A method for preparing copper-zirconium-lithium alloy rods

Abstract

This invention discloses a method for preparing copper-zirconium-lithium alloy rods, belonging to the field of copper alloy technology. The method includes: melting copper-zirconium master alloy and copper-lithium master alloy with a copper source; casting the resulting billet to obtain an ingot; radially forging the ingot; solution treating the obtained forged billet; performing a first cold drawing on the solution-treated billet to obtain a copper-zirconium-lithium alloy rod of a first diameter; aging the first diameter copper-zirconium-lithium alloy rod; performing a second cold drawing on the aged first diameter copper-zirconium-lithium alloy rod to obtain a second diameter copper-zirconium-lithium alloy rod; and aging the second diameter copper-zirconium-lithium alloy rod to obtain the finished copper-zirconium-lithium alloy rod. The method of this invention incorporates lithium to improve the alloy's plasticity and thermal stability, and uses radial forging to process the alloy into rods, avoiding problems caused by low weld interface strength and inhomogeneous microstructure and properties.

Description

Technical Field

[0001] This invention belongs to the field of copper alloy technology, specifically relating to a method for preparing copper-zirconium-lithium alloy rods. Background Technology

[0002] High-strength, high-conductivity copper-zirconium alloys are cutting-edge specialty copper alloy materials, combining high technology content with broad application prospects. These alloys stand out for their exceptional strength and electrical conductivity, while also possessing excellent thermal conductivity, wear resistance, corrosion resistance, resistance to high-temperature softening, and resistance to stress relaxation. They have wide applications in several key areas, including high-power asynchronous traction motors, critical load-bearing cables and contact wires in electrified railways, high-end connectors, and lead frames for large-scale integrated circuits. Their applications cover multiple industries such as rail transportation, aerospace, 5G communication technology, new energy vehicles, and semiconductors. Furthermore, zirconium content of approximately 3.0 at.% to 7.0 at.% can replace beryllium copper alloys, maintaining high strength while possessing high conductivity, making it a more environmentally friendly copper alloy.

[0003] However, in the field of metallurgy, strength and electrical conductivity constitute a pair of mutually restrictive contradictions. On the one hand, alloying elements are beneficial to improving the strength of copper alloys, but they can also introduce defects into the copper crystal structure, reducing conductivity. Copper-zirconium alloys are precipitation-strengthened alloys; during preparation, fine, dispersed intermetallic compound particles are formed in the copper matrix, improving the alloy's mechanical properties but simultaneously reducing conductivity. Furthermore, due to the different melting points of the constituent elements, uneven strain during compound formation can lead to localized stress concentrations, potentially causing defects or even cracks during subsequent cold working. On the other hand, the preparation of copper-zirconium alloy bars generally employs continuous extrusion. This method results in uneven deformation of the alloy structure during deformation, also leading to localized stress concentrations and defects such as inclusions and porosity. Additionally, during continuous extrusion, zirconium is prone to oxidation, resulting in low weld interface strength. Furthermore, oxide layers may form on the material surface, affecting the bonding between materials and reducing weld quality, thus hindering mass production. Moreover, in actual processing, continuous extrusion presses have short lifespans, limited extrusion ratios, and low material utilization.

[0004] Therefore, developing a copper-zirconium alloy that balances strength and conductivity is of great significance for the engineering application of copper alloys. Summary of the Invention

[0005] Based on this, and to address the shortcomings of the existing technology, a method for preparing high-strength, high-conductivity copper-zirconium-lithium alloy rods is proposed.

[0006] To achieve the above objectives, the following technical solution is adopted:

[0007] This invention provides a method for preparing copper-zirconium-lithium alloy rods, comprising the following steps:

[0008] S101. The copper-zirconium master alloy and the copper-lithium master alloy are smelted with a copper source, and the resulting billet is cast to obtain an ingot.

[0009] S102. Radial forging of the ingot;

[0010] S103. The forging billet obtained in step S102 is subjected to solution treatment;

[0011] S104. The solution-treated billet is subjected to a cold drawing process to obtain a copper-zirconium-lithium alloy rod with the first diameter.

[0012] S105. The copper-zirconium-lithium alloy rod of the first diameter is subjected to aging treatment.

[0013] S106. The copper-zirconium-lithium alloy rod with the first diameter after aging treatment is subjected to a second cold drawing treatment to obtain a copper-zirconium-lithium alloy rod with the second diameter.

[0014] S107. The copper-zirconium-lithium alloy rod of the second diameter is subjected to aging treatment to obtain the finished copper-zirconium-lithium alloy rod.

[0015] In some embodiments, the oxygen content in the smelting process is between 700 ppm and 2000 ppm by mass.

[0016] In some embodiments, the melting temperature is 1100~1300℃; the melting atmosphere is a vacuum atmosphere or an inert gas atmosphere.

[0017] In some embodiments, the billet comprises the following components by atomic percentage:

[0018] Zirconium 3.0%~7.0%, lithium ≤0.05%, the remainder is copper.

[0019] In some embodiments, the radial forging process includes: initial forging temperature controlled at 850°C to 900°C, holding at that temperature for 60 minutes; and final forging temperature controlled at 800°C to 830°C.

[0020] In some embodiments, the solution treatment temperature is selected to be between 900°C and 930°C.

[0021] In some embodiments, the cross-sectional area reduction rate of a single cold drawing process is 35-55%; the cross-sectional area reduction rate of a second cold drawing process is 25-40%.

[0022] In some embodiments, the first diameter of the copper-zirconium-lithium alloy rod is larger than the second diameter.

[0023] In some embodiments, step S105 includes the following steps: heating and holding a copper-zirconium-lithium alloy rod of the first diameter in an atmosphere-protected furnace at a heating temperature of 450-480°C for 1.5-3 hours, followed by furnace cooling to below 100°C and then air cooling.

[0024] In some embodiments, step S107 includes the following steps: heating and holding the copper-zirconium-lithium alloy rod of the second diameter in an atmosphere-protected furnace at a heating temperature of 400°C to 450°C for 2 to 3 hours, followed by furnace cooling to below 100°C and then air cooling.

[0025] The present invention has the following beneficial technical effects:

[0026] The method for preparing copper-zirconium-lithium alloy rods of the present invention refines the grain size and improves the plasticity of the alloy by adding lithium. Furthermore, the good binding ability between lithium and hydrogen reduces the harmful effects of hydrogen during casting, and the zirconium-lithium alloy has a strong hydrogen absorption capacity, which improves casting fluidity. Simultaneously, the addition of lithium helps improve the thermal stability of the alloy.

[0027] The method for preparing copper-zirconium-lithium alloy rods of the present invention employs radial forging. Compared to the conventional continuous extrusion method, this method effectively avoids the problem of low weld strength caused by zirconium oxidation during continuous extrusion. Furthermore, radial forging has a high forging ratio, resulting in a more uniform distribution of the second phase in the copper-zirconium alloy under large deformation, with finer and more dispersed particles, which better promotes dispersion strengthening and thus improves the mechanical properties of the alloy. In addition, the uniform material deformation during radial forging effectively reduces anisotropy. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart of the preparation method of the high-strength, high-conductivity copper-zirconium-lithium alloy rod of the present invention;

[0030] Figure 2 This is a scanning electron microscope image of the copper-zirconium-lithium alloy rod of Embodiment 1 of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0032] It should be understood that the embodiments of the invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments have been described in detail in this invention, those skilled in the art will readily recognize that various modifications are possible without substantially departing from the teachings of the invention. Accordingly, all such modifications should be included within the scope of the invention. Other substitutions, modifications, variations, and deletions can be made to the design, operating conditions, and parameters of the following exemplary embodiments without departing from the spirit of the invention.

[0033] This invention aims to improve the plasticity and thermal stability of copper-zirconium alloys, solve the problem of uneven microstructure and properties in traditional bar manufacturing processes, and address the issue of low weld interface strength during continuous extrusion, which prevents mass production.

[0034] To achieve the above objectives, a first aspect of the present invention provides a method for preparing copper-zirconium-lithium alloy rods. Figure 1 The diagram shown is a schematic flowchart of the method.

[0035] The preparation method of copper-zirconium-lithium alloy rods includes the following steps:

[0036] S101. The copper-zirconium master alloy and the copper-lithium master alloy are smelted with a copper source, and the resulting billet is cast to obtain an ingot.

[0037] S102. Radial forging of the ingot;

[0038] S103. The forging billet obtained in step S102 is subjected to solution treatment;

[0039] S104. The solution-treated billet is subjected to a cold drawing process to obtain a copper-zirconium-lithium alloy rod with the first diameter.

[0040] S105. The copper-zirconium-lithium alloy rod of the first diameter is subjected to aging treatment.

[0041] S106. The copper-zirconium-lithium alloy rod with the first diameter after aging treatment is subjected to a second cold drawing treatment to obtain a copper-zirconium-lithium alloy rod with the second diameter.

[0042] S107. The copper-zirconium-lithium alloy rod of the second diameter is subjected to aging treatment to obtain the finished copper-zirconium-lithium alloy rod.

[0043] Specifically, in step S101, the copper-zirconium master alloy can be selected from Cu-20wt.%Zr master alloy, Cu-30wt.%Zr master alloy, Cu-40wt.%Zr master alloy, or Cu-50wt.%Zr master alloy, preferably Cu-40wt.%Zr master alloy; the copper-lithium master alloy can be selected from Cu-5wt.%Li master alloy, Cu-10wt.%Li master alloy, Cu-15wt.%Li master alloy, or Cu-20wt.%Li master alloy, preferably Cu-5wt.%Li master alloy; the copper source can be electrolytic copper plate. The ingot is cast using a round bar crystallizer, preferably an ingot with a diameter of Φ300~400mm. The temperature of the injected melt is preferably 1000℃~1250℃, more preferably 1050℃~1200℃.

[0044] The smelting process employs either high-frequency induction melting or suspension melting. High-frequency induction melting allows for the melting of large quantities of materials at once, while suspension melting can suppress the introduction of impurities from crucibles and other sources.

[0045] In a preferred embodiment of the present invention, the oxygen content during the smelting process is 700 ppm to 2000 ppm by mass. More preferably, the oxygen content is 800 ppm to 1500 ppm, as the presence of oxygen can promote the amorphization of the Cu9Zr2 phase.

[0046] In a preferred embodiment of the present invention, the melting temperature is 1100~1300°C; the melting atmosphere is a vacuum atmosphere or an inert gas atmosphere. Inert gas atmospheres, for example, can be nitrogen, argon, helium, etc. The pressure of the inert gas atmosphere is preferably between 0.5 MPa and 2.0 MPa.

[0047] In a preferred embodiment of the present invention, the cast billet comprises the following components by atomic percentage:

[0048] Zirconium 3.0 at.%~7.0 at.%, lithium ≤0.05 at.%, the remainder is copper.

[0049] "at.%" is an abbreviation for "Atomic Percent." Here's a detailed explanation: Atomic percentage refers to the proportion of a particular element's atoms to the total number of atoms in an alloy or compound, expressed as a percentage. Atomic percentage provides a more intuitive reflection of the atomic composition of elements in an alloy, facilitating the analysis of microscopic properties such as crystal structure and chemical bonding.

[0050] Specifically, in step S102, the ingot is preferably forged into a bar stock with a diameter of 100~150mm and a length of 1.2m~1.5m using a high-speed forging mill, and then subjected to a radial forging process. Preferably, the final forged billet has a diameter of 22~50mm and a length of 10m~15m.

[0051] In a preferred embodiment of the present invention, the radial forging process includes: initial forging temperature controlled at 850°C to 900°C, holding at that temperature for 60 minutes; and final forging temperature controlled at 800°C to 830°C.

[0052] Radial forging is performed using a radial forging mill. The initial forging temperature is controlled at 850℃~900℃, with a holding time of 60 minutes, ensuring no cracks appear on the forging surface. The final forging temperature is controlled at 800℃~830℃, ensuring a uniform microstructure in the forging. The higher temperature and shorter holding time result in a more uniform and finer distribution of the Cu9Zr2 phase. The high-frequency impact of the radial forging mill (up to 240~1800 times per minute) helps reduce the residence time of the metal at high temperatures, thus reducing the risk of thermal damage. It also avoids the problem of weak surfaces appearing at the weld interface during continuous extrusion.

[0053] Due to the high-frequency hammer blows, radial forging mills offer high production efficiency, making them suitable for short-duration, high-volume production. Furthermore, they avoid the pressure residue and shrinkage that occur in continuous extrusion processes, resulting in high material utilization. Radial forging mills are not limited by the extrusion ratio, allowing for large deformation of materials, which is beneficial for refining grain size and microstructure, and can also process irregular profiles.

[0054] In a preferred embodiment of the present invention, the solution treatment temperature is selected to be between 900°C and 930°C.

[0055] In a preferred embodiment of the present invention, the cross-sectional area reduction rate of the first cold drawing process is 35-55%; the cross-sectional area reduction rate of the second cold drawing process is 25-40%.

[0056] The reduction rate of cross-section (%) is calculated using the following formula:

[0057] Cross-sectional area reduction rate (%) = {(cross-sectional area before drawing - cross-sectional area after drawing) × 100} ÷ (cross-sectional area before drawing).

[0058] In a preferred embodiment of the present invention, the first diameter of the copper-zirconium-lithium alloy rod is larger than the second diameter.

[0059] Preferably, the first diameter is Φ14mm~40mm; the second diameter is Φ10mm~30mm.

[0060] In a preferred embodiment of the present invention, step S105 includes the following steps: heating and holding a copper-zirconium-lithium alloy rod of the first diameter in an atmosphere-protected furnace at a heating temperature of 450-480°C for 1.5-3 hours, followed by furnace cooling to below 100°C and then air cooling.

[0061] In a preferred embodiment of the present invention, step S107 includes the following steps: heating and holding the copper-zirconium-lithium alloy rod of the second diameter in an atmosphere-protected furnace at a heating temperature of 400°C to 450°C for 2 to 3 hours, and then air cooling the furnace to below 100°C.

[0062] The method for preparing copper-zirconium-lithium alloy rods of the present invention refines the grain size and improves the plasticity of the alloy by adding lithium. Furthermore, the good binding energy between lithium and hydrogen reduces the harmful effects of hydrogen during casting, and the zirconium-lithium alloy has a strong hydrogen absorption capacity, which improves casting fluidity. Simultaneously, the addition of lithium helps improve the thermal stability of the alloy.

[0063] The method for preparing copper-zirconium-lithium alloy rods of the present invention employs radial forging. Compared to the conventional continuous extrusion method, this method effectively avoids the problem of low weld strength caused by zirconium oxidation during continuous extrusion. Furthermore, radial forging has a high forging ratio, resulting in a more uniform distribution of the second phase in the copper-zirconium alloy under large deformation, with finer and more dispersed particles, which better promotes dispersion strengthening and thus improves the mechanical properties of the alloy. In addition, the uniform material deformation during radial forging effectively reduces anisotropy.

[0064] This invention improves the plasticity and thermal stability of copper-zirconium alloys with a zirconium content of 3.0 at.% to 7.0 at.% by adding lithium. In terms of process, the alloy is processed into bars by radial forging, which avoids the problem of poor weld quality caused by low weld interface strength due to oxidation compared to the previous continuous extrusion method. At the same time, the microstructure is more uniform during deformation, avoiding the problems caused by anisotropy.

[0065] The present invention is further illustrated by the following examples. Tables 1-3 show the properties of the alloy bars obtained in Examples 1-3.

[0066] Tensile strength is the maximum tensile stress a material can withstand during the tensile process, from the start to the point of fracture, and is measured in MPa (megapascals). When the tensile force on a material reaches its tensile strength, the material begins to exhibit necking and eventually fractures.

[0067] Conductivity (%IACS) is an important indicator of a material's electrical conductivity; a higher value indicates better conductivity. %IACS, or International Standard for Annealed Copper, is a unit characterizing conductivity. This standard uses the conductivity of internationally annealed copper as a reference, defining it as 100% IACS. For other metallic materials, their conductivity can be calculated by comparing them to the conductivity of internationally annealed copper and converting the result to a %IACS value. In practical applications, a high %IACS value signifies better electron transport efficiency and conductivity, which is crucial for applications requiring high-quality, high-conductivity metallic materials. Therefore, when selecting alloy materials, a higher %IACS value is generally preferred.

[0068] Elongation refers to the percentage of total elongation to the original gauge length after tensile fracture, and is used to characterize the plastic deformation capacity of a material.

[0069] Example 1

[0070] (1) Melting and casting

[0071] The raw materials consist of a Cu-40wt.%Zr master alloy, Cu-5wt.%Li, and electrolytic copper plates. High-frequency induction melting was employed. Simultaneously, the oxygen content was 1500 ppm by mass, the melting temperature was 1300℃, and the melting atmosphere was argon at a pressure of 0.5 MPa. The resulting ingot composition was 5.0 at.% zirconium, 0.05 at.% lithium, and the remainder copper. A Φ300mm ingot was obtained using a round bar mold, with the melt temperature injected at 1200℃ and a melting time of 60 minutes.

[0072] (2) Radial forging

[0073] The billet was forged into a Φ150mm bar with a length of 1.2m using a high-speed forging mill. It was then forged using a radial forging mill, with an initial forging temperature of 900℃ and a holding time of 60 minutes to ensure no cracks appeared on the forging surface; the final forging temperature was 830℃ to ensure a uniform microstructure. The higher temperature and shorter holding time resulted in a more uniform and finer distribution of the Cu9Zr2 phase. The final forging had a Φ50mm diameter and a length of 10m.

[0074] (3) Solution treatment

[0075] The obtained forging billet was subjected to solution treatment at a temperature of 930℃.

[0076] (4) Cold drawing in one step

[0077] The solution-treated billet was cold-drawn, resulting in a cross-sectional area reduction of 55%. The cross-sectional area reduction rate (%) was expressed as {(cross-sectional area before drawing - cross-sectional area after drawing) × 100} ÷ (cross-sectional area before drawing). A copper-zirconium-lithium alloy rod with a diameter of Φ33mm was obtained.

[0078] (5) Timeliness processing

[0079] The cold-worked copper-zirconium-lithium alloy rods were subjected to aging treatment by heating and holding in an atmosphere-protected furnace at a temperature of 480°C for 3 hours. The furnace was then cooled to below 100°C before air cooling.

[0080] (6) Secondary cold drawing

[0081] The aged bar was subjected to a second cold drawing process, resulting in a 40% reduction in cross-section. This yielded a copper-zirconium-lithium alloy bar with a diameter of Φ25mm.

[0082] (7) Timeliness processing

[0083] To further improve conductivity, the bar material that was cold-drawn for the second time was subjected to a second aging treatment. The aging treatment temperature was controlled at 450℃ and held for 3 hours.

[0084] Table 1. Properties of Cu-5.0 at.% Zr-0.05 at.% Li alloy bars from Example 1

[0085]

[0086] Among them, regarding the "cast billet obtained after melting" (referred to as "copper liquid") in the melting and casting process of step (1), the hydrogen content in the copper liquid was determined to be 4.1 ppm by rapid decompression.

[0087] Example 2

[0088] (1) Melting and casting

[0089] The raw materials consist of Cu-40wt.%Zr master alloy, Cu-5wt.%Li, and electrolytic copper plates. Suspension melting was employed. Simultaneously, the oxygen content was 1000ppm by mass, the melting temperature was 1250℃, and the melting atmosphere was argon at a pressure of 0.5MPa. The resulting ingot composition was 4.0 at.% zirconium, 0.04 at.% lithium, and the remainder copper. A Φ350mm ingot was obtained using a round bar crystallizer, with the melt injection temperature at 1150℃ and a melting time of 60 minutes.

[0090] (2) Radial forging

[0091] The billet was forged into a Φ120mm bar with a length of 1.5m using a high-speed forging mill. It was then forged using a radial forging mill, with an initial forging temperature of 870℃ and a holding time of 60 minutes to ensure no cracks appeared on the forging surface; the final forging temperature was 820℃ to ensure a uniform microstructure. The higher temperature and shorter holding time resulted in a more uniform and finer distribution of the Cu9Zr2 phase. The final forging had a Φ40mm diameter and a length of 13.5m.

[0092] (3) Solution treatment

[0093] The obtained forging billet was subjected to solution treatment at a temperature of 920℃.

[0094] (4) Cold drawing in one step

[0095] The solution-treated billet was cold-drawn, resulting in a 50% reduction in cross-section; a copper-zirconium-lithium alloy rod with a diameter of Φ28mm was obtained.

[0096] (5) Timeliness processing

[0097] The cold-worked copper-zirconium-lithium alloy rods were subjected to aging treatment by heating and holding in an atmosphere-protected furnace at a temperature of 480°C for 3 hours. The furnace was then cooled to below 100°C before air cooling.

[0098] (6) Secondary cold drawing

[0099] The aged bar was subjected to a second cold drawing process, resulting in a 35% reduction in cross-section. This yielded a copper-zirconium-lithium alloy bar with a diameter of Φ22mm.

[0100] (7) Timeliness processing

[0101] To further improve conductivity, the bar material that was cold-drawn for the second time was subjected to a second aging treatment. The aging treatment temperature was controlled at 420℃ and held for 3 hours.

[0102] Table 2. Properties of Cu-4.0 at.% Zr-0.04 at.% Li alloy bars from Example 2

[0103]

[0104] Among them, regarding the "cast billet obtained after melting" (referred to as "copper liquid") in the melting and casting process of step (1), the hydrogen content in the copper liquid was determined to be 4.6 ppm by rapid decompression.

[0105] Example 3

[0106] (1) Melting and casting

[0107] The raw materials used were Cu-40wt.%Zr master alloy, Cu-5wt.%Li, and electrolytic copper plates. Suspension melting was employed. Simultaneously, the oxygen content was 900 ppm by mass, the melting temperature was 1200℃, and the melting atmosphere was argon at a pressure of 0.5 MPa. The resulting ingot composition was 3.0 at.% zirconium, 0.03 at.% lithium, and the remainder copper. A Φ400mm ingot was obtained using a round bar crystallizer, with the melt injection temperature at 1150℃ and a melting time of 60 minutes.

[0108] (2) Radial forging

[0109] The billet was forged into a Φ100mm bar with a length of 1.5m using a high-speed forging mill. It was then forged using a radial forging mill, with an initial forging temperature of 870℃ and a holding time of 60 minutes to ensure no cracks appeared on the forging surface; the final forging temperature was 820℃ to ensure a uniform microstructure. The higher temperature and shorter holding time resulted in a more uniform and finer distribution of the Cu9Zr2 phase. The final forging had a Φ25mm diameter and a length of 12m.

[0110] (3) Solution treatment

[0111] The obtained forging billet was subjected to solution treatment at a temperature of 900℃.

[0112] (4) Cold drawing in one step

[0113] The solution-treated billet was cold-drawn, resulting in a 35% reduction in cross-section; a copper-zirconium-lithium alloy rod with a diameter of Φ20mm was obtained.

[0114] (5) Timeliness processing

[0115] The cold-worked copper-zirconium-lithium alloy rods were subjected to aging treatment by heating and holding in an atmosphere-protected furnace at a temperature of 450°C for 3 hours. The furnace was then cooled to below 100°C before air cooling.

[0116] (6) Secondary cold drawing

[0117] The aged bar was subjected to a second cold drawing process, resulting in a 30% reduction in cross-section. This yielded a copper-zirconium-lithium alloy bar with a diameter of Φ16mm.

[0118] (7) Timeliness processing

[0119] To further improve conductivity, the bar material that was cold-drawn for the second time was subjected to a second aging treatment. The aging treatment temperature was controlled at 420℃ and held for 3 hours.

[0120] Table 3. Properties of Cu-3.0 at.% Zr-0.03 at.% Li alloy bars from Example 3

[0121]

[0122] Among them, regarding the "cast billet obtained after melting" (referred to as "copper liquid") in the melting and casting process of step (1), the hydrogen content in the copper liquid was determined to be 5.1 ppm by rapid decompression.

[0123] Comparative Example

[0124] (1) Melting and casting

[0125] The raw materials used were a Cu-40wt.%Zr master alloy and electrolytic copper plates. High-frequency induction melting was employed. Simultaneously, the oxygen content was 1500ppm by mass, the melting temperature was 1300℃, and the melting atmosphere was argon at a pressure of 0.5MPa. The resulting ingot contained 5.0 at.% zirconium, with the remainder being copper. A Φ300mm ingot was cast using a round bar mold, with the melt injection temperature at 1200℃ and a melting time of 60 minutes.

[0126] (2) Radial forging

[0127] The billet was forged into a Φ150mm bar with a length of 1.2m using a high-speed forging mill. It was then forged using a radial forging mill, with an initial forging temperature of 900℃ and a holding time of 60 minutes to ensure no cracks appeared on the forging surface; the final forging temperature was 830℃ to ensure a uniform microstructure. The higher temperature and shorter holding time resulted in a more uniform and finer distribution of the Cu9Zr2 phase. The final forging had a Φ50mm diameter and a length of 10m.

[0128] (3) Solution treatment

[0129] The obtained forging billet was subjected to solution treatment at a temperature of 930℃.

[0130] (4) Cold drawing in one step

[0131] The solution-treated billet was cold-drawn, resulting in a cross-sectional area reduction of 55%. The cross-sectional area reduction rate (%) was expressed as {(cross-sectional area before drawing - cross-sectional area after drawing) × 100} ÷ (cross-sectional area before drawing). A copper-zirconium alloy rod with a diameter of Φ33mm was obtained.

[0132] (5) Timeliness processing

[0133] The cold-worked copper-zirconium alloy bars were subjected to aging treatment by heating and holding in an atmosphere-protected furnace at a temperature of 480°C for 3 hours. The furnace was then cooled to below 100°C before air cooling.

[0134] (6) Secondary cold drawing

[0135] The aged bar was subjected to a second cold drawing process, resulting in a 40% reduction in cross-section. This yielded a copper-zirconium alloy bar with a diameter of Φ25mm.

[0136] (7) Timeliness processing

[0137] To further improve conductivity, the bar material that was cold-drawn for the second time was subjected to a second aging treatment. The aging treatment temperature was controlled at 450℃ and held for 3 hours.

[0138] Table 4. Properties of Cu-5.0 at.% Zr alloy bars (comparative examples)

[0139] Among them, regarding the "cast billet obtained after melting" (referred to as "copper liquid") in the melting and casting process of step (1), the hydrogen content in the copper liquid was determined to be 15 ppm by rapid decompression.

[0140] from Figure 2 The scanning electron microscope (SEM) image of the copper-zirconium-lithium alloy rod of Example 1 shows that the darker, dotted areas are the second phase, which is uniformly distributed throughout the alloy. The preparation method of the copper-zirconium-lithium alloy rod of the present invention results in a more uniform distribution of the second phase in the copper-zirconium alloy under large deformation, with finer and more dispersed particles, which better promotes dispersion strengthening and thus improves the mechanical properties of the alloy. Furthermore, the uniform deformation of the material during radial forging effectively reduces anisotropy.

[0141] As can be seen from the hydrogen content in the copper liquid of Examples 1-3 and the comparative example above, the hydrogen content of Examples 1-3 with added Li is in the range of about 4-5 ppm, while the hydrogen content of the comparative example without added Li is 15 ppm, which is more than three times higher than that of Examples 1-3. This shows that the preparation method of copper zirconium lithium alloy rod of the present invention can reduce the harm of hydrogen in the casting process by adding lithium, and the zirconium lithium alloy has a strong hydrogen absorption effect, which can improve casting fluidity.

[0142] The comparative examples are those obtained using the preparation method of Example 1 without the addition of lithium. As can be seen from Table 4, the tensile strength, electrical conductivity, and elongation of the alloys obtained in the comparative examples are all lower than those of Example 1. The preparation method of the copper-zirconium-lithium alloy rod of the present invention can refine the grains by adding lithium, thereby improving the plasticity of the alloy; the addition of lithium also helps to improve the thermal stability of the alloy.

[0143] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. Although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular number.

[0144] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for preparing copper-zirconium-lithium alloy rods, characterized in that, Includes the following steps: S101. The copper-zirconium master alloy and the copper-lithium master alloy are smelted with a copper source, and the resulting billet is cast to obtain an ingot. S102. The ingot is radially forged; wherein, the radial forging process includes: the initial forging temperature is controlled at 850℃~900℃; the final forging temperature is controlled at 800℃~830℃; S103. The forging billet obtained in step S102 is subjected to solution treatment; S104. The solution-treated billet is subjected to a cold drawing process to obtain a copper-zirconium-lithium alloy rod with the first diameter. S105. The copper-zirconium-lithium alloy rod of the first diameter is subjected to aging treatment; wherein, the aging treatment process includes: heating and holding the copper-zirconium-lithium alloy rod of the first diameter in an atmosphere-protected furnace at a heating temperature of 450-480℃ for a holding time of 1.5-3h, and then cooling it in the furnace to below 100℃ and then air cooling it. S106. The copper-zirconium-lithium alloy rod with the first diameter after aging treatment is subjected to a second cold drawing treatment to obtain a copper-zirconium-lithium alloy rod with the second diameter. S107. The copper-zirconium-lithium alloy rod of the second diameter is subjected to aging treatment to obtain the finished copper-zirconium-lithium alloy rod; wherein, the aging treatment process includes: heating and holding the copper-zirconium-lithium alloy rod of the second diameter in an atmosphere-protected furnace at a heating temperature of 400℃~450℃ for 2~3 hours, and then cooling it in the furnace to below 100℃ and then air cooling it. The billet contains the following components by atomic percentage: zirconium 3.0%~7.0%, lithium ≤0.05%, and the remainder is copper.

2. The method for preparing copper-zirconium-lithium alloy rods according to claim 1, characterized in that, The oxygen content during the smelting process is between 700 ppm and 2000 ppm by mass.

3. The method for preparing copper-zirconium-lithium alloy rods according to claim 2, characterized in that, The melting temperature is 1100~1300℃; the melting atmosphere is a vacuum atmosphere or an inert gas atmosphere.

4. The method for preparing copper-zirconium-lithium alloy rods according to claim 1, characterized in that, The solution treatment temperature is selected between 900℃ and 930℃.

5. The method for preparing copper-zirconium-lithium alloy rods according to claim 1, characterized in that, The cross-sectional area reduction rate after a single cold drawing process is 35-55%; the cross-sectional area reduction rate after a double cold drawing process is 25-40%.

6. The method for preparing copper-zirconium-lithium alloy rods according to claim 1, characterized in that, The first diameter of the copper-zirconium-lithium alloy rod is larger than the second diameter.

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