A rolling process for layered molybdenum-copper composite materials
By constructing a three-dimensional texture on the surface of molybdenum-copper composite materials and depositing a barrier layer and a gradient functional layer, combined with vacuum warm rolling and gradient cooling, the problems of residual stress and oxidation at the interface were solved, and the bonding strength and thermal conductivity of the material were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEYUAN KAIYUAN CEMENTED CARBIDE CO LTD
- Filing Date
- 2026-03-09
- Publication Date
- 2026-06-02
AI Technical Summary
Existing technologies for preparing layered molybdenum-copper composites suffer from problems such as high residual stress at the interface, easy oxidation, and the formation of brittle phases, leading to poor bonding strength and warping cracks.
A three-dimensional surface texture was constructed by scanning with a short pulse energy beam to form an amorphous/nanocrystalline activation layer, a barrier layer and a gradient functional layer were deposited, and a composite material was formed by warm rolling and gradient cooling annealing in a vacuum environment.
It effectively prevents oxidation, improves interfacial bonding strength, reduces the formation of brittle phases, eliminates residual stress, and ensures the flatness and thermal conductivity of the material.
Smart Images
Figure CN122125056A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of metal layered composite material preparation technology, and in particular to a rolling process for layered molybdenum-copper composite materials. Background Technology
[0002] Molybdenum-copper composites are widely used in high-end electronic packaging, aerospace heat sinks, and nuclear fusion devices due to their excellent high-temperature strength, thermal and electrical conductivity, and adjustable coefficient of thermal expansion. Layered composites are the mainstream method for preparing this material, and its performance hinges on the quality of interfacial bonding.
[0003] Currently, the main methods for preparing layered molybdenum-copper composites include direct hot rolling, explosive bonding, and powder sintering. Among these, hot rolling has attracted much attention due to its high efficiency and relatively low cost. However, traditional hot rolling also has some drawbacks:
[0004] 1. The physical properties of molybdenum (Mo) and copper (Cu) differ greatly, such as melting point, hardness and coefficient of thermal expansion. During rolling deformation and subsequent cooling, huge residual stress is easily generated at the interface, which can lead to material warping or even interface cracking.
[0005] 2. Molybdenum and copper have extremely poor miscibility at high temperatures and easily form brittle intermetallic compounds. These brittle phases can become the source of interfacial cracks, severely weakening the bond strength.
[0006] 3. During high-temperature processing, the interface is easily oxidized, and the resulting oxide film will block the atomic diffusion and metallurgical bonding between the metals, seriously affecting the composite.
[0007] In response, some improvements have been made in the existing technology, such as using an intermediate transition layer, such as nickel foil or titanium foil, to alleviate thermal mismatch, or rolling under a protective atmosphere to prevent oxidation;
[0008] However, the introduced transition layer itself may become a new weak bonding link or form other brittle phases; the protective atmosphere is difficult to completely eliminate localized oxidation. In addition, some studies have used surface mechanical polishing or grooving to increase mechanical interlocking, but roughened surfaces are often accompanied by more severe contamination and oxidation, and the effect is unstable.
[0009] In view of this, the present invention provides a rolling process for layered molybdenum-copper composite materials to solve the above problems. Summary of the Invention
[0010] To achieve the above objectives, the present invention provides the following technical solution: a rolling process for layered molybdenum-copper composite materials, comprising the following steps:
[0011] S1. Surface texturing construction and activation treatment: The surfaces of the molybdenum matrix material and the copper matrix material to be composited are subjected to short pulse energy beam scanning treatment to construct three-dimensional surface textures and form amorphous / nanocrystalline activation layers on the surfaces of the molybdenum matrix material and the copper matrix material.
[0012] S2. Gradient transition layer deposition: Under vacuum conditions, a barrier layer and a gradient functional layer with gradually changing composition are deposited on the surface of the activated layer, respectively;
[0013] S3. Vacuum encapsulation and warm rolling: The treated molybdenum matrix material and copper matrix material are stacked and vacuum encapsulated, and then subjected to multi-pass warm rolling at a temperature between the recrystallization temperature of copper and molybdenum to form a composite material;
[0014] S4. Gradient heat treatment: The composite material after warm rolling is subjected to gradient cooling annealing with a continuous change along the spatial direction.
[0015] Preferably, the microscopic three-dimensional surface texture in S1 includes periodic grooves, cones, or arrays of holes.
[0016] Preferably, the barrier layer in S2 includes a first barrier layer deposited on the surface of a molybdenum substrate and a second barrier layer deposited on the surface of a copper substrate.
[0017] Preferably, the first barrier layer is a tungsten or tantalum layer; the second barrier layer is a chromium or titanium layer.
[0018] Preferably, the composition of the gradient functional layer in S2 continuously changes from the elements of the barrier layer to the copper substrate material.
[0019] Preferably, the vacuum sealing in S3 is performed using a flexible metal sealing container with a vacuum level not exceeding 1×10⁻⁶. -2 The experiment was conducted under the condition of Pa.
[0020] Preferably, the total reduction rate of the warm rolling in S3 is 40%-70%, and the single-pass reduction rate is no more than 25%.
[0021] Preferably, the highest temperature of the gradient cooling annealing temperature field in S4 is comparable to the warm rolling temperature in S3, the lowest temperature is not higher than 300℃, and the temperature gradient is 5-20℃ / cm.
[0022] Preferably, S1 and S2 are performed continuously under an inert atmosphere or in a vacuum environment.
[0023] A layered molybdenum-copper composite material was prepared using the above-described method.
[0024] The beneficial effects of this invention are:
[0025] 1. This invention uses high-vacuum flexible metal encapsulation to essentially isolate the interface to be composite from oxygen throughout the entire process from lamination, heating to rolling, thus preventing oxidation and effectively improving the reliability of the bonding.
[0026] 2. This invention effectively blocks the direct interdiffusion between molybdenum and copper by depositing a barrier layer that matches the matrix lattice, thereby avoiding the formation of brittle intermetallic compounds and improving interface toughness;
[0027] 3. This invention transforms some interfacial tensile stress into compressive stress through plastic deformation interlocking of three-dimensional surface texture, and achieves a smooth transition of thermal expansion coefficient and elastic modulus through a gradient functional layer with continuously varying composition. Combined with gradient heat treatment process, it can maximize the elimination and homogenization of residual stress at the interface. Attached Figure Description
[0028] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.
[0029] Figure 1 This is a schematic diagram of the process structure of the present invention. Detailed Implementation
[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.
[0031] The rolling process of the layered molybdenum-copper composite material of the present invention, such as Figure 1 As shown, it includes the following steps:
[0032] S1. Surface texturing construction and activation treatment: The surfaces of the molybdenum matrix material and the copper matrix material to be composite are subjected to short pulse energy beam scanning treatment to construct three-dimensional surface textures and form amorphous / nanocrystalline activation layers on the surfaces of the molybdenum matrix material and the copper matrix material.
[0033] Specifically, the cut molybdenum and copper plates are subjected to routine ultrasonic cleaning with acetone and alcohol to remove macroscopic oil stains; the cleaned plates are then placed into a high-vacuum chamber (vacuum degree ≤10). -3Pa); A short-pulse fiber laser (such as a picosecond laser) is used to scan and process the surfaces of the molybdenum and copper plates to be composited, etching periodically arranged micron-sized trenches and conical arrays on their surfaces, while simultaneously forming an amorphous / nanocrystalline activation layer with a controllable thickness (approximately 10-50 nanometers); after the laser treatment is completed, the textured surface is immediately bombarded with a light amount of argon ion beam sputtering in a vacuum chamber to further remove any possible extremely thin contamination layer;
[0034] The ultrafast energy deposition characteristics of short-pulse lasers enable cold processing of materials. On one hand, this creates a regular three-dimensional microstructure on the surface, significantly increasing the mechanical interlocking area and interfacial interlocking effect during subsequent rolling. On the other hand, rapid melting and solidification form an amorphous / nanocrystalline activation layer on the surface. This layer has extremely high atomic activity, significantly reducing the activation energy required for subsequent diffusion welding. The argon ion beam then acts as an in-situ vacuum cleaner, removing trace amounts of vapor deposits that may be introduced during laser processing, ensuring that the activated layer atoms are directly exposed to ultra-high vacuum, creating an atomically clean surface for the next deposition step.
[0035] S2. Gradient transition layer deposition: Under vacuum conditions, a barrier layer and a gradient functional layer with gradually changing composition are deposited on the surface of the activated layer.
[0036] Specifically, within the same vacuum chamber as described above, without disrupting the vacuum, immediately start the multi-target magnetron sputtering system (such as the MS-400D vacuum magnetron multi-target co-sputtering system or the CKJ-450 multi-target ultra-high vacuum magnetron sputtering instrument); firstly, deposit a pure tungsten (W) nanolayer on the textured surface of the molybdenum plate, with a thickness of approximately 20-50 nanometers; then, without shutting down the tungsten target, slowly increase the power of the copper (Cu) target while simultaneously decreasing the power of the tungsten target, achieving a continuous compositional transition deposition from W to W-Cu gradient layer to pure Cu layer within a thickness range of approximately 100-200 nanometers.
[0037] On the surface of the copper plate, using the same principle, a pure chromium (Cr) nanolayer (approximately 20 nanometers) and a Cr-Cu gradient layer are deposited.
[0038] Among them, the tungsten nanolayer, W, has the same crystal structure and lattice constant as Mo, and can form a near-perfect coherent interface with the Mo substrate, exhibiting extremely strong bonding. Simultaneously, W has very low miscibility with Cu, effectively preventing direct interdiffusion between Mo and Cu during subsequent heat treatment, thus completely suppressing the formation of brittle intermetallic compounds (such as MoCu2, MoCu4, etc.). The chromium (Cr) nanolayer, on the other hand, has limited solid solubility with Cu and strong reactivity with CuO. Its role is to tightly bond with the copper substrate and to "capture" any trace oxygen that may be present at the interface during subsequent heat treatment, forming stable Cr2O3 and purifying the interface.
[0039] The gradient transition layer achieves a gradient transition in thermal expansion coefficient and elastic modulus from Mo (or Cu) to pure Cu through continuous changes in composition. This can greatly alleviate the residual stress at the interface caused by the difference in physical properties of the matrix and prevent cracking.
[0040] S3. Vacuum encapsulation and warm rolling: The treated molybdenum matrix material and copper matrix material are stacked and vacuum encapsulated, and then subjected to multiple warm rolling passes at a temperature between the recrystallization temperature of copper and molybdenum to form a composite material.
[0041] Specifically, the molybdenum plate with the deposited transition layer is laminated with the copper plate in an ultra-clean environment. The laminate is then placed in a flexible sealed bag made of high-temperature alloy foil and evacuated to a high vacuum (≤10). -2 After sealing (Pa), a "vacuum package" is formed. The package is then sent into a roller furnace with precise temperature control. Infrared temperature measurement and / or embedded micro thermocouples are used to monitor the temperature near the interface. When the temperature rises to the set rolling temperature (e.g., 650-750℃), it is held for a period of time to make the temperature uniform. Then, it is quickly sent into a hot rolling mill for multi-pass, low-reduction warm rolling. The first pass has a reduction rate of about 15-20%, which focuses on making the microstructure fully plastically deformed and interlocked. The subsequent passes have a reduction rate of 10-15%.
[0042] Among them, high-temperature alloy foil vacuum packaging bags typically use ultra-thin stainless steel foil (such as 316L), high-temperature nickel-based alloy foil (such as Incol nickel alloy), or Hastelloy foil with a thickness of 0.05-0.2mm. The above metal foils are cut and folded, and then made into a "vacuum bag" that can completely wrap the molybdenum-copper laminate by high-precision welding (such as electron beam welding or laser welding). The "vacuum bag" is reserved with a suction nozzle. After being drawn to a high vacuum, the suction nozzle is sealed and welded to form a completely sealed vacuum chamber. Its function is to create an oxygen-free microenvironment and prevent interface oxidation from the heating to rolling process.
[0043] Using infrared temperature measurement and / or embedded micro thermocouples to monitor the temperature near the interface ensures that the rolling temperature is precisely controlled within a warm rolling range that is higher than the recrystallization temperature of copper but much lower than the recrystallization temperature of molybdenum. This allows the copper layer to soften and flow sufficiently to fill the texture on the molybdenum surface.
[0044] S4. Gradient heat treatment: The composite material after warm rolling is subjected to gradient cooling annealing with a continuous change along the spatial direction.
[0045] Specifically, after rolling, the vacuum-sealed composite material is immediately fed into a gradient annealing furnace connected to the rolling mill. The annealing furnace is divided into multiple independent temperature control zones along the length of the plate. After entering from the rolling temperature, the plate undergoes a continuously decreasing temperature field along the transport direction (e.g., from 700°C to 300°C).
[0046] During the cooling process, atoms in the W-Cu, Cr-Cu gradient transition layers diffuse fully under thermal drive, forming a strong metallurgical bond. At the same time, the gradient temperature field gradually relaxes the stress in the material. After cooling to room temperature, the outer high-temperature alloy foil packaging bag is cut open and peeled off to obtain the layered molybdenum-copper composite material.
[0047] By continuously decreasing the temperature field, the composite material gradually completes interfacial atomic diffusion and stress relaxation from the high-temperature end to the low-temperature end, so as to optimally eliminate the macroscopic internal stress caused by deformation and uneven cooling, and avoid the excessive coarsening of the transition layer or the decline of matrix properties that may be caused by long-term high-temperature isothermal annealing.
[0048] Example 1
[0049] This embodiment provides a rolling process for a layered molybdenum-copper composite material, used to prepare a molybdenum / copper composite material with a thickness ratio of 1:3.
[0050] A molybdenum plate (purity >99.95%) with dimensions of 100mm × 50mm × 1mm (thickness) and a copper plate (oxygen-free copper, purity >99.99%) with dimensions of 100mm × 50mm × 3mm (thickness) were selected. The plates were ultrasonically cleaned for 15 minutes each with acetone and anhydrous ethanol, and then dried for later use.
[0051] The cleaned substrate was placed in a glove box filled with high-purity argon gas (O2 < 1 ppm). A picosecond laser (wavelength 1064 nm, pulse width 10 ps) was used to scan the surfaces of the molybdenum and copper plates to be composited. Laser parameters were set as follows: energy density 5 J / cm², scanning speed 500 mm / s, and scan line spacing 30 μm. This process formed a regular array of trenches with a spacing of 30 μm and a depth of approximately 15 μm on the surface. Simultaneously, an amorphous / nanocrystalline hybrid activation layer of approximately 30 nm thickness was formed on the trench surface. After processing, the substrate was immediately transferred to the sample inlet chamber of a magnetron sputtering device.
[0052] The sample is transferred into the magnetron sputtering main chamber (background vacuum 5×10⁻⁶). -5 First, a tungsten (W) layer of 80 nm thickness is deposited on the surface of a molybdenum plate using DC magnetron sputtering as the first barrier layer. Then, while keeping the W target power fixed, the power of the copper (Cu) target is linearly increased to achieve a continuous gradient transition from W to Cu within a deposition thickness of 120 nm (W-Cu gradient layer). Subsequently, a chromium (Cr) layer of 30 nm thickness is deposited on the surface of the copper plate as the second barrier layer, followed by the deposition of an 80 nm thick Cr-Cu gradient layer (with the composition gradually changing from Cr to Cu).
[0053] Inside the cleanroom, the prepared molybdenum plate (transition layer down) and copper plate (transition layer up) are precisely stacked. They are then placed in a vacuum bag made of 0.1mm thick 316L stainless steel foil and evacuated to a vacuum level of 5×10⁻⁶. -3 After Pa, the package is sealed. The package is placed in a box-type resistance furnace and heated to 680°C (above the recrystallization temperature of copper and below the recrystallization temperature of molybdenum), and held for 20 minutes. Then it is quickly transferred to a hot rolling mill for three passes of warm rolling: 18% reduction in the first pass, 12% in the second pass, and 10% in the third pass, for a total reduction of approximately 35%.
[0054] The rolled sheet is immediately fed into an annealing furnace. The sheet passes through three temperature zones at a speed of 10 mm / s, set at 650℃, 450℃, and 250℃ respectively, with a dwell time of approximately 3 minutes in each zone, achieving slow, gradient cooling. After cooling to room temperature, the stainless steel vacuum bag is cut open and peeled off to obtain the final layered molybdenum-copper composite plate.
[0055] Example 2
[0056] The main difference between this embodiment and Embodiment 1 lies in the optimization of process parameters, which aims to obtain higher bonding strength.
[0057] Similarly, a molybdenum plate (purity >99.95%) with dimensions of 100mm × 50mm × 1mm (thickness) and a copper plate (oxygen-free copper, purity >99.99%) with dimensions of 100mm × 50mm × 3mm (thickness) were selected. The plates were ultrasonically cleaned for 15 minutes each with acetone and anhydrous ethanol, and then dried for later use.
[0058] The cleaned substrate was placed in a glove box filled with high-purity argon gas (O2 < 1 ppm). A femtosecond laser (wavelength 1030 nm, pulse width 300 fs), energy density 2 J / cm², scanning speed 2000 mm / s, and cross-scanning strategy were used. Under these parameters, a finer micron-sized pore and nanofiber composite structure was formed on the surface, resulting in a more uniform activation layer with a thickness of approximately 20 nm.
[0059] Using the same process as in Example 1 above, the first barrier layer is a 50nm thick tantalum (Ta) layer, followed by a 200nm thick Ta-Cu gradient layer; a 20nm thick titanium (Ti) layer and a 150nm thick Ti-Cu gradient layer are deposited on the copper plate surface. A thicker gradient layer provides better stress buffering.
[0060] The vacuum sealing bag material was changed to Hastelloy foil, which has higher temperature resistance. The heating temperature was set to 720℃, and four warm rolling processes were carried out (reduction rate: 15%, 12%, 10%, 8%, total reduction rate 40%).
[0061] It adopts a five-temperature gradient furnace with temperatures set at 700℃, 580℃, 460℃, 340℃, and 220℃, and a transfer speed of 5mm / s, resulting in a smoother cooling rate.
[0062] Comparative Example 1 (using traditional hot rolling composite process)
[0063] Molybdenum and copper plates of the same specifications were sanded to a surface roughness Ra≈3.2μm, then acid-washed (NaOH+H2O2 solution for molybdenum plates, HCl solution for copper plates) to remove oxide scale, washed with water and dried; the two plates were stacked together, tied and fixed with stainless steel wire around the edges, and then directly placed in a tube furnace under argon protection and heated to 850℃, held for 30 minutes; they were quickly removed and hot-rolled in air in a single pass with a reduction rate of 60%; after rolling, they were placed in an argon-protected furnace and annealed at 750℃ for 1 hour, and then cooled in the furnace.
[0064] The molybdenum-copper composite materials obtained in Examples 1, 2 and Comparative Example 1 were tested and compared, as shown in Table 1 below.
[0065] Example 1 Example 2 Comparative Example 1 Interfacial shear strength (MPa) 152 168 89 Thermal conductivity of composite materials (W / m·K) 245 251 195 Board flatness (mm) ≤0.5 ≤0.3 ≥2.0
[0066] Table 1
[0067] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 process for a layered molybdenum-copper composite material, characterized in that: Includes the following steps: S1. Surface texturing construction and activation treatment: The surfaces of the molybdenum matrix material and the copper matrix material to be composited are subjected to short pulse energy beam scanning treatment to construct three-dimensional surface textures and form amorphous / nanocrystalline activation layers on the surfaces of the molybdenum matrix material and the copper matrix material. S2. Gradient transition layer deposition: Under vacuum conditions, a barrier layer and a gradient functional layer with gradually changing composition are deposited on the surface of the activated layer, respectively; S3. Vacuum encapsulation and warm rolling: The treated molybdenum matrix material and copper matrix material are stacked and vacuum encapsulated, and then subjected to multiple warm rolling passes at a temperature between the recrystallization temperature of copper and molybdenum to form a composite material; S4. Gradient heat treatment: The composite material after warm rolling is subjected to gradient cooling annealing with a continuous change along the spatial direction.
2. The rolling process for layered molybdenum-copper composite materials as described in claim 1, characterized in that: The three-dimensional surface texture in S1 includes periodic grooves, cones, or arrays of holes.
3. The rolling process for layered molybdenum-copper composite materials as described in claim 1, characterized in that: The barrier layer in S2 includes a first barrier layer deposited on the surface of a molybdenum substrate and a second barrier layer deposited on the surface of a copper substrate.
4. The rolling process for layered molybdenum-copper composite materials as described in claim 3, characterized in that: The first barrier layer is a tungsten or tantalum layer; the second barrier layer is a chromium or titanium layer.
5. The rolling process for layered molybdenum-copper composite materials as described in claim 3, characterized in that: In S2, the composition of the gradient functional layer changes continuously from the elements of the barrier layer to the copper matrix material.
6. The rolling process for layered molybdenum-copper composite materials as described in claim 1, characterized in that: The vacuum sealing in S3 uses a flexible metal sealing container with a vacuum level not exceeding 1×10⁻⁶. -2 The experiment was conducted under the condition of Pa.
7. The rolling process for layered molybdenum-copper composite materials as described in claim 6, characterized in that: The total reduction rate of the S3 warm rolling is 40%-70%, and the single-pass reduction rate is no more than 25%.
8. The rolling process for layered molybdenum-copper composite materials as described in claim 1, characterized in that: The highest temperature of the gradient cooling annealing temperature field in S4 is comparable to the warm rolling temperature in S3, and the lowest temperature is no higher than 300℃, with a temperature gradient of 5-20℃ / cm.
9. The rolling process for layered molybdenum-copper composite materials as described in any one of claims 1-8, characterized in that: S1 and S2 are performed continuously under inert atmosphere protection or vacuum environment.
10. A layered molybdenum-copper composite material, characterized in that: It is prepared by the rolling process of the layered molybdenum-copper composite material according to any one of claims 1-9.