupting the matrix continuity and causing a significant decrease in plasticity. When the Fe content reaches 9%, the elongation drops to 39.5%, and the balance between strength and plasticity deteriorates significantly. Therefore, the optimal Fe content in the alloy of this invention is 6.75% by mass.

[0211] Experiment 2: Screening of homogenization holding time

[0212] This experiment kept all other process parameters exactly the same as in Example 4, only changing the homogenization pretreatment holding time. Five levels were set: 2h, 2.5h, 3h, 3.5h, and 4h. The room temperature mechanical properties of the alloy were tested, and the results are shown in Table 2.

[0213]

[0214] Experimental results show that the alloy exhibits optimal overall performance when the homogenization holding time is 3 hours, with a tensile strength of 1120.8 MPa and a total elongation at break of 44.2%. When the holding time is less than 3 hours, the segregation of the as-cast structure is not sufficiently eliminated, and the degree of compositional homogenization is inadequate, leading to uneven microstructure and lower performance after subsequent heat treatment. When the holding time is longer than 3 hours, excessive grain growth occurs, the grain boundary strengthening effect weakens, and energy consumption and production cycle increase, resulting in a slight decrease in overall performance rather than an improvement. Therefore, the optimal holding time for homogenization pretreatment is 3 hours.

[0215] Experiment 3: Screening of solution treatment temperature

[0216] This experiment kept all other process parameters exactly the same as in Example 4, only changing the solution treatment temperature. Five levels were set: 780℃, 815℃, 850℃, 885℃, and 920℃. The room temperature mechanical properties of the alloy were tested, and the results are shown in Table 3.

[0217]

[0218] Experimental results show that the alloy exhibits optimal overall performance at a solution treatment temperature of 850℃, with a tensile strength of 1120.8 MPa and a total elongation at break of 44.2%. Below 850℃, the alloying elements are not fully dissolved, resulting in insufficient supersaturated solid solution concentration, limiting subsequent age-hardening potential and leading to lower strength. Above 850℃, abnormal grain growth occurs, intragranular defects decrease, and both plasticity and strength decline simultaneously; furthermore, high temperatures easily induce element burn-off and microstructural distortion, further deteriorating overall performance. Therefore, the optimal solution treatment temperature is 850℃.

[0219] Experiment 4: Screening of Quenching Transfer Time

[0220] This experiment kept all other process parameters exactly the same as in Example 4, only changing the transfer time of the sample to the quenching medium after solution treatment. Five levels were set: 1s, 2s, 3s, 4s, and 5s. The room temperature mechanical properties of the alloy were tested, and the results are shown in Table 4.

[0221]

[0222] Experimental results show that the alloy exhibits optimal comprehensive performance when the quenching transfer time is 3 seconds, with a tensile strength reaching 1120.8 MPa and a total elongation at break of 44.2%. When the transfer time is less than 3 seconds, operational stability decreases, production requirements become too stringent, and performance improvement is not significant. When the transfer time is longer than 3 seconds, coarse phases precipitate prematurely in the air due to the high-temperature solid solution structure, resulting in a substantial loss of supersaturation and a significant reduction in the subsequent aging strengthening effect, leading to a simultaneous decrease in both strength and elongation. Therefore, the optimal quenching transfer time is 3 seconds.

[0223] Experiment 5: Screening of the first-stage heat preservation time for graded aging treatment

[0224] This experiment kept all other process parameters exactly the same as in Example 4, except for the first-stage aging holding time, setting 5 levels of 7h, 8h, 9h, 10h, and 11h, and tested the room temperature mechanical properties of the alloy. The results are shown in Table 5.

[0225]

[0226] Experimental results show that the alloy exhibits optimal overall performance when the first-stage aging holding time is 9 hours, with a tensile strength reaching 1120.8 MPa and a total elongation at break of 44.2%. When the holding time is shorter than 9 hours, the nucleation of precipitated phases is insufficient and their size is too small, resulting in incomplete strengthening effect. When the holding time is longer than 9 hours, the precipitated phases coarsen and mature, the dispersion strengthening effect diminishes, and the matrix continuity is disrupted, leading to decreased strength and reduced plasticity. Therefore, the optimal holding time for the first-stage aging is 9 hours.

[0227] Experiment 6: Screening of the second-stage aging temperature in graded aging treatment

[0228] This experiment kept all other process parameters exactly the same as in Example 4, except for the second-stage aging temperature, which was set at five levels: 270℃, 280℃, 290℃, 300℃, and 310℃. The room temperature mechanical properties of the alloy were tested, and the results are shown in Table 6.

[0229]

[0230] Experimental results show that the alloy exhibits optimal comprehensive performance at a second-stage aging temperature of 290℃, with a tensile strength reaching 1120.8 MPa and a total elongation at break of 44.2%. Below 290℃, atomic diffusion motive force is insufficient, and the size and distribution of precipitates do not reach their optimal state, limiting the strengthening potential. Above 290℃, the precipitates rapidly coarsen, lose their dispersed distribution characteristics, and the strength-ductility balance deteriorates significantly. Therefore, the optimal temperature for the second-stage aging is 290℃.

[0231] Experiment 7: Screening of the second-stage heat preservation time in graded aging treatment

[0232] This experiment kept all other process parameters exactly the same as in Example 4, except for the second-stage aging holding time, which was changed to five levels: 1.0h, 1.25h, 1.5h, 1.75h, and 2.0h. The room temperature mechanical properties of the alloy were tested, and the results are shown in Table 7.

[0233]

[0234] Experimental results show that the alloy exhibits optimal overall performance when the second-stage aging holding time is 1.5 hours, with a tensile strength reaching 1120.8 MPa and a total elongation at break of 44.2%. When the holding time is shorter than 1.5 hours, the precipitated phases do not fully adjust to their optimal size, resulting in insufficient strengthening effect. When the holding time is longer than 1.5 hours, the precipitated phases continue to grow and aggregate, leading to a decrease in strengthening effect and a simultaneous decline in plasticity. Therefore, the optimal holding time for the second-stage aging is 1.5 hours.

[0235] Performance test results:

[0236] For all specimens in this section, all tensile property tests were performed in accordance with GB / T228.1-2021 "Metallic materials - Tensile testing - Part 1: Test at room temperature", and the results are shown in Table 8.

[0237]

[0238] Performance data comparison and analysis:

[0239] 1. Overall performance comparison between the present invention and existing technologies

[0240] Compared to existing commercial B10 cupronickel (Comparative Example 1, tensile strength 822.5 MPa, elongation 43.5%), the minimum Fe content example of this invention (Example 1) achieves a tensile strength of 1006.3 MPa, an increase of 22.3%, and an elongation of 48.2%. The graded aging process of this invention (Example 4) achieves a tensile strength of 1120.8 MPa, an increase of 36.3%, and an elongation of 44.2%, achieving a simultaneous improvement in strength and plasticity.

[0241] Compared with conventional empirical processes in the prior art (Comparative Example 8, tensile strength 962.8 MPa, elongation 42.5%), the optimal process of the present invention (Example 4) increases the tensile strength by 16.4% and the elongation by 4.0%, proving that the process design system of the present invention based on first principles completely breaks through the performance bottleneck of the traditional empirical trial and error method and achieves technical effects that cannot be predicted by those skilled in the art.

[0242] 2. Verification of the necessity of core process steps

[0243] In Comparative Example 2, after omitting the homogenization pretreatment step, the tensile strength of the alloy decreased to 992.6 MPa and the elongation decreased to 42.1%, failing to meet the performance standards. This proves that homogenization pretreatment is a necessary prerequisite for ensuring the final performance of the alloy.

[0244] Comparative Examples 3 and 4 were respectively set at temperatures lower and higher than the solution temperature range selected in this invention (750℃ for Comparative Example 3 and 950℃ for Comparative Example 4). Comparative Example 3 had a tensile strength of 988.3 MPa and an elongation of 42.8%, which did not meet the standards. Comparative Example 4 had a tensile strength of 985.2 MPa and an elongation of 42.5%, which was inferior to the optimal process of this invention. This proves that the solution temperature range of 780℃-920℃ selected in this invention is the core guarantee for achieving sufficient solution of alloying elements and precise control of grain size.

[0245] Comparative Example 5 used a quenching transfer time that exceeded the scope of this invention. The alloy had a tensile strength of 1005.4 MPa and an elongation of 42.9%, proving that a quenching transfer time of ≤5 s is the key to suppressing premature precipitation of the alloy and preserving the supersaturated solid solution structure.

[0246] Comparative Examples 6 and 7 were respectively set at temperatures below / above the first-stage aging temperature range selected in this invention. Comparative Example 6 had a tensile strength of 993.2 MPa and an elongation of 43.0%; Comparative Example 7 had a tensile strength of 1016.5 MPa and an elongation of 42.2%, proving that the first-stage aging temperature range of 340℃-390℃ selected in this invention is the core parameter for achieving the dispersed precipitation of nano-precipitates and balancing strength and plasticity.

[0247] 3. Verification of process parameter range

[0248] As the Fe content increased from 1.6% to 6.75%, the alloy tensile strength increased from 1006.3 MPa to 1120.8 MPa, reaching a peak at 6.75% Fe content. When the Fe content increased to 7.49%, the tensile strength dropped back to 1085.2 MPa, and the elongation decreased to 43.9%. This proves that the Fe content selected in this invention, ranging from 1.6% to 7.49%, is a reasonable addition range, with 6.75% being the performance peak point.

[0249] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the inventive concept, and all such substitutions or modifications should be considered within the scope of protection of the present invention.

[0250] Although the invention and its advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made without departing from the spirit and scope of the invention. Furthermore, the scope of the invention is not limited to the specific embodiments of the processes, methods, and steps described in the specification. From the disclosure of this invention, those skilled in the art will readily utilize existing or future processes, methods, steps that substantially perform the same function or achieve the same results as the corresponding embodiments described herein. Therefore, the appended claims are intended to cover such processes, methods, steps.

Claims

1. A heat treatment process for thermodynamically assisted design of Cu-Ni-Fe alloys, characterized in that, Includes the following steps: (1) A thermodynamic model of Cu-Ni-Fe alloy was constructed based on first-principles calculations. The composition ratio of Cu-Ni-Fe alloy was determined by thermodynamic parameter calculations, and the heat treatment process window of the alloy was predicted. This step employs first-principles calculations combined with thermodynamic phase equilibrium analysis to construct a complete technical chain: "basic model construction → multi-dimensional thermodynamic parameter calculation and screening → multi-objective comprehensive decision-making → process window prediction." It determines the alloy composition ratio and heat treatment process parameters, first clarifying the basic calculation conditions, then screening according to the priority of "stability → performance potential → process adaptability," and finally comprehensively determining the optimal solution. Specifically, it includes the following steps: 1) Setting up basic calculation conditions and constructing alloy models First-principles calculations were performed using density functional theory and the VASP software package. The exchange-correlation functional was the PBE generalized gradient approximation. The plane wave cutoff energy was fixed at 450 eV. The Brillouin zone K-point grid used a 3×3×1 Monkhorst-Pack scheme. The energy convergence criterion for the electronic self-consistent iteration was 10. -5 eV / atom; the force convergence criterion for ion relaxation is 0.01 eV / Å; Based on the face-centered cubic crystal structure of Cu, a 2×2×2 supercell was constructed. With the Ni mass fraction fixed at 10%, Fe atoms were introduced by replacing Cu atoms in the supercell, resulting in seven Cu-10Ni-xFe alloy supercell models with Fe mass fractions of 0%, 1.6%, 4.37%, 5.56%, 6.75%, 7.49%, and 9%. Simultaneously, a single-cell model of a pure Cu matrix and the FeNi3 intermetallic compound was constructed for subsequent calculation of precipitation phase parameters. Lattice constant optimization and atomic position full relaxation were performed on all constructed models to obtain the stable crystal structures of the alloys with each composition. 2) Calculation of multidimensional thermodynamic parameters and component screening 2-1) Gibbs free energy calculation and matrix phase stability screening Calculation method: Within the temperature range of 298K-1200K, the Gibbs free energy of the alloy is calculated using the quasi-harmonic approximation. The calculation formula is as follows: G(T)=E0+F vib (T)-TS(T); Where E0 is the total electron energy at 0K, F vib (T) is the lattice vibrational free energy, and TS(T) is the total entropy of the system; Screening criteria: The Gibbs free energy of the alloy matrix is ​​lower than that of all competing phases at the same temperature, ensuring that the alloy is a single-phase FCC solid solution structure in the range from room temperature to solution temperature. 2-2) Calculation of precipitation phase formation energy and screening of aging enhancement potential Calculation method: The formation energy of FeNi3 nanoprecipitates in Cu matrix is ​​calculated using the following formula: ΔE form =E alloy(析出相) -E alloy(固溶体) -n×(E FeNi3 -E Cu ); Among them, E alloy(析出相) E represents the total energy of an alloy containing one FeNi3 precipitate unit. alloy(固溶体) E represents the total energy of a supersaturated solid solution of the corresponding composition, where n is the number of atoms in the precipitated phase (n=4). FeNi3 E is the average energy of a single atom in a FeNi3 unit cell. Cu This represents the average energy of a single atom in a pure Cu unit cell. Screening criteria: The precipitation phase formation energy is controlled within the range of 0.05-0.18 eV / atom; 2-3) Calculation of elastic constants and screening of mechanical property potential Calculation method: The independent elastic constants C of alloys with different Fe contents were calculated using the stress-strain method. 11 C 12 C 44 Based on the Voigt-Reuss-Hill approximation, the bulk modulus K, shear modulus G, Young's modulus E, and Poisson's ratio v of the alloy are calculated using the following formulas: K=(C 11 +2C 12 ) / 2,G=(C 11 -C 12 +3C 44 ) / 5; E=9KG / (3K+G), v=(3K-2G) / 2(3K+G); Screening criteria: bulk modulus K≥120GPa, Poisson's ratio v≥0.34, ensuring that the alloy has both sufficient strength enhancement potential and good plasticity. 2-4) Calculation of heat capacity and coefficient of thermal expansion and screening of heat treatment process suitability Calculation method: Within the temperature range of 298K-1000K, the isobaric heat capacity C of the alloy is calculated using the quasi-harmonic approximation. P With the coefficient of thermal expansion α; Screening criteria: The deviation of the coefficient of thermal expansion from that of pure Cu is ≤15%; the heat capacity curve shows no abrupt change in the solution temperature range of 780℃-920℃, ensuring a stable microstructure transformation during heat treatment; 2-5) Phonon spectrum calculation and dynamic stability screening Calculation method: Phonon dispersion curves and phonon density of states of alloys with different Fe contents were calculated using density functional perturbation theory; Screening criteria: The phonon dispersion curve has no imaginary frequency throughout the entire Brillouin zone; 3) Multi-parameter integrated decision-making and heat treatment process window prediction Based on the calculation and screening results of the five dimensions in step 2), and following the principle of "phase stability as the sole veto factor, strengthening potential as the priority, and process adaptability as the bottom line", a multi-objective comprehensive decision was made, and the optimal composition ratio of Cu-Ni-Fe alloy was finally determined to be: 10% Ni mass fraction, 1.6%-4.37% Fe mass fraction, with the balance being Cu and unavoidable impurities. (2) According to the composition ratio determined in step (1), Cu-Ni-Fe alloy ingots are prepared by melting and casting. (3) The Cu-Ni-Fe alloy ingot is subjected to homogenization pretreatment to eliminate compositional segregation of the as-cast structure. The temperature of the homogenization pretreatment is 680℃-760℃ and the holding time is 2h-4h. (4) Machining the alloy ingot after homogenization pretreatment to prepare alloy samples that meet the heat treatment requirements; (5) The alloy sample is placed in a box-type resistance furnace for solution treatment, so that the alloying elements are fully dissolved in the copper matrix to obtain a single-phase supersaturated solid solution structure. The solution treatment temperature is 780℃-920℃ and the holding time is 3h-11h. (6) The alloy sample that has undergone solution treatment is quenched and rapidly cooled to retain the supersaturated solid solution structure at high temperature; (7) Based on the thermodynamic model calculation results of step (1), determine the aging process parameters of the alloy, perform aging treatment on the quenched alloy sample, and control the type, size and distribution of precipitates in the matrix. The aging treatment is a graded aging treatment, which includes a first-stage aging and a second-stage aging. The first-stage aging temperature is 340℃-390℃ and the holding time is 7h-11h. The second-stage aging temperature is 270℃-310℃ and the holding time is 1h-2h. After each stage of aging is completed, the sample is taken out and air-cooled to room temperature. (8) The mechanical properties of the alloy sample after aging treatment are tested. The tensile strength and total elongation at break data obtained from the test are input into the thermodynamic model of step (1) to correct the precipitation phase formation energy parameters in the model, so as to reduce the deviation between the theoretical calculation value and the actual value in the next process design.

2. The heat treatment process for thermodynamically assisted design of Cu-Ni-Fe alloys according to claim 1, characterized in that, In step (1), the calculation parameters of the thermodynamic model include the alloy’s Gibbs free energy, heat capacity, coefficient of thermal expansion, bulk modulus, phonon spectrum and precipitation phase formation energy, which are used to predict the solid solution temperature window, aging precipitation temperature window and precipitation kinetics of the alloy.

3. The heat treatment process for thermodynamically assisted design of Cu-Ni-Fe alloys according to claim 1, characterized in that, In step (6), the quenching process uses room temperature deionized water as the cooling medium.

4. The heat treatment process for thermodynamically assisted design of Cu-Ni-Fe alloys according to claim 1, characterized in that, The time for transferring the sample after solution treatment in step (6) to the quenching medium is ≤5s.

5. The heat treatment process for thermodynamically assisted design of Cu-Ni-Fe alloys according to claim 1, characterized in that, In step (8), the mechanical property test is a room temperature tensile test, and the test indicators include tensile strength and total elongation at break; the tensile strength of the alloy is >1000MPa and the total elongation at break is >43%.

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