High-strength and high-fatigue-resistance rare earth copper alloy wire and preparation method thereof

Abstract

The application discloses a high-strength and high-fatigue-resistance rare earth copper alloy wire and a preparation method thereof, and belongs to the field of copper alloy materials. The wire contains Sc 0.03%~0.05% and the balance of Cu and inevitable impurities in terms of mass percentage. In the preparation, first, an alloy rod with a diameter of 8~14 mm is obtained by vacuum directional solidification and a lower guide device; then, first multi-pass drawing with a total deformation of 95%~99%, rapid annealing and second multi-pass drawing with a total deformation of 95%~99% are sequentially performed; the rapid annealing adopts a staged heating mode, the temperature of each holding section is in the range of 600~700 DEG C, the cumulative holding time is 15~21 s, the single-stage holding time is 5~7 s, and then air cooling to room temperature. The average grain size of the obtained wire is not more than 0.5 mu m, the tensile strength is not less than 466 MPa, the conductivity is not less than 97% IACS, and the fatigue strength is not less than 130 MPa. The application controls the strength, the conductivity and the fatigue resistance of the wire through the cooperation of drawing, short-time rapid annealing and re-drawing.

Description

Technical Field

[0001] This invention relates to the field of copper alloy materials, and more specifically, to a high-strength, high-fatigue-resistant rare-earth copper alloy wire and its preparation method. Background Technology

[0002] Pure copper conductors possess excellent electrical conductivity, corrosion resistance, and processing properties, making them widely used in electrical equipment wiring, communication cables, magnet wire, high-fidelity conductors, and electrified railway contact wires. However, pure copper has relatively low strength, only 230-290 MPa in its soft state. While cold working can increase its strength to approximately 400 MPa, its elongation drops sharply to around 2%, making it increasingly difficult to meet the demands of industrial development. For example, applications such as resistance welding electrodes, seam welding rollers, and integrated circuit lead frames require materials that not only possess excellent electrical conductivity but also high strength, fatigue resistance, and reliability.

[0003] To address the insufficient strength of pure copper, existing technologies typically employ alloying for strengthening. For example, Chinese patent CN103971781A discloses a high-strength, high-conductivity rare-earth copper alloy electromagnetic wire and its preparation process. This electromagnetic wire contains Cu, Ni, Zr, La, Y, and Sc, with the following content: Ni 1.05~1.10wt%, Zr 0.55~0.60wt%, La 0.25~0.30wt%, Y 0.25~0.30wt%, Sc≤0.10wt%, and the remainder being Cu. This approach achieves strengthening by adding various alloying elements such as nickel, zirconium, lanthanum, yttrium, and scandium. However, while traditional strengthening elements (such as Ni, Sn, Zn, Fe, and P) significantly improve the strength of copper alloys, they also severely exacerbate electron scattering, leading to a substantial decrease in conductivity. Although the aforementioned patent incorporates multiple rare-earth elements, the sheer variety and high total amount of these alloying elements limit the potential for improved conductivity, making it difficult to meet the stringent conductivity requirements of applications. For example, Chinese patent CN107012357B discloses a copper alloy wire and its preparation method. This wire is composed of multiple elements including silicon, magnesium, zinc, potassium, chromium, manganese, yttrium, scandium, samarium, tantalum, cobalt, iridium, zirconium, and platinum, with the remainder being copper and unavoidable non-metallic impurities. Its tensile strength reaches 551 MPa, and its conductivity is 85.3% IACS. This method employs a complex composition system with more than ten alloying elements, and prepares the wire through multiple processes such as segmented melting, refining, casting, homogenization annealing, extrusion, and drawing. Although it achieves high tensile strength, its conductivity is only 85.3% IACS, far lower than that of pure copper. This compromise between high strength and low conductivity is difficult to apply in fields such as aerospace cables and high-precision electronic components, where conductivity and reliability requirements are extremely stringent.

[0004] In addition, existing technologies also include research on the microalloying of copper alloys using rare earth elements. For example, Chinese patent CN121555844A discloses a rare earth microalloyed semi-hard flat copper coil containing 0.05% La, 0.01% Zr, 0.04% Y, 0.02% Te, 0.005% Ag, and other rare earth and trace elements. Another example is Chinese patent CN106555073B, which discloses a high-strength, high-conductivity rare earth copper-magnesium alloy contact wire containing 0.1-0.8% magnesium, 0.1-0.4% nickel, 0.1-0.4% zinc, 0.1-0.4% silver, and 0.05-0.15% rare earth elements. These solutions all employ a strategy of adding multiple alloying elements in combination. While this achieves a certain degree of strength improvement, the conductivity is generally below 90% IACS, failing to achieve the high conductivity required for pure copper.

[0005] Scandium (Sc), as a rare earth element, has extremely low equilibrium solid solubility in copper matrix and causes minimal damage to conductivity, making it a potential microalloying element. However, existing research on copper-scandium alloys mainly focuses on developing high-strength materials, with Sc addition generally exceeding 0.2%, and even exceeding 1%. At this content, although the alloy strength is high, the conductivity loss is severe (usually below 80% IACS), failing to achieve the high conductivity required for pure copper. When the Sc addition is reduced to a "trace" level below 0.1%, a series of new technical challenges arise: (1) the extremely low content of active elements is easily oxidized and burned during the smelting process, making it difficult to precisely control the composition; (2) during solidification, trace Sc atoms are prone to segregation, making it difficult to distribute evenly and form effective dispersion strengthening.

[0006] More importantly, at extremely low addition levels, the selection of alloying elements and the preparation process are two core keys to unlocking the synergistic effect of "high strength and high conductivity." Incorrect element addition or inappropriate process routes can disrupt the balance between strength and conductivity, making it difficult to simultaneously meet both performance indicators. Therefore, how to achieve significant strength enhancement and excellent fatigue resistance using extremely low amounts of Sc with almost no loss of conductivity remains a critical technical bottleneck that urgently needs to be addressed in this field. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a high-strength and high-fatigue-resistant rare earth copper alloy wire and its preparation method, so as to improve the problem that it is difficult to balance strength, conductivity and microstructure refinement in existing copper alloy wires, and to avoid the use of long-term solution treatment and aging treatment.

[0008] To solve the above-mentioned technical problems, this invention provides a high-strength, high-fatigue-resistant rare-earth copper alloy wire. By mass percentage, the rare-earth copper alloy wire comprises 0.03%~0.05% Sc, with the balance being Cu and unavoidable impurities. The rare-earth copper alloy wire has a slender grain structure oriented along the drawing direction, with an average grain size not exceeding 0.5 μm, a tensile strength not less than 466 MPa, a conductivity not less than 97% IACS, and a fatigue strength not less than 130 MPa. (Rotational bending, stress ratio R=-1, cycle number N=10) 7 Second-rate).

[0009] Furthermore, the mass percentage of Sc is 0.03%~0.04%, and the average grain size is 0.2~0.3 μm.

[0010] In addition, the present invention also provides a method for preparing a high-strength, high-fatigue-resistant rare-earth copper alloy wire, the preparation method comprising the following steps: (1) Vacuum directional solidification: Using oxygen-free copper and pure scandium with a purity of not less than 99.995% as raw materials, a vacuum directional solidification continuous directional solidification device is used to prepare copper-scandium alloy casting rods with directional columnar crystal structure or fine equiaxed crystal structure by controlling the temperature gradient and directional solidification speed at the solid-liquid interface. (2) First stage multi-pass drawing: The rare earth copper alloy rod is drawn in multiple passes, and the total deformation of the first multi-pass drawing is 95%~99%, to obtain the first drawn wire. (3) Rapid annealing: Rapid annealing is performed on the first stage drawn wire. The rapid annealing adopts a staged heating method. The temperature of each heat preservation section is in the range of 600~700℃, the cumulative heat preservation time is 15~21 s, the single stage heat preservation time is 5~7s, and then it is air cooled to room temperature.

[0011] (4) Second stage multi-pass drawing: The wire after rapid annealing and air cooling is drawn in multiple passes. The total deformation of the second multi-pass drawing is 95%~99%, and the rare earth copper alloy wire is obtained.

[0012] Furthermore, in step (1), the purity of the copper raw material is not less than 99.995%, the smelting is carried out under vacuum or protective atmosphere, and the diameter of the rare earth copper alloy rod is 8~14mm.

[0013] Furthermore, the total deformation is calculated based on the reduction rate of the wire cross-sectional area before and after drawing; when the wire before and after drawing is a circular cross-section, the total deformation η = [1 - (d 后 / d 前 )²]×100%, where d before is the diameter before drawing in this stage, and d after is the diameter after drawing in this stage.

[0014] Furthermore, the rapid annealing includes at least two holding sections; the cumulative holding time is the sum of the holding times of each holding section.

[0015] Furthermore, the rapid annealing process is as follows: holding at 600℃ for 5 seconds, holding at 650℃ for 5 seconds, and holding at 700℃ for 5 seconds, with a total holding time of 15 seconds, and finally air-cooled to room temperature.

[0016] Further, in step (2), the rare earth copper alloy rod with a diameter of 8 mm is drawn to a diameter of 1 mm, and the total deformation calculated by the cross-sectional area reduction rate is 98.44%; in step (4), the annealed wire with a diameter of 1 mm is drawn to a diameter of 0.14 mm, and the total deformation calculated by the cross-sectional area reduction rate is 98.04%.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: 1. This invention strictly limits the composition of high-strength and high-fatigue-resistant rare-earth copper alloy wire, which consists only of 0.03%~0.05%Sc and Cu with a purity ≥99.995%. Based on this, a vacuum directional solidification continuous down-drawing process is matched to prepare copper alloy wire with a tensile strength ≥466MPa and a conductivity ≥97%IACS.

[0018] 2. This invention employs a vacuum directional solidification continuous downward drawing process. By establishing a steep temperature gradient and a controllable slow downward drawing speed, the solid-liquid interface is smoothly advanced, allowing Sc atoms sufficient time to diffuse and distribute uniformly during solidification, resulting in axially growing directional columnar crystal structures.

[0019] 3. The vacuum directional solidification continuous downward drawing device used in this invention integrates vacuum protection, directional solidification and continuous downward drawing functions, ensuring that trace amounts of active element Sc are smelted under conditions without oxidation and burn-off, and achieve uniform distribution in the subsequent controllable directional solidification process, eliminating component segregation and casting defects from the source, and solving the technical bottleneck of uniform addition and efficient utilization of trace rare earth elements in copper matrix.

[0020] 4. This invention uses only industrial-grade scandium and conventional high-purity electrolytic copper as raw materials. Through the synergistic effect of a pure matrix, ultrafine grains (≤0.5 μm), and an initial structure of oriented columnar crystals, the resulting wire exhibits excellent repeated bending fatigue performance under stress levels of 30%-60% of its tensile strength, with a fatigue strength of not less than 130 MPa. The oriented columnar crystals have very few grain boundaries along the axial direction, minimizing electron scattering and improving conductivity; simultaneously, the straight grain boundaries and consistent orientation enhance fatigue resistance. This characteristic makes the wire of this invention particularly suitable for applications with extremely stringent requirements for conductivity, reliability, and durability, such as aerospace cables, high-speed railway contact lines, and high-precision electronic components.

[0021] 5. The present invention adopts a continuous process route of smelting and casting, first-stage multi-pass drawing, multi-stage rapid annealing and second-stage multi-pass drawing using a vacuum directional solidification device, without the need for long-term solution treatment and aging steps, and the process links and states of each stage are clearly defined. Attached Figure Description

[0022] The invention will be further understood from the following description taken in conjunction with the accompanying drawings. The components in the drawings are not necessarily drawn to scale, but rather the emphasis is on illustrating the principles of the embodiments. In different views, the same reference numerals designate corresponding parts.

[0023] Figure 1 This is a process flow diagram of the preparation method of the present invention; Figure 2 This is a TEM bright-field image of the copper-scandium alloy wire after the first stage of multi-pass drawing (total deformation of 98.44%) in Embodiment 1 of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be understood that the embodiments described are for illustrative purposes only and are not intended to limit the scope of protection of this invention.

[0025] Unless otherwise stated, all percentages in this article are mass percentages; wire diameters refer to the equivalent diameter of a circular cross-section; and the total drawing deformation is calculated based on the cross-sectional area reduction rate. The term "average grain size of columnar crystals" as used in this article refers to the average transverse dimension measured on the longitudinal section of the wire for slender grains oriented along the drawing direction, and is hereinafter referred to as average grain size.

[0026] According to one embodiment of the present invention, a high-strength and high-fatigue-resistant rare-earth copper alloy wire comprises, by mass percentage, 0.03% to 0.05% Sc, with the balance being Cu and unavoidable impurities; the rare-earth copper alloy wire has a slender grain structure oriented along the drawing direction, with an average grain size not greater than 0.5 μm, a tensile strength not less than 466 MPa, a conductivity not less than 97% IACS, and a fatigue strength not less than 130 MPa.

[0027] In one embodiment, the mass percentage of Sc is 0.03% to 0.04%, and the average grain size is 0.2 to 0.3 μm.

[0028] The above technical solution benefits from a pure matrix and optimized grain boundary structure, enabling the wire to exhibit excellent repeated bending fatigue performance under stress levels of 30%-60% of its tensile strength. The strength of the wire produced by this invention is more than 30% higher than that of pure copper wire produced using the same process. By precisely adding trace amounts of scandium (0.03%~0.05%) to the pure copper matrix, and utilizing the extremely low solid solubility of Sc in the copper matrix and its grain refinement properties, a significant decrease in conductivity caused by excessive solid solution elements is avoided.

[0029] This invention provides a method for preparing high-strength, high-fatigue-resistant rare-earth copper alloy wire, such as... Figure 1 As shown, the preparation method sequentially includes melting and casting, a first-stage multi-pass drawing, multi-stage rapid annealing, and a second-stage multi-pass drawing. The alloy rod obtained by melting and casting has a diameter of 8-14 mm; the total deformation of the first and second multi-pass drawing is 95-99%; the preparation method specifically includes the following steps: (1) Vacuum directional solidification: Using oxygen-free copper and pure scandium with a purity of not less than 99.995% as raw materials, a vacuum directional solidification continuous directional solidification device is used to prepare copper-scandium alloy casting rods with directional columnar crystal structure or fine equiaxed crystal structure by controlling the temperature gradient and directional solidification speed at the solid-liquid interface. (2) First stage multi-pass drawing: The rare earth copper alloy rod is drawn in multiple passes, and the total deformation of the first multi-pass drawing is 95%~99%, to obtain the first drawn wire. (3) Rapid annealing: Rapid annealing is performed on the first stage drawn wire. The rapid annealing adopts a staged heating method. The temperature of each heat preservation section is in the range of 600~700℃, the cumulative heat preservation time is 15~21 s, the single stage heat preservation time is 5~7s, and then it is air cooled to room temperature.

[0030] (4) Second stage multi-pass drawing: The wire after rapid annealing and air cooling is drawn in multiple passes. The total deformation of the second multi-pass drawing is 95%~99%, and the rare earth copper alloy wire is obtained.

[0031] In one embodiment, in step (1), the purity of the copper raw material is not less than 99.995%, the smelting is carried out under vacuum or protective atmosphere, and the diameter of the rare earth copper alloy rod is 8~14mm.

[0032] In one embodiment, the total deformation is calculated based on the reduction rate of the wire cross-sectional area before and after drawing; when the wire before and after drawing has a circular cross-section, the total deformation η = [1 - (d 后 / d 前 )²]×100%, where d before is the diameter before drawing in this stage, and d after is the diameter after drawing in this stage.

[0033] In one embodiment, the rapid annealing includes at least two holding sections; the cumulative holding time is the sum of the holding times of each holding section.

[0034] In one embodiment, the rapid annealing process is as follows: holding at 600°C for 5 seconds, holding at 650°C for 5 seconds, and holding at 700°C for 5 seconds, for a total holding time of 15 seconds, and finally air-cooling to room temperature.

[0035] In one embodiment, the rapid annealing process is as follows: holding at 600°C for 7 seconds, holding at 650°C for 7 seconds, and holding at 700°C for 7 seconds, with a total holding time of 21 seconds, and finally air-cooled to room temperature.

[0036] In one embodiment, the rapid annealing process is as follows: holding at 600°C for 6 seconds, holding at 650°C for 6 seconds, and holding at 700°C for 6 seconds, with a total holding time of 18 seconds, and finally air-cooled to room temperature.

[0037] In one embodiment, the rapid annealing process is as follows: holding at 630°C for 5 seconds, holding at 660°C for 5 seconds, and holding at 690°C for 5 seconds, for a total holding time of 15 seconds, and finally air-cooled to room temperature.

[0038] In one embodiment, in step (2), a rare earth copper alloy rod with a diameter of 8 mm is drawn to a diameter of 1 mm, and the total deformation calculated by the cross-sectional area reduction rate is 98.44%; in step (4), an annealed wire with a diameter of 1 mm is drawn to a diameter of 0.14 mm, and the total deformation calculated by the cross-sectional area reduction rate is 98.04%.

[0039] The preparation method provided by this invention uses oxygen-free copper and pure scandium with a purity of not less than 99.995% as raw materials. Unlike traditional casting processes, this invention requires the use of a vacuum directional solidification continuous downward drawing device to prepare copper-scandium alloy casting rods with a diameter of 8-14 mm. This device mainly consists of a vacuum melting chamber, a crystallizer, a traction mechanism, and a water-cooling system. Its core lies in establishing a stable and steep temperature gradient (G) at the solid-liquid interface front by precisely controlling the height and cooling intensity of the water-cooled crystallizer, while simultaneously controlling the downward drawing speed (R, i.e., solidification rate) of the casting rod through an adjustable traction mechanism. According to solidification theory, the solidification microstructure of the casting rod can be actively controlled by adjusting the G / R value: this invention obtains a high G / R value by controlling process parameters, enabling the casting rod to form an axially growing, oriented columnar crystal structure with few and straight grain boundaries. This unique initial as-cast structure is crucial for subsequent performance. The axially minimal grain boundaries of the oriented columnar crystals minimize electron scattering, which is beneficial for conductivity; at the same time, the straight grain boundaries and consistent orientation improve fatigue resistance. This device integrates vacuum protection, directional solidification, and continuous downward drawing functions, ensuring that trace amounts of the active element Sc are melted under conditions free from oxidation and burn-off, and that they are uniformly distributed during the subsequent controlled directional solidification process, eliminating compositional segregation and casting defects at the source. Subsequent short-process drawing and heat treatment processes are based on and serve this specific initial microstructure, working synergistically to produce high-strength, high-fatigue-resistant rare-earth copper alloy wires.

[0040] Example 1: A method for preparing a high-strength, high-fatigue-resistant rare-earth copper alloy wire, the method comprising the following steps: (1) Vacuum directional solidification continuous downward drawing: Using oxygen-free copper and pure scandium blocks with a purity ≥99.995% as raw materials, the raw materials are weighed according to the mass percentage of Cu-0.03Sc; the raw materials are placed in the vacuum induction melting furnace of the vacuum directional solidification continuous downward drawing device, the melting temperature is 1180±20℃, and the temperature is held for 10min after complete melting. By adjusting the flow rate and position of the cooling water in the crystallizer, a steep temperature gradient (G) is established, and the downward drawing speed (R) is controlled to be 10 mm / min to obtain a high G / R value, and a Cu-0.03Sc alloy casting rod with a diameter of 8 mm and an axially growing columnar crystal structure is obtained; (2) First stage multi-pass drawing: The rare earth copper alloy rod is drawn in multiple passes, and the total deformation of the first multi-pass drawing is 98.44%, and a first drawn wire with a diameter of 1mm is obtained. (3) Rapid annealing: Rapid annealing is carried out on the first stage drawn wire. The rapid annealing adopts a staged heating method, holding at 600℃ for 5 s, 650℃ for 5 s and 700℃ for 5 s, with a total holding time of 15 s. Finally, it is air-cooled to room temperature. (4) Second stage multi-pass drawing: The wire after rapid annealing and air cooling is drawn in multiple passes. The total deformation of the second multi-pass drawing is 98.04%, and the rare earth copper alloy wire with a diameter of 0.14 mm is obtained.

[0041] Example 2: Example 2 differs from Example 1 only in that the mass percentage of Sc in the ingredients is adjusted to 0.04%, resulting in a Cu-0.04Sc alloy wire with a diameter of 0.14 mm. Everything else is the same as in Example 1.

[0042] Example 3: Example 3 differs from Example 1 only in that the mass percentage of Sc in the ingredients is adjusted to 0.05%, resulting in a Cu-0.05Sc alloy wire with a diameter of 0.14 mm. Everything else is the same as in Example 1.

[0043] Example 4: A method for preparing a high-strength, high-fatigue-resistant rare-earth copper alloy wire, the method comprising the following steps: (1) Vacuum directional solidification continuous downward drawing: Using oxygen-free copper and pure scandium blocks with a purity ≥99.995% as raw materials, the raw materials are weighed according to the mass percentage of Cu-0.03Sc; the raw materials are placed in the vacuum induction melting furnace of the vacuum directional solidification continuous downward drawing device, the melting temperature is 1180±20℃, and the temperature is held for 10min after complete melting. By adjusting the flow rate and position of the cooling water in the crystallizer, a steep temperature gradient (G) is established, and the downward drawing speed (R) is controlled to be 10 mm / min to obtain a high G / R value, and a Cu-0.03Sc alloy casting rod with a diameter of 8 mm and an axially growing columnar crystal structure is obtained; (2) First stage multi-pass drawing: The rare earth copper alloy rod is drawn in multiple passes, and the total deformation of the first multi-pass drawing is 95%, to obtain a first drawn wire with a diameter of 1.79 mm. (3) Rapid annealing: Rapid annealing is carried out on the first stage drawn wire. The rapid annealing adopts a staged heating method, holding at 600℃ for 5 s, 650℃ for 5 s and 700℃ for 5 s, with a total holding time of 15 s. Finally, it is air-cooled to room temperature. (4) Second stage multi-pass drawing: The wire after rapid annealing and air cooling is drawn in multiple passes. The total deformation of the second multi-pass drawing is 95%, and the rare earth copper alloy wire with a diameter of 0.40 mm is obtained.

[0044] Example 5: Compared with Example 4, Example 5 differs in that the total deformation of both stages of drawing is adjusted to 97%: in the first stage, the 8 mm diameter cast rod is drawn to approximately 1.39 mm, and in the second stage, it is drawn to approximately 0.24 mm to obtain the finished alloy wire. Everything else is the same as in Example 4.

[0045] Example 6: Compared with Example 4, Example 6 differs in that the total deformation of both stages of drawing is adjusted to 99%: in the first stage, the 8 mm diameter cast rod is drawn to 0.8 mm, and in the second stage, it is drawn to 0.08 mm to obtain the finished alloy wire. Everything else is the same as in Example 4.

[0046] Example 7: Compared with Example 1, Example 7 differs only in that the rapid annealing process is adjusted to: holding at 600°C for 6 seconds, holding at 650°C for 6 seconds, and holding at 700°C for 6 seconds, for a total holding time of 18 seconds, followed by air cooling to room temperature, to obtain an alloy wire with a diameter of 0.14 mm. Everything else is the same as in Example 1.

[0047] Example 8: Compared with Example 1, Comparative Example 8 differs only in that the rapid annealing process is adjusted to: holding at 600°C for 7 seconds, holding at 650°C for 7 seconds, and holding at 700°C for 7 seconds, for a total holding time of 21 seconds, followed by air cooling to room temperature to obtain an alloy wire with a diameter of 0.14 mm. Everything else is the same as in Example 1.

[0048] Example 9: Compared with Example 1, Example 9 differs only in that the rapid annealing temperature gradient is adjusted to: 630℃ for 5 s, 660℃ for 5 s, and 690℃ for 5 s, with a total holding time of 15 s, followed by air cooling to room temperature to obtain an alloy wire with a diameter of 0.14 mm. Everything else is the same as in Example 1.

[0049] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 uses oxygen-free copper with a purity ≥99.995% and does not add Sc element to obtain pure copper wire with a diameter of 0.14 mm. Everything else is the same as in Example 1.

[0050] Comparative Example 2: Comparative Example 2 is the same as Example 1, except that the raw material used in Comparative Example 2 is industrial pure copper with a purity of 99.95%, without the addition of Sc element, to obtain pure copper wire with a diameter of 0.14 mm. Everything else is the same as in Example 1.

[0051] The samples prepared in Examples 1-9 and the samples prepared in the comparative examples were subjected to performance tests. The test results are shown in Table 1 below: Table 1: Performance Test Results

[0052] Analysis of the data in Table 1 shows that within the range of 0.03% to 0.05% Sc, as the Sc content increases, the tensile strength of the alloy gradually increases, the fatigue strength generally shows an upward trend, the conductivity slightly decreases, and the grain size gradually becomes finer. This is because the increased Sc content inhibits grain growth during annealing; however, the slight increase in the amount of Sc atoms in the trace solution slightly enhances the scattering effect on electrons, thus the conductivity shows a slow downward trend, but remains at a high level above 97.6% IACS. Within the range of 95% to 99% total deformation, as the drawing deformation increases, the work hardening effect of the alloy is enhanced, the grains are significantly refined, the tensile strength and fatigue strength continue to increase, and the conductivity slightly decreases. Within the annealing parameter range set in this invention, as the holding time is extended, the degree of alloy recovery and recrystallization increases, the dislocation density decreases, therefore the tensile strength slightly decreases, the conductivity slightly increases, and the grain size slightly increases. Even under the maximum condition of 21 s of cumulative heat preservation, the alloy still maintains excellent properties such as average grain size ≤0.5 μm, tensile strength ≥466 MPa, and fatigue strength ≥130 MPa.

[0053] Compared to 99.995% high-purity copper produced using the same process, the Cu-0.03Sc alloy of this invention exhibits approximately 31.8% higher tensile strength, approximately 37.8% higher fatigue strength, and only a decrease in conductivity of approximately 1.1% IACS. This achieves a significant improvement in strength and fatigue resistance with almost no loss of conductivity. Compared to 99.95% industrial pure copper, the alloy of this invention shows approximately 26.9% higher strength and comparable or better conductivity, fully demonstrating the technical advantages of the synergistic process of micro-alloying with trace amounts of Sc combined with directional solidification, large deformation drawing, and rapid annealing.

[0054] in addition, Figure 2 This is a TEM bright-field image from Embodiment 1 of the present invention. From... Figure 2 As can be seen, under the influence of a large cold deformation of 98.44%, the original cast columnar crystals were significantly elongated and broken along the drawing axis, forming a fibrous deformed structure parallel to the drawing direction. The grains were drastically refined laterally, forming a large number of deformed subgrains / dislocation cells, with lateral dimensions mostly concentrated in the range of 100~300 nm, exhibiting a typical fibrous structure morphology. The microstructure characteristics of cold work hardening were completely preserved.

[0055] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0056] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A high-strength, high-fatigue-resistant rare-earth copper alloy wire, characterized in that, The rare earth copper alloy wire comprises, by mass percentage, 0.03% to 0.05% Sc, with the balance being Cu and unavoidable impurities; the rare earth copper alloy wire has a slender grain structure oriented along the drawing direction, with an average grain size not greater than 0.5 μm, a tensile strength not less than 466 MPa, a conductivity not less than 97% IACS, and a fatigue strength not less than 130 MPa.

2. The rare earth copper alloy wire according to claim 1, characterized in that, The mass percentage of Sc is 0.03%~0.04%, and the average grain size is 0.2~0.3 μm.

3. A method for preparing a high-strength, high-fatigue-resistant rare-earth copper alloy wire, characterized in that, The preparation method is used to prepare the high-strength, high-fatigue-resistant rare-earth copper alloy wire as described in claim 1 or 2, and the preparation method includes the following steps: (1) Vacuum directional solidification: Using oxygen-free copper and pure scandium with a purity of not less than 99.995% as raw materials, a vacuum directional solidification continuous directional solidification device is used to prepare copper-scandium alloy casting rods with directional columnar crystal structure or fine equiaxed crystal structure by controlling the temperature gradient and directional solidification speed at the solid-liquid interface. (2) First stage multi-pass drawing: The rare earth copper alloy rod is drawn in multiple passes, and the total deformation of the first multi-pass drawing is 95%~99%, to obtain the first drawn wire. (3) Rapid annealing: Rapid annealing is performed on the first stage drawn wire. The rapid annealing adopts a staged heating method. The temperature of each heat preservation section is in the range of 600~700℃, the cumulative heat preservation time is 15~21 s, the single stage heat preservation time is 5~7s, and then it is air cooled to room temperature. (4) Second stage multi-pass drawing: The wire after rapid annealing and air cooling is drawn in multiple passes. The total deformation of the second multi-pass drawing is 95%~99%, and the rare earth copper alloy wire is obtained.

4. The preparation method according to claim 3, characterized in that, In step (1), the purity of the copper raw material is not less than 99.995%, the smelting is carried out under vacuum or protective atmosphere, and the diameter of the rare earth copper alloy rod is 8~14mm.

5. The preparation method according to claim 3, characterized in that, The total deformation is calculated based on the reduction rate of the wire cross-sectional area before and after drawing; when both the wire before and after drawing have circular cross-sections, the total deformation η = [1 - (d 后 / d 前 )²]×100%, where d before is the diameter before drawing in this stage, and d after is the diameter after drawing in this stage.

6. The preparation method according to claim 3, characterized in that, The rapid annealing includes at least two holding sections; the cumulative holding time is the sum of the holding times of each holding section.

7. The preparation method according to claim 6, characterized in that, The rapid annealing process is as follows: holding at 600℃ for 5 seconds, holding at 650℃ for 5 seconds, and holding at 700℃ for 5 seconds, for a total holding time of 15 seconds, and finally air-cooling to room temperature.

8. The preparation method according to any one of claims 3 to 6, characterized in that, In step (2), the rare earth copper alloy rod with a diameter of 8 mm is drawn to a diameter of 1 mm, and the total deformation calculated by the cross-sectional area reduction rate is 98.44%; in step (4), the annealed wire with a diameter of 1 mm is drawn to a diameter of 0.14 mm, and the total deformation calculated by the cross-sectional area reduction rate is 98.04%.

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