A rolling composite process for improving the interfacial bonding strength of aluminum-copper heteromaterials

Abstract

This invention discloses a rolling composite process for improving the interfacial bonding strength of aluminum-copper heteromaterials, belonging to the field of metal composite material preparation technology. The process includes: constructing a dual-scale interlocking interface on the surface of an aluminum substrate, comprising micron-scale asymmetric wedge-shaped grooves and nano-scale roughness; depositing a rare-earth-doped tin-zinc-cerium nanoscale self-depleting intermediate layer using physical vapor deposition; performing warm rolling under the assistance of a pulsed current and ultrasonic vibration coupling field; and finally, online pressure holding and offline gradient stress-relief annealing. This invention effectively solves the problems of interfacial welding defects, brittle cracking, and thermal delamination by actively breaking down the oxide film through micro / nano structures, suppressing excessive growth of brittle phases through the rare-earth grain boundary pinning effect, and releasing thermal mismatch stress through gradient cooling, significantly improving the bonding strength and conductivity of the material.

Description

Technical Field

[0001] This invention relates to the field of metal composite material preparation technology, and in particular to a rolling composite process for improving the interfacial bonding strength of aluminum-copper heteromaterials. Background Technology

[0002] Aluminum-copper layered composite materials combine the excellent electrical and thermal conductivity of copper with the lightweight and low cost of aluminum, showing broad application prospects in recent years in the fields of new energy power battery tabs, 5G base station heat dissipation components, and power electronic transmission. To achieve efficient bonding of these two metals with vastly different physicochemical properties, solid-state rolling composite technology has become the mainstream industrial approach due to its high production efficiency and suitability for continuous manufacturing. In conventional rolling composite processes, the oxide layer on the substrate surface is typically removed by wire brush grinding or chemical cleaning, followed by metallurgical bonding at the interface through a combination of high reduction rate and high-temperature annealing.

[0003] However, although existing rolling composite technologies have achieved bimetallic bonding of aluminum and copper to some extent, they still face insurmountable technical contradictions in the preparation of high-performance, high-reliability composite strips. First, aluminum has an extremely high chemical affinity for oxygen. Even after mechanical grinding to remove the surface oxide layer, a dense micro-oxide film easily forms again on its surface just before entering the rolls. This natural oxide barrier hinders direct contact between aluminum and copper atoms, resulting in composite interfaces prepared by existing processes often exhibiting only localized point-like bonding, the so-called "point-like weak weld" phenomenon, with a low effective bonding area and difficulty in significantly improving peel strength. Second, to overcome the oxide film barrier and promote diffusion, existing technologies often tend to increase annealing temperature or extend holding time, but this introduces the more intractable problem of brittle phases. Aluminum and copper have a large interdiffusion coefficient, and at high temperatures, they are prone to violent reactive diffusion, forming hard and brittle intermetallic compounds (IMCs, such as...). , (etc.). Once the thickness of the continuous brittle IMC layer exceeds the critical value, the material is very prone to brittle cracking along the interface under the thermal shock environment during subsequent bending, stamping or service.

[0004] Furthermore, aluminum and copper have significantly different coefficients of thermal expansion (aluminum is approximately 1000 ohms). Copper is approximately This inherent physical mismatch leads to significant residual shear stress at the interface during the cooling process after traditional annealing. Existing cooling processes lack targeted stress control methods, causing residual thermal stress to become a potential cause of interfacial delamination or fatigue failure. While some existing solutions attempt to introduce a thicker nickel layer as a barrier to suppress diffusion, this not only increases process complexity and cost but also introduces additional interfacial resistance, diminishing the composite material's application value in conductive fields. Therefore, there is an urgent need to develop a new aluminum-copper rolling composite process that can simultaneously address the three core challenges of residual interfacial oxide film, uncontrolled growth of brittle compounds, and excessive residual stress due to thermal mismatch. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a rolling composite process for improving the interfacial bonding strength of aluminum-copper heteromaterials. This process effectively overcomes key challenges such as residual oxide film, brittle compound formation, and residual thermal stress at the aluminum-copper composite interface by constructing a micro / nano dual-scale physically interlocked interface, introducing a rare-earth-doped self-depleted interlayer, and employing a combined strategy of multi-field coupled warm rolling and gradient heat treatment.

[0006] According to one aspect of the present invention, a rolling composite process for improving the interfacial bonding strength of aluminum-copper heteromaterials is provided, which mainly includes the following steps:

[0007] S1. Substrate pretreatment: Cleaning treatment is performed on aluminum substrate and copper substrate respectively.

[0008] S2. Surface micro-nano texturing: texture processing is performed on the surface of the aluminum substrate to be composited to construct a micro-nano dual-scale physical interlocking interface containing oriented micron-level trenches and nano-level secondary roughness.

[0009] S3. Intermediate layer deposition: Using physical vapor deposition technology, a rare earth-doped alloy intermediate layer is deposited on the micro-nano dual-scale physical interlocking interface of the aluminum substrate.

[0010] S4. Multi-field coupling rolling: The copper substrate and the aluminum substrate with the intermediate layer are stacked together and warm-rolled in a protective atmosphere under the condition of applying an external energy field to obtain a composite strip.

[0011] S5. Gradient heat treatment: The composite strip is subjected to online pressure holding treatment and offline gradient stress relief annealing treatment; wherein, the offline gradient stress relief annealing treatment specifically includes a first stage of rapid cooling and a second stage of slow cooling.

[0012] Furthermore, according to a preferred embodiment of the present invention, the surface micro / nano texturing in step S2 is described in detail:

[0013] The cross-sectional shape of the directional micron-scale trench is designed as an asymmetric wedge, with one side being a steep surface and the other side being a gentle surface; meanwhile, the nanoscale secondary roughness is distributed on the inner surface of the directional micron-scale trench.

[0014] The mechanism of using an asymmetric wedge structure instead of a traditional symmetrical structure is that, at the instant of rolling deformation, the asymmetric inclined structure can induce microscopic shear slip along the rolling direction in the aluminum matrix. This tangential shear force is more effective than simple normal pressure in tearing the hard oxide film on the aluminum surface. This forces fresh metal to be extruded from the cracks. The nanoscale roughness inside the trenches significantly increases the specific surface area, providing more nucleation sites and mechanical interlocking sites for the subsequently deposited atomic layers.

[0015] More preferably, the geometric parameters of the oriented micron-scale trench are set as follows:

[0016] Depth to Pitch is to Furthermore, the extension direction of the groove is perpendicular to the rolling direction. to Angle; the roughness value Ra of the nanoscale secondary roughness is to .

[0017] 1. Regarding depth and pitch ( / If the depth is lower than The trenches lack sufficient capacity to hold broken oxide scale, thus failing to form an effective mechanical interlock; if the depth is higher than... This can easily lead to macroscopic voids or stress concentration at the interface, reducing peel strength.

[0018] 2. Regarding the included angle ( The reason for choosing this angle range, rather than parallel or perpendicular to the rolling direction, is to generate a composite stress field (with both tensile and shear components) during the rolling process, maximizing the breakage rate of the oxide film, while preventing gas from being trapped in the groove and unable to escape.

[0019] 3. Regarding roughness (Ra) This nanoscale roughness range is most favorable for the adhesion of physical vapor deposition (PVD) layers. If Ra is too large ( This will cause discontinuities in the PVD layer coverage; if Ra is too small ( If the mechanical anchoring effect is not obvious, then the mechanical anchoring effect is not obvious.

[0020] Furthermore, according to a preferred embodiment of the present invention, the deposition of the intermediate layer in step S3 is described in detail:

[0021] The rare earth-doped alloy intermediate layer is designed as a double-layer structure, consisting of a bottom layer directly deposited on the surface of the aluminum substrate and a main functional layer deposited on the bottom layer; wherein, the bottom layer is a titanium (Ti) layer and the main functional layer is a tin-zinc-rare earth (Sn-Zn-Ce) alloy layer.

[0022] A titanium underlayer is introduced as an activation layer, utilizing the excellent chemical affinity between titanium and aluminum to solve the wettability problem between dissimilar metals. The main functional layer uses a Sn-Zn based alloy, which utilizes its low melting point to achieve "liquid phase / semi-solid phase assisted sintering" during warm rolling, rapidly filling microscopic interface voids.

[0023] More preferably, the thickness and composition of the intermediate layer are controlled as follows:

[0024] The thickness of the bottom layer is to The thickness of the main functional layer is to The main functional layer comprises, by mass percentage: Zn Ce The remainder is Sn.

[0025] 1. Regarding layer thickness (nanometer level): This invention strictly controls the total thickness of the intermediate layer to the nanometer level (total thickness of the intermediate layer). The purpose is to achieve a "self-depletion" effect. That is, after subsequent diffusion treatment, the intermediate layer will be completely transformed into a solid solution or an extremely thin dispersed phase, avoiding the residual layer of a continuous high-resistivity, low-strength heterogeneous layer as in traditional micron-scale coatings.

[0026] 2. Regarding the doping of rare earth element Ce ( This is the core formulation point of this invention. Rare earth element Ce has a large atomic radius and tends to segregate at grain boundaries. Its mechanism of action lies in the "grain boundary pinning effect": Ce atoms can effectively occupy vacancies and hinder the long-range rapid diffusion of Al and Cu atoms, thereby significantly suppressing brittle intermetallic compounds (such as...). , Excessive growth of Ce. If the Ce content is lower than... The inhibitory effect is not obvious; if it is higher than Rare earth elements are prone to aggregate and form coarse cerium-rich phases, which can become crack initiation sites.

[0027] Furthermore, according to a preferred embodiment of the present invention, the multi-field coupled rolling in step S4 is described in detail:

[0028] The applied energy field is selected from at least one of a pulsed electric field and an ultrasonic vibration field; preferably, they are applied simultaneously, in which case the pulsed current flows through the deformation zone and the ultrasonic vibration is applied to the surface of the roll or the substrate.

[0029] The specific process parameters are set as follows: the temperature for warm rolling composite is... to The first pass reduction rate to The parameters of the pulsed electric field include: current density. to ,frequency to Duty cycle The parameters of the ultrasonic vibration field include: frequency. ,amplitude to .

[0030] 1. Warm rolling temperature ( This temperature range is slightly below the overall melting point of the Sn-Zn interlayer, but far below the critical temperature for rapid IMC formation in aluminum and copper. The interlayer participates in deformation in a solid / metastable state, and with a reduction rate of 40%-50%, it ensures the amount of plastic deformation required for physical interlocking. At the same time, the transient Joule heat generated by the high-density pulsed current flowing through the micro-contact points (high-resistance regions) of the interface can cause the local micro-area temperature to exceed the melting point of the interlayer, achieving micro-area fusion welding. The complete liquid-phase assisted diffusion welding is completed in the subsequent online pressure holding stage (280-300°C), at which point the interlayer completely melts and achieves dense atomic-level bonding under surface pressure.

[0031] 2. The role of pulsed current: When high-density pulsed current passes through the micro-contact points (high resistance areas) of the interface, it generates local Joule heating, realizing micro-area fusion welding, while the substrate remains at a low temperature; at the same time, it utilizes the electroplastic effect to reduce the metal's resistance to deformation.

[0032] 3. The role of ultrasound: Ultrasonic vibration can not only reduce the friction coefficient between the roll and the strip, but its high-frequency vibration energy can also further break up the residual oxide film and improve the atomic bonding rate.

[0033] Furthermore, according to a preferred embodiment of the present invention, the gradient heat treatment in step S5 is described in detail:

[0034] First, an online pressure holding process is performed: the rolled composite strip is immediately passed through a heating and pressurizing channel, in... to At the temperature, apply to The surface pressure, held for a time of to .

[0035] The interfacial bonding is unstable immediately after rolling. Short-term high-temperature diffusion under surface pressure can promote the inter-atomic interdiffusion to form metallic bonds, while preventing micro-separation caused by rebound, thus completing "atomic-level welding".

[0036] Subsequently, an offline gradient stress-relief annealing process is performed, specifically including: heat preservation of the composite strip in an inert atmosphere (preferably in...). Keep warm for 30 minutes).

[0037] Then, the first stage of rapid cooling is performed: at a first cooling rate ( to Cool to the first temperature point ( to );

[0038] Next, the second stage of slow cooling is performed: at a second cooling rate ( to Cool to the second temperature point ( to );

[0039] The first cooling rate is significantly greater than the second cooling rate.

[0040] The coefficient of thermal expansion of aluminum ( ) is much higher than copper ( ).

[0041] 1. First stage: rapid cooling (to avoid brittleness): arrive The region is a brittle phase. The most dynamic growth region. (Through...) The purpose of rapid cooling is to quickly traverse this "dangerous temperature zone," freeze the interfacial structure, and prevent the brittle layer from thickening.

[0042] 2. Second stage slow cooling (pressure relief): When the temperature drops to... At this point, residual stress caused by thermal mismatch begins to accumulate. At this time, an extremely slow... Cooling rate is determined by the creep properties of metals at warm temperatures, allowing the crystal lattice sufficient time to release accumulated thermal stress through microscopic plastic deformation. If cooling is too rapid during this stage, the enormous shear stress will directly lead to interface delamination or reduced service life.

[0043] This invention addresses the challenge of bonding aluminum-copper heterogeneous materials by constructing a "micro-nano dual-scale physical interlocking interface," introducing a "rare-earth microalloyed self-depletion transition layer," and employing a combined strategy of "multi-field coupled warm rolling and gradient stress-relief annealing." This approach addresses the challenges from three dimensions: physical interlocking, chemical bonding, and stress regulation, achieving significant technical results. Firstly, this invention abandons traditional disordered surface roughening treatments. Instead, it constructs asymmetric wedge-shaped microgrooves and nanoscale roughness within these grooves on the aluminum substrate surface. During rolling, ultrasonic vibration and pulsed current are introduced, utilizing directional microscopic shear force and ultrasonic cavitation effect to achieve a "crushing" destruction of the robust oxide film on the aluminum surface. This micro-nano dual-scale physical interlocking structure not only increases the oxide film breakage rate to nearly 100%, resulting in a fresh metal contact area that is more than 40% larger than traditional processes, but also significantly increases the mechanical interlocking points at the interface, laying the foundation for high-strength physical bonding. Secondly, this invention utilizes physical vapor deposition (PVD) technology to introduce an ultrathin tin-zinc alloy interlayer containing rare-earth cerium (Ce) at the interface, creatively resolving the contradiction between bonding strength and brittle phase control. In this system, the low-melting-point Sn-Zn component undergoes liquid-phase or semi-solid-phase assisted sintering during warm rolling and pressure holding stages, rapidly filling microscopic voids and achieving dense atomic-level bonding. More importantly, the segregation effect (pinning effect) of rare-earth element Ce at grain boundaries effectively hinders the long-range rapid diffusion of aluminum and copper atoms, significantly suppressing... Excessive growth of brittle intermetallic compounds is prevented. Due to the nanoscale thickness of the intermediate layer, it transforms into an extremely thin and dispersed solid solution after diffusion, achieving "self-depletion." This ensures a significant increase in peel strength (stabilized at 15-20 N / mm) while avoiding high interfacial resistance caused by a thick intermediate layer, maintaining the material's excellent electrical conductivity. Finally, the unique gradient stress-relief annealing process of this invention plays a decisive role in addressing the residual stress caused by the thermal expansion mismatch between aluminum and copper. The first stage of rapid cooling allows the material to quickly traverse the sensitive temperature range where brittle phases easily form, freezing the optimized interfacial structure. Subsequently, the second stage of extremely slow cooling utilizes the creep characteristics of metals at warm temperatures, giving the lattice sufficient time for microscopic plastic adjustment, thereby releasing the shear stress accumulated due to the difference in thermal expansion. This gradient heat treatment scheme reduces the residual thermal stress of the composite material by more than 60%, greatly improving the structural stability and anti-delamination ability of the material under subsequent processing and thermal cycling conditions. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the composite process of the present invention;

[0045] Figure 2 This is a schematic diagram of the "micro-nano dual-scale" structure on the surface of the aluminum substrate of the present invention;

[0046] Figure 3 These are combined SEM interface observations of Embodiment 1 and Comparative Example 4 of the present invention. Detailed Implementation

[0047] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0048] This invention provides an aluminum-copper rolling composite process that utilizes the synergistic effect of micro / nano dual-scale physical interlocking and a rare-earth self-depleting interlayer. The core of this invention lies in achieving "active breakage" of the oxide film through asymmetric microgrooves, achieving "chemical micro-welding" at low temperatures and suppressing the growth of brittle phases through a rare-earth Sn-Zn-Ce interlayer, and finally controlling residual stress through gradient heat treatment.

[0049] Raw material specifications:

[0050] Aluminum substrate: 1060 industrial pure aluminum strip, O temper (fully annealed), 1.0 mm thick, 200 mm wide. Initial grain size is approximately 30-40 μm.

[0051] Copper substrate: T2 copper strip, semi-hard state, 1.0mm thick, 200mm wide.

[0052] Target material:

[0053] Pure Ti target (99.99% purity);

[0054] Sn-Zn-Ce alloy target (customized composition, prepared by vacuum melting);

[0055] Comparison with Sn-Zn target (without rare earth elements).

[0056] 2. General Flowchart of Preparation Process

[0057] All embodiments follow the general process described below, with specific parameters detailed in each embodiment:

[0058] 1. Pretreatment: Aluminum and copper strips are degreased by alkaline washing (5% NaOH, 50℃) and brightened by acid washing (10% HNO3), then rinsed with deionized water and dried.

[0059] 2. Texturing (aluminum side only): Micro-nano structures are pressed onto the surface of aluminum strip using a custom-made embossing roller that combines laser etching and precision grinding.

[0060] 3. PVD deposition: in environments with a vacuum level superior to... In the magnetron sputtering chamber, Ti underlayer and Sn-Zn-Ce main functional layer are deposited sequentially.

[0061] 4. Billet Assembly and Rolling: Billets are assembled in a nitrogen-protected glove box and then fed into a multi-field coupled rolling mill for single-pass warm rolling. The rolling mill is equipped with a pulse current generator (introduced by the conductive roll) and an ultrasonic transducer (acting on the roll with an amplitude transformer).

[0062] 5. Heat treatment: including online hot pressing (simulating continuous heating channels in industrial production) and offline gradient annealing (box-type atmosphere annealing furnace).

[0063] To objectively evaluate the technical effects of this invention, the following standard methods were used for testing:

[0064] 1. Interface peel strength

[0065] Standards: Refer to GB / T2790-1995 "Adhesives - 180° Peel Strength Test Method" and ASTM D1876.

[0066] Conditions: Specimen width 15mm, tensile speed 100mm / min, record the average load during the peeling process.

[0067] 2. Interface contact resistance

[0068] Method: Kelvin four-terminal method was used.

[0069] Conditions: Apply a constant current of 1A in the thickness direction of the composite strip, measure the voltage drop between the aluminum layer and the copper layer, and calculate the contact resistance per unit area. ).

[0070] 3. Intermetallic compound (IMC) layer thickness

[0071] Methods: Cross-sectional metallographic samples were prepared, polished by ion grinding, and the interface was observed using field emission scanning electron microscopy (FET) combined with energy dispersive spectroscopy (EDS) to analyze the composition. The IMC layer thickness was measured at 10 randomly selected points within a 50 μm length range, and the average value was taken.

[0072] 4. Thermal shock resistance

[0073] Method: Simulating extreme working conditions. The sample was placed in... Keep warm in the oven for 30 minutes, then quickly put it in. Freeze in an ethanol bath for 10 minutes; this constitutes one cycle.

[0074] Metric: After 100 cycles, test the peel strength again and calculate the strength retention rate (strength after cycles / initial strength × 100%).

[0075] Example 1

[0076] S2 texture: asymmetric wedge-shaped grooves, deep Pitch included angle Ra in the groove .

[0077] S3 intermediate layer: Ti bottom layer Sn-Zn-Ce layer (Ingredients: Sn-10Zn-0.8Ce).

[0078] S4 rolling: Temperature reduction rate Pulse current Ultrasonic amplitude .

[0079] S5 heat treatment:

[0080] Online: Surface pressure , 45s.

[0081] Offline: Insulation; rapid cooling section ( to ); slow cooling section ( to ); and cool to room temperature with the furnace.

[0082] Example 2

[0083] S2 texturing: Same as Example 1.

[0084] S3 intermediate layer: Ti bottom layer Sn-Zn-Ce layer (Ingredients: Sn-8Zn-0.5Ce).

[0085] S4 rolling: Temperature reduction rate (Lower limit); Pulse current .

[0086] S5 heat treatment: Same as in Example 1.

[0087] Example 3

[0088] S2 texturing: Same as Example 1.

[0089] S3 intermediate layer: Ti bottom layer Sn-Zn-Ce layer (Ingredients: Sn-15Zn-1.0Ce).

[0090] S4 rolling: Temperature reduction rate Pulse current .

[0091] S5 heat treatment: Same as in Example 1.

[0092] Example 4

[0093] S2 texturing: depth (Shallower), pitch included angle .

[0094] S3-S5: Parameters are the same as in Example 1.

[0095] Example 5

[0096] S2-S4: Parameters are the same as in Example 1.

[0097] S5 heat treatment: Rapid cooling section rate adjusted to... The slow cooling rate is adjusted to .

[0098] Comparative Example 1

[0099] S2: The aluminum surface is randomly polished using a stainless steel wire brush, Ra approximately Irregular grooves.

[0100] S3-S5: Completely consistent with Example 1 (including intermediate layers and subsequent processes).

[0101] Comparative Example 2

[0102] S3: The deposited layer does not contain Ce and has the composition Sn-10Zn. The remaining thickness and structure are the same as in Example 1.

[0103] S1, S2, S4, S5: Same as in Example 1.

[0104] Comparative Example 3

[0105] S5: After offline annealing and holding, it is directly cooled naturally in the furnace (average rate approximately...). (No slow cooling and decompression phase).

[0106] S1-S4: Same as Example 1.

[0107] Comparative Example 4S3: No intermediate layer, aluminum and copper in direct contact.

[0108] S4: The rolling temperature needs to be increased to... Only then can the combination (simulating traditional cold / hot rolling processes) be achieved without the aid of electric / sound fields.

[0109] S5: Standard annealing ( ).

[0110] Table 1: Performance test data of each embodiment and comparative example

[0111] Example 1 19.8 19.2 97.0% 0.35 0.85 Aluminum lateral toughness tear Example 2 16.5 15.8 95.8% 0.28 0.92 Mixed destruction Example 3 18.4 17.5 95.1% 0.72 0.88 Aluminum side tear Example 4 17.2 16.6 96.5% 0.38 0.90 Mixed destruction Example 5 19.1 17.8 93.2% 0.36 0.86 Aluminum side tear Comparative Example 1 12.4 10.5 84.7% 0.45 2.10 Interface delamination (residual oxide film) Comparative Example 2 18.2 6.5 35.7% 2.80 0.95 Brittle fracture (IMC layer cracking) Comparative Example 3 19.5 11.2 57.4% 0.40 0.86 Interface fatigue stratification Comparative Example 4 9.5 3.2 33.7% 3.50 1.80 brittle fracture

[0112] Results analysis:

[0113] 1. The film-breaking effect of micro / nano textures (Example 1 vs. Comparative Example 1):

[0114] The initial peel strength of Example 1 (19.8 N / mm) was significantly higher than that of Comparative Example 1 (12.4 N / mm) treated with a conventional wire brush, and Comparative Example 1 had a contact resistance as high as 2.10 Ω. .

[0115] Although Comparative Example 1 has a large macroscopic roughness, it cannot completely break down the dense material. The film leads to numerous "point-like poor welds," obstructing the current channel. However, the asymmetric wedge-shaped groove of this invention, under the action of rolling shear force, forcibly induces the aluminum substrate to slip, turning over fresh metal like "plowing the land"; combined with nanoscale roughness, the PVD intermediate layer can adhere tightly, achieving "surface bonding" rather than "point bonding."

[0116] 2. Grain boundary pinning and blocking effects of rare earth element Ce (Example 1 vs. Comparative Example 2):

[0117] This is the most unexpected comparison of technical effects. Example 1 and Comparative Example 2 showed little difference in initial strength (19.8 vs 18.2 N / mm), indicating good wettability of Sn-Zn itself. However, after 100 thermal shocks, the strength of Comparative Example 2, which did not contain rare earth elements, plummeted to 6.5 N / mm, and the IMC thickness increased dramatically to 2.80 mm. .

[0118] During high temperature and thermal cycling, Al and Cu atoms undergo vigorous interdiffusion. In Comparative Example 2, diffusion is unimpeded, rapidly forming a hard and brittle material. The presence of Ce atoms leads to interfacial embrittlement. In Example 1, trace amounts of Ce atoms segregated at grain and phase boundaries, exhibiting significant "solute dragging" and "pinning" effects, drastically reducing atomic diffusion flux and effectively locking the IMC layer thickness at a specific value. Within the safe range (generally considered) (This is the toughness safety zone), thus ensuring excellent aging resistance.

[0119] 3. Stress relief mechanism of gradient cooling (Example 1 vs. Comparative Example 3):

[0120] Although Comparative Example 3 had proper IMC control (with Ce), its strength retention rate after thermal shock was only 57.4%.

[0121] Comparative Example 3 used conventional cooling, and the Al / Cu interface generated huge residual shear stress due to the difference in thermal expansion coefficients. During subsequent cycling from -40°C to 150°C, this internal stress, combined with thermal shock stress, exceeded the interfacial bonding strength, leading to fatigue delamination. The slow cooling section of this invention utilizes the metal's... The creep characteristics of the range provide the lattice with sufficient time for microscopic plastic deformation, effectively releasing more than 60% of the internal stress, enabling the material to maintain structural integrity even under extreme temperature changes.

[0122] 4. "Self-depletion" design of intermediate layer thickness:

[0123] The contact resistance in all embodiments is lower than This is far superior to Comparative Example 4. This confirms that the nanoscale Sn-Zn-Ce layer does not form a continuous high-resistivity layer after diffusion, but rather transforms into a diffusely distributed solid solution, which does not constitute a significant barrier to electron transport, thus achieving a balance between high strength and high conductivity.

[0124] In summary, this invention, through the organic synergy of its various technical features, successfully solves three major problems in aluminum-copper composite materials: interface oxidation, brittle phase growth, and residual thermal stress, and has extremely high industrial application value.

[0125] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A rolling composite process for improving the interfacial bonding strength of aluminum-copper heteromaterials, characterized in that, Includes the following steps: S1. Substrate pretreatment: Cleaning treatment is performed on aluminum substrate and copper substrate respectively; S2. Surface micro-nano texturing: Texture processing is performed on the surface of the aluminum substrate to be composited to construct a micro-nano dual-scale physical interlocking interface containing oriented micron-level trenches and nano-level secondary roughness. S3. Intermediate layer deposition: Using physical vapor deposition technology, a rare earth-doped alloy intermediate layer is deposited on the micro-nano dual-scale physical interlocking interface of the aluminum substrate. S4. Multi-field coupling rolling: The copper substrate and the aluminum substrate with the intermediate layer are stacked together and warm rolled in a protective atmosphere under the condition of applying an external energy field to obtain a composite strip. S5. Gradient heat treatment: The composite strip is subjected to online pressure holding treatment and offline gradient stress relief annealing treatment; the offline gradient stress relief annealing treatment includes a first stage of rapid cooling and a second stage of slow cooling.

2. The rolling composite process according to claim 1, characterized in that, In step S2, the cross-sectional shape of the oriented micron-scale trench is an asymmetric wedge, with one side of the asymmetric wedge being a steep surface and the other side being a gentle surface; the nanoscale secondary roughness is distributed on the inner surface of the oriented micron-scale trench.

3. The rolling composite process according to claim 2, characterized in that, The directional micron-level trench has a depth of 5 μm to 12 μm, a pitch of 20 μm to 50 μm, and the extension direction of the trench forms an angle of 15° to 30° with the rolling direction; the roughness value Ra of the nano-level secondary roughness is 0.1 μm to 0.3 μm.

4. The rolling composite process according to claim 1, characterized in that, In step S3, the rare earth-doped alloy intermediate layer has a double-layer structure, consisting of a bottom layer deposited on the surface of the aluminum substrate and a main functional layer deposited on the bottom layer; the bottom layer is a titanium layer and the main functional layer is a tin-zinc-rare earth alloy layer.

5. The rolling composite process according to claim 4, characterized in that, The thickness of the bottom layer is 5nm to 10nm; the thickness of the main functional layer is 50nm to 100nm, and the composition of the main functional layer by mass percentage includes: Zn 8%-15%, Ce 0.5%-1.0%, and the balance being Sn.

6. The rolling composite process according to claim 1, characterized in that, In step S4, the applied energy field is selected from at least one of a pulsed electric field and an ultrasonic vibration field; when a pulsed electric field and an ultrasonic vibration field are applied simultaneously, the pulsed current flows through the deformation zone, and the ultrasonic vibration is applied to the surface of the roll or the substrate.

7. The rolling composite process according to claim 6, characterized in that, In step S4, the temperature of the warm rolling composite is 150°C to 180°C, and the first pass reduction rate is 40% to 50%. The parameters of the pulsed electric field include: current density 80 A / mm². 2 Up to 120A / mm 2 Frequency 400Hz to 600Hz, duty cycle 30% ± 5%; The parameters of the ultrasonic vibration field include: frequency 20kHz±2kHz, amplitude 5μm to 10μm.

8. The rolling composite process according to claim 1, characterized in that, In step S5, the online pressure holding process specifically involves: immediately passing the rolled composite strip through a heating and pressurizing channel, applying a surface pressure of 5MPa to 10MPa at a temperature of 280°C to 300°C, and holding it for 30s to 60s.

9. The rolling composite process according to claim 1, characterized in that, In step S5, the specific steps of the offline gradient stress relief annealing process are as follows: Insulate the composite strip under an inert atmosphere; Perform the first stage of rapid cooling: cool to a first temperature point at a first cooling rate, where the first temperature point is 180°C to 220°C; Perform the second stage of slow cooling: cool to a second temperature point at a second cooling rate, the second temperature point being 80°C to 120°C; Wherein, the first cooling rate is greater than the second cooling rate.

10. The rolling composite process according to claim 9, characterized in that, The heat preservation conditions are: heat preservation at 280°C for 30 minutes; the first cooling rate is 10°C / min to 15°C / min; and the second cooling rate is 2°C / min to 3°C / min.

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