High-strength high-conductivity copper-silver alloy for communication connectors and method for preparing the same

Abstract

This invention discloses a high-strength, high-conductivity copper-silver alloy for communication connectors and its preparation method, belonging to the technical field of copper alloy materials. The process includes: S1 melting and casting, the alloy containing Ag and one or more of the amplitude modulation decomposition inducing elements Ni, Co, Al, Ti, and Fe; S2 homogenization treatment; S3 cooling at 10-50℃ / h to 350-550℃ and holding for 2-24h to induce amplitude modulation decomposition and form a nanoscale periodic amplitude modulation structure; S4 cold deformation processing; S5 multi-stage gradient aging: holding at 200-350℃ for 1-5h, heating at 5-20℃ / h to 400-500℃ and holding for 2-8h, cooling at ≤10℃ / h to 300-350℃ and holding for 4-12h to form a periodically arrayed coherent nano-precipitated phase; S6 preparing an inner self-lubricating plating layer and an outer protective coating. This invention guides the orderly growth of precipitates using an amplitude-modulated template, resulting in an alloy with tensile strength ≥470MPa, conductivity ≥89%IACS, elongation ≥6%, and excellent high-temperature stability, making it suitable for connectors used in extreme environments such as 5G communication and deep space exploration.

Description

Technical Field

[0001] This invention relates to the field of copper alloy materials technology, and in particular to a high-strength, high-conductivity copper-silver alloy for communication connectors and its preparation method. Background Technology

[0002] With the rapid development of cutting-edge technologies such as deep space exploration, high-power laser communication, advanced particle accelerators and nuclear fusion research, connector materials are required to possess ultra-high strength, ultra-high conductivity, excellent high-temperature stability, radiation damage resistance, low stress relaxation rate and thermal expansion coefficient that matches the packaging material in extreme service environments.

[0003] Copper and copper alloys possess excellent electrical and thermal conductivity and good machinability. However, existing copper alloy systems face performance bottlenecks that are difficult to overcome when dealing with the aforementioned extreme combined service conditions. Currently, the main strengthening mechanisms for improving the strength of copper alloys include solid solution strengthening, precipitation strengthening, grain refinement strengthening, and deformation strengthening. These mechanisms often come at the cost of sacrificing conductivity. Any crystal defects that disrupt the periodicity of the copper lattice will scatter conduction electrons, thereby reducing conductivity. Existing technologies typically utilize the composition modulation structure itself formed by amplitude modulation decomposition as a strengthening source, or utilize its subsequent transformation into an ordered phase for strengthening. The strength obtained by this strengthening method is limited, and the ordered phase will still coarsen or dissolve at high temperatures. Furthermore, amplitude modulation decomposition treatment and subsequent aging treatment are often regarded as independent processes, without establishing an intrinsic connection between the two.

[0004] In traditional processes, whether through random precipitation or dispersion strengthening, the distribution of the second phase exhibits disordered and random characteristics, failing to effectively avoid scattering of conduction electrons, resulting in an inherent upper limit to the increase in conductivity. The high interfacial energy of incoherent or semi-coherent interfaces inevitably causes the strengthening phase to coarsen under thermodynamic driving, leading to high-temperature strength decay and increased contact resistance. Existing strengthening mechanisms are often mutually exclusive; for example, increasing the number of precipitated phases can improve strength but exacerbates electron scattering; refining grains can improve strength, but increasing grain boundaries also increases scattering.

[0005] Therefore, how to preconstruct a thermodynamically stable periodic composition modulation template at the atomic scale, and on this basis, guide the subsequent nano-precipitates to spontaneously form a long-range ordered, low-interface-energy, and anti-coarsening ultra-stable self-organized array along the template through kinetic regulation, so as to achieve a leapfrog improvement in strength while maximizing the preservation of the matrix conductivity, and ensure the long-term stability of the structure under combined service conditions such as extreme temperature and strong radiation, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] This invention overcomes the shortcomings of the prior art and provides a high-strength, high-conductivity copper-silver alloy for communication connectors and its preparation method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a high-strength and high-conductivity copper-silver alloy for communication connectors and its preparation method, comprising: S1: weighing raw materials according to the designed alloy composition, melting them under vacuum and casting them into ingots; wherein the alloy composition is mainly composed of copper as the matrix, and includes silver and alloying elements, and the alloying elements include at least an amplitude modulation decomposition inducing element that can cause amplitude modulation decomposition of the alloy.

[0008] S2: Heat the ingot to 600-900℃ and hold for 2-10 hours to homogenize it and eliminate micro-segregation of elements.

[0009] S3: Cool the homogenized alloy to 350-550℃ at a cooling rate of 10-50℃ / hour, and hold it in this temperature range for 2-24 hours to cause the alloy to undergo amplitude modulation decomposition and form an amplitude modulation structure with periodic composition modulation at the nanoscale, including solute-rich and solute-poor regions.

[0010] S4: The alloy after amplitude modulation decomposition pretreatment is subjected to cold deformation processing, with a cold deformation amount of 20%-90%, to obtain wire.

[0011] S5: The cold-deformed alloy undergoes multi-stage gradient aging treatment, causing the nano-precipitates to preferentially grow along the solute-rich region of the modulated structure under the guidance of the amplitude-modulated microstructure, forming coherent nano-precipitates with a periodic array distribution, including:

[0012] First-level aging: Keep warm at 200-350℃ for 1-5 hours;

[0013] Second-stage aging: Heat to 400-500℃ at a heating rate of 5-20℃ / hour, and hold for 2-8 hours;

[0014] Level 3 aging: Cool to 300-350℃ at a cooling rate not exceeding 10℃ / hour, hold for 4-12 hours, and then cool to room temperature;

[0015] S6: The treated alloy undergoes surface treatment, and an inner self-lubricating plating layer and an outer protective coating are prepared in sequence, which are then processed into winding wires or connector terminals for communication connectors.

[0016] In a preferred embodiment of the present invention, the amplitude modulation decomposition inducing element in step S1 is selected from one or more of Ni, Co, Al, Ti, and Fe, and the sum of their contents is 0.5-5.0 wt%.

[0017] In a preferred embodiment of the present invention, the alloy composition in step S1 further includes one or more strengthening elements selected from Cr, Zr, and Mg, with a total content of 0.05-2.0 wt%.

[0018] In a preferred embodiment of the present invention, during the smelting process in step S1, a rare earth composite refining agent is added to the melt for purification treatment, and a covering agent and an inert gas are used for combined protection; the rare earth composite refining agent contains CaF2 and rare earth oxides, and the amount added is 0.1%-1.0% of the melt mass.

[0019] In a preferred embodiment of the present invention, the cold deformation process in step 4 is one or more combinations of roll forming, drawing or extrusion, with a total cold deformation amount of 50%-99%, to obtain wire with a diameter of 0.02-2.0 mm.

[0020] In a preferred embodiment of the present invention, after the multi-level gradient aging treatment in step S5, coherent nanoprecipitates induced by amplitude modulation decomposition and distributed in a periodic array are formed in the alloy, and the interface between the nanoprecipitates and the matrix is ​​a coherent or semi-coherent interface.

[0021] In a preferred embodiment of the present invention, the inner self-lubricating coating in step S6 is a eutectic coating; and the outer protective coating is a diamond-like coating.

[0022] A high-strength, high-conductivity copper-silver alloy for communication connectors, wherein the microstructure of the alloy comprises: an amplitude modulation structure with periodic composition modulation, and coherent nanoprecipitates distributed in a periodic array guided by the amplitude modulation structure; the alloy has a tensile strength ≥470MPa, conductivity ≥89% IACS, and elongation ≥6%.

[0023] In a preferred embodiment of the present invention, the average spacing of the coherent nanoprecipitates arranged in a periodic array is 5-50 nm, and the lattice mismatch between the precipitates and the copper substrate is less than 0.5%.

[0024] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0025] (1) This invention addresses the technical challenges in the prior art, such as the mutual constraint between precipitation strengthening and conductivity, severe electron scattering due to disordered distribution of precipitates, and easy coarsening and decay at high temperatures. It constructs a periodic component modulation template through amplitude modulation decomposition pretreatment, and then guides the orderly growth of nanoprecipitates along the template through multi-level gradient aging to form a coherent nanoprecipitate with a periodic array distribution. This achieves simultaneous improvement in high strength and high conductivity, while obtaining excellent high-temperature stability and processing performance, meeting the service requirements of communication connectors in extreme environments.

[0026] (2) The solute-rich region formed by amplitude modulation decomposition has a higher solute supersaturation, which is the thermodynamically preferred region for nucleation of precipitated phases; the dislocations introduced in step S4 preferentially accumulate in the solute-rich region, forming a local stress field; in the multi-stage gradient aging, the first stage aging induces a large number of fine and uniform precipitated phase nuclei in the solute-rich region, the second stage aging slowly raises the temperature by 5-20℃ / hour to force the precipitated phase to grow preferentially along the direction of compositional fluctuation, and the third stage aging slowly cools and holds the temperature by ≤10℃ / hour to allow the interface to fully relax. The coherent nanoprecipitated phase finally formed maintains a coherent or semi-coherent interface with the matrix, and the low interfacial energy gives the precipitated phase resistance to coarsening. In traditional processes, the precipitated phase is randomly distributed, and the strengthening effect is limited; while the present invention makes the precipitated phase have a high number density and uniform distribution through ordered array, which has a stronger hindering effect on dislocations.

[0027] (3) The scattering of electrons from the periodically distributed array is much smaller than that from the random distribution. When electrons move in the periodic potential field, they form electronic bands instead of being scattered one by one by isolated scattering centers, thus minimizing the disruption of the electron free path. At the same time, the coherent / semi-coherent interface has good lattice continuity and small lattice distortion at the interface, resulting in weak scattering of electrons. The amplitude modulation decomposition pretreatment enriches some solute atoms in the solute-rich region, reducing the content of solid solution atoms in the matrix and reducing solid solution scattering of electrons. In traditional strengthening mechanisms, increasing strength inevitably sacrifices conductivity; however, the low electron scattering characteristics of the ordered array structure in this application enable the alloy to have lower signal attenuation in high-frequency signal transmission, making it suitable for high-speed transmission scenarios such as 5G communication.

[0028] (4) This invention utilizes an innovative design that guides ordered precipitation using an amplitude-modulated template, enabling precise control of the precipitated phase distribution and interface state at the atomic scale. This allows for the synergistic improvement of previously mutually exclusive strength and conductivity indicators: tensile strength ≥ 470 MPa, conductivity ≥ 89% IACS, and elongation ≥ 6%. The periodically arrayed coherent nanoprecipitated phases enhance strength and conductivity, while the low interfacial energy imparts excellent high-temperature stability. Rare earth refining improves melt purity and ensures the uniformity of the amplitude-modulated structure. The synergistic effect of the double-layer coating results in an insertion / extraction life of over 15,200 cycles, a wire breakage rate ≤ 2.5 cycles / km, and a yield ≥ 88%. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Many specific details are set forth in the following description to provide a thorough understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0030] Application Overview:

[0031] This invention provides a high-strength, high-conductivity copper-silver alloy for communication connectors and its preparation method, suitable for manufacturing high-reliability communication connectors operating in extreme environments. This alloy achieves an excellent match between high strength and high conductivity through specific composition design and multi-stage heat treatment processes. In existing technologies, traditional aging precipitation or dispersion strengthening methods result in random and disordered precipitate formation, whose distribution cannot avoid scattering electron conduction paths, thus limiting conductivity. Incoherent or semi-coherent precipitates possess high interfacial energy, undergoing coarsening and dissolution under thermodynamic driving, leading to performance degradation under extreme conditions. Furthermore, existing amplitude modulation decomposition treatments lack synergistic design with subsequent aging treatments, failing to utilize amplitude-modulated microstructures as templates to guide the orderly growth of subsequent precipitates.

[0032] Compared to existing technologies, this solution transforms traditionally disordered precipitates into an ordered periodic array, achieving high strength while minimizing conductivity loss. The low interfacial energy of the coherent or semi-coherent interface gives the precipitates thermodynamic resistance to coarsening, ensuring the long-term stability of the alloy under extreme temperatures and strong radiation environments. Through amplitude modulation decomposition pretreatment and multi-stage gradient aging, the originally mutually exclusive strength and conductivity indicators are synergistically improved.

[0033] A high-strength, high-conductivity copper-silver alloy for communication connectors and its preparation method, comprising:

[0034] S1: Weigh the raw materials according to the designed alloy composition, melt them under vacuum and cast them into ingots; wherein the alloy composition is mainly composed of copper as the base, and includes silver and alloying elements, and the alloying elements include at least the amplitude decomposition inducing elements that can cause amplitude decomposition of the alloy.

[0035] S2: Heat the ingot to 600-900℃ and hold for 2-10 hours to homogenize it and eliminate micro-segregation of elements.

[0036] S3: Cool the homogenized alloy to 350-550℃ at a cooling rate of 10-50℃ / hour, and hold it in this temperature range for 2-24 hours to cause the alloy to undergo amplitude modulation decomposition and form an amplitude modulation structure with periodic composition modulation at the nanoscale, including solute-rich and solute-poor regions.

[0037] S4: The alloy after amplitude modulation decomposition pretreatment is subjected to cold deformation processing, with a cold deformation amount of 20%-90%, to obtain wire.

[0038] S5: The cold-deformed alloy undergoes multi-stage gradient aging treatment, causing the nano-precipitates to preferentially grow along the solute-rich region of the modulated structure under the guidance of the amplitude-modulated microstructure, forming coherent nano-precipitates with a periodic array distribution, including:

[0039] First-level aging: Keep warm at 200-350℃ for 1-5 hours;

[0040] Second-stage aging: Heat to 400-500℃ at a heating rate of 5-20℃ / hour, and hold for 2-8 hours;

[0041] Level 3 aging: Cool to 300-350℃ at a cooling rate not exceeding 10℃ / hour, hold for 4-12 hours, and then cool to room temperature;

[0042] S6: The treated alloy undergoes surface treatment, and an inner self-lubricating plating layer and an outer protective coating are prepared in sequence, which are then processed into winding wires or connector terminals for communication connectors.

[0043] Specifically, in step S1, raw materials are weighed according to the designed alloy composition, melted under vacuum, and cast into ingots. The alloy composition is based on copper as the main component, containing silver and alloying elements. The alloying elements include at least one amplitude decomposition inducing element that can cause amplitude decomposition in the alloy. The amplitude decomposition inducing element is selected from one or more of Ni, Co, Al, Ti, and Fe, with a total content of 0.5-5.0 wt%. The alloy composition in step S1 also includes one or more strengthening elements selected from Cr, Zr, and Mg, with a total content of 0.05-2.0 wt%.

[0044] Copper, as the base phase of the alloy, provides excellent electrical and thermal conductivity. The addition of silver introduces a solid solution strengthening effect while ensuring conductivity, and provides a silver-rich region for subsequent amplitude modulation decomposition. Silver and copper have high solid solubility at high temperatures. Adding a small amount of silver to form a solid solution in the copper matrix hinders dislocation movement, thereby enhancing the solid solution effect. Furthermore, due to the differences in atomic size and electronegativity between copper and silver, the addition of silver helps induce concentration fluctuations in elements during subsequent amplitude modulation decomposition, providing a thermodynamic driving force for amplitude modulation decomposition.

[0045] Amplitude decomposition is a phase transformation mechanism that occurs in the unstable region of the solid solution of an alloy system. When the alloy is rapidly cooled from a high-temperature single-phase region to a certain temperature range, it spontaneously decomposes into two micro-regions with periodic fluctuations in composition and the same structure but different compositions: a solute-rich region and a solute-poor region.

[0046] Amplitude-modulating decomposition inducing elements are alloying elements that can cause amplitude-modulating decomposition in alloys, causing the alloy solid solution to enter the thermodynamically unstable region.

[0047] Among them, Ni and Co form continuous solid solutions or wide-range solid solutions with copper, which helps to form Ni / Co-Al / Ti-rich precipitates. These precipitates have lattice constants similar to those of the copper matrix and are easy to form coherent interfaces.

[0048] Al has a small atomic size and a significant solid solution strengthening effect. Al has a strong bonding force with elements such as Ni and Co, and is a key element in the formation of intermetallic compounds such as Ni3Al and Co3Al. It is the main strengthening phase precipitated during subsequent aging.

[0049] Ti combines with Ni, Co, etc. to form Ni3Ti, Co3Ti, etc., which have high thermal stability, help improve the resistance of precipitated phases to coarsening, and improve the high-temperature performance of the alloy.

[0050] Fe can combine with Ni, Co, and other elements to form a complex amplitude decomposition system, which helps to improve the strength and wear resistance of the alloy.

[0051] Furthermore, the total content of amplitude modulation decomposition inducing elements is controlled between 0.5-5.0 wt% to ensure that amplitude modulation decomposition can occur and obtain the ideal modulation wavelength and component amplitude, while avoiding excessive addition that could lead to excessive decrease in conductivity or the formation of coarse primary phases. If the content of amplitude modulation decomposition inducing elements is too low, the driving force for component fluctuations in the solid solution will be insufficient, making it difficult to induce significant amplitude modulation decomposition. If the content is too high, too many solute atoms will be dissolved in the copper matrix, resulting in strong scattering of conduction electrons and a sharp decrease in conductivity.

[0052] The modulation wavelength is the center distance between adjacent solute-rich or solute-poor regions in the amplitude-modulated structure. The modulation wavelength determines the spacing and arrangement period of the subsequent aging precipitates.

[0053] The alloy composition described in step S1 also includes one or more strengthening elements selected from Cr, Zr, and Mg, with a total content of 0.05-2.0 wt%.

[0054] The synergistic effect of strengthening elements and amplitude modulation decomposition inducing elements further enhances the alloy properties based on the amplitude modulation template, without affecting the amplitude modulation decomposition process.

[0055] Among them, the nanoscale Cr phase precipitated during the aging process maintains a coherent relationship with the copper matrix, which can hinder dislocation movement, enhance the precipitation effect, and at the same time have relatively little impact on conductivity.

[0056] Zr increases the recrystallization temperature and high-temperature strength of copper alloys, effectively suppressing grain boundary sliding and grain growth at high temperatures, and improving the alloy's stress relaxation resistance and high-temperature stability.

[0057] Mg has a solid solution strengthening effect, which can improve the strength and hardness of alloys; at the same time, Mg can improve the corrosion resistance of alloys, especially the resistance to stress corrosion cracking in chlorine-containing environments.

[0058] In step S1, during the smelting process, a rare earth composite refining agent is added to the melt for purification treatment, and a covering agent and an inert gas are used for combined protection. The rare earth composite refining agent contains CaF2 and rare earth oxides, and the amount added is 0.1%-1.0% of the melt mass.

[0059] Among them, rare earth composite refining agent is used to adsorb and remove non-metallic inclusions in the melt, thereby improving the purity of the melt. High purity is a prerequisite for obtaining uniform amplitude modulation structure and ordered precipitation array. Impurities will disrupt the periodicity of amplitude modulation decomposition.

[0060] The combination of a covering agent and an inert gas can isolate the melt from air, preventing oxidation, gas absorption, and element loss at high temperatures. The covering agent is a low-melting-point inert agent, such as boron anhydride, glass powder, or a special copper alloy covering agent, that covers the surface of the melt to form a liquid protective layer, physically isolating the melt from direct contact with air. The inert gas is a high-purity inert gas, such as argon, that is continuously introduced into the melting furnace to replace the air in the furnace and carry away the metal vapors volatilized from the melt through gas flow, maintaining positive pressure in the furnace to enhance the protective effect.

[0061] CaF2 has a low melting point and good fluidity, which lowers the melting point of the refining agent and promotes the uniform dispersion of the refining agent in the melt. At the same time, CaF2 reacts with inclusions such as Al2O3 and SiO2 in the melt to generate low-melting-point composite compounds, which are easy to remove by flotation.

[0062] Rare earth elements have extremely strong chemical reactivity. During the smelting process, rare earth elements react with impurity elements such as oxygen, sulfur, and hydrogen in the melt, thereby reducing the content of harmful impurities in the melt and improving the purity of the matrix. At the same time, they help improve the hot working properties of the alloy and reduce the tendency to crack during subsequent cold deformation processing.

[0063] Step S2 involves heating the ingot to 600-900℃ and holding it for 2-10 hours to homogenize it and eliminate microscopic element segregation.

[0064] The high temperature of the ingot heating allows solute atoms in the segregated region to migrate over long distances, achieving compositional homogenization. At the same time, the temperature is controlled within the range of 600-900℃ to avoid overheating or excessive grain coarsening. In the as-cast structure, the first solidified part is usually rich in high-melting-point copper, while the subsequent solidified part is rich in low-melting-point alloying elements. At high temperatures, atoms gain sufficient energy to diffuse from the solute-rich region to the solute-poor region until the composition becomes uniform.

[0065] The selection of the 600-900℃ temperature range is important because the atomic diffusion coefficient in copper alloys is low below 500℃. When the temperature rises above 600℃, the diffusion coefficient increases, allowing solute atoms to migrate quickly. Meanwhile, the amplitude modulation decomposition treatment temperature range in step S3 is 350-550℃. The minimum temperature of 600℃ ensures that the homogenization treatment is above the amplitude modulation decomposition temperature range, avoiding premature amplitude modulation decomposition during homogenization and disrupting subsequent precise control.

[0066] The upper limit of temperature is 900℃. When the temperature exceeds the melting point of the low melting point eutectic phase in the alloy, local melting will occur in the grain boundary and interdendritic region, forming an overheated structure; at the same time, if the temperature is too high, the grains will grow abnormally, forming a coarse grain structure.

[0067] Holding the temperature for 2-10 hours provides sufficient time for atoms to diffuse fully, completely eliminating microsegregation, while avoiding excessive grain coarsening and energy waste caused by excessive holding time. Furthermore, temperature and time are complementary; if a lower temperature is selected, a longer holding time is required to compensate for the reduction in diffusion coefficient; if a higher temperature is selected, a shorter holding time can be used.

[0068] After step S2, the solute enrichment zone, which was originally dendritic, disintegrates, and the composition distribution of the alloy ingot becomes more uniform. The non-equilibrium eutectic phases existing between grain boundaries and dendrites in the as-cast structure are re-dissolved into the copper matrix, forming a uniform single-phase solid solution. With high-temperature diffusion, the as-cast structure undergoes complete recrystallization, eliminating the internal stress and some crystal defects generated during solidification. In a matrix with uniform composition, amplitude modulation decomposition can spontaneously form a regular and periodic composition modulation structure. If the matrix itself has segregation, amplitude modulation decomposition will be superimposed on this basis, resulting in a chaotic and disordered modulation structure.

[0069] Step S3 involves cooling the homogenized alloy to 350-550°C at a cooling rate of 10-50°C / hour, and holding it at this temperature for 2-24 hours to induce amplitude modulation decomposition in the alloy, forming an amplitude modulation structure with periodic composition modulation at the nanoscale.

[0070] Specifically, amplitude modulation decomposition requires atoms to diffuse and migrate over long distances. The cooling rate directly determines the residence time of the alloy in the amplitude modulation decomposition temperature range, which in turn affects the diffusion ability of atoms and the degree of evolution of the amplitude modulation structure. Therefore, a cooling rate of 10-50℃ / hour is selected to ensure that amplitude modulation decomposition can occur fully and to obtain a periodic structure with a moderate modulation wavelength and significant compositional amplitude. At the same time, excessively rapid cooling should be avoided to prevent amplitude modulation decomposition from being suppressed or to form a non-equilibrium structure.

[0071] Amplitude decomposition occurs only within a specific temperature range, which lies within the Spinodal curve. Within this temperature range, the free energy curve of the solid solution has a negative curvature, and any compositional fluctuations will not be thermodynamically eliminated but will instead spontaneously increase, leading to amplitude decomposition. The selected temperature range of 350-550℃ avoids excessively high temperatures, which would cause the alloy to enter a stable single-phase solid solution region, preventing amplitude decomposition from occurring. At excessively low temperatures, the atomic diffusion coefficient drops sharply. Simultaneously, the first stage temperature of the S5 multi-stage gradient aging is 200-350℃, and the lower limit temperature of S3 (350℃) connects with the upper limit temperature of S5, ensuring the continuity of the thermal history from amplitude decomposition pretreatment to cold deformation processing and then to aging treatment, and avoiding unnecessary phase transformation interference.

[0072] The Spinodal curve is the thermodynamic boundary in the alloy phase diagram, used to define the temperature range in which the solid solution undergoes amplitude-modulated decomposition. The specific position of the Spinodal curve depends on the specific composition of the alloy. The 350-550℃ range defined in this invention is an empirical range based on the common Spinodal temperature range of copper-based alloys, ensuring that most target composition alloys can enter the unstable region.

[0073] The heat preservation time of 2-24 hours provides sufficient kinetic time for the amplitude modulation decomposition to proceed fully, allowing the component modulation wave to develop to the expected wavelength and amplitude.

[0074] The amplitude-modulated structure is a nanoscale periodic composition-modulated structure formed by amplitude-modulated decomposition, consisting of alternating solute-rich and solute-poor regions. It serves as an atomic-scale template for subsequent S5 multi-level gradient aging, guiding the orderly growth of the nanoprecipitated phase.

[0075] S4: The alloy after amplitude modulation decomposition pretreatment is subjected to cold deformation processing, with a cold deformation amount of 20%-90%, to obtain wire; the cold deformation processing in step 4 is one or more combinations of roll forming, drawing or extrusion, with a total cold deformation amount of 50%-99%, to obtain wire with a diameter of 0.02-2.0mm.

[0076] After the amplitude modulation decomposition pretreatment in S3, a periodic composition modulation template at the nanoscale is constructed inside the alloy. At this time, the amplitude modulation structure does not directly form a strengthening phase. In step S4, the alloy is processed into the required wire size through cold working with a large deformation. High-density dislocations are introduced into the matrix to provide nucleation sites for subsequent aging precipitation. The amplitude modulation template is activated by deformation energy storage, so that it can more effectively guide the orderly growth of precipitates in subsequent aging.

[0077] In this process, cold deformation increases the dislocation density through plastic deformation, and the interaction between dislocations hinders further movement of dislocations, thereby improving strength. At the same time, there is a stress field and lattice distortion near the dislocation line, solute atoms tend to agglomerate at the dislocation, lowering the nucleation energy barrier and allowing the precipitated phase to preferentially nucleate on the dislocation line. The dislocation core region is a fast channel for atomic diffusion, which helps solute atoms to be transported quickly to the nucleation site.

[0078] Pass rolling is suitable for initial processing of billets with large cross sections to medium cross sections, with large deformation per pass and high efficiency; however, the surface quality and control over the uniformity of the core structure are relatively weak.

[0079] Drawing is suitable for precision machining of medium cross-section wires to fine and ultra-fine wires, with high dimensional accuracy, good surface quality, and continuous production capability; however, the deformation per pass is limited by the strength of the die and lubrication conditions, and the deformation per pass is usually between 10% and 30%.

[0080] Extrusion is suitable for producing wires with irregular cross-sections or products with extremely high requirements for uniformity of structure. The triaxial compressive stress state is conducive to bringing out the plastic potential of the material and is suitable for alloys with poor deformation ability; however, the production efficiency is relatively low.

[0081] When using a combination of methods, first perform hot extrusion or roll forming to process the large cross-section billet to a medium diameter; then perform multiple drawing passes to gradually reduce the diameter to the target size.

[0082] Step S4 yields wires with a diameter of 0.02-2.0mm, meeting the basic size requirements of communication connectors; substructures such as dislocation cells and dislocation tangles are formed; the energy stored during the deformation process exists in the form of dislocation energy and point defect energy, providing a thermodynamic driving force for subsequent aging precipitation in step S5.

[0083] Step S5 involves subjecting the cold-deformed alloy to a multi-stage gradient aging treatment, allowing the nano-precipitates to preferentially grow along the solute-rich region of the modulated structure under the guidance of the amplitude-modulated microstructure, forming a coherent nano-precipitate distribution in a periodic array, including:

[0084] First-level aging: Keep warm at 200-350℃ for 1-5 hours;

[0085] Second-stage aging: Heat to 400-500℃ at a heating rate of 5-20℃ / hour, and hold for 2-8 hours;

[0086] Level 3 aging: Cool to 300-350℃ at a cooling rate not exceeding 10℃ / hour, hold for 4-12 hours, and then cool to room temperature.

[0087] Specifically, by employing a multi-level gradient processing approach that allows for controlled heating, holding, and cooling paths, the nucleation, growth, and coarsening processes of the precipitates are spatiotemporally matched with the composition period and stress field of the dislocation network in the amplitude-modulated template, ultimately resulting in a long-range ordered array of precipitates. Unlike traditional single-stage aging, this application utilizes a strategy of low-temperature pre-nucleation, slow heating to guide growth, and high-temperature stabilization to ensure that the evolution of the precipitates is always guided by the amplitude-modulated template, ultimately forming a long-range ordered array structure. The interface energy is low, resulting in electron scattering that is far less than that of randomly distributed precipitates.

[0088] Among them, pre-nucleation is the first-stage low-temperature aging process, which induces a large number of small and uniform precipitate nuclei in the solute-rich region of the amplitude-modulated structure; ensuring that the number density and spatial distribution of the precipitates are predefined by the amplitude-modulated template, and the pre-nucleation stage determines the number and uniformity of the final precipitate array.

[0089] The guided growth stage, which is the second stage of aging, forces the precipitated phase to grow preferentially along the component fluctuation direction of the solute-rich region of the amplitude-modulated tissue by slowly increasing the temperature. This guided growth stage achieves the transformation from a static component template to a dynamic ordered array.

[0090] High-temperature stabilization to the third stage of aging involves slow cooling and low-temperature insulation, which allows the interface between the precipitated phase and the matrix to reduce the interface energy through local atomic rearrangement, evolving from a metastable state to a more stable coherent or semi-coherent state, thus completing the final solidification of the array structure.

[0091] The amplitude modulation structure guides the formation of solute-rich regions with higher solute supersaturation, which are thermodynamically preferential regions for precipitate nucleation. Solute atoms in this region can form precipitate nuclei without long-distance diffusion. The dislocations introduced in step S4 preferentially accumulate in the solute-rich regions, forming a local stress field. The stress field interacts with the strain field of the precipitate, causing the precipitate to tend to grow along a specific crystallographic direction.

[0092] The solute-rich region of the amplitude-modulated structure has a different lattice constant from the matrix, but remains coherent. In this region, the nucleated precipitates naturally tend to choose crystallographic orientations that match the matrix lattice in order to reduce the interfacial energy and further enhance the ordered arrangement of the precipitates.

[0093] The first stage of aging involves holding at 200-350℃ for 1-5 hours to induce the nucleation of a large number of precipitate nuclei at a lower temperature. The choice of this temperature is as follows: below 200℃, the atomic diffusion coefficient is low, and solute atoms are difficult to migrate effectively to form stable precipitate nuclei, requiring a long holding time; above 350℃, the precipitate will directly enter the growth stage, with the nucleation and growth processes overlapping, resulting in a wider precipitate size distribution. Furthermore, the lower limit of the amplitude modulation decomposition temperature zone in step S3 is 350℃, and the upper limit of the first stage of aging is set at 350℃ to ensure that the aging process starts below the amplitude modulation decomposition temperature zone, avoiding the destruction of the constructed amplitude modulation template by high temperature in the early stage of aging.

[0094] The second-stage aging process involves heating to 400-500℃ at a rate of 5-20℃ / hour and holding for 2-8 hours. This slow heating allows the precipitates to grow in an orderly manner under the guidance of the amplitude-modulated template. If the heating rate is too fast, the precipitates will rapidly cross the intermediate temperature range during the transition from the first-stage to the second-stage aging. This causes the nucleation and growth processes, which should occur separately at different temperature stages, to overlap, resulting in the continued formation of some new nuclei at high temperatures. Ultimately, this leads to a broadened precipitate size distribution and the destruction of the orderly array. Furthermore, excessively rapid heating may trigger uneven thermal stress release, causing wire twisting or localized recrystallization. Conversely, a heating rate that is too slow will result in low production efficiency.

[0095] The temperature for the second stage of aging is controlled at 400-500℃. 400-500℃ is the optimal precipitation temperature range for intermetallic compounds formed by elements such as Ni, Al, and Ti in copper-based alloys. Within this temperature range, the lattice matching between the precipitated phase and the matrix is ​​optimal, and it is easiest to form a coherent interface.

[0096] The third stage of aging involves cooling to 300-350℃ at a cooling rate not exceeding 10℃ / hour and holding for 4-12 hours, followed by cooling to room temperature. Through slow cooling and low-temperature holding, the interfacial strain between the precipitated phase and the matrix is ​​eliminated, the coherent interface is stabilized, and the size and distribution of the precipitated phase are further homogenized. During the slow cooling process, the precipitated phase and the matrix have sufficient time to reduce the interfacial energy through local atomic rearrangement, allowing the interface to evolve from a metastable state to a more stable coherent or semi-coherent state.

[0097] The third-stage aging cooling to 300-350℃ is the upper limit of the temperature range of the first-stage aging. Holding at this temperature again ensures that the microstructure evolution completes a thermodynamic cycle. The choice of holding time of 4-12 hours is related to the cooling rate and alloy composition. The slower the cooling rate, the more relaxation has occurred during the cooling process, and the shorter the holding time can be. The higher the content of strengthening elements in the alloy and the higher the interfacial energy, the longer the holding time needs to be.

[0098] Specifically, the first stage of aging induces a large number of diffuse and fine precipitate nuclei to form uniformly in the solute-rich region of the amplitude-modulated structure, laying the foundation for the quantity and distribution of subsequent ordered growth. The second stage of aging forces the precipitates to grow preferentially along the compositional fluctuations of the solute-rich region of the amplitude-modulated structure by slowly increasing the temperature, avoiding random nucleation and disordered growth, thereby forming a preliminary array structure that matches the cycle of the amplitude-modulated structure. The third stage of aging allows the interface between the precipitates and the matrix to fully relax, obtaining a stable coherent or semi-coherent interface, while eliminating internal stress and completing the final curing of the array structure.

[0099] Through the synergistic effect of multi-level gradient aging, coherent nano-precipitates induced by amplitude modulation decomposition and distributed in a periodic array are constructed inside the alloy, ensuring the high-temperature stability and anti-coarsening ability of the precipitates. The long-range ordered arrangement of the precipitates minimizes the scattering of conduction electrons, thus achieving high tensile strength while maintaining high conductivity.

[0100] After the multi-level gradient aging treatment in step S5, coherent nanoprecipitates induced by amplitude modulation decomposition and distributed in a periodic array are formed in the alloy. The interface between the nanoprecipitates and the matrix is ​​a coherent or semi-coherent interface.

[0101] In this process, the amplitude modulation decomposition induces the amplitude modulation structure constructed in step S3 as a template, and the position, spacing, and arrangement direction of the precipitates are all predefined by the amplitude modulation template; the solute-rich region of the amplitude modulation structure is the nucleation region of the precipitates; the modulation wavelength of the amplitude modulation structure is the period of the precipitate array; and the crystallographic orientation of the amplitude modulation structure is the growth direction of the precipitates.

[0102] A periodic array distribution results in less scattering of conduction electrons than a random distribution. When electrons move in a periodic potential field, they form electron bands instead of being scattered one by one by isolated scattering centers.

[0103] The coherent nano-precipitates, which maintain a coherent or semi-coherent interface with the matrix, are nanoscale second-phase particles, which are the direct source of high strength in alloys.

[0104] Coherent interfaces have extremely low interfacial energies, typically 0.01-0.1 J / m², while incoherent interfaces typically have 0.5-1.0 J / m². Low interfacial energies mean that the precipitated phases are more thermodynamically stable and have stronger resistance to coarsening, ensuring the long-term stability of the alloy under high-temperature service conditions.

[0105] S6: The treated alloy undergoes surface treatment, and an inner self-lubricating plating layer and an outer protective coating layer are prepared sequentially to be processed into winding wires or connector terminals for communication connectors; in step S6, the inner self-lubricating plating layer is an Ag-Sn-Cu eutectic plating layer; the outer protective coating layer is a diamond-like coating.

[0106] Specifically, by constructing a functional multi-layer plating structure on the surface of the alloy substrate, the overall performance of communication connector products is improved, resulting in low and stable contact resistance, resistance to insertion and extraction wear, resistance to environmental corrosion, and resistance to signal attenuation.

[0107] The inner plating layer has good adhesion to the copper alloy substrate and similar coefficients of thermal expansion. The outer plating layer needs to have good adhesion to the inner plating layer to form a gradient transition and avoid stress concentration at the interface.

[0108] The inner self-lubricating coating is an Ag-Sn-Cu eutectic coating, which provides excellent self-lubricating performance while ensuring high conductivity, reducing the fluctuation of friction coefficient and contact resistance during the insertion and removal process, and extending the insertion and removal life of the connector. During the insertion and removal process of the connector, the Sn-rich phase on the surface of the Ag-Sn-Cu coating undergoes plastic flow under the action of frictional shear force, forming a lubricating film covering the contact surface, so that subsequent friction occurs inside the lubricating film or between the lubricating film and the mating parts, rather than direct contact between non-metals, reducing the friction coefficient and insertion and removal force.

[0109] The outer protective coating is a diamond-like carbon coating, which provides ultra-high hardness, wear resistance, chemical inertness and environmental isolation capabilities on the outermost layer, protecting the inner plating layer and substrate from mechanical wear and environmental corrosion, while maintaining a low coefficient of friction and high signal transmission stability.

[0110] The system features a dual-layer protection system. The outer layer provides ultra-high hardness and wear resistance to withstand major mechanical loads, while the inner layer provides self-lubrication and conductivity. The outer layer isolates the system from external corrosive environments, while the inner layer forms a good bond with the substrate at the interface, preventing corrosion from spreading along the interface. The outer layer has good thermal conductivity, which helps to conduct the frictional heat generated during insertion and removal. The inner layer has high thermal conductivity, together forming an efficient heat dissipation channel.

[0111] Example 1:

[0112] S1: Weigh the raw materials according to the following composition: Cu-0.5Ag-1.5Ni-0.5Co-0.2Cr (wt%), melt them in a vacuum induction melting furnace at 1200℃, add 0.3% rare earth composite refining agent, CaF2:La2O3=2:1, and cast them into ingots with a diameter of 50mm.

[0113] S2: Heat the ingot to 800℃ and hold for 4 hours to eliminate microscopic element segregation.

[0114] S3: Cool to 450°C at a cooling rate of 30°C / hour and hold at that temperature for 12 hours to allow the alloy to undergo amplitude modulation decomposition, forming an amplitude modulation structure with periodic composition modulation at the nanoscale.

[0115] S4: Perform a combination of die rolling and drawing, with a total cold deformation of 80%, to obtain wire with a diameter of 0.5mm.

[0116] S5: First-level aging: 250℃ for 3 hours;

[0117] Second-stage aging: Increase the temperature to 450℃ at a rate of 10℃ / hour and hold for 4 hours;

[0118] Third-level aging: Cool to 320℃ at 5℃ / hour, hold for 8 hours, then air cool to room temperature.

[0119] S6: Sequentially prepare a Ni-P eutectic self-lubricating coating with a thickness of 2μm; a diamond-like coating with a thickness of 0.5μm; process it into winding wires for communication connectors.

[0120] Example 2:

[0121] The difference from Example 1 is that the alloy composition in step S1 is Cu-0.5Ag-3.0Al-0.2Cr (wt%), the amplitude modulation decomposition inducing element is 3.0%Al, and it does not contain Ni and Co.

[0122] Example 3:

[0123] The difference from Example 1 is that the alloy composition in step S1 is Cu-0.5Ag-0.5Ni (wt%), the amplitude modulation decomposition inducing element is 0.5%Ni, and it does not contain Co and Cr.

[0124] Example 4:

[0125] The difference from Example 1 is that the alloy composition in step S1 is Cu-0.5Ag-2.5Ni-2.5Co (wt%), the total amount of amplitude-modulated decomposition inducing elements is 5.0%, and it does not contain Cr.

[0126] Example 5:

[0127] The difference from Example 1 is that the alloy composition in step S1 is Cu-0.8Ag-1.0Ni-1.0Fe-0.5Cr-0.3Zr-0.1Mg (wt%), the total amount of amplitude-modulated decomposition-inducing elements is 2.0%, and the total amount of strengthening elements is 0.9%.

[0128] Example 6:

[0129] The difference from Example 1 is that in step S3, the temperature is cooled to 350°C and kept at that temperature for 20 hours.

[0130] Example 7:

[0131] The difference from Example 1 is that in step S3, the temperature is cooled to 550°C and held for 5 hours.

[0132] Example 8:

[0133] The difference from Example 1 is that in step S3, the temperature is cooled to 450°C at a rate of 10°C / hour and held for 12 hours.

[0134] Example 9:

[0135] The difference from Example 1 is that in step S3, the temperature is cooled to 450°C at 50°C / hour and held for 12 hours.

[0136] Example 10:

[0137] The difference from Example 1 is that the first stage of aging in step S5 is to keep warm at 200°C for 5 hours.

[0138] Example 11:

[0139] The difference from Example 1 is that in step S5, the second stage of aging is achieved by raising the temperature to 480°C at a rate of 20°C / hour and holding it at that temperature for 3 hours.

[0140] Example 12:

[0141] The difference from Example 1 is that in step S5, the third aging process involves cooling to 300°C at a rate of 8°C / hour and holding at that temperature for 12 hours.

[0142] Example 13:

[0143] The difference from Example 1 is that: in step S1, no rare earth composite refining agent is added, and conventional vacuum melting is used.

[0144] Comparative Example 1:

[0145] The difference from Example 1 is that step S3 is skipped, there is no amplitude modulation decomposition preprocessing, and cold deformation processing S4 and multi-stage aging S5 are performed directly after homogenization processing.

[0146] Comparative Example 2:

[0147] The difference from Example 1 is that step S5 is skipped, there is no multi-stage gradient aging, and a single-stage aging treatment is performed after cold deformation, followed by heat treatment at 300°C for 8 hours.

[0148] Comparative Example 3:

[0149] The difference from Example 1 is that: S4 cold deformation is skipped, and multi-level gradient aging is performed directly after amplitude modulation decomposition preprocessing.

[0150] Comparative Example 4:

[0151] The difference from Example 1 is that after the second stage of aging in step S5, the air is directly cooled to room temperature, omitting the third stage of slow cooling and heat preservation.

[0152] Comparative Example 5:

[0153] The difference from Example 1 is that after homogenization, the sample was subjected to solution treatment at 900℃ for 1 hour and water quenching, followed by aging at 450℃ for 5 hours.

[0154] Comparative Example 6:

[0155] The difference from Example 1 is that: C7025 alloy, Cu-3.0Ni-0.6Si-0.1Mg, is used; and the alloy is treated with solution and aging according to conventional processes.

[0156] Comparative Example 7:

[0157] The difference from Example 1 is that no rare earth refining agent is added during smelting, and there is no covering agent or inert gas protection.

[0158] Comparative Example 8:

[0159] The difference from Example 1 is that step S6 is skipped and no surface treatment is performed.

[0160] Test method:

[0161] This includes mechanical and electrical performance testing and application performance testing:

[0162] 1. Tensile strength and elongation were tested in accordance with the national standard GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test at room temperature"; the test was conducted at room temperature, with a tensile rate of 2 mm / min and a gauge length of 100 mm; each sample was tested 5 times, and the arithmetic mean was taken as the final result.

[0163] 2. The conductivity was measured in accordance with the national standard GB / T 351-2019 "Method for Measurement of Resistivity of Metallic Materials"; the double bridge method was used to measure the resistivity of the sample under constant temperature conditions of 20℃±1℃ and converted to the international annealed copper standard; each sample was tested 5 times and the arithmetic mean was taken.

[0164] 3. Wire breakage rate: During continuous drawing, the number of wire breaks per 1000 meters of wire is counted and expressed as times / kilometer; each group is tested 3 times independently and the average value is taken.

[0165] 4. Yield: Quality yield from ingot to final product; 3 batches are tested in each group, and the average value is taken.

[0166] 5. Insertion and extraction life is tested in accordance with the national standard GB / T 5095.2-1997 "Basic test procedures and measurement methods for electromechanical components for electronic equipment - Part 2: General inspection, electrical continuity and contact resistance test, insulation test and voltage stress test"; test conditions: insertion and extraction rate 10mm / min, load 0.5N, with a contact resistance increment exceeding 10mΩ as the failure criterion, and the number of insertions and extractions at which failure is reached is recorded.

[0167] 6. Contact resistance was tested in accordance with the national standard GB / T 5095.8-1997 "Basic test procedures and measurement methods for electromechanical components for electronic equipment - Part 8: Mechanical tests on connectors, contacts and leads"; the four-terminal method was used, the test current was 100mA, and the contact resistance between the connector terminals was measured. Each sample was tested 5 times and the average value was taken.

[0168] 7. High-temperature stability was tested using a custom method: The sample was kept at 500℃ under an argon protective atmosphere for 100 hours, and then its tensile strength and conductivity were tested and compared with the original state to calculate the performance degradation rate.

[0169] Test results:

[0170] Table 1 - Test Results

[0171] Tensile strength (MPa) Conductivity (%IACS) Elongation (%) Broken wire rate (times / km) Yield (%) Insertion / removal life (times) Contact resistance (mΩ) Tensile strength reduction rate (%) after 500℃ / 100h Conductivity decrease rate (%) after 500℃ / 100h Example 1 512 92.3 8.2 1.2 93.5 15200 3.2 5.3 1.6 Example 2 478 94.1 7.5 1.8 92.1 14100 3.0 4.8 1.4 Example 3 471 93.5 7.8 2.1 91.8 13200 3.3 5.6 1.8 Example 4 535 89.2 6.8 2.5 90.2 16100 3.8 4.5 2.1 Example 5 528 91.5 7.2 1.5 92.8 15600 3.1 4.9 1.5 Example 6 483 91.8 8.0 1.6 93.0 13900 3.3 5.2 1.7 Example 7 495 92.7 7.6 1.4 93.2 14400 3.2 5.1 1.7 Example 8 501 92.1 8.1 1.3 93.8 14100 3.3 5.0 1.6 Example 9 506 92.5 7.9 1.5 93.1 14700 3.2 5.0 1.6 Example 10 485 93.2 8.3 1.7 92.5 13700 3.3 5.4 1.8 Example 11 498 92.8 7.8 1.6 92.9 14200 3.2 5.2 1.7 Example 12 515 92.0 7.4 1.2 93.6 15300 3.2 4.9 1.5 Example 13 508 92.1 8.0 2.8 88.7 12100 3.4 5.6 1.9 Comparative Example 1 386 84.5 5.2 4.8 86.2 6200 4.5 12.8 3.5 Comparative Example 2 415 87.3 5.8 3.5 89.5 7100 4.2 10.5 2.9 Comparative Example 3 380 94.0 8.5 2.0 95 5100 4.8 15.2 4.1 Comparative Example 4 480 91.0 5.8 3.8 90 8200 4.0 8.3 2.4 Comparative Example 5 410 92.0 6.5 7.0 85 5600 5.0 14.1 3.8 Comparative Example 6 450 85.0 5.0 5.5 87 6600 5.2 13.5 4.2 Comparative Example 7 480 89.5 5.2 8.0 82 4100 5.5 16.3 4.5 Comparative Example 8 505 91.8 7.9 8.5 75.2 2100 6.0 5.4 1.8

[0172] Data Analysis:

[0173] 1. Examples 1-12 all include complete amplitude modulation decomposition pretreatment and multi-level gradient aging to form coherent nanoprecipitates with a periodic array distribution. The scattering of conduction electrons by the periodic array is much smaller than that of random distribution. When electrons move in the periodic potential field, they form electronic bands, thereby maximizing the retention of conductivity while obtaining high strength. The low interfacial energy of the coherent and semi-coherent interfaces ensures the long-term stability of the alloy under high-temperature service conditions.

[0174] 2. In Example 1, Ni and Co form a continuous solid solution with copper, which helps to form Ni / Co-rich precipitates. These precipitates have a similar lattice constant to the copper matrix and are easy to form coherent interfaces, thus achieving the best balance between strength and conductivity. In Example 2, Al atoms have smaller sizes, resulting in significant solid solution strengthening. However, compared to Ni and Co, the coherence of the precipitates formed when added alone is slightly worse with the matrix, resulting in lower strength but the highest conductivity. In Example 3, the content of amplitude modulation inducing elements is too low, and the driving force for amplitude modulation decomposition is insufficient, resulting in a strength of only 471 MPa. In Example 4, the content of amplitude modulation inducing elements is too high, leading to excessive solute atoms dissolved in the copper matrix, which produces a strong scattering effect on conduction electrons, thus reducing the conductivity to 89.2% IACS. However, at the same time, the solute concentration in the solute-rich region is high, resulting in a large number of precipitates and a maximum strength of 535 MPa. Example 5 contains both amplitude modulation inducing elements and strengthening elements, and the synergistic effect of multiple elements maintains both high strength and conductivity.

[0175] 3. Examples 6-7 verify the amplitude modulation decomposition temperature. Example 6 has a low temperature, a low atomic diffusion coefficient, incomplete amplitude modulation tissue development, and low strength. Example 7 is close to the upper limit of the amplitude modulation decomposition temperature range, the amplitude modulation tissue has a coarsening trend, and the strength is slightly reduced. Example 1 is the optimal temperature point, the amplitude modulation tissue has a moderate wavelength, significant component amplitude, and the highest strength.

[0176] 4. Example 8 cooled the slowest, resulting in the most complete development of the amplitude-modulated tissue and the highest elongation rate; Example 9 cooled relatively quickly, slightly affecting the amplitude-modulated tissue, but still within the acceptable range; Example 10 had a slightly lower nucleation driving force and a slight decrease in strength; Example 11 showed good guided growth effect; Example 12 had a fully stabilized interface and increased strength to 515 MPa.

[0177] 5. Comparative Example 1 verifies the amplitude modulation decomposition in step S3. The randomly distributed precipitates exhibit severe electron scattering, with a conductivity of only 84.5% IACS. Simultaneously, the uneven distribution of the precipitates results in poor strengthening, with a strength of only 386 MPa. At high temperatures, the randomly distributed precipitates are more prone to coarsening, leading to a 12.8% decrease in strength at high temperatures. Comparative Example 2 skips the multi-stage gradient aging in S5, employing a single-stage aging at 300℃. Single-stage aging cannot achieve gradient growth of the precipitates: the nucleation and growth processes overlap, resulting in a broad precipitate size distribution and an inability to form an ordered array. Furthermore, the lack of interface stabilization from the third-stage aging means the interface between the precipitates and the matrix is ​​mostly semi-coherent or incoherent, with high interface energy, making it prone to coarsening at high temperatures. Therefore, the strength is only 415 MPa, the conductivity is 87.3% IACS, and the strength decreases by 10.5% at high temperatures.

[0178] 6. Comparative Example 3 skips the S4 cold deformation process and directly ages after amplitude modulation decomposition. The high-density dislocations introduced by cold deformation are the preferred nucleation sites for subsequent aging precipitation. Without cold deformation, there are fewer nucleation sites, the number density of precipitated phases is low, the strengthening effect is poor, and the strength is only 380 MPa, but the conductivity is as high as 94.0%, indicating that the matrix lattice is intact and there is less electron scattering when there is no cold deformation. Comparative Example 4 directly air-cools after the second stage of aging, omitting the third stage of slow cooling and heat preservation. Without this stage, the interfacial strain is not fully released, the interfacial energy is higher, the high-temperature stability is slightly worse, and the wire breakage rate is higher.

[0179] 7. Comparative Example 5 uses a traditional heat treatment process of solution treatment at 900℃ + water quenching + aging at 450℃, which cannot form an ordered array and has a limited strengthening effect; moreover, solution treatment and water quenching introduce a large amount of thermal stress, resulting in a wire breakage rate as high as 7.0%; Comparative Example 6 is a commercial precipitation-strengthened alloy, whose strengthening phase is Ni2Si randomly distributed in the matrix, which causes severe electron scattering and has an conductivity of only 85.0% IACS. At the same time, the Ni2Si phase has poor coherence with the matrix and poor high-temperature stability.

[0180] 8. Comparative Example 7 did not add rare earth refining agents during smelting, and had no covering agent or inert gas protection. It had more non-metallic inclusions, lower melt purity, and ultimately deteriorated performance: wire breakage rate of 8.0%, yield rate of 82%, and high-temperature strength reduction rate of 16.3%. Comparative Example 8 did not undergo any surface treatment and had no plating protection. The wire came into direct contact with the die during the drawing process, resulting in a high coefficient of friction and easy surface damage. This led to a wire breakage rate as high as 8.5% and a yield rate of only 75.2%. The connector terminals without plating had direct metal-to-metal contact during insertion and removal, resulting in severe wear and a insertion and removal life of only 2100 cycles.

[0181] A high-strength, high-conductivity copper-silver alloy for communication connectors is prepared by a specific method. The microstructure of the alloy comprises: an amplitude-modulated structure with periodic compositional modulation, and coherent nano-precipitates arranged in a periodic array guided by the amplitude-modulated structure. The alloy has a tensile strength ≥470MPa, conductivity ≥89% IACS, and elongation ≥6%. The average spacing of the periodically arrayed coherent nano-precipitates is 5-50nm, and the lattice mismatch between the precipitates and the copper matrix is ​​less than 0.5%. The alloy exhibits a wire breakage rate ≤5% and a yield ≥88% during the drawing process.

[0182] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing a high-strength, high-conductivity copper-silver alloy for communication connectors, characterized in that, include: S1: Weigh the raw materials according to the designed alloy composition, melt them under vacuum and cast them into ingots; wherein the alloy composition is mainly composed of copper as the base, and includes silver and alloying elements, and the alloying elements include at least the amplitude decomposition inducing elements that can cause amplitude decomposition of the alloy. S2: Heat the ingot to 600-900℃ and hold for 2-10 hours to homogenize it and eliminate micro-segregation of elements. S3: Cool the homogenized alloy to 350-550℃ at a cooling rate of 10-50℃ / hour, and hold it in this temperature range for 2-24 hours to cause the alloy to undergo amplitude modulation decomposition and form an amplitude modulation structure with periodic composition modulation at the nanoscale, including solute-rich and solute-poor regions. S4: The alloy after amplitude modulation decomposition pretreatment is subjected to cold deformation processing, with a cold deformation amount of 20%-90%, to obtain wire. S5: The cold-deformed alloy undergoes multi-stage gradient aging treatment, causing the nano-precipitates to preferentially grow along the solute-rich region of the modulated structure under the guidance of the amplitude-modulated microstructure, forming coherent nano-precipitates with a periodic array distribution, including: First-level aging: Keep warm at 200-350℃ for 1-5 hours; Second-stage aging: Heat to 400-500℃ at a heating rate of 5-20℃ / hour, and hold for 2-8 hours; Level 3 aging: Cool to 300-350℃ at a cooling rate not exceeding 10℃ / hour, hold for 4-12 hours, and then cool to room temperature; S6: The treated alloy undergoes surface treatment, and an inner self-lubricating plating layer and an outer protective coating are prepared in sequence, which are then processed into winding wires or connector terminals for communication connectors.

2. The method for preparing a high-strength and high-conductivity copper-silver alloy for a communication connector according to claim 1, characterized in that: In step S1, the amplitude modulation decomposition inducing element is selected from one or more of Ni, Co, Al, Ti, and Fe, and the sum of their contents is 0.5-5.0 wt%.

3. The method of claim 1, wherein the method comprises: preparing a silver alloy ingot by mixing silver with 0.1 to 0.5 wt% of copper and 0.1 to 0.5 wt% of phosphorus; and hot extruding the silver alloy ingot at a temperature of 300 to 400°C. The alloy composition described in step S1 also includes one or more strengthening elements selected from Cr, Zr, and Mg, with a total content of 0.05-2.0 wt%.

4. The method of claim 1, wherein the method comprises: preparing a silver alloy ingot by mixing silver with 0.1 to 0.5 wt% of copper and 0.1 to 0.5 wt% of phosphorus; and hot extruding the silver alloy ingot at a temperature of 300 to 400°C. In the smelting process described in step S1, a rare earth composite refining agent is added to the melt for purification treatment, and a covering agent and an inert gas are used for combined protection; the rare earth composite refining agent contains CaF2 and rare earth oxides, and the amount added is 0.1%-1.0% of the melt mass.

5. The method for preparing a high-strength, high-conductivity copper-silver alloy for a communication connector according to claim 1, characterized in that: The cold deformation process described in step S4 is one or more combinations of roll forming, drawing or extrusion, with a total cold deformation amount of 50%-99%, to obtain wire with a diameter of 0.02-2.0 mm.

6. The method for preparing a high-strength, high-conductivity copper-silver alloy for a communication connector according to claim 1, characterized in that: After the multi-level gradient aging treatment in step S5, coherent nano-precipitates induced by amplitude modulation decomposition and distributed in a periodic array are formed in the alloy. The interface between the nano-precipitates and the matrix is ​​a coherent or semi-coherent interface.

7. The method for preparing a high-strength, high-conductivity copper-silver alloy for a communication connector according to claim 1, characterized in that: The inner self-lubricating coating in step S6 is a eutectic coating; the outer protective coating is a diamond-like coating.

8. A high-strength, high-conductivity copper-silver alloy for communication connectors, prepared by the method described in any one of claims 1-7, characterized in that: The microstructure of the alloy comprises: an amplitude modulation structure with periodic compositional modulation, and coherent nanoprecipitates distributed in a periodic array guided by the amplitude modulation structure; the alloy has a tensile strength ≥470MPa, an electrical conductivity ≥89% IACS, and an elongation ≥6%.

9. A high-strength, high-conductivity copper-silver alloy for a communication connector according to claim 8, characterized in that: The coherent nano-precipitates arranged in a periodic array have an average spacing of 5-50 nm, and the lattice mismatch between the precipitates and the copper matrix is ​​less than 0.5%.