Ni / Al nano multilayer film electroplasticity and current-assisted roll-bonding forming method

Abstract

The invention belongs to the technical field of rolling, and discloses a Ni / Al nano multilayer film electroplasticity and current-assisted ply rolling forming method. The Ni / Al multilayer film is an energetic material and is used as a brazing heat source and a welding flux. According to the method, millimeter-level Ni foil and Al foil serve as raw materials, the thickness ratio of all layers is determined according to the maximum self-propagating heat release amount, a six-roller precision rolling mill is used for conducting multi-pass electroplastic ply rolling under pulse current, the pass deformation is 60%, and electric pulse annealing is conducted after rolling (the temperature is lower than a reaction critical value), and the Ni / Al nanometer multilayer brazing thin film with the total thickness being 50 micrometers and composed of thousands of layers of nanometer thin films is prepared. The method overcomes the problems of low production efficiency, high cost, narrow application range and the like in the prior art, and compared with a magnetron sputtering method, the method is low in manufacturing cost, short in period, large in area and good in mechanical property; compared with an accumulative ply rolling technology, interface recombination is excellent, nickel layer breakage is light, and heat release is high; and the material is low in deformation resistance and good in plasticity, multi-layer film ply rolling forming property integrated forming is achieved, and industrial application is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of roll forming of metal layered composite materials, and specifically relates to a roll-forming method that combines electroplastic effect with current-assisted technology to achieve efficient and high-quality preparation of Ni / Al nano multilayer films. Background Art

[0002] As an energetic structural functional material with both high strength and high energy density, Ni / Al nano-multilayer film can trigger a violent self-propagating high-temperature synthesis (SHS) under high temperature or high-speed impact conditions, releasing up to 1000 J·g -1 This characteristic gives it great application potential in fields such as micro-connections (such as brazing heat source and solder), energetic devices (ignition bridges, micro-thrusters), and weaponry. In particular, in the field of brazing, Ni / Al multilayer films require only a low voltage of 9V to instantly trigger a reaction and complete welding, eliminating the need for complex and expensive high-temperature equipment. They can achieve high-strength welding of ≥60MPa in extreme environments such as vacuum, underwater, and low temperatures, meeting international standards, greatly simplifying the process, improving efficiency, and reducing costs.

[0003] Currently, magnetron sputtering is the mainstream technology for producing Ni / Al multilayer films. While this method can precisely control layer thickness down to the nanometer level, ensuring excellent heat release performance, it suffers from high manufacturing costs, lengthy production cycles, low efficiency, limited fabrication area, thin film thickness, and insufficient mechanical properties. This method is only suitable for microelectronic energetic bridge components and is difficult to meet the demands of large-scale, high-performance weaponry structural components.

[0004] Accumulative Roll Bonding (ARB), an effective method for preparing large-scale, micro-laminated, ultra-fine-grained metal sheets, also faces challenges in the preparation of Ni / Al multilayer boards. For example, SIM ES et al. used ARB technology to prepare Ni / Al multilayer boards. After 11 passes of rolling, the nickel layer thickness was reduced from 126 μm to 460 nm, and the heat release reached 768 J·g -1 However, as the number of rolling passes increases, traditional ARB technology faces challenges such as increased operational difficulty, severe fracture of the nickel layer, and the formation of numerous holes and defects at the interface. This not only limits further increases in the reaction exotherm but also significantly reduces the overall mechanical properties of the material. Therefore, an innovative process is urgently needed to address the current technological bottlenecks. Summary of the Invention

[0005] The present invention aims to overcome the technical bottlenecks of the existing magnetron sputtering method, such as high cost, low efficiency, and limited area, as well as the traditional cumulative rolling technology with many interface defects, difficulty in achieving high-pass nano-lamination, and poor mechanical properties, and provide an efficient, low-cost, scalable electroplastic and current-assisted rolling forming method for the preparation of large-size, high-interface quality, nano-layer-thick Ni / Al multilayer composite films.

[0006] Technical Solution

[0007] To achieve the above objectives, the present invention provides a Ni / Al nano-multilayer film electroplastic and current-assisted roll-bonding method, characterized in that the method introduces high-energy pulse current during the rolling and bonding process, utilizing its electroplastic effect to reduce the material's rheological stress, promote plastic deformation and dynamic recrystallization, and combines it with a precisely controlled electric pulse annealing process to promote interface diffusion and inhibit self-propagating reactions, thereby achieving layer multiplication and nano-sizing through a multi-stage roll-bonding process. Specifically, the method comprises the following steps:

[0008] 1. Preparation of initial composite sheet:

[0009] Raw material preparation: Select Ni foil and Al foil with millimeter thickness, and determine the initial thickness ratio of the two based on the optimal stoichiometric ratio required for the self-propagating reaction of Ni and Al to achieve maximum heat release (usually Ni:Al≈1:1 atomic ratio).

[0010] Surface treatment: All the contact surfaces of the Ni foil and the Al foil to be composited (a total of 4 surfaces) were subjected to online texturing treatment using a wire roller brush to increase surface activity and mechanical bite.

[0011] Electroplastic rolling and lamination: Rolling and laminating is performed under heated conditions (preferably at approximately 300°C) using a multi-roll precision rolling mill (preferably a 6-roll mill) equipped with a pulse current application system. High-energy pulse current (preferably at a frequency of approximately 600 Hz) is applied during the rolling process. Key process parameters include: working roll diameter of approximately 300 mm, roll length of approximately 400 mm, and rolling speed of approximately 5 m / min. -1 , rolling force is about 5×10 5 N, the deformation of a single rolling pass is strictly controlled to be above 60% (preferably 60%-65%). Through this step, two initial composite plates are obtained: Ni / Al / Ni three-layer plate and Al / Ni / Al three-layer plate.

[0012] Electric Pulse Annealing: Immediately after rolling, the composite plate undergoes an online electric pulse annealing treatment. Critical Control Point: The annealing temperature must be strictly below the critical initiation temperature of the Ni / Al self-propagating reaction (controlled at 10-20°C below the critical temperature) to avoid uncontrolled reactions. This annealing step aims to eliminate rolling internal stress and work hardening, and promote atomic interdiffusion at the Ni / Al interface, forming a good metallurgical bond.

[0013] 2. Secondary compound:

[0014] The Ni / Al / Ni three-layer plate and the Al / Ni / Al three-layer plate obtained in step (1) are used as new raw materials.

[0015] Repeat the surface treatment, electroplastic rolling compounding (under the same key parameters, the deformation amount of a single pass is ≥ 60%) and electric pulse annealing process in step (1).

[0016] Through this step, composite films with higher number of layers can be obtained: Ni / Al / Ni / Al / Ni / Al / Ni / Al / Ni seven-layer board and Al / Ni / Al / Ni / Al / Ni / Al / Ni / Al seven-layer film.

[0017] 3. Three-time compound:

[0018] The seven-layer composite board obtained in step (2) is used as raw material.

[0019] Repeat the complete process of step (1) (surface treatment, electroplastic rolling and bonding, electric pulse annealing).

[0020] Through this step, a 27-layer composite film of Ni / Al alternating layers was obtained.

[0021] 4. Multiple compounding:

[0022] The above composite process is continuously repeated (i.e., the composite board obtained in the previous step is used as raw material each time, and the process of step (1) is repeated).

[0023] 81-layer, 243-layer, and 729-layer Ni / Al alternating composite films were prepared in sequence.

[0024] Finally, through a sufficient number of roll-bonding (for example, achieving 2187 layers), a Ni / Al nano-multilayer composite film with a total thickness of about 50 microns and a thickness of each layer reaching the nanometer level (for example, about 23 nm) is obtained.

[0025] Key process controls:

[0026] The entire multi-stage rolling process adopts the electroplastic rolling technology.

[0027] The electric pulse annealing treatment is required after each rolling pass.

[0028] The single-pass deformation of all rolling passes is maintained at 60% or higher.

[0029] The electric pulse annealing temperature must always be strictly lower than the critical temperature of the Ni / Al self-propagating reaction.

[0030] The rolling mill is preferably a high-precision multi-roll rolling mill (such as a 6-roll rolling mill) to ensure the accuracy of the plate shape and thickness of the rolled thin strip.

[0031] Beneficial effects of the present invention

[0032] The electroplasticity and current-assisted roll-forming method provided by the present invention has the following significant advantages over the prior art:

[0033] Compared with magnetron sputtering:

[0034] Significant cost reduction: Expensive vacuum equipment and target material consumption are avoided.

[0035] Production efficiency is greatly improved: continuous or semi-continuous production can be achieved with short cycle time.

[0036] Large product size and controllable thickness: It is easy to prepare large-area composite foils with a total thickness of up to tens of microns to meet the needs of structural parts.

[0037] Excellent mechanical properties: The rolling process itself gives the material better strength and toughness, and the electroplastic effect further optimizes the microstructure.

[0038] Compared with traditional Accumulative Roll Bonding (ARB) technology:

[0039] The interface composite quality is significantly improved: the electroplastic effect of the pulse current effectively reduces the rolling resistance and the tendency of brittle fracture of the nickel layer; at the same time, electric pulse annealing accurately promotes interface diffusion, greatly reducing or even eliminating interface holes and defects.

[0040] A higher number of layers and nano-scaling can be achieved: current assistance significantly improves the plastic deformation ability of the material. It reduces work hardening, making it possible to perform more passes (such as ≥10 passes) of intense rolling deformation, thereby successfully obtaining thousands of layers of nano-scale structures.

[0041] Higher reaction exotherm: Good interface bonding and nanolayer thickness are the key to achieving high exothermic performance. The heat release of the material prepared by the present invention is expected to be better than that of traditional ARB products.

[0042] Excellent weld / interface mechanical properties: High interface quality and nanostructure contribute to the excellent mechanical properties of the final material.

[0043] Synergistic advantages of electroplastic rolling and electric pulse annealing:

[0044] Significantly reduce deformation resistance: High-energy pulse current (600Hz) can reduce the material's flow stress by more than 20%, making the rolling of difficult-to-deform materials easier.

[0045] Optimizing microstructure and properties: Under the action of electric pulses, especially at large deformations (>30%), the material is prone to dynamic recrystallization. Higher current frequency accelerates atomic diffusion and dislocation motion, speeding up the recrystallization rate and resulting in finer grains, thus achieving a perfect match between high strength and high ductility (after electric rolling, the hardness and tensile strength of the sample are lower than those after cold rolling, but the elongation is significantly higher, and this gap increases with increasing frequency and deformation).

[0046] Effectively inhibit work hardening: The electroplastic effect significantly reduces the degree of work hardening and improves the subsequent plastic deformation ability of the material.

[0047] Reduce or even omit intermediate annealing: Under reasonable electrical parameters, the deformation amount of a single pass can be increased or the number of intermediate full annealings can be reduced, thereby improving the overall processing efficiency and making it easier to obtain ultra-thin strips.

[0048] Energy saving and environmental protection: The electroplastic effect itself can save energy, and electric pulse assisted annealing can lower the recrystallization temperature and reduce heat energy consumption.

[0049] Safe and reliable: The electric pulse annealing temperature can be precisely controlled below the SHS critical point, ensuring process safety and avoiding uncontrolled reactions in the material during the preparation stage.

[0050] Solve the core problem of multi-layer rolling: Successfully overcome the difficulties of high-pass rolling and interlayer defects caused by material hardening and interface weakening in traditional rolling.

[0051] Efficient process: It has the advantages of relatively few processing passes, short production cycle and low equipment loss.

[0052] "Green" composite forming: replaces the traditional "coating" process to produce coating materials, is pollution-free, and the coating metal has high density, uniform thickness and good bonding quality.

[0053] In summary, the present invention innovatively applies electroplastic rolling and electric pulse annealing technology to the cumulative rolling forming process of Ni / Al multilayer films, providing a new approach with great industrial prospects for solving the problem of efficient preparation of Ni / Al multilayer films with high interface quality, nanolayer thickness, and large size, and realizing the integrated manufacturing of material forming (geometric nano-scaling) and performance regulation (interface optimization, microstructure refinement). BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 Schematic diagram of the electroplasticity and current-assisted rolling composite production line for initially preparing Ni / Al / Ni and Al / Ni / Al three-layer initial composite films in an embodiment of the present invention.

[0055] Figure 2 Schematic diagram of an electroplastic and current-assisted roll-bonding production line for subsequent roll-bonding of a multi-layer composite film according to an embodiment of the present invention.

[0056] Description of the marks in the figure:

[0057] Figure 1 :1-unwinder; 2-aluminum foil or nickel foil; 3-unwinder; 4-wire roller brush; 5-guide roller; 6-nickel foil or aluminum foil; 7-charged roller; 8-electric pulse annealing device; 9-coiler; 10-nickel / aluminum / nickel and aluminum / nickel / aluminum three-layer composite film.

[0058] Figure 2 :1-unwinder; 2-nickel / aluminum / nickel composite foil; 3-unwinder; 4-wire roller brush; 5-guide roller; 6-aluminum / nickel / aluminum composite foil; 7-charged roller; 8-electric pulse annealing device; 9-coiler; 10-nickel-aluminum multilayer composite film. DETAILED DESCRIPTION

[0059] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0060] The following examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0061] Example 1

[0062] 1. Key equipment: Electroplastic rolling mill system (briefly describe the core components, emphasizing the current application scheme)

[0063] This embodiment uses a precision 6-high rolling mill system integrated with a high-power pulse current application function, which mainly includes:

[0064] Rolling mill body: high-strength stand, work rolls (conductive materials, such as special copper alloy roll sleeves, with internal cooling and insulated bearing seat design), backup rolls, and precision screw-down system.

[0065] * High-power pulse power supply system: Outputs stable and adjustable DC pulses (frequency range covers 600Hz) with current capacity of tens of thousands of amperes.

[0066] * Current introduction and circuit system (Scheme 1 example): The working roller acts as one pole, and the current is introduced into the rotating roller through a high-load-bearing collector ring and carbon brushes;

[0067] The other pole forms a circuit through the working roll or fixed conductive block on the other side of the strip. The system is equipped with strong cooling (roller internal cooling, contact point cooling) and insulation protection.

[0068] * Measurement and control system: Real-time monitoring and coordinated control of current, voltage, rolling force, roll gap, speed, temperature (infrared temperature measurement), tension and other parameters.

[0069] * Auxiliary systems: uncoiler, coiler, tension control, wire brushing device, guide roller, electric pulse annealing device (integrated in the production line).

[0070] 2. Raw material preparation:

[0071] Select millimeter-sized pure Ni foil and pure Al foil of appropriate thickness. Calculate and determine the initial thickness ratio of the Ni foil to the Al foil based on an atomic ratio of Ni:Al≈1:1 (corresponding to the NiAl compound with the maximum heat release). Load the Ni foil and Al foil onto uncoilers (1, 3), respectively.

[0072] 3.Surface treatment:

[0073] The production line is started, and the upper and lower surfaces (a total of 4 surfaces) of the Ni foil (2 or 6) and the Al foil (6 or 2) to be composited are subjected to online roughening treatment by means of a steel wire roller brush (4).

[0074] 4. Electroplastic rolling compounding (initial compounding):

[0075] * The Ni foil and Al foil after the texturing treatment enter the rolling zone composed of charged rollers (7) through the guide rollers (5).

[0076] Rolling parameters: rolling temperature: 300°C; working roll: 300mm diameter, 400mm length; rolling speed: 5m / min -1 ; Rolling force: 5×10 5 N; apply pulse current: frequency 600 Hz, current density is adjusted according to the material cross section.

[0077] *Key control: Single-pass rolling deformation: 65%.

[0078] *Product: A well-bonded Ni / Al / Ni three-layer composite foil and an Al / Ni / Al three-layer composite foil (10) were obtained.

[0079] 5. Electric pulse annealing:

[0080] *After the composite foil leaves the roller, it immediately passes through the online electric pulse annealing device (8).

[0081] Key Control: The annealing temperature is precisely controlled to be 10°C below the critical temperature of the Ni / Al self-propagating reaction (for example, if the critical temperature is 350°C, set it to 340°C). This step promotes interfacial diffusion and eliminates stress hardening.

[0082] 6. Coiling:

[0083] The annealed three-layer composite foil is coiled by a coiler (9).

[0084] 7. Subsequent compounding (preparation of nano multilayer films):

[0085] * The wound three-layer composite foil (Ni / Al / Ni and Al / Ni / Al) is used as new raw material and rewound to the unwinder (such as Figure 2 2 and 6).

[0086] * Secondary composite: repeat steps 3 (surface treatment), 4 (electroplastic rolling composite, single-pass deformation ≥ 60%) and 5 (electric pulse annealing, temperature 10°C below the critical point) to obtain a seven-layer composite foil (10).

[0087] *Third-stage lamination: Using seven layers of composite foil as raw material, repeat steps 3, 4, and 5 again to obtain 27 layers of composite foil.

[0088] * Multiple lamination: The above lamination process (surface treatment - electroplastic rolling lamination (single pass deformation ≥ 60%) - electric pulse annealing (temperature strictly below the critical point)) was repeated continuously to produce 81-layer, 243-layer, and 729-layer composite foils, respectively.

[0089] Final product: After n composite cycles (for example, achieving 2187 layers), a Ni / Al nano-multilayer composite film with a total thickness of approximately 50 μm and a single layer thickness of approximately 23 nm is obtained. Throughout the entire process, electric pulse annealing is performed after each rolling pass to ensure interface quality.

[0090] Example 2

[0091] Equipment: Same as Example 1.

[0092] Process differences:

[0093] Electroplastic rolling composite (initial and subsequent): The single-pass rolling deformation is controlled at 62%.

[0094] Electric pulse annealing: The annealing temperature is controlled at 15°C below the critical temperature of Ni / Al self-propagating reaction.

[0095] Results: A Ni / Al nano-multilayer composite film with a total thickness of approximately 50 μm and 2187 layers was successfully produced, meeting product quality requirements. This example demonstrates that within the framework of the core process parameters (current assistance, large deformation, and low-temperature annealing), appropriate adjustments to the deformation and annealing temperature can still effectively implement the present invention and produce qualified products.

[0096] Example 3

[0097] .Key equipment: Use the precision 6-high rolling mill system of Example 1, optimize the cooling efficiency of the current introduction circuit, and ensure stable operation of the equipment under high-frequency current.

[0098] .Raw material preparation: Select Ni foil (thickness 0.3mm) and Al foil (thickness 0.25mm) with a purity of ≥99.9%, and calculate the initial thickness ratio based on the Ni:Al atomic ratio of 1:1 to ensure maximum reaction heat release.

[0099] .Surface treatment: Use a wire roller brush to perform bidirectional texturing on the surfaces of the Ni foil and Al foil to be composited. The texturing depth is controlled at 5-8μm to strengthen the mechanical bite of the interface.

[0100] Electroplastic rolling composite (initial composite)

[0101] Rolling temperature: set to 280℃ to verify the feasibility of low temperature process.

[0102] Pulse current parameters: frequency adjusted to 500 Hz, comparison of electroplastic effect, current density 200 A / mm 2 .

[0103] Rolling force: 4.8×10 5 N.

[0104] Single-pass deformation: 60% of the process lower limit.

[0105] Product: Ni / Al / Ni and Al / Ni / Al three-layer composite foils were obtained, with an interface bonding strength of ≥55 MPa.

[0106] Electric pulse annealing: The annealing temperature is strictly controlled at 20°C below the critical temperature of the Ni / Al self-propagating reaction (for example, if the critical temperature is 350°C, it is set to 330°C), and the annealing time is 15s (adjusted by pulse width) to eliminate stress while suppressing excessive interface diffusion.

[0107] Subsequent lamination: Using three layers of composite foil as raw material, repeated surface treatment, electroplastic rolling lamination, and electric pulse annealing processes were performed, with the deformation of each pass always maintaining 60%. After seven lamination cycles, a Ni / Al nano-multilayer film with a total thickness of approximately 50 μm and 2187 layers was obtained. The thickness of each layer was approximately 23 nm, and the heat release reached 980 J·g. -1 The results show that despite the decrease in rolling temperature and current frequency, the material still achieves a nano-layered structure with no obvious holes at the interface. This proves that when the process parameters of the present invention are adjusted within a certain range, qualified products can still be efficiently produced, showing strong adaptability and flexibility.

Claims

1. A Ni / Al nano multilayer electroplastic and current-assisted roll-forming method, characterized in that: The method comprises the following steps: using Ni foil and Al foil of millimeter thickness as raw materials, determining the thickness ratio of the two foils based on the maximum heat release of the self-propagating reaction of Ni and Al, and using a specific device to perform electroplastic rolling and laminating under the action of a 600Hz pulse current to obtain two types of composite plates, Ni / Al / Ni and Al / Ni / Al. The rolling and laminating process comprises uncoiling - surface texturing treatment - electroplastic rolling and laminating - electric pulse annealing - coiling. Before rolling, the four surfaces to be laminated are texturized online using a wire roller brush. The rolling and laminating is performed at 300°C, with a rolling deformation of more than 60% per pass. Subsequently, electric pulse annealing is performed, and the annealing temperature is lower than the critical temperature of the self-propagating reaction of Ni and Al. Using the Ni / Al / Ni and Al / Ni / Al composite films obtained by rolling and compounding in step (1) as raw materials, repeating the rolling and compounding process of step (1) to obtain Ni / Al / Ni / Al / Ni / Al / Ni / Al / Ni and Al / Ni / Al / Ni / Al / Ni / Al / Ni / Al composite films; The Ni / Al / Ni / Al / Ni / Al / Ni / Al / Ni and Al / Ni / Al / Ni / Al / Ni / Al / Ni / Al composite films obtained by rolling and compounding in step (2) are used as raw materials, and the process of step (1) is continued to be laminated and compounded to obtain a 27-layer composite film with Ni / Al alternating layers; Continuing the above operation, 81, 243, and 729 layers of Ni / Al alternating layers were obtained, and finally a 2187-layer Ni / Al nano-multilayer composite film with a total thickness of about 50 microns and a thickness of each layer reaching the nanometer level was obtained. The entire lamination process uses a 6-roll precision rolling mill for electroplastic rolling, with each rolling deformation of 60%. Electric pulse annealing is performed after each rolling pass to eliminate internal stress and work hardening and promote the mutual diffusion of interface phase components. The annealing temperature is lower than the critical temperature of the self-propagating reaction of Ni and Al.

2. The Ni / Al nano multilayer film electroplasticity and current-assisted roll bonding forming method according to claim 1, characterized in that: The surface texturing treatment adopts online texturing with a wire roller brush.

3. The Ni / Al nano multilayer film electroplasticity and current-assisted roll bonding forming method according to claim 1, characterized in that: The rolling composite is carried out at 300° C., and the deformation of one rolling pass is greater than 60%.

4. The Ni / Al nano multilayer film electroplasticity and current-assisted roll bonding forming method according to claim 1, characterized in that: The electric pulse annealing temperature is lower than the critical temperature of the self-propagating reaction of Ni and Al.

5. The Ni / Al nano multilayer film electroplasticity and current-assisted roll bonding forming method according to claim 1, characterized in that: The rolling process is carried out using a 6-roll precision rolling mill with a working roll diameter of 300 mm and a length of 400 mm. The rolling speed is set at 5 m / min. -1 , the load is 5×105N.

Images