Method for preparing ultrahigh-strength high-conductivity copper-silver alloy by combining directional solidification with pre-deformation

Abstract

The invention discloses a method for preparing an ultrahigh-strength and high-conductivity copper-silver alloy by combining directional solidification with pre-deformation, which comprises the following steps: preparing a Cu-Ag-RE alloy casting rod by adopting a directional solidification process, carrying out hot forging synergistic equal channel angular pressing or low-temperature rotary forging on the Cu-Ag-RE alloy casting rod, and then carrying out aging treatment to obtain the ultrahigh-strength and high-conductivity copper-silver alloy, according to the ultrahigh-strength high-conductivity copper-silver alloy and the preparation method thereof, the Cu-Ag-RE alloy is prepared through directional solidification, a fine and uniform directional eutectic (alpha-Cu + Ag) and Cu dendritic crystal structure is obtained, a dispersed and fine second-phase particle and twin crystal coupling layer fault mixed structure is obtained in combination with pre-deformation and aging treatment, and the ultrahigh-strength high-conductivity copper-silver alloy is obtained. And a structure basis is provided for obtaining the unidirectional ultrahigh-strength high-conductivity copper-silver alloy profile through final-state deformation.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-performance copper alloy preparation, and relates to a method for preparing ultra-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation. Background Art

[0002] In many fields such as pulsed high magnetic field coil windings, magnetizing machine coils, and overhead conductors for high-speed electric locomotives, the performance requirements for conductor materials are getting higher and higher. Currently developed conductor materials mainly include Cu-Nb, Cu-Ti, Cu-Al2O3 / TiB2, Cu-Cr-Zr, Cu-Ag, etc. Research shows that the tensile strength of Cu-Nb alloy wires / wire rods prepared by cold drawing can reach 2 GPa, but the conductivity is only about 60% IACS, and the melting points of Cu and Nb differ greatly, so there are many challenges in smelting preparation. The tensile strength of Cu-Ti alloy sheets prepared by cold rolling can reach 1.4 GPa, but the conductivity is only about 15% IACS. In the Cu-Ag alloy, Cu and Ag have the same slip system, good deformation coordination, and low electron scattering ability at the phase boundary, so a high conductivity can be obtained. After large deformation, the uniformly distributed eutectic (α-Cu + Ag) is transformed into a duplex fiber / lamellar structure, which can greatly improve the mechanical properties of the Cu-Ag alloy.

[0003] To obtain ultra-high strength and high conductivity Cu-Ag alloy wires / wire rods and sheets, it is a very effective method to improve the as-cast structure of Cu-Ag alloy by adding a third element and controlling the solidification conditions, or to preheat the Cu-Ag alloy before deformation. However, the addition of traditional third-phase elements such as Fe, Cr, Zr, etc. can greatly improve the mechanical properties of Cu-Ag alloy, but at the same time, it will greatly reduce the conductivity of Cu-Ag alloy, making it unable to be applied in the manufacturing field of high-conductivity electrical components. In the traditional induction melting preparation of Cu-Ag alloy, it is difficult to avoid dendrite segregation, shrinkage porosity, gas holes and other defects during the solidification process, which will have an adverse impact on subsequent deformation. In the traditional direct deformation combined with annealing treatment, due to insufficient precipitation phase regulation and excessive annealing treatment will lead to a decrease in strength, it is difficult to effectively achieve the strength-conductivity matching. Summary of the Invention

[0004] An object of the present invention is to provide a method for preparing ultra-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation, which solves the problems that the Cu-Ag alloy prepared by the existing casting process has element segregation, many casting defects, and too much residual solute in the copper matrix, making it difficult to obtain ultra-high strength and high conductivity copper-silver alloy profiles in the subsequent deformation process.

[0005] Another object of the present invention is to provide an ultra-high strength and high conductivity copper-silver alloy.

[0006] The first technical solution adopted by the present invention is a method for preparing an ultra-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation, which includes preparing a Cu-Ag-RE alloy ingot by directional solidification process. The Ag content in the ingot is 6-20 wt.%, the RE content is 0.02-0.1 wt.%, and the balance is Cu. The Cu-Ag-RE alloy ingot is subjected to pre-deformation treatment, including hot forging combined with equal-channel angular pressing or low-temperature rotary forging of the Cu-Ag-RE alloy ingot, followed by aging treatment, and finally cold rolling or cold drawing of the aged Cu-Ag-La alloy to obtain the ultra-high strength and high conductivity copper-silver alloy.

[0007] Specifically, it includes the following steps: Step 1: Using electrolytic Cu, high-purity Ag particles, and Cu-RE master alloy as raw materials, a Cu-Ag-RE alloy ingot is prepared by directional solidification process. Step 2: The Cu-Ag-RE alloy ingot obtained in Step 1 is subjected to pre-deformation treatment. The pre-deformation treatment is hot forging combined with equal-channel angular pressing or low-temperature rotary forging. Hot forging combined with equal-channel angular pressing includes first hot forging the Cu-Ag-RE alloy ingot to obtain a slab-shaped Cu-Ag-RE alloy blank with a thickness and width of 15 mm to 20 mm, and then subjecting the slab-shaped Cu-Ag-RE alloy blank to equal-channel angular pressing, and the number of pressing times is 3 to 5 times. Step 3: The Cu-Ag-RE alloy bar after pre-deformation treatment in Step 2 is subjected to aging treatment in a rapid heat treatment furnace, and the aged Cu-Ag-La alloy is cold rolled or cold drawn to obtain the ultra-high strength and high conductivity copper-silver alloy.

[0008] In Step 1, when preparing the Cu-Ag-RE alloy ingot by directional solidification process, it includes loading electrolytic Cu and high-purity Ag particles in the raw materials into a graphite crucible. After the furnace chamber is pre-evacuated, argon is introduced as a protective gas. After Cu and Ag are completely melted, they are kept warm for a period of time. Then, the Cu-RE master alloy is added to the alloy melt. After starting electromagnetic stirring and keeping warm for another period of time, the servo pulling mechanism is used to pull it into the liquid metal at a constant rate for directional solidification to obtain a Cu-Ag-RE alloy ingot with a directional structure.

[0009] In Step 1, the directional solidification process adopts the liquid metal cooling method. The melting temperature is 1100 - 1250 °C. After Cu and Ag are completely melted, keep them warm for 10 min - 30 min. During this period, electromagnetic stirring is carried out on the alloy melt every 3 min - 5 min to ensure the uniform composition of the melt. After the heat preservation ends, add Cu-RE master alloy into the alloy melt by using a feeding device, and then heat up to 1350 - 1450 °C again, keep it warm for 10 min - 30 min. During this period, electromagnetic stirring of the alloy melt is carried out continuously. After the heat preservation ends, the servo pulling mechanism drags the graphite crucible filled with the alloy melt into the liquid metal at a constant pulling rate of 10 - 100 μm / s for directional solidification, and a Cu-Ag-RE alloy ingot with a diameter of 20 mm - 60 mm is obtained.

[0010] In the Cu-RE master alloy, RE is rare earth La, Ce or Y, and the liquid metal is Ga-In-Sn or Ga-In.

[0011] In Step 2, hot forging is carried out on the Cu-Ag-RE alloy ingot, including heating the temperature of the box-type resistance furnace to 700 - 800 °C, and then putting the Cu-Ag-RE alloy ingot into the furnace in the way of putting it into the furnace when it reaches the temperature, keep it warm for 10 min - 30 min to ensure the uniform temperature distribution in the alloy ingot. Take out the alloy ingot and put it into the forging die for hot forging. The deformation method is to forge along the radial direction. During the hot forging process, rotate the alloy ingot along the axial direction, rotate 90° counterclockwise or clockwise, and the transformation frequency is to carry out single-pass forging or multi-pass forging in each direction. Keep it warm for 10 min - 30 min for each pass, and the forging ratio for each pass is 3% - 5%. Finally, a slab-shaped Cu-Ag-RE alloy blank with a thickness and width of 15 mm - 20 mm is obtained.

[0012] In Step 2, equal-channel angular pressing includes putting the slab-shaped Cu-Ag-RE alloy blank after hot forging into the vertical channel entrance of the square die, the channel angle is 90 - 120°, and extrude at a speed of 100 - 300 mm / min. The extrusion path is that the billet extruded each time rotates 90° in the opposite direction or the billet extruded each time rotates 180° in the same direction.

[0013] In Step 2, for low-temperature rotary forging, pre-cool the rotary forging die for 10 min - 15 min before each pass. Soak the Cu-Ag-RE alloy in liquid nitrogen for 60 min - 120 min before each pass, and then send the Cu-Ag-RE alloy into the rotary forging machine and feed at a speed of 20 - 40 mm / s. The rotary forging ratio for each pass is 8% - 16%. Finally, a rotary-forged Cu-Ag-RE alloy bar with a diameter of 2 mm - 5 mm is obtained.

[0014] In Step 3, the aging treatment temperature is 400 - 500 °C, the holding time is 10 min - 20 min, the furnace charging method is charging when reaching the temperature, and the cooling method is air cooling.

[0015] The second technical solution adopted in the present invention is a super high strength and high conductivity copper-silver alloy prepared by the method of directional solidification combined with pre-deformation for preparing the super high strength and high conductivity copper-silver alloy.

[0016] The beneficial effects of the present invention are as follows: (1) By adding rare earth element RE, the rare earth element can react with impurities to remove impurities in the Cu melt, improving the conductivity of the alloy. It can also refine the as-cast structure of the alloy to a certain extent, increase the amount of eutectic structure, and the rare earth element can react with Cu and Ag to form Cu6La and Ag 51 La 14 particles, enhancing the precipitation strengthening effect and strengthening the mechanical properties of the alloy; (2) Using the directional solidification process to prepare the Cu-Ag-RE alloy, rapid solidification is achieved through an extremely high temperature gradient during the directional solidification process, forming a metastable solid solution, improving composition segregation, thus significantly refining the as-cast structure of the alloy. At the same time, directional Cu dendrites and eutectic structure are obtained, laying an organizational foundation for the subsequent preparation of unidirectional super high strength Cu-Ag-RE profiles; (3) Adding the Cu-RE master alloy after Cu and Ag are completely melted, and introducing the third component into the Cu-Ag melt by means of electromagnetic stirring can avoid the burning loss problem caused by large melting point differences and long holding times between components and the problem of component composition segregation caused by large density differences between components, thus ensuring that the alloy has a good as-cast structure; (4) Pre-deforming and pre-aging the alloy before final deformation can significantly improve the comprehensive properties of the material by synergistically optimizing the microstructure. The pre-deformation treatment can increase the deformation energy storage of the alloy, providing sufficient driving force for the precipitation of nano-precipitates during the subsequent pre-aging treatment. The nano-precipitates can not only produce precipitation strengthening, but also reduce the scattering of solute atoms to electrons, improving the conductivity. Moreover, they can be transformed into a high-density needle-like Ag fiber structure during the subsequent final deformation process, synergistically strengthening the mechanical properties of the alloy with the lamellar structure transformed from the eutectic structure. At the same time, pre-deforming the Cu-Ag alloy ingot can also obtain billets of corresponding shapes, which is conducive to subsequent wire drawing for preparing wires / wire rods and rolling for preparing plates; (5) Introducing high-density dislocations through pre-deformation provides more nucleation sites for subsequent aging. Then, adopting the "high temperature and short time" aging process to obtain fine and dispersed second phases significantly improves the strength of the alloy. Pre-deformation can also homogenize the internal stress distribution of the alloy. The precipitates generated by pre-aging pin the dislocations, thus reducing dislocation tangles and microcracks in the final deformed alloy and enhancing the stability of the alloy; (6) Pre-deformation: Select hot forging combined with equal-channel angular pressing or low-temperature rotary forging. Hot forging can effectively eliminate defects such as pores and shrinkage porosity in alloy ingots. After hot forging, the dislocation density of the alloy billet is low and evenly distributed, which can avoid the occurrence of microcracks or fractures during the equal-channel angular pressing deformation process. Low-temperature rotary forging adopts a rapid feeding method to match a large single-pass deformation amount. Rotary forging is not only beneficial to uniform alloy deformation but also can improve the plasticity of the alloy. However, severe plastic deformation will cause the alloy to heat up and induce recrystallization, while a low-temperature environment can effectively inhibit the growth of recrystallized grains, achieving the effect of grain refinement; the Cu-Ag-RE alloy has a medium stacking fault energy. Both the extremely high strain rate of equal-channel angular pressing and the extremely low deformation temperature of low-temperature rotary forging can increase the slip stress, thereby effectively inhibiting the cross-slip of dislocations, increasing the tendency of the alloy to undergo twinning deformation, and thus obtaining a high-density twin-coupled stacking fault mixed structure, significantly improving the mechanical properties of the alloy while minimizing the loss of electrical conductivity. Description of the Drawings

[0017] Figure 1 is a schematic flow chart of the method for preparing an ultra-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation according to the present invention; Figure 2 is the directional microstructure of the Cu-Ag-La alloy ingot in Example 2 of the present invention; Figure 3 is the morphology of the nano-Cu phase precipitated in the eutectic Ag phase of the Cu-Ag-La alloy after aging treatment in Example 2 of the present invention; Figure 4 is the distribution of the nano-Cu precipitated phase in the eutectic Ag phase of the Cu-Ag-La alloy after aging treatment in Example 2 of the present invention; Figure 5 is the distribution of Ag in the eutectic Ag phase of the Cu-Ag-La alloy after aging treatment in Example 2 of the present invention; Figure 6 is the distribution of La in the eutectic Ag phase of the Cu-Ag-La alloy after aging treatment in Example 2 of the present invention; Figure 7 is the morphology of the nano-Ag phase precipitated in the Cu matrix of the Cu-Ag-La alloy after aging treatment in Example 2 of the present invention; Figure 8 is the distribution of Cu in the Cu matrix of the Cu-Ag-La alloy after aging treatment in Example 2 of the present invention; Figure 9 is the distribution of the nano-Ag precipitated phase in the Cu matrix of the Cu-Ag-La alloy after aging treatment in Example 2 of the present invention; Figure 10 is the distribution of La in the Cu matrix of the Cu-Ag-La alloy after aging treatment in Example 2 of the present invention; Figure 11 It is the morphology of the twin structure generated after low-temperature rotary forging of the Cu-Ag-La alloy in Example 3 of the present invention; Figure 12 It is the morphology of the stacking fault and deformation twin coupling structure generated after low-temperature rotary forging of the Cu-Ag-La alloy in Example 3 of the present invention. Specific Embodiments

[0018] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] Example 1 A method for preparing a super-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation, see Figure 1 , which specifically includes the following steps: Step 1, preparing a Cu-Ag-RE alloy ingot by directional solidification process Using electrolytic Cu, high-purity Ag particles and Cu-RE master alloy as raw materials, weighing 6-20 wt.% Ag, 0.02-0.1 wt.% RE respectively by weight percentage, and the balance is Cu; adopting the directional solidification process, loading the weighed electrolytic Cu and high-purity Ag particles into a graphite crucible, after the furnace cavity is pre-evacuated, introducing argon as a protective gas, the melting temperature is 1100-1250 °C, after Cu and Ag are completely melted, holding for 10 min-30 min, during which the alloy melt is subjected to electromagnetic stirring every 3 min-5 min to ensure uniform melt composition, after the holding is completed, adding the Cu-RE master alloy to the alloy melt by a feeding device, heating up to 1350-1450 °C again, holding for 10 min-30 min, during which the alloy melt is continuously subjected to electromagnetic stirring, after the holding is completed, using a servo pulling mechanism to drag the graphite crucible containing the alloy melt into the liquid metal at a constant rate of 10-100 μm / s for directional solidification, obtaining a Cu-Ag-RE alloy ingot with a directional structure, and the diameter of the Cu-Ag-RE alloy ingot is 20 mm-60 mm; RE in the Cu-RE master alloy is rare earth La, Ce or Y, and the liquid metal is Ga-In-Sn or Ga-In.

[0020] Step 2, performing pre-deformation treatment on the Cu-Ag-RE alloy ingot obtained in Step 1, and the pre-deformation treatment is hot forging combined with equal-channel angular pressing or low-temperature rotary forging. The hot forging combined with equal-channel angular pressing includes first hot forging the Cu-Ag-RE alloy ingot and then performing equal-channel angular pressing; Hot forging is carried out on the Cu-Ag-RE alloy cast rod, including heating the temperature of the box resistance furnace to 700-800 °C, then putting the Cu-Ag-RE alloy cast rod into the furnace in the way of putting it into the furnace when the temperature reaches, keeping it warm for 10 min to 30 min to ensure uniform temperature distribution in the alloy cast rod, taking out the alloy cast rod and putting it into the forging die for hot forging. The deformation method is to forge along the radial direction, and rotate the alloy cast rod along the axial direction during hot forging, rotate 90° counterclockwise or clockwise, and the transformation frequency is single-pass forging or multi-pass forging in each direction. Keep it warm for 10 min to 30 min in each pass, and the forging ratio in each pass is 3% to 5%. Finally, a slab-shaped Cu-Ag-RE alloy blank with a thickness and width of 15 mm to 20 mm is obtained.

[0021] Equal-channel angular pressing includes putting the slab-shaped Cu-Ag-RE alloy blank after hot forging into the vertical channel entrance of the square-mouth die. The channel angle is 90-120°, and it is pressed at a speed of 100-300 mm / min. The pressing path is that the billet extruded each time rotates 90° in the opposite direction or the billet extruded each time rotates 180° in the same direction, and the number of pressing times is 3-5 times.

[0022] Low-temperature rotary forging: Pre-cool the rotary forging die for 10 min to 15 min before each pass. Soak the Cu-Ag-RE alloy in liquid nitrogen for 60 min to 120 min before each pass, then send the Cu-Ag-RE alloy into the rotary forging machine and feed it at a speed of 20-40 mm / s. The rotary forging ratio in each pass is 8% to 16%. Finally, a rotary-forged Cu-Ag-RE alloy rod with a diameter of 2 mm to 5 mm is obtained.

[0023] Step 3: Perform aging treatment on the Cu-Ag-RE alloy rod after pre-deformation treatment in step 2 in a rapid heat treatment furnace. The aging treatment temperature is 400-500 °C, and the holding time is 10 min to 20 min. The furnace charging method is to charge when the temperature reaches, and the cooling method is air cooling. Finally, cold rolling or cold drawing is carried out on the aged Cu-Ag-La alloy to obtain an ultra-high-strength and high-conductivity copper-silver alloy.

[0024] Example 2 A method for preparing an ultra-high-strength and high-conductivity copper-silver alloy by directional solidification combined with pre-deformation specifically includes the following steps: Step 1: Prepare a Cu-Ag-La alloy cast rod by directional solidification process Using electrolytic Cu, high-purity Ag particles, and a Cu-La master alloy as raw materials, the surface impurities of the raw materials were pre-cleaned and ultrasonically cleaned. Then, 12 wt.% Ag and 0.05 wt.% La were weighed according to weight percentage, and the balance was Cu. Using the directional solidification process, the weighed electrolytic Cu and high-purity Ag particles were loaded into a graphite crucible. After the furnace chamber was pre-evacuated, argon was introduced as a protective gas. The melting temperature was 1180 °C. After Cu and Ag were completely melted, it was held for 25 min. During this period, the alloy melt was subjected to electromagnetic stirring every 4 min to ensure uniform melt composition. After the holding was completed, the Cu-La master alloy was added to the alloy melt using a feeding device, and the temperature was raised to 1380 °C again and held for 15 min. During this period, the alloy melt was continuously subjected to electromagnetic stirring. After the holding was completed, the graphite crucible containing the alloy melt was dragged into the liquid metal Ga-In-Sn at a constant rate of 60 μm / s using a servo-pulling mechanism for directional solidification to obtain a Cu-Ag-La alloy ingot with a directional structure. The diameter of the Cu-Ag-La alloy ingot was 40 mm, and its directional microstructure was as shown in Figure 2 shown; Step 2: Perform hot forging combined with equal-channel angular pressing pre-deformation treatment on the Cu-Ag-La alloy ingot obtained in Step 1, including first hot forging the Cu-Ag-La alloy ingot and then performing equal-channel angular pressing; Hot forging the Cu-Ag-La alloy ingot includes raising the temperature of the box-type resistance furnace to 750 °C, and then putting the Cu-Ag-La alloy ingot into the furnace in the way of putting it into the furnace when the temperature reaches. Hold for 30 min to ensure uniform temperature distribution inside the alloy ingot. Take out the alloy ingot and put it into the forging die for hot forging. The deformation method is to forge along the radial direction. During hot forging, rotate the alloy ingot along the axial direction, rotate counterclockwise by 90 °, and the transformation frequency is to perform single-pass forging or multi-pass forging in each direction. Hold for 10 min for each pass, and the forging ratio for each pass is 5%. Finally, a slab-shaped Cu-Ag-La alloy blank with a cross-section of 16 mm × 16 mm is obtained.

[0025] Equal-channel angular pressing includes putting the hot-forged slab-shaped Cu-Ag-La alloy blank into the vertical channel entrance of a square die. The cross-section of the square die is 16 mm × 16 mm, and the channel angle is 90 °. Extrude at a speed of 300 mm / min. The extrusion path is that the billet extruded in each pass rotates 180 ° in the same direction, and it is extruded repeatedly 4 times to obtain the extruded Cu-Ag-La alloy.

[0026] Step 3: Perform aging treatment on the extruded Cu-Ag-La alloy in a rapid heat treatment furnace. Use the method of putting it into the furnace when the temperature reaches. The aging treatment temperature is 500 °C, and the aging time is 10 min. After the holding is completed, air-cool it. Finally, cold roll the aged Cu-Ag-La alloy to obtain an ultra-high-strength and high-conductivity copper-silver alloy sheet with a thickness of 0.4 mm.

[0027] The microstructure of the aged Cu-Ag-La alloy was characterized. The microstructure of the eutectic Ag phase is shown in Figures 3 - 6 , Figure 3 which is the morphology of the nano Cu phase precipitated in the eutectic Ag phase of the Cu-Ag-La alloy after aging treatment, Figures 4 - 6 and is the scanning transmission energy spectrum of the eutectic Ag phase of the Cu-Ag-La alloy after aging treatment (i.e., the STEM-EDS result). Figures 4 - 6 In , the red color represents the distribution of the nano Cu phase precipitated in the eutectic Ag phase, the yellow color represents the distribution of Ag in the eutectic Ag phase, and the green color represents the distribution of rare earth La in the eutectic Ag phase; The microstructure of the Cu matrix is shown in Figures 7 - 10 , Figure 7 which is the morphology of the nano Ag phase precipitated in the Cu matrix of the Cu-Ag-La alloy after aging treatment, Figures 8 - 10 and is the scanning transmission energy spectrum of the Cu matrix of the Cu-Ag-La alloy after aging treatment (i.e., the STEM-EDS result). Figures 8 - 10 In , the red color represents the distribution of Cu in the Cu matrix, the yellow color represents the distribution of the nano Ag phase precipitated in the Cu matrix, and the green color represents the distribution of rare earth La in the Cu matrix.

[0028] From Figures 3 - 6 it can be seen that the nano Cu phase precipitated in the eutectic Ag phase of the Cu-Ag-La alloy after aging treatment has a size of about 5-40 nm, and the rare earth La in the eutectic Ag phase is uniformly distributed; from Figures 7 - 10 it can be seen that the nano Ag precipitated phase in the Cu matrix has a size of about 40 nm and is distributed in a pearl necklace shape in the Cu matrix, and the rare earth La in the Cu matrix is uniformly distributed; from Figures 3 - 10 it can be seen that pre-deformation combined with aging treatment can promote the formation of nano-precipitated phases, thereby improving the mechanical properties of the material.

[0029] The electrical properties of the copper-silver alloy sheet prepared in Example 2 were tested, and its conductivity was measured to be 75.6% IACS. Its mechanical properties were tested, and its tensile strength was measured to be 1107.4 MPa.

[0030] Example 3 A method for preparing a super high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation specifically includes the following steps: Step 1, preparing a Cu-Ag-La alloy ingot by directional solidification process Using electrolytic Cu, high-purity Ag particles, and Cu-La master alloy as raw materials, weigh 6 wt.% Ag, 0.1 wt.% rare earth La, and the balance is Cu according to weight percentage; adopt the directional solidification process, put the weighed electrolytic Cu and high-purity Ag particles into a graphite crucible, after the furnace chamber is pre-evacuated, introduce argon as the protective gas, the melting temperature is 1120 °C, after Cu and Ag are completely melted, keep warm for 15 min, during which the alloy melt is subjected to electromagnetic stirring every 5 min to ensure uniform melt composition. After the heat preservation is over, use the feeding device to add Cu-La master alloy to the alloy melt, raise the temperature to 1400 °C again, keep warm for 30 min, during which the alloy melt is continuously subjected to electromagnetic stirring. After the heat preservation is over, use the servo pulling mechanism to drag the graphite crucible containing the alloy melt into the liquid metal Ga-In at a constant rate of 100 μm / s for directional solidification to obtain a Cu-Ag-La alloy ingot with a directional structure. The diameter of the Cu-Ag-La alloy ingot is 30 mm; Step 2, perform cryogenic rotary forging on the Cu-Ag-La alloy ingot obtained in Step 1. Pre-cool the rotary forging die before each pass, the pre-cooling time is 10 min. Before the first pass, pre-soak the Cu-Ag-La alloy in liquid nitrogen for 90 min, and then soak for 60 min for each subsequent pass. Send the Cu-Ag-La alloy into the rotary forging machine, feed at a speed of 40 mm / s, and the rotary forging ratio for each pass is 16%. Finally, obtain a rotary-forged Cu-Ag-La alloy with a diameter of 2 mm.

[0031] Perform TEM characterization on the microstructure of the rotary-forged Cu-Ag-La alloy, as Figure 11 and Figure 12 shown. It can be seen from Figure 11 that the Cu-Ag-La alloy forms a twin structure after cryogenic rotary forging. Combining Figure 12 it can be seen that the twins do not exist alone, but are coupled with stacking faults to form a "symbiotic" structure. Compared with the single twin structure, the "symbiotic" structure has a stronger improvement in mechanical properties.

[0032] Step 3, perform aging treatment on the rotary-forged Cu-Ag-La alloy in a rapid heat treatment furnace. Use the method of putting it into the furnace when reaching the temperature. The aging treatment temperature is 400 °C, the aging time is 20 min, after the heat preservation is over, air-cool it, and finally perform cold drawing on the aged Cu-Ag-La alloy to obtain an ultra-high strength and high conductivity copper-silver alloy wire with a diameter of 20 μm.

[0033] Perform electrical property testing on the copper-silver alloy wire / rod prepared in Example 3, and measure its conductivity to be 70.3% IACS. Perform mechanical property testing on it, and measure its tensile strength to be 1048.2 MPa.

[0034] Example 4 A method for preparing a super-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation, specifically including the following steps: Step 1, preparing a Cu-Ag-Ce alloy ingot by directional solidification process Using electrolytic Cu, high-purity Ag particles and Cu-Ce master alloy as raw materials, pre-cleaning the surface impurities of the raw materials and ultrasonic cleaning, and then weighing 6wt.% Ag, 0.1wt.% Ce respectively according to the weight percentage, and the balance is Cu; adopting the directional solidification process, loading the weighed electrolytic Cu and high-purity Ag particles into a graphite crucible, after the furnace cavity is pre-evacuated, introducing argon as the protective gas, the melting temperature is 1100 °C, after Cu and Ag are completely melted, holding for 30 min, during which the alloy melt is subjected to electromagnetic stirring every 3 min to ensure uniform melt composition, after the holding is completed, adding Cu-Ce master alloy into the alloy melt by using a feeding device, heating up to 1350 °C again, holding for 10 min, during which the alloy melt is continuously subjected to electromagnetic stirring, after the holding is completed, using a servo pulling mechanism to drag the graphite crucible containing the alloy melt into liquid metal Ga-In-Sn at a constant rate of 10 μm / s for directional solidification, obtaining a Cu-Ag-Ce alloy ingot with a directional structure, and the diameter of the Cu-Ag-Ce alloy ingot is 40 mm; Step 2, performing hot forging combined with equal-channel angular pressing pre-deformation treatment on the Cu-Ag-Ce alloy ingot obtained in Step 1, including first hot forging the Cu-Ag-Ce alloy ingot and then performing equal-channel angular pressing; Hot forging the Cu-Ag-Ce alloy ingot includes heating the temperature of a box-type resistance furnace to 700 °C, then putting the Cu-Ag-Ce alloy ingot into the furnace in the way of putting it into the furnace when the temperature reaches, holding for 20 min to ensure uniform temperature distribution in the alloy ingot, taking out the alloy ingot and putting it into a forging die for hot forging, the deformation method is to forge along the radial direction, rotating the alloy ingot along the axial direction during hot forging, rotating 90° clockwise, the transformation frequency is to perform multi-pass forging in each direction, holding for 20 min for each pass, and the forging ratio for each pass is 4%, finally obtaining a slab-shaped Cu-Ag-Ce alloy blank with a cross-section of 15 mm × 15 mm.

[0035] Equal-channel angular pressing includes putting the hot-forged slab-shaped Cu-Ag-Ce alloy blank into the vertical channel entrance of a square die, the cross-section of the square die is 15 mm × 15 mm, the channel angle is 90°, extruding at a speed of 200 mm / min, and the extrusion path is that the billet extruded in each pass rotates 90° in the opposite direction, and extruding repeatedly 3 times to obtain an extruded Cu-Ag-Ce alloy.

[0036] Step 3: Perform aging treatment on the extruded Cu-Ag-Ce alloy in a rapid thermal processing furnace. Use the method of putting the alloy into the furnace when it reaches the set temperature. The aging treatment temperature is 450 °C, the aging time is 15 min. After the heat preservation is completed, air cooling is carried out. Finally, cold rolling is performed on the aged Cu-Ag-Ce alloy to obtain an ultra-high strength and high conductivity copper-silver alloy sheet with a thickness of 0.3 mm.

[0037] Example 5 A method for preparing ultra-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation, specifically including the following steps: Step 1: Prepare a Cu-Ag-Y alloy ingot by directional solidification process Using electrolytic Cu, high-purity Ag particles and Cu-Y master alloy as raw materials, pre-clean the impurities on the surface of the raw materials and perform ultrasonic cleaning. Then, weigh 20 wt.% Ag, 0.02 wt.% Y respectively according to the weight percentage, and the balance is Cu; adopt the directional solidification process, put the weighed electrolytic Cu and high-purity Ag particles into a graphite crucible. After the furnace cavity is pre-evacuated, introduce argon as the protective gas. The melting temperature is 1250 °C. After Cu and Ag are completely melted, keep the temperature for 10 min. During this period, electromagnetic stirring is carried out on the alloy melt every 4 min to ensure the uniformity of the melt composition. After the heat preservation is completed, use the feeding device to add Cu-Y master alloy into the alloy melt, and then raise the temperature to 1450 °C again, keep the temperature for 30 min. During this period, electromagnetic stirring of the alloy melt is carried out continuously. After the heat preservation is completed, use the servo drawing mechanism to drag the graphite crucible containing the alloy melt into the liquid metal Ga-In-Sn at a constant rate of 50 μm / s for directional solidification to obtain a Cu-Ag-Y alloy ingot with a directional structure. The diameter of the Cu-Ag-Y alloy ingot is 60 mm; Step 2: Perform hot forging combined with equal-channel angular pressing pre-deformation treatment on the Cu-Ag-Y alloy ingot obtained in Step 1, including first performing hot forging on the Cu-Ag-Y alloy ingot, and then performing equal-channel angular pressing; Perform hot forging on the Cu-Ag-Y alloy ingot, including raising the temperature of the box-type resistance furnace to 750 °C, then putting the Cu-Ag-Y alloy ingot into the furnace by the method of putting it into the furnace when it reaches the set temperature, keep the temperature for 10 min to ensure uniform temperature distribution inside the alloy ingot. Take out the alloy ingot and put it into the forging die for hot forging. The deformation method is to forge along the radial direction. During the hot forging process, rotate the alloy ingot along the axial direction, rotate clockwise by 90 °, and the transformation frequency is to perform multi-pass forging in each direction. Keep the temperature for 10 min for each pass, and the forging ratio for each pass is 5%. Finally, obtain a slab-shaped Cu-Ag-Y alloy blank with a cross-section of 18 mm × 18 mm.

[0038] Equal-channel angular pressing includes putting a slab-shaped Cu-Ag-Y alloy blank after hot forging into the vertical channel entrance of a square die. The cross-section of the square die is 18 mm × 18 mm, the channel angle is 120°, extrusion is carried out at a speed of 100 mm / min, the extrusion path is that the blank extruded in each pass rotates 90° in the opposite direction, and extrusion is repeated 5 times to obtain an extruded Cu-Ag-Y alloy.

[0039] Step 3, solution treatment of the extruded Cu-Ag-Y alloy is carried out in a rapid heat treatment furnace by the method of putting it into the furnace when the temperature reaches. The solution treatment temperature is 400 °C, the solution treatment time is 20 min, after heat preservation, it is air-cooled, and finally the solution-treated Cu-Ag-Y alloy is cold-rolled to obtain an ultra-high strength and high conductivity copper-silver alloy sheet with a thickness of 0.5 mm.

[0040] Example 6 A method for preparing an ultra-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation specifically includes the following steps: Step 1, preparing a Cu-Ag-La alloy ingot by directional solidification process Using electrolytic Cu, high-purity Ag particles and Cu-La master alloy as raw materials, weighing 6 wt.% Ag, 0.1 wt.% rare earth La respectively according to weight percentage, and the balance is Cu; adopting the directional solidification process, loading the weighed electrolytic Cu and high-purity Ag particles into a graphite crucible, after the furnace chamber is pre-evacuated, introducing argon as a protective gas, the melting temperature is 1120 °C, after Cu and Ag are all melted, heat preservation is carried out for 15 min, during which the alloy melt is subjected to electromagnetic stirring every 5 min to ensure uniform melt composition, after heat preservation, the Cu-La master alloy is added to the alloy melt by a feeding device, and the temperature is raised to 1400 °C again, heat preservation is carried out for 30 min, during which the alloy melt is continuously subjected to electromagnetic stirring, after heat preservation, the graphite crucible containing the alloy melt is dragged into liquid metal Ga-In at a constant rate of 100 μm / s by a servo pulling mechanism for directional solidification to obtain a Cu-Ag-La alloy ingot with a directional structure, and the diameter of the Cu-Ag-La alloy ingot is 30 mm; Step 2, carrying out low-temperature rotary forging on the Cu-Ag-La alloy ingot obtained in Step 1, pre-cooling the rotary forging die before each pass, the pre-cooling time is 15 min, before the first pass, the Cu-Ag-La alloy pre-alloy is pre-soaked in liquid nitrogen for 120 min, and then soaked for 90 min in each subsequent pass, feeding the Cu-Ag-La alloy into a rotary forging machine, feeding at a speed of 20 mm / s, and the rotary forging ratio in each pass is 8%, finally obtaining a rotary-forged Cu-Ag-La alloy with a diameter of 5 mm.

[0041] Step 3: Perform aging treatment on the swaged Cu-Ag-La alloy in a rapid thermal processing furnace. Use the method of putting the sample into the furnace when it reaches the set temperature. The aging temperature is 500 °C, the aging time is 10 min, and after the heat preservation is completed, air cooling is carried out. Finally, cold drawing is performed on the aged Cu-Ag-La alloy to obtain an ultra-high strength and high conductivity copper-silver alloy wire / rod with a diameter of 22 μm.

Claims

1. A method for preparing an ultra-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation, characterized in that: The method comprises adopting a directional solidification process to prepare a Cu-Ag-RE alloy cast rod, wherein the Ag content in the cast rod is 6-20wt.%, the RE content is 0.02-0.1wt.%, and the balance is Cu, and the Cu-Ag-RE alloy cast rod is subjected to a pre-deformation treatment, including hot forging and coordinated equal-diameter angular extrusion or low-temperature rotary forging of the Cu-Ag-RE alloy cast rod, and then an aging treatment is performed, and finally the aged Cu-Ag-La alloy is cold rolled or cold drawn to obtain an ultra-high strength and high-conductivity copper-silver alloy.

2. The method for preparing an ultra-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation according to claim 1, characterized in that: The specific steps include: Step 1, using electrolytic Cu, high-purity Ag particles and Cu-RE master alloy as raw materials, and adopting a directional solidification process to prepare a Cu-Ag-RE alloy casting rod; Step 2, pre-deforming the Cu-Ag-RE alloy cast rod obtained in step 1, wherein the pre-deforming treatment is hot forging combined with equal-diameter angular extrusion or low-temperature rotary forging, wherein the hot forging combined with equal-diameter angular extrusion comprises first hot forging the Cu-Ag-RE alloy cast rod to obtain a slab-shaped Cu-Ag-RE alloy billet having a thickness and a width of 15 mm to 20 mm, and then performing equal-diameter angular extrusion on the slab-shaped Cu-Ag-RE alloy billet for 3 to 5 times; Step 3, performing aging treatment on the Cu-Ag-RE alloy bar after the pre-deformation treatment in step 2 in a rapid heat treatment furnace, and cold rolling or cold drawing the aged Cu-Ag-La alloy to obtain an ultra-high strength and high conductivity copper-silver alloy.

3. The method for preparing an ultra-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation according to claim 2, characterized in that: In the step 1, a directional solidification process is adopted to prepare a Cu-Ag-RE alloy cast rod, including loading electrolytic Cu and high-purity Ag particles in the raw materials into a graphite crucible, introducing argon as a protective gas after the furnace chamber is pre-vacuumed, and keeping the temperature for a period of time after Cu and Ag are completely melted, adding a Cu-RE intermediate alloy to the alloy melt, starting electromagnetic stirring and keeping the temperature for a period of time again, and then using a servo pulling mechanism to pull it into the liquid metal at a constant rate for directional solidification to obtain a Cu-Ag-RE alloy cast rod with a directional structure.

4. The method for preparing an ultra-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation according to claim 3, characterized in that: In the step 1, the directional solidification process adopts a liquid metal cooling method, the melting temperature is 1100-1250°C, and after Cu and Ag are completely melted, they are kept warm for 10-30 minutes, during which the alloy melt is electromagnetically stirred every 3-5 minutes to ensure that the melt composition is uniform. After the insulation is completed, a Cu-RE intermediate alloy is added to the alloy melt by a feeding device, and the temperature is raised to 1350-1450°C again, and kept warm for 10-30 minutes, during which the alloy melt is electromagnetically stirred continuously. After the insulation is completed, a servo pulling mechanism drags a graphite crucible containing the alloy melt into the liquid metal at a constant pulling rate of 10-100 μm / s for directional solidification to obtain a Cu-Ag-RE alloy cast rod with a diameter of 20 mm to 60 mm.

5. The method for preparing an ultra-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation according to claim 4, characterized in that: In the Cu-RE master alloy, RE is rare earth La, Ce or Y, and the liquid metal is Ga-In-Sn or Ga-In.

6. The method for preparing an ultra-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation according to claim 4, characterized in that: In the step 2, the Cu-Ag-RE alloy cast rod is hot forged, including raising the temperature of the box-type resistance furnace to 700-800°C, then placing the Cu-Ag-RE alloy cast rod into the furnace by the method of heating it to the temperature, keeping it warm for 10-30 minutes to ensure that the temperature distribution in the alloy cast rod is uniform, taking out the alloy cast rod and placing it into a forging die for hot forging, and deforming it by radial forging. During the hot forging process, the alloy cast rod is rotated axially by 90° counterclockwise or clockwise, and the switching frequency is single-pass forging or multi-pass forging in each direction, each pass is kept warm for 10-30 minutes, and the forging ratio of each pass is 3%-5%, and finally a slab-shaped Cu-Ag-RE alloy billet with a thickness and width of 15 mm to 20 mm is obtained.

7. The method for preparing an ultra-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation according to claim 6, characterized in that: In step 2, the equal-diameter angular extrusion includes placing the hot-forged plate-shaped Cu-Ag-RE alloy billet into the vertical channel inlet of the square-mouth die, the channel angle is 90 to 120 degrees, and extrusion is performed at a speed of 100 to 300 mm / min. The extrusion path is that the billet is rotated 90 degrees in the opposite direction each time it is extruded, or the billet is rotated 180 degrees in the same direction each time it is extruded.

8. The method for preparing an ultra-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation according to claim 7, characterized in that: In the step 2, low-temperature rotary forging is performed, and the rotary forging die is precooled before each pass, and the precooling time is 10 min to 15 min. Before each pass, the Cu-Ag-RE alloy is pre-immersed in liquid nitrogen for 60 min to 120 min, and then the Cu-Ag-RE alloy is fed into the rotary forging machine at a speed of 20 to 40 mm / s. The rotary forging ratio of each pass is 8% to 16%, and finally a rotary forging Cu-Ag-RE alloy rod with a diameter of 2 mm to 5 mm is obtained.

9. The method for preparing an ultra-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation according to claim 8, characterized in that: In step 3, the temperature of the aging treatment is 400-500° C., the holding time is 10-20 minutes, the furnace is put into the furnace at the temperature, and the cooling method is air cooling.

10. An ultra-high strength and high conductivity copper-silver alloy prepared by the method for preparing an ultra-high strength and high conductivity copper-silver alloy by directional solidification combined with pre-deformation as described in any one of claims 1 to 9.

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