Processing method of cast-rolled Al / Cu composite board with high interface bonding strength

Abstract

The invention discloses a processing method of a cast-rolled Al / Cu composite board with high interface bonding strength. The method comprises the following operation steps: polishing the surface of a cast-rolled Al / Cu composite plate to remove an oxide layer, and carrying out annealing treatment in a heat treatment furnace; the annealed Al / Cu composite board is subjected to cold rolling twice; and then secondary annealing is conducted for 3 h at the temperature of 250 DEG C. Annealing treatment and multi-pass cold rolling treatment are carried out on the Al / Cu composite board prepared through the cast rolling technology, heat treatment promotes interface atoms to diffuse to generate metallurgical bonding, the thickness of the board is reduced through rolling, and interfaces are meshed with one another under the action of rolling stress; not only is the bonding strength of the interface of the Al / Cu composite board improved, but also good tensile strength and plasticity are kept; according to the method, the requirement for rolling mill equipment is low, and Al / Cu composite boards with different thicknesses can be flexibly prepared; according to the method, the requirement for machining equipment is simple, the machining efficiency is high, the interface bonding performance of the Al / Cu composite board is effectively improved, and meanwhile good strength and plasticity are reserved.

Description

Technical Field

[0001] The invention belongs to the field of multi-metal composite materials and relates to a processing method for a cast-rolled Al / Cu composite plate with high interface bonding strength. Background Art

[0002] Al / Cu bimetallic composite plate is an advanced metal layered composite material, which combines the high electrical and thermal conductivity of copper with the low density and low price of aluminum, making aluminum and copper take advantage of each other in terms of performance and cost, and obtain good comprehensive performance. At the same time, replacing copper with aluminum helps to optimize the utilization of national copper resources and promote the industrial structure adjustment of the non-ferrous metal industry. Al / Cu composite plate can reduce weight by 30-50% and reduce cost by about 40-60%. It has been widely used in power batteries, photovoltaic power generation, aerospace, power electronics, communication devices and architectural decoration.

[0003] Al / Cu composite plates need to be rolled to reduce thickness for practical use. However, during the rolling process, the Al / Cu composite plates have problems such as low interface bonding strength and easy interface cracking. Usually, Al / Cu composite plates are rolled with a large deformation rate, which has high requirements on the equipment of the rolling mill, and one-time processing is not conducive to interface bonding. Summary of the invention

[0004] In view of the above problems, the present invention aims to provide a processing method with high processing efficiency and improved interface bonding strength of Al / Cu composite plates.

[0005] The technical solution of the present invention is: a processing method of a cast-rolled Al / Cu composite plate with high interface bonding strength according to the present invention comprises the following steps: grinding the surface of the cast-rolled Al / Cu composite plate to remove the oxide layer, annealing the surface in a heat treatment furnace, and grinding the surface with sandpaper to remove the oxide layer;

[0006] Then the annealed Al / Cu composite plate is subjected to two cold rolling treatments;

[0007] The Al / Cu composite plate after cold rolling is subjected to secondary annealing, and the surface is polished with sandpaper to remove the oxide layer, thereby obtaining an Al / Cu composite plate with high interface bonding strength.

[0008] Furthermore, the Al / Cu composite plate is prepared by a casting and rolling process, in which molten aluminum is cast on a surface-treated solid copper strip and introduced into a roller with cooling water circulation inside for rolling. After the aluminum liquid contacts the roller, it quickly cools and solidifies, and after rolling, it is prepared into an Al / Cu composite plate of the required thickness.

[0009] Furthermore, the thickness of the original sample of the cast-rolled Al / Cu composite plate is 3-7 mm, the Al plate is 1060 aluminum, and the Cu plate is T2 pure copper.

[0010] Furthermore, the temperatures of the two heat treatments are 240 - 260 °C, the heat treatment time is 2 - 3.5 h, the optimal heat treatment temperature is 250 °C, and the heat treatment time is 3 h.

[0011] Furthermore, the cold rolling treatment is carried out by using a two - roll cold rolling experimental machine for two cold rollings. The single - pass rolling rate is 35%, the total rolling rate is 70%, and the rolling speed is 10 mm / s.

[0012] Furthermore, after the cold rolling and two heat treatment processes, the maximum interfacial bonding strength of the Al / Cu composite plate reaches 93.49 MPa, and the tensile strength and elongation are 154.80 MPa and 36.92% respectively.

[0013] Furthermore, the primary IMC formed during the first annealing in the processing of the cast - rolled Al / Cu composite plate is broken during the cold rolling process and forms a serrated structure with the matrix at the interface. The secondary annealing forms a thin secondary IMC, enabling good metallurgical bonding at the interface.

[0014] The preparation principle of the present invention: During the heat treatment process of the Al / Cu composite plate, intermetallic compound transformation occurs at the interface, forming a diffusion layer. Within a certain thickness, the hard and brittle diffusion layer realizes metallurgical bonding, improving the interfacial bonding strength. At the same time, the heat treatment can also eliminate the residual strain generated during the cast - rolling and cold - rolling processes and cause recovery and recrystallization to refine the grains. During the cold rolling process, the aluminum plate and the copper plate deform synergistically, and at the same time, the interfaces bite each other under the action of rolling stress.

[0015] The present invention adopts a combination of annealing treatment and cold rolling treatment processes. Without reducing (even improving) the tensile strength and plasticity of the Al / Cu composite plate, it improves the interfacial bonding performance of the Al / Cu composite plate and solves the problem of easy cracking at the interface during the processing of the Al / Cu composite plate.

[0016] The beneficial effects of the present invention are as follows: Annealing treatment and multi - pass cold rolling treatment are carried out on the Al / Cu composite plate prepared by the cast - rolling process. The heat treatment promotes the atomic diffusion at the interface to achieve metallurgical bonding, and the rolling reduces the thickness of the plate and makes the interfaces bite each other under the action of rolling stress; not only improves the interfacial bonding strength of the Al / Cu composite plate, but also retains good tensile strength and plasticity; the present invention has simple requirements for rolling mill equipment, a simple processing flow, high processing efficiency, and can flexibly prepare Al / Cu composite plates with different thicknesses. Brief Description of the Drawings

[0017] Figure 1 It is the interfacial microstructure morphology diagram of Example 1 in the present invention;

[0018] Figure 2It is the interfacial microstructure morphology diagram of Example 2 in the present invention;

[0019] Figure 3 It is the interfacial microstructure morphology diagram of Example 3 in the present invention;

[0020] Figure 4 It is the interfacial microstructure morphology diagram of Example 4 in the present invention;

[0021] Figure 5 It is the TEM diagram of the interface at 250°C heat treatment for 3h in the present invention;

[0022] Figure 6 It is the TEM diagram of the interface of the as-cast-rolled Al / Cu composite plate in the present invention. Detailed implementation manners

[0023] The following further elaborates on the specific technical solutions of the present invention in conjunction with specific examples.

[0024] Example 1

[0025] A processing method for a cast-rolled Al / Cu composite plate with high interfacial bonding strength includes the following steps:

[0026] (1). Anneal the 7-mm-thick cast-rolled Al / Cu composite plate at 250°C for 3h, and use sandpaper to polish off the surface oxide layer; a 1.36-μm diffusion layer is formed at the Al / Cu composite plate interface, and the tensile strength of the annealed Al / Cu composite plate is measured to be 138.83 MPa, and the elongation is 43.94%;

[0027] (2). Cold-roll the annealed Al / Cu composite plate 7 times, with a single-pass rolling rate of 10% and a total rolling rate of 70%;

[0028] (3). After cold-rolling, perform secondary annealing at 250°C for 3h. The interfacial bonding strength is measured to be 39.10 MPa, and the interfacial microstructure morphology is as Figure 1 shown. Cold rolling causes the diffusion layer generated during the first annealing process to break, and cracks expand along the direction perpendicular to the diffusion layer until they contact the metal matrices on both sides and stop, causing the diffusion layer to transform into individual intermetallic compound fragments. Cold rolling causes the matrix metals on both sides to squeeze into the gaps between the intermetallic compound fragments, but there are voids at the ends of the broken IMC fragments, and the matrix metals on both sides do not contact and bond. The second annealing enables the matrix metals in contact in the gaps between the broken intermetallic compound fragments to form a thin diffusion layer to achieve metallurgical bonding, and at the same time reduces a large amount of residual stress generated during the rolling process.

[0029] Example 2

[0030] A processing method for a cast-rolled Al / Cu composite plate with high interfacial bonding strength, comprising the following steps:

[0031] (1) Anneal the cast-rolled Al / Cu composite plate with a thickness of 7 mm at 250 °C for 3 h, and polish the surface oxide layer with sandpaper; a diffusion layer with a thickness of 1.36 μm is formed at the interface of the Al / Cu composite plate. The tensile strength of the annealed Al / Cu composite plate is measured to be 138.83 MPa, and the elongation is 43.94%;

[0032] (2) Cold-roll the annealed Al / Cu composite plate 4 times, with a single-pass rolling rate of 18% and a total rolling rate of 72%;

[0033] (3) After cold-rolling, perform secondary annealing at 250 °C for 3 h. The interfacial bonding strength is measured to be 64.57 MPa, and the microstructure morphology at the interface is as Figure 2 shown. Cold rolling causes the diffusion layer generated during the first annealing process to break, forming individual intermetallic compound fragments. With the increase in the single-pass rolling rate, greater shear stress is generated at the interface, causing the broken intermetallic compound fragments to rotate. At the same time, cold rolling causes the matrix metals on both sides to squeeze into the gaps between the intermetallic compound fragments; secondary annealing enables the matrix metals in contact in the gaps between the broken intermetallic compound fragments to form a thin diffusion layer to achieve metallurgical bonding, reducing the defects at the interface and reducing a large amount of residual stress generated during the rolling process.

[0034] Example 3

[0035] A processing method for a cast-rolled Al / Cu composite plate with high interfacial bonding strength, comprising the following steps:

[0036] (1) Anneal the cast-rolled Al / Cu composite plate with a thickness of 7 mm at 250 °C for 3 h, and polish the surface oxide layer with sandpaper; a diffusion layer with a thickness of 1.36 μm is formed at the interface of the Al / Cu composite plate. The tensile strength of the annealed Al / Cu composite plate is measured to be 138.83 MPa, and the elongation is 43.94%;

[0037] (2) Cold-roll the annealed Al / Cu composite plate 3 times, with a single-pass rolling rate of 24% and a total rolling rate of 72%;

[0038] (3) After cold-rolling, perform secondary annealing at 250 °C for 3 h. The interfacial bonding strength is measured to be 78.29 MPa, and the microstructure morphology at the interface is as Figure 3As shown in the figure, cold rolling treatment causes the diffusion layer generated during the first annealing process to break, forming individual intermetallic compound fragments. With a further increase in the single-pass rolling rate, the greater shear stress at the interface causes the rotation angle of the broken intermetallic compound fragments to increase. At the same time, cold rolling causes the matrix metals on both sides to squeeze into the gaps between the intermetallic compound fragments. The increase in the single-pass rolling rate results in an increase in the vertical compressive stress at the interface, enhancing the mechanical bonding effect of the matrix metals at the gaps, which is more conducive to the mutual diffusion of metal atoms during the second annealing process to achieve metallurgical bonding. Meanwhile, it reduces the defects at the interface and a large amount of residual stress generated during the rolling process.

[0039] Example 4

[0040] A processing method for a cast-rolled Al / Cu composite plate with high interface bonding strength includes the following steps:

[0041] (1) Anneal a 7-mm-thick cast-rolled Al / Cu composite plate at 250 °C for 3 h, and use sandpaper to polish and remove the surface oxide layer; a 1.36-μm diffusion layer is formed at the interface of the Al / Cu composite plate. The tensile strength of the annealed Al / Cu composite plate is measured to be 138.83 MPa, and the elongation is 43.94%.

[0042] (2) Cold roll the annealed Al / Cu composite plate twice, with a single-pass rolling rate of 35% and a total rolling rate of 70%.

[0043] (3) After cold rolling treatment, perform secondary annealing treatment at 250 °C for 3 h. The measured interface bonding strength is 93.49 MPa, and the microstructure morphology at the interface is as Figure 4 shown in the figure. Cold rolling treatment causes the diffusion layer generated during the first annealing process to break, forming individual intermetallic compound fragments. With a further increase in the single-pass rolling rate, the greater shear stress at the interface causes the rotation angle of the broken intermetallic compound fragments to further increase. The interface is uneven, showing a serrated interlocking. The second annealing enables the matrix metals in contact in the gaps between the broken intermetallic compound fragments to form a thin diffusion layer to achieve metallurgical bonding, reducing the defects at the interface and a large amount of residual stress generated during the rolling process.

[0044] Comparative Example 1:

[0045] A heat treatment method for an Al / Cu composite plate includes the following steps:

[0046] (1) Heat treat a 7-mm-thick cast-rolled Al / Cu composite plate, and use sandpaper to polish and remove the surface oxide layer;

[0047] (2) The interfacial bonding strength of the annealed Al / Cu composite plate annealed at 250°C for 3 h was measured to be 91.86 MPa, the tensile strength was 138.83 MPa, and the elongation was 43.94%. The TEM morphology at the interface was as shown in Figure 5 shown. Three intermetallic compounds were formed at the interface, and the interface was flat without obvious defects.

[0048] The treatment results are shown in the following table.

[0049] Under low-temperature heat treatment (<250°C), the diffusion layer at the interface of the Al / Cu composite plate grew slowly. As the heat treatment temperature increased, the growth rate of the diffusion layer accelerated; Table 1 shows the interfacial shear tensile strength of the Al / Cu composite plate under different heat treatment conditions. The thicknesses of the intermetallic compound diffusion layers after annealing at 100°C, 150°C, 200°C for 24 h and 250°C for 3 h were all less than 2 μm. After annealing at 300°C for 1.75 h and 400°C for 3 h, the diffusion layer thicknesses were 2.13 μm and 20.39 μm respectively, indicating that when the diffusion layer thickness exceeded 2 μm, the bonding strength of the Al / Cu composite plate began to decline. When the diffusion layer was too thick, the bonding performance would decline sharply and would be much less than the bonding strength in the as-cast and rolled state.

[0050] Table 1 Interfacial shear tensile strength of Al / Cu composite plate under different heat treatment conditions

[0051]

[0052] Comparative Example 2:

[0053] A cold rolling process for an Al / Cu composite plate includes the following steps:

[0054] (1) The surface oxide layer of the as-cast and rolled Al / Cu composite plate with a thickness of 7 mm was removed by sanding. There was a 0.3-μm diffusion layer at the interface of the Al / Cu composite plate, and the TEM morphology of the interface was as shown in Figure 6 shown;

[0055] (2) The as-cast and rolled Al / Cu composite plate was cold-rolled in multiple passes.

[0056] The treatment results are shown in the following table.

[0057] When the single-pass rolling rate was 10%, separation occurred in the third pass of rolling. When the single-pass rolling rate of the as-cast and rolled Al / Cu composite plate was less than 18%, the front end of the Al / Cu composite plate was extremely prone to cracking and separation during rolling, and the total rolling rate could not reach 70%. By increasing the single-pass rolling rate, no cracking occurred during the rolling of the Al / Cu composite plate. As the single-pass rolling rate increased, the rolling stress at the interface also increased, and the corresponding interfacial bonding strength also increased.

[0058] Table 2 Interfacial shear tensile strength of Al / Cu composite plates with different single-pass cold rolling

[0059]

Claims

1. A processing method for a cast-rolled Al / Cu composite plate with high interface bonding strength, characterized in that, The operation steps are as follows: Step (1): Grind the surface of the cast-rolled Al / Cu composite plate to remove the oxide layer, perform annealing treatment in a heat treatment furnace, and then grind the surface with sandpaper to remove the oxide layer; Step (2): Perform two cold rolling treatments on the annealed Al / Cu composite plate; Step (3): Perform secondary annealing on the cold-rolled Al / Cu composite plate, and then grind the surface with sandpaper to remove the oxide layer to obtain an Al / Cu composite plate with high interfacial bonding strength.

2. The processing method of a cast-rolled Al / Cu composite plate with high interfacial bonding strength according to claim 1, characterized in that: In step (1), the Al / Cu composite plate is prepared by a casting and rolling process. The specific process is as follows: Pour the molten aluminum liquid onto the surface-treated solid copper strip, and introduce a rolling mill with internal circulating cooling water for rolling. After the aluminum liquid contacts the rolling mill, it cools and solidifies, and is prepared into an Al / Cu composite plate with the required thickness through rolling.

3. The processing method of a cast-rolled Al / Cu composite plate with high interfacial bonding strength according to claim 2, characterized in that: The thickness of the original specimen of the cast-rolled Al / Cu composite plate is 3 - 7 mm.

4. The processing method of a cast-rolled Al / Cu composite plate with high interfacial bonding strength according to claim 3, characterized in that: Among them, the Al plate is 1060 aluminum, and the Cu plate is T2 pure copper.

5. The processing method of a cast-rolled Al / Cu composite plate with high interface bonding strength according to claim 1, characterized in that: In step (1), the annealing temperature is 240 - 260 °C, and the annealing time is 2 - 3.5 h.

6. The processing method of a cast-rolled Al / Cu composite plate with high interface bonding strength according to claim 1, characterized in that: In step (2), the cold rolling treatment is performed twice using a two-roll cold rolling experimental machine.

7. A processing method for a roll-cast Al / Cu composite plate with high interfacial bonding strength according to claim 6, characterized in that: Among them, the single-pass rolling rate is 35%, the total rolling rate is 70%, and the rolling speed is 10 mm / s.

8. The processing method of a cast-rolled Al / Cu composite plate with high interface bonding strength according to claim 1, characterized in that: In step (3), the heat treatment temperature for the secondary annealing is 240 - 260 °C, and the heat treatment time is 2 - 3.5 h.

9. The processing method of a cast-rolled Al / Cu composite plate with high interface bonding strength according to claim 1, characterized in that: After the processing in step (3), the maximum interfacial bonding strength of the Al / Cu composite plate reaches 93.49 MPa, and the tensile strength and elongation are 154.80 MPa and 36.92% respectively.

10. The processing method of a cast-rolled Al / Cu composite plate with high interface bonding strength according to claim 1, characterized in that: During the processing of the cast-rolled Al / Cu composite plate, the primary IMC formed during the first annealing is broken during cold rolling and forms a serrated structure with the matrix at the interface. The secondary annealing forms a thin secondary IMC, enabling metallurgical bonding at the interface.

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