A multi-level layered heterogeneous copper-aluminum composite material and its preparation method

Abstract

The present invention discloses a multi-level layered heterogeneous copper-aluminum composite material and a preparation method thereof. Using a "hot pressing sintering + rolling + heat treatment" composite control technology, the composite material exhibits a Cu / Al layered structure on a macroscopic scale. The Cu and Al layers exhibit a layered mixed crystal heterogeneity composed of ultrafine-grained lamellae and partially recrystallized lamellae on a microscopic scale. The interface exhibits a Cu / Al2Cu / Al layered heterogeneity on a microscopic scale. This results in the preparation of a multi-level layered heterogeneous copper-aluminum composite material that integrates excellent electrical and thermal conductivity with high-strength, plasticity, and toughness. This composite material effectively leverages the strengthening and toughening effects of its multi-level, multi-scale layered heterogeneity, achieving excellent performance with matched strength and plasticity, and is suitable for applications in aerospace, electrical appliances, and other fields.

Description

Technical Field

[0001] The present invention relates to the technical field of copper-aluminum composite material processing, and more particularly to a multi-level layered heterogeneous copper-aluminum composite material and a preparation method thereof. Background Art

[0002] With the urgent demand for lightweight and high-performance critical equipment in industries such as aerospace, transportation, and electronic communications, traditional single metal materials are unable to meet the comprehensive performance requirements. Copper-aluminum layered composites combine the advantages of copper's good electrical conductivity and high thermal conductivity with aluminum's light weight and high plasticity and toughness. They are structurally and functionally integrated composite materials with excellent overall performance and have broad application prospects in aerospace, electrical appliances, new energy vehicles, 5G communications, and other fields.

[0003] Vacuum hot pressing sintering technology can provide excellent thermodynamic and kinetic conditions for the preparation of composite materials. The higher sintering temperature and greater loading pressure provide the necessary advantages for atomic diffusion and effective interface bonding. Vacuum hot pressing sintering can achieve good bonding of the copper-aluminum interface, with excellent mechanical, electrical and thermal conductivity properties. In addition, the composite material has better tensile plasticity than pure copper and pure aluminum, but the tensile strength needs to be further improved to meet the comprehensive development requirements of the new generation of high-end equipment for lightweight, high-strength and tough copper-aluminum composite materials. The rolling method can effectively refine the grains of the copper and aluminum layers in the copper-aluminum composite material, thereby significantly improving the tensile strength of the material, but the tensile plasticity is significantly reduced, showing a clear strength-plasticity inversion relationship.

[0004] Therefore, how to further improve the tensile strength of copper-aluminum composite materials while maintaining their excellent tensile plasticity has become a scientific problem that urgently needs to be solved in copper-aluminum layered composite materials. Summary of the Invention

[0005] In order to address the deficiencies in the prior art, the present invention provides a multi-level layered heterogeneous copper-aluminum composite material and a preparation method thereof. The composite material presents a Cu / Al layered structure at a macroscopic level, and the Cu and Al layers present a layered mixed crystal isomerism composed of ultrafine grain lamellar sheets and partially recrystallized lamellar sheets at a microscopic level. The interface presents a Cu / Al2Cu / Al layered composite isomerism at a microscopic level. The composite material can effectively exert the strengthening and toughening effect of the multi-level and multi-scale layered heterogeneity, and obtain excellent performance with matching strength and plasticity.

[0006] In order to achieve the above object, the specific scheme adopted by the present invention is:

[0007] A multi-level layered heterogeneous copper-aluminum composite material, wherein the composite material presents a Cu / Al layered structure at a macroscopic level, the Cu and Al layers present a layered mixed crystal isomerism composed of ultrafine grain lamellae and partially recrystallized lamellae at a microscopic level, and the interface presents a Cu / Al2Cu / Al layered composite isomerism at a microscopic level.

[0008] As a preferred solution, the Cu layer of the composite material has a macroscopic thickness of 1 to 2 mm, and the Al layer has a macroscopic thickness of 5 to 7 mm.

[0009] As a preferred embodiment, in the layered mixed crystal heterogeneous Cu layer and Al layer composed of ultrafine grained lamellae and partially recrystallized lamellae, the distance between adjacent recrystallized lamellae is less than 5 μm.

[0010] As a preferred solution, the thickness of Al2Cu at the interface of the composite material is 200-300 nm.

[0011] A method for preparing a multi-level layered heterogeneous copper-aluminum composite material mainly comprises the following steps:

[0012] Step 1: Ingredients: Use industrial pure copper plate and pure aluminum plate as raw materials, cut samples for standby use, and then pre-treat the surface of the copper and aluminum plates;

[0013] Step 2: Sintering: First, the pretreated copper plate and aluminum plate are placed in a graphite mold for vacuum hot pressing and sintering. Under the action of high temperature, high pressure, and interfacial heat and mass transfer, the copper and aluminum atoms in the two layers of the interface diffuse with each other, thereby achieving effective bonding of the interface and preparing the first copper-aluminum composite plate with uniform coarse-grained structure.

[0014] Step 3, cold rolling: The equipment adopts a double-roll asynchronous rolling mill to first perform surface decontamination treatment on the first copper-aluminum composite plate, and then perform asynchronous multi-pass hard plate rolling (HPR) treatment at room temperature to obtain a second copper-aluminum composite plate with ultrafine grain lamellar structure in the copper layer and the aluminum layer.

[0015] Step 4: Heat treatment: subjecting the second copper-aluminum composite plate to a high-temperature homogenization annealing treatment to recover and recrystallize some of the ultrafine-grained lamellar lamellar structures in the copper layer and the aluminum layer, thereby preparing a multi-level layered heterogeneous copper-aluminum composite material.

[0016] As a preferred solution, the pretreatment method in step one is: use mechanical grinding to remove the oxide layer on the surface of the pure copper plate and the pure aluminum plate, and then place them in acetone and alcohol solutions in turn for ultrasonic decontamination treatment and blow dry for use.

[0017] As a preferred solution, in step 2, the vacuum hot pressing sintering temperature is 520°C and the vacuum degree is 3.5×10 -2 ~2.1×10 -1The holding time is 10 min and the sintering pressure is 60 MPa. This hot pressing composite technology can effectively achieve effective diffusion bonding of pure copper plates and pure aluminum plates.

[0018] As a preferred embodiment, in step 2, the thickness of the first copper-aluminum composite plate obtained by vacuum hot pressing and sintering is 6 to 9 mm, of which the copper strip thickness accounts for 10% to 25%, the grain size of the aluminum layer is 0.5 to 2.0 μm, and the grain size of the copper layer is 1.0 to 2.5 μm.

[0019] As a preferred solution, in step three, the surface of the first copper-aluminum composite plate is decontaminated and subjected to asynchronous multi-pass hard plate rolling (HPR) treatment, wherein the speed ratio of the upper and lower rollers is 1: (1.15 to 1.25), and the reduction rate of the composite plate after the rolling process is 60% to 80%. The purpose is to obtain ultrafine-grained lamellar structure in both the Cu layer and the Al layer of the copper-aluminum composite plate. The specific method is: using hardened steel PH15-7Mo as the upper and lower rolling plates, the thickness of which is 2mm, the hardened steel PH15-7Mo is sandwiched with the first copper-aluminum composite plate and fed from the rolling mill entrance for rolling. The present invention uses hardened steel plates to assist in rolling, mainly because the room temperature elongation of copper and aluminum is different, especially when large rolling deformation occurs, it will cause severe bending of the copper-aluminum composite plate.

[0020] As a preferred solution, in step three, the copper layer and aluminum layer of the composite plate are rolled simultaneously using two sets of upper and lower rollers to obtain an ultrafine-grained lamellar structure, wherein the grain size of the aluminum layer is 0.1-0.5 μm and the grain size of the copper layer is 0.2-1.0 μm.

[0021] As a preferred embodiment, in step 4, the second copper-aluminum composite plate is placed in a heat treatment furnace for high-temperature homogenization annealing at a temperature of 300-450°C for 5 minutes to 1 hour. This is to partially recover and recrystallize the fine-grained lamellar structure obtained by cold rolling, thereby obtaining a heterogeneous layered, heterogeneous copper-aluminum composite material composed of alternating coarse-grained and fine-grained layers.

[0022] As a preferred embodiment, in step four, the ratio of partially recrystallized lamellar structure to ultrafine grain lamellar structure of the copper layer and the aluminum layer is 1:(3-5), wherein the ultrafine grain lamellar spacing is 1-3 μm, and the average crystal size of the partially recrystallized lamellar is less than 3 μm.

[0023] Beneficial effects:

[0024] Based on the concept of multi-level, multi-scale layered heterogeneity, this invention utilizes a composite control technology of "hot pressing, sintering, rolling, and heat treatment" to achieve a composite material with a macroscopic Cu / Al layered structure. The Cu and Al layers exhibit a microscopic layered mixed-crystal heterogeneity composed of ultrafine-grained lamellae and partially recrystallized lamellae, and a microscopic Cu / Al2Cu / Al layered heterogeneity at the interface. This results in a multi-level layered heterogeneous copper-aluminum composite material with excellent comprehensive mechanical properties. Compared to traditional single composite preparation techniques, this improves the composite material's strength while maintaining a certain level of plasticity and toughness, effectively achieving the goal of matching strength and plasticity. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The figure is a schematic diagram of the process flow for preparing the copper-aluminum composite material according to the present invention.

[0026] Figure 2 Schematic diagram of the preparation process of the copper-aluminum composite material of the present invention. DETAILED DESCRIPTION

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0028] A multi-level layered heterogeneous copper-aluminum composite material presents a Cu / Al layered structure at a macroscopic level, wherein the Cu and Al layers present a layered mixed crystal isomerism composed of ultrafine grained lamellae and partially recrystallized lamellae at a microscopic level, and a Cu / Al2Cu / Al layered composite isomerism at a microscopic level.

[0029] The composite material has a Cu layer thickness of 1 to 2 mm and an Al layer thickness of 5 to 7 mm.

[0030] In the layered mixed-crystal heterogeneous Cu and Al layers composed of ultrafine-grained lamellae and partially recrystallized lamellae, the spacing between adjacent recrystallized lamellae is less than 5 μm.

[0031] The thickness of Al2Cu at the interface of the composite material is 200-300nm.

[0032] A method for preparing a multi-layered heterogeneous copper-aluminum composite material, please refer to Figure 1 and Figure 2 , mainly including the following steps:

[0033] Step 1: Prepare the ingredients: Cut the industrial pure copper plate and pure aluminum plate as raw materials, remove the oxide layer on the surface of the pure copper plate and aluminum plate by mechanical grinding, then place them in acetone and alcohol solution for ultrasonic decontamination treatment and blow dry for later use;

[0034] Step 2: Sintering: First, place the pre-treated copper and aluminum plates into a Φ30mm graphite mold and sinter them under a vacuum of 3.5×10 -2 ~2.1×10 -1 Pa furnace for hot pressing sintering, with a holding time of 10 minutes and a sintering pressure of 60MPa. Under the action of high temperature, high pressure, and interfacial heat and mass transfer, the copper and aluminum atoms of the two layers of the interface diffuse with each other, thereby achieving effective bonding of the interface and preparing the first copper-aluminum composite plate with uniform coarse-grained structure. The thickness of the first copper-aluminum composite plate is 6 to 9 mm, of which the copper strip thickness accounts for 10% to 25%, the grain size of the aluminum layer is 0.5 to 2.0 μm, and the grain size of the copper layer is 1.0 to 2.5 μm;

[0035] Step 3, cold rolling: The first copper-aluminum composite plate is first subjected to surface decontamination treatment, and then asynchronous multi-pass hard plate rolling treatment is performed at room temperature, the speed ratio of the upper and lower rollers is 1: (1.15-1.25), and 2 mm thick hardened steel PH15-7Mo is used as the upper and lower rolling plates. The hardened steel PH15-7Mo is sandwiched between the first copper-aluminum composite plate and fed from the inlet of the double-roller asynchronous rolling mill for rolling. The copper layer and the aluminum layer of the composite plate are rolled simultaneously by the upper and lower sets of rollers. After the cold rolling process, the reduction rate of the composite plate is 60% to 80%, thereby obtaining a second copper-aluminum composite plate with ultrafine grain lamellar structure in the copper layer and the aluminum layer; wherein the grain size of the aluminum layer is 0.1 to 0.5 μm, and the grain size of the copper layer is 0.2 to 1.0 μm;

[0036] Step 4, heat treatment: the second copper-aluminum composite plate is kept at 300 ° C to 450 ° C for 5 minutes to 1 hour for high temperature homogenization annealing treatment, so that part of the ultrafine grain lamellar structure of the copper layer and the aluminum layer is recovered and recrystallized, thereby preparing a multi-level layered heterogeneous copper-aluminum composite material; wherein the ratio of the partially recrystallized lamellar structure to the ultrafine grain lamellar structure of the copper layer and the aluminum layer is 1: (3 to 5), wherein the ultrafine grain lamellar spacing is 1 to 3 μm, and the average crystal size of the partially recrystallized lamellar structure is less than 3 μm.

[0037] The technical solutions in the embodiments of the present invention are described clearly and completely below.

[0038] Example 1

[0039] A method for preparing a multi-layered heterogeneous copper-aluminum composite material, please refer to Figure 1 and Figure 2 , mainly including the following steps:

[0040] Step 1. Ingredients: Use industrial pure copper plates and pure aluminum plates as raw materials, cut samples for later use, and then pretreat the surface of the plates; the pretreatment method is: use mechanical grinding to remove the oxide layer on the surface of the pure copper plates and pure aluminum plates, and then place them in acetone and alcohol solutions in turn for ultrasonic decontamination treatment and blow dry for later use.

[0041] Step 2: Sintering: Place the pre-treated copper and aluminum plates into a Φ30mm graphite mold and sinter them under a vacuum of 3.5×10 -2 ~2.1×10 -1 Hot pressing and sintering were performed in a furnace at 1000 Pa, with a holding time of 10 minutes and a sintering pressure of 60 MPa. Under the action of high temperature, high pressure, and interfacial heat and mass transfer, the copper and aluminum atoms in the two layers of the interface diffused into each other, thereby achieving effective interface bonding and preparing the first copper-aluminum composite plate with a uniform coarse-grained structure. The thickness of the first copper-aluminum composite plate was 8 mm, of which the thickness of the Al2Cu at the interface was 200-300 nm, the copper strip thickness accounted for approximately 15%, the grain size of the aluminum layer was 0.5-2.0 μm, and the grain size of the copper layer was 1.0-2.5 μm.

[0042] Step 3: Cold rolling: The equipment uses a twin-roll asynchronous rolling mill to perform asynchronous multi-pass hard plate rolling (HPR) on the first copper-aluminum composite plate at room temperature. The speed ratio of the upper and lower rollers is 1:1.25. After the rolling process, the composite plate has a reduction ratio of approximately 60%, resulting in a second copper-aluminum composite plate (the grain size of the aluminum layer is 0.1-0.5μm, and the grain size of the copper layer is 0.2-1.0μm). The specific implementation method is as follows: using hardened steel PH15-7Mo as the upper and lower rolling plates, with a thickness of approximately 2mm, the hardened steel PH15-7Mo is sandwiched between the first copper-aluminum composite plate and fed from the rolling mill entrance for rolling;

[0043] Step 4: Heat Treatment: The second copper-aluminum composite plate is annealed at 300°C for 5 minutes to cause the ultrafine-grained lamellar structures in the copper and aluminum layers to recrystallize, thereby producing a multi-level layered heterogeneous copper-aluminum composite material. Under these heat treatment conditions, the ratio of recrystallized lamellar structure to ultrafine-grained lamellar structure is 1:3, and the recrystallized lamellar grain size is approximately 1.5μm.

[0044] Example 2

[0045] The method for preparing the multi-level layered heterogeneous copper-aluminum composite material of this embodiment is identical to steps 1 through 3 in Example 1, except that the annealing temperature is 300°C and the annealing time is 30 minutes. Under these heat treatment conditions, the ratio of recrystallized lamellar structure to ultrafine-grained lamellar structure is 1:4, and the recrystallized lamellar grain size is approximately 1.8 μm.

[0046] Example 3

[0047] In this example, the method for preparing the multi-level layered heterogeneous copper-aluminum composite material follows the same procedures as steps 1 to 3 in Example 1, except that the annealing temperature is 350°C and the annealing time is 30 minutes. Under these heat treatment conditions, the ratio of recrystallized lamellar structure to ultrafine-grained lamellar structure is 1:4, and the recrystallized lamellar grain size is approximately 2 μm.

[0048] Example 4

[0049] In this example, the method for preparing the multi-level layered heterogeneous copper-aluminum composite material follows the same procedures as steps 1 to 3 in Example 1, except that the annealing temperature is 400°C and the annealing time is 1 hour. Under these heat treatment conditions, the ratio of recrystallized lamellar structure to ultrafine-grained lamellar structure is 1:5, and the recrystallized lamellar grain size is approximately 2.7 μm.

[0050] Example 5

[0051] In this example, the method for preparing the multi-level layered heterogeneous copper-aluminum composite material follows the same procedures as steps 1 to 3 in Example 1, except that the annealing temperature is 400°C and the annealing time is 1 hour. Under these heat treatment conditions, the ratio of recrystallized lamellar structure to ultrafine-grained lamellar structure is 1:5, and the recrystallized lamellar grain size is approximately 2.5 μm.

[0052] Comparative Example

[0053] The method for preparing a multi-level layered heterogeneous copper-aluminum composite material in this embodiment differs from that in Example 1 in that, in step 3, the first copper-aluminum composite sheet is directly rolled using rollers using an asynchronous rolling method. During the rolling process, the copper-aluminum composite sheet bends and deforms, resulting in uneven deformation of the copper and aluminum layers and significant stress concentration. In this embodiment, the annealing temperature is 300°C and the annealing time is 5 minutes. Under these heat treatment conditions, the ratio of recrystallized lamellar structure to ultrafine-grained lamellar structure is 1:3, and the recrystallized lamellar grain size is approximately 2.8 μm.

[0054] Performance Testing

[0055] The tensile strength and elongation at break of the copper-aluminum composite materials prepared in Examples 1-5 and the comparative example were tested, and the results are shown in Table 1.

[0056] Table 1 Test results of tensile strength and elongation at break of copper-aluminum composite materials prepared in Examples 1-5 and Comparative Examples

[0057]

[0058] In summary, the copper-aluminum composite material prepared by the preparation method of the present invention has a good matching relationship between strength and plasticity and toughness, and when asynchronous multi-pass hard plate rolling (HPR) treatment is adopted and the annealing process parameters are 300℃ / 5min, the prepared multi-level layered heterogeneous copper-aluminum composite material has the best strength and plasticity matching and has excellent comprehensive mechanical properties.

[0059] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any equivalent changes or modifications made based on the essence of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-level layered heterogeneous copper-aluminum composite material, characterized by: The composite material presents a Cu / Al layered structure at a macroscopic level, the Cu and Al layers present a layered mixed crystal isomerism composed of ultrafine grain lamellae and partially recrystallized lamellae at a microscopic level, and a Cu / Al2Cu / Al layered composite isomerism at a microscopic level; The preparation method of the multi-level layered heterogeneous copper-aluminum composite material comprises the following steps: Step 1: Ingredients: Use industrial pure copper plates and pure aluminum plates as raw materials, cut samples for standby use, and then pre-treat the plate surface; Step 2: Sintering: First, the pretreated copper plate and aluminum plate are placed in a graphite mold for vacuum hot pressing and sintering. Under the action of high temperature and high pressure as well as interfacial heat and mass transfer, the copper and aluminum atoms of the two layers at the interface diffuse with each other, thereby achieving effective bonding of the interface and preparing a first copper-aluminum composite plate with uniform coarse-grained structure. Step 3, cold rolling: The first copper-aluminum composite plate is first subjected to surface decontamination treatment, and then subjected to asynchronous multi-pass hard plate rolling at room temperature. The speed ratio of the upper and lower rollers is 1: (1.15-1.25). The reduction rate of the composite plate after the cold rolling process is 60%-80%, thereby obtaining a second copper-aluminum composite plate having ultrafine grain lamellar structure in the copper layer and the aluminum layer; Step 4: Heat treatment: The second copper-aluminum composite plate is subjected to high-temperature homogenization annealing treatment at 300°C to 450°C for 5 minutes to 1 hour, so that the ultrafine-grained lamellar structures of the copper layer and the aluminum layer undergo recovery recrystallization, thereby preparing a multi-level layered heterogeneous copper-aluminum composite material; In step 4, the ratio of partially recrystallized lamellar structure to ultrafine grain lamellar structure of the copper layer and the aluminum layer is 1:(3~5), wherein the ultrafine grain lamellar spacing is 1~3μm, and the average crystal size of the partially recrystallized lamellar is less than 3μm.

2. The multi-level layered heterogeneous copper-aluminum composite material according to claim 1, characterized in that: The composite material has a Cu layer thickness of 1-2 mm and an Al layer thickness of 5-7 mm.

3. The multi-level layered heterogeneous copper-aluminum composite material according to claim 1, characterized in that: In the layered mixed-crystal heterogeneous Cu and Al layers composed of ultrafine-grained lamellae and partially recrystallized lamellae, the spacing between adjacent recrystallized lamellae is less than 5 μm.

4. The multi-level layered heterogeneous copper-aluminum composite material according to claim 1, characterized in that: The thickness of Al2Cu at the interface of the composite material is 200~300nm.

5. The multi-level layered heterogeneous copper-aluminum composite material according to claim 1, characterized in that: In step 1, the pretreatment method is: use mechanical grinding to remove the oxide layer on the surface of the pure copper plate and the pure aluminum plate, and then place them in acetone and alcohol solutions in turn for ultrasonic decontamination treatment and blow dry for use.

6. The multi-level layered heterogeneous copper-aluminum composite material according to claim 1, characterized in that: In step 2, the vacuum hot pressing sintering temperature is 520°C and the vacuum degree is 3.5×10 -2 ~2.1×10 -1 Pa, the holding time is 10min, and the sintering pressure is 60MPa.

7. The multi-level layered heterogeneous copper-aluminum composite material according to claim 1, characterized in that: In step 2, the thickness of the first copper-aluminum composite plate is 6-9 mm, of which the copper layer accounts for 10%-25% of the thickness, the aluminum layer has a grain size of 0.5-2.0 μm, and the copper layer has a grain size of 1.0-2.5 μm.

8. The multi-level layered heterogeneous copper-aluminum composite material according to claim 1, characterized in that: In step three, 2mm-thick hardened PH15-7Mo steel is used as the upper and lower rolling plates. The hardened PH15-7Mo steel is sandwiched between the first copper-aluminum composite plate and fed through the inlet of a twin-roll asynchronous rolling mill for rolling. The upper and lower sets of rollers simultaneously roll the copper and aluminum layers of the composite plate to obtain an ultrafine-grained lamellar structure. The grain size of the aluminum layer is 0.1~0.5μm, and the grain size of the copper layer is 0.2~1.0μm.

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