High-strength high-conductivity copper-silver alloy and preparation method thereof

Abstract

The high-strength high-conductivity copper-silver alloy disclosed by the application has the following weight percentage composition: 0.5-12% of Ag, 0.1-1.5% of B, 0.1-2.0% of Mn, the balance of Cu and inevitable impurities. The application simultaneously adds Mn and B elements in the Cu-Ag alloy to form a high-melting-point B-Mn compound at high temperature, thereby improving the strength of the alloy, having little influence on the electrical conductivity, and due to the combined action of the dispersion strengthening of the high-melting-point hard B-Mn compound and the work hardening of the Ag fiber phase and Cu matrix, the alloy has excellent comprehensive properties such as thermal stability, tensile strength, hardness and electrical conductivity. The tensile strength of the alloy is above 600 MPa, the electrical conductivity is above 65% IACS, the Vickers hardness is above 200 HV, and after being kept at 180 DEG C for 24 hours, the reduction rate of the tensile strength is not more than 8%, and the alloy can be applied to the power, electronic, communication and electromagnetic conversion industries.

Description

Technical Field

[0001] This invention relates to the field of copper alloys, specifically a high-strength, high-conductivity copper-silver alloy and its preparation method. Background Technology

[0002] Copper alloys are materials with excellent electrical conductivity and are widely used in many sectors of the national economy. In recent years, with the rapid development of electronic technology, the performance requirements for copper alloys have become increasingly stringent. In particular, the demand for miniaturization and multifunctionality of electronic components requires copper alloys to not only have excellent electrical conductivity but also high strength and good formability. Copper-silver alloys, as representatives of high-strength, high-conductivity copper alloys, can meet these performance requirements and are often used in high-end wire harnesses and other products.

[0003] Copper-silver alloys are typical work-hardening alloys, often requiring significant plastic processing during production to improve mechanical properties, but this reduces electrical conductivity. This is because dislocations accumulate during processing; the higher the processing rate, the greater the density of dislocations, and thus the higher the alloy's strength. The high strength of copper-silver alloys stems from this process. However, the large number of dislocations accumulated after high processing rates is unstable. Under high-temperature conditions, with increasing temperature and time, their mechanical properties deteriorate severely, leading to material failure or even scrap. Therefore, copper-silver alloys have poor thermal stability, posing problems for their application in some high-power components. Summary of the Invention

[0004] The first technical problem to be solved by the present invention is to provide a high-strength, high-conductivity copper-silver alloy with excellent thermal stability, in order to address the shortcomings of the prior art.

[0005] The technical solution adopted by the present invention to solve the first technical problem is: a high-strength and high-conductivity copper-silver alloy, wherein the weight percentage composition of the alloy is: 0.5-12% Ag, 0.1-1.5% B, 0.1-2.0% Mn, and the balance is Cu and unavoidable impurities.

[0006] In this invention, Ag is the main alloying element. It forms a supersaturated solid solution within the copper matrix, precipitating as a phase to enhance the alloy's strength and hardness. As the Ag content increases, the alloy's mechanical properties gradually improve while its electrical conductivity gradually decreases. Depending on the degree of processing, the Ag precipitates may also exhibit fibrous formation, further improving the alloy's mechanical properties. Silver is known to have the least impact on the conductivity of copper among metallic elements. If the Ag content is too high, the improvement in mechanical properties is extremely limited, and the high strength and hardness of the alloy significantly increase processing difficulty and waste costs. Conversely, if the Ag content is too low, the precipitation strengthening and work hardening effects are insufficient, and the alloy's strength and hardness cannot meet the requirements. Therefore, the Ag content in this invention is controlled at 0.5-12 wt%.

[0007] Boron (B) has very low solubility in copper alloys and is generally added as a deoxidizer. Trace amounts of B in the copper matrix are distributed in elemental form at the grain boundaries, worsening the alloy's plasticity. However, on the other hand, it can refine the grains, improving the alloy's strength and hardness. Typically, the amount of B added to copper alloys for deoxidation and microstructure refinement does not exceed 0.1 wt%, as excessive B addition can cause elemental agglomeration, significantly negatively impacting the mechanical properties of the copper alloy. In the alloy of this invention, the B content is 0.1-1.5 wt%. More importantly, B interacts strongly with Mn to produce high-melting-point B-Mn hard intermetallic compound precipitates, thus providing dispersion strengthening and improving the alloy's mechanical properties. If the B content is less than 0.1 wt%, the number of B-containing precipitate particles will decrease, resulting in insufficient resistance to dislocation movement and failing to achieve the desired strengthening effect. If the B content exceeds 1.5 wt%, the excessively high B content will lead to the aggregation and segregation of the B-containing phase, thereby affecting the mechanical and processing properties of the copper alloy, and also making it difficult to maintain high conductivity.

[0008] Manganese (Mn) can be dissolved in copper alloys indefinitely, and its extensive dissolution in the copper matrix provides solid solution strengthening. Mn enhances the strength and hardness of copper alloys, but the significant lattice distortion caused by solid solution also increases electron scattering, substantially reducing the conductivity of the copper alloy. Therefore, existing high-conductivity copper alloys often do not contain manganese. The alloy of this invention preferably contains 0.1-2.0 wt% Mn. By adding an appropriate amount of Mn, a strong interaction occurs between Mn and boron (B), producing a high-melting-point B-Mn hard intermetallic compound precipitate that is uniformly distributed in the copper matrix, providing dispersion strengthening. This, in turn, improves the thermal stability of the alloy while maintaining its mechanical properties.

[0009] Preferably, the weight percentage content of B and Mn in the alloy satisfies the condition: 0.1 ≤ Mn / B ≤ 8. The thermal stability of the alloy of this invention is significantly affected by the content of B and Mn. As the alloy processing rate increases, the dislocation density gradually rises, and the stability at high temperatures deteriorates accordingly. Under conditions of high dislocation density, trace amounts of B distributed at the grain boundaries of the copper matrix can alleviate excessive concentration of dislocation density during processing deformation, but excessive B tends to segregate within the matrix. A certain amount of Mn can promote the formation of high-melting-point hard B-Mn compounds, preventing excessive B from accumulating in the copper matrix in elemental form; however, excessive Mn dissolution significantly reduces the alloy's electrical conductivity and processing performance. Therefore, this invention controls the weight percentage content of B and Mn to 0.1 ≤ Mn / B ≤ 8.

[0010] Preferably, the number of B-Mn compound particles on the cross-section of the alloy is 0.005-0.2 particles / μm. 2 This invention adds appropriate amounts of Mn and B elements to a Cu-Ag alloy. The interaction of B and Mn in the high-temperature molten metal forms a uniformly distributed B-Mn compound. This B-Mn compound exhibits high hardness. The combined effect of work hardening of the Ag fibrous phase and copper matrix, along with the dispersion strengthening effect of the hard B-Mn compound, further improves the alloy's mechanical properties. Furthermore, since the B-Mn compound is a high-melting-point compound (exceeding 1800℃), its uniform distribution within the alloy matrix effectively improves the alloy's thermal stability.

[0011] Preferably, the alloy also includes 0.001-0.5 wt% of element X, selected from at least one of Mg, Co, Si, Fe, La, Ce, Pr, and Nd. The addition of this element X helps refine the grains, deoxidize and remove carbon, improving alloy purity and thus enhancing electrical conductivity. Furthermore, some elements of element X can form precipitated strengthening phases through deformation heat treatment, promoting the precipitation of alloying elements and enhancing the strengthening effect, resulting in higher strength and hardness. The aforementioned strengthening effect is achieved when the content of element X is greater than or equal to 0.001 wt%. However, if the added content exceeds 0.5 wt%, it will reduce the solubility limit of element X, coarsen the precipitated phase particles, and reduce the mechanical properties of the alloy, which is detrimental to alloy processing and applications. Therefore, this invention controls the content of element X to 0.001-0.5 wt%.

[0012] Preferably, the alloy has a tensile strength of over 600 MPa, a conductivity of over 65% IACS, a Vickers hardness of over 200 HV, and a tensile strength reduction rate of no more than 8% after being held at 180°C for 24 hours.

[0013] The second technical problem to be solved by the present invention is to provide a method for preparing a high-strength, high-conductivity copper-silver alloy with excellent thermal stability, in view of the shortcomings of the prior art.

[0014] The technical solution adopted by this invention to solve the second technical problem is as follows: a method for preparing a high-strength, high-conductivity copper-silver alloy. The preparation process includes: melting and casting, hot working, solution treatment, aging treatment, and cold working. Depending on the specific specifications of the final product, hot working can be carried out by hot rolling, hot forging, extrusion, etc., and cold working can be carried out by cold rolling, stretching, etc. In addition, the aging treatment and cold working processes can be changed in order or repeated as needed.

[0015] Preferably, the solution treatment temperature is 700-950℃, and the holding time is 4-6 hours. To obtain a uniform solid solution microstructure with minimal segregation, the solution treatment temperature and holding time need to be controlled. Since the solubility of elements such as Ag, Mn, and B in Cu increases with temperature, the degree of solidification in the matrix also increases with temperature. However, if the temperature is too high, it can lead to excessively coarse microstructure and melting of low-melting-point microstructures and grain boundaries, affecting the alloy's properties. This invention controls the holding time of the solution treatment to 4-6 hours to ensure sufficient Ag dissolution. On the other hand, it provides sufficient time for B and Mn to diffuse in the matrix, effectively reducing the tendency of B to segregate in the copper matrix and grain boundaries, and providing favorable conditions for the precipitation of B-Mn compounds during subsequent aging treatment. If the holding time is too short, the solution and diffusion effects are insufficient; if the holding time is too long, the electrical scattering effect of the dissolved atoms is too large, causing a sharp decrease in the alloy's electrical conductivity. Therefore, the present invention controls the solution temperature at 700-950℃ and the holding time at 4-6h to obtain a uniform solid solution structure with minimal segregation, while providing sufficient power for subsequent aging precipitation.

[0016] Compared with the prior art, the advantages of the present invention are as follows:

[0017] (1) This invention improves the problem of B segregation in the alloy by simultaneously adding Mn and B elements to Cu-Ag alloy, taking advantage of the characteristic that B and Mn form high-melting-point B-Mn compounds at high temperature, thereby increasing the strength of the alloy, while having little effect on the conductivity.

[0018] (2) This invention forms a high-melting-point hard B-Mn compound in high-temperature copper melt through the interaction of Mn and B. Through the dispersion strengthening of B-Mn compound and the combined effect of Ag fiber phase and Cu matrix work hardening, the alloy is strengthened, and finally the alloy achieves excellent comprehensive properties such as thermal stability, tensile strength, hardness and electrical conductivity.

[0019] (3) The alloy of the present invention can achieve tensile strength of more than 600MPa, conductivity of more than 65%IACS, Vickers hardness of more than 200HV, and tensile strength reduction rate of no more than 8% after being kept at 180℃ for 24h; while having high strength and high conductivity, it also has excellent thermal stability and can be applied to industries such as power, electronics, communications, and electromagnetic conversion. Attached Figure Description

[0020] Figure 1 This is a scanning electron microscope image of the wire sample from Example 4. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the embodiments.

[0022] The ingredients were prepared according to the formulations of Examples 1-15 and Comparative Examples 1-4. The alloy wire is manufactured through a process of melting and casting → extrusion → solution treatment → aging treatment → stretching → finished product, including the following steps:

[0023] (1) Prepare the ingredients according to the embodiments and comparative components in Table 1, melt them at 1200-1400℃, and cast them into ingots with a thickness of 100-300mm after the melt composition is found to be qualified.

[0024] (2) The above-mentioned ingots are extruded at 700-980℃ with a processing rate of not less than 75% to obtain Ф20-70mm wire rods;

[0025] (3) After extrusion, the solution is kept at a temperature of 700-950℃ for 4-6 hours for solution treatment, followed by water cooling or air cooling treatment, with the cooling rate controlled at 100-1000℃ / s.

[0026] (4) The solution-treated wire blank is aged at 350-600℃ for 3-12 hours.

[0027] (5) After cooling, the wire is subjected to diameter reduction stretching with a processing rate of not less than 70%, and finally a wire sample with a diameter of Ф5mm is obtained.

[0028] The characteristics of the obtained wire samples were evaluated under the following conditions.

[0029] Tensile strength: The tensile strength of the wire sample was tested at room temperature in accordance with GB / T 228.1-2010 Metallic materials, tensile testing - Part 1: Test method at room temperature.

[0030] Conductivity: The conductivity of the wire samples was tested according to GB / T 32791-2016 "Eddy Current Test Method for Conductivity of Copper and Copper Alloys".

[0031] Vickers hardness: The hardness of the wire sample was tested on a digital Vickers hardness tester in accordance with GB-T 4340.1-2009 Metallic Materials Vickers Hardness Test Part 1: Test Method. The test conditions were: power 49.03N, power holding time 10s.

[0032] Thermal stability: The wire sample was heated to 180℃, kept at that temperature for 24 hours, and then cooled to room temperature. The tensile strength was measured, and the rate of decrease in tensile strength was calculated. The calculation formula is: (original strength - strength after heating) ÷ original strength) × 100%, which is used to evaluate thermal stability.

[0033] Number of B-Mn compound particles: The microstructure of the wire sample was observed using a scanning electron microscope. Ten fields of view were selected under a field of view of 10 μm × 10 μm. The number of particles containing both B and Mn was calculated. Particles with a major diameter greater than 1 μm were identified as B-Mn compound particles, and their average number was calculated.

[0034] The alloy compositions of Examples 1-15 and Comparative Examples 1-4 are shown in Table 1, and their properties are shown in Table 2.

[0035] Figure 1 The scanning electron microscope image of the wire sample in Example 4 shows that the B-Mn compound is uniformly and diffusely distributed in the matrix in the form of small-sized particles. Figure 1 Chinese "spectrum" Figure 1 The energy spectrum analysis results at the point are shown in Table 3.

[0036] By comparing the comprehensive performance of the alloy examples of the present invention with that of the comparative alloys, it was found that the alloy of the present invention exhibits excellent comprehensive properties such as tensile strength, hardness, and electrical conductivity, and also has excellent thermal stability. Its tensile strength is above 600 MPa, its electrical conductivity is above 65% IACS, its Vickers hardness is above 200 HV, and after being held at 180°C for 24 hours, the decrease rate of tensile strength is no more than 8%, indicating that it has both high strength and high electrical conductivity as well as excellent thermal stability.

[0037] Table 1. Composition of alloys in the examples and comparative examples.

[0038]

[0039] Table 2. Properties of the alloys in the examples and comparative examples.

[0040]

[0041] Table 3. Energy dispersive spectroscopy (EDS) analysis results of the wire samples from Example 4.

[0042] element wt% Atomic percentage B 15.15 49.80 Mn 38.39 24.84 Cu 43.69 24.44 Ag 2.78 0.91 Total 100.00 100.00

Claims

1. A high-strength, high-conductivity copper-silver alloy, characterized in that, The alloy has the following weight percentage composition: 0.5-12% Ag, 0.1-1.5% B, 0.1-2.0% Mn, with the balance being Cu and unavoidable impurities. The alloy's microstructure contains B-Mn compound particles with a major diameter greater than 1 μm, and the number of B-Mn compound particles per μm on the cross-section is 0.005-0.2 particles / μm. 2 .

2. The high-strength, high-conductivity copper-silver alloy according to claim 1, characterized in that, In the alloy, the weight percentage content of B and Mn satisfies the following condition: 0.1≤Mn / B≤8.

3. The high-strength, high-conductivity copper-silver alloy according to claim 1, characterized in that, The alloy also includes 0.001-0.5 wt% of element X, which is selected from at least one of Mg, Co, Si, Fe, La, Ce, Pr, and Nd.

4. The high-strength, high-conductivity copper-silver alloy according to any one of claims 1-3, characterized in that, The alloy has a tensile strength of over 600 MPa, a conductivity of over 65% IACS, a Vickers hardness of over 200 HV, and a tensile strength reduction rate of no more than 8% after being held at 180℃ for 24 hours.

5. The method for preparing the high-strength, high-conductivity copper-silver alloy according to any one of claims 1-3, characterized in that, The preparation process includes: melting and casting, hot working, solution treatment, aging treatment and cold working.

6. The method for preparing the high-strength, high-conductivity copper-silver alloy according to claim 5, characterized in that, The solution treatment temperature is 700-950℃, and the holding time is 4-6 hours.

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