Method for reducing grafting printing deformation of plate-shaped copper alloy part

Abstract

The invention discloses a method for reducing grafting printing deformation of a plate-shaped copper alloy part, and belongs to the technical field of grafting printing. The printing method comprises the following steps: processing countersunk head screw holes in a pure copper substrate (avoiding a printing area), and locking the countersunk head screw holes to a printing bottom plate by using screws; printing parameters are as follows: the slice layer thickness is 0.03 mm, the laser power is 180-220 W, the scanning speed is 950-1050 mm / s, checkerboard scanning is performed, and interlayer cooling is performed for 10-20 s; during powder laying and printing, first-layer remelting is carried out to enhance combination; annealing treatment: keeping the temperature at 600 DEG C for 2 hours, and then cooling; and finally, the screws are taken down to obtain the low-deformation plate-shaped part. The thermal expansion coefficient difference between the copper alloy and the pure copper substrate is improved through the specific copper alloy material, the deformation risk is avoided, and the good heat-conducting property and mechanical property of the product can be guaranteed; and secondly, in combination with a printing process, residual stress is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of grafting printing, in particular to a method for reducing deformation of plate-shaped copper alloy parts during grafting printing. Background Art

[0002] Research into additive manufacturing of copper alloys is not uncommon. Liquid-cooled heat sinks, with their superior heat dissipation performance, are becoming a core solution for dissipating heat from high-power chips. These components are plate-shaped copper alloy parts consisting of a base plate that contacts the heat source and a fine heat dissipation structure attached to the base plate for contact with the cooling medium. This fine heat dissipation structure rapidly transfers heat from the base plate to the cooling medium, thereby rapidly cooling heat-generating components (such as chips). The fine heat dissipation structure requires higher mechanical properties, and therefore is typically manufactured from copper alloys rather than pure copper.

[0003] For the combination of substrate and fine structure, simple machining cannot achieve integrated molding. Using additive manufacturing for overall manufacturing is not advisable from the perspective of processing difficulty and cost-effectiveness. It has the problem of increasing the possibility of defects on large-area panels, and also greatly increases the construction time and cost. Therefore, the method of grafting fine structures onto machined substrates has gradually become the preferred option, but it has also brought about a new problem: due to the different processing methods and materials between the fine structure as the grafted part and the substrate, there are also differences. Therefore, warping and deformation are prone to occur during the grafting process and heat treatment, seriously affecting product quality.

[0004] The main improvement methods currently used are: (1) preheating the substrate at high temperature; (2) optimizing the scanning strategy based on the specific part geometry; (3) adding support structures, balancing the constraint effect and removability to avoid introducing new problems. Edge constraints and gradient supports are commonly used strategies; (4) adding heat treatment fixtures; (5) combining multiple technologies, such as high-temperature preheating + optimized island scanning strategy + edge constraint support. Among the above methods, (1) the substrate preheating function is not available on all equipment, and high-temperature preheating of the substrate improves the adhesion between the large-area substrate and the grafted structure, but it cannot improve the problem of unequal residual stress in different materials; (2) improving the scanning strategy based on the structure can avoid local deformation caused by heating at the same location for too long. However, when the grafted structure is too complex and local stress concentration occurs, changing the scanning strategy has no improvement effect. Moreover, when the process matures, changing the scanning strategy may cause internal defects in the parts; (3) Adding support structures is suitable for simple structural parts. For refined structures, the addition of supports may cause problems such as damage to the part structure and residual support traces when removing support constraints; (4) Heat treatment fixtures are currently the most commonly used method to improve deformation. However, the addition of heat treatment fixtures needs to be determined according to the structure; some structures do not support the use of fixtures or require additional design and customization, which increases the difficulty and cost of the work; (5) When used alone or in combination, the existing technical solutions are not universal and require additional processing methods according to the structure, resulting in additional time and cost, or changes in performance. Summary of the Invention

[0005] In view of this, the present invention proposes a method for reducing the deformation of plate-shaped copper alloy parts during grafting printing, which is used to solve the problem that when a new structure is constructed on a substrate by grafting printing, there is stress imbalance between the subsequent grafted structure and the substrate, which leads to warping during the printing process and aggravated deformation during the subsequent performance annealing process, affecting the subsequent processing and assembly.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: A method for reducing deformation of plate-shaped copper alloy parts during grafting and printing, comprising the following steps: S1. Prepare a pure copper substrate and symmetrically machine at least four countersunk screw holes on each substrate (if the length of the substrate exceeds 150mm, the number of countersunk screw holes can be appropriately increased, for example, six. The positions of the countersunk screw holes should be staggered from the area to be grafted and printed, and preferably located at the periphery of the substrate); S2. Fix the base plate to the printing base plate by means of countersunk screws; Preferably, if the substrate thickness is 1.5 mm < 3 mm, use M2 countersunk screws; 3mm≤substrate thickness<4mm, use M3 countersunk screws; S3. Use Materialise slicing software to slice the model of the grafted part, setting the layer thickness to 0.03mm, and generate the corresponding slice file. Use the upper surface of the substrate as the grafting printing surface for leveling and air cleaning, and then apply copper alloy powder layer by layer on the substrate. Remelt the first layer to increase adhesion and raise the substrate temperature (100-150°C) to avoid local deformation of the substrate due to uneven temperature between the substrate and the printed layer. Use a printing strategy of lower laser power and higher scanning speed (180-220W, 950-1050 mm / s). Excessive laser power or slow scanning speed can lead to heat accumulation. Partition scanning: adopts a checkerboard scanning strategy to avoid local overheating (jumping areas in the same layer to avoid repeated heat input in adjacent areas); Interlayer cooling: Increase the interlayer cooling time (10~20s) to reduce residual stress (by adjusting the software to set the interlayer jump interval time and extend the interlayer cooling time); S4. After printing, the entire part is placed in a vacuum furnace along with the printed base plate for annealing (without removing the fixing screws). The temperature is raised to 600°C ± 3°C at a rate of 5-10°C / min, held for 2 hours, then cooled to 70°C ± 10°C with argon gas. Finally, the part is removed and allowed to cool to room temperature in the air to achieve optimal thermal conductivity and mechanical properties. If the structure of the grafted printed part is too complex, the heating time can be appropriately extended (the heating rate can be reduced) to avoid deformation caused by excessive stress release in the complex structure. S5. After the entire surface is completely cooled, remove the screws and check the flatness of the substrate.

[0007] The copper alloy powder includes the following components in percentage by mass: Cr: 0.8-1.2%, Zr 0.1-0.3%, Ti 0.05~0.15%, nano-Al2O3 0.3~0.5%, and the balance copper.

[0008] The characteristics of each element in the copper alloy powder are shown in Table 1.

[0009] Table 1 Introduction to the characteristics of each element in copper alloy powder

[0010] Improvement mechanism of each element on thermal stress and deformation ①The role of Cr CTE matching: the alloy CTE is increased from 17×10 -6 / ℃ dropped to about 15×10 -6 / ℃, reducing thermal mismatch with the substrate.

[0011] High temperature strength: Cr-rich phase (such as CrCu2) precipitates during the aging process, inhibiting high temperature deformation and reducing stress concentration during cooling.

[0012] ②Synergistic effect of Zr and Ti Grain boundary strengthening: Zr is concentrated at the grain boundaries, hindering dislocation movement and reducing residual stress accumulation.

[0013] Interface bonding: Ti preferentially reacts with oxides on the substrate surface to form a metallurgical bonding layer, thus avoiding interface peeling.

[0014] ③ Dispersion of nano-Al2O3 Stress redistribution: Nanoparticles act as local stress buffers, dispersing stress concentration at the interface.

[0015] Inhibit deformation: hinder grain boundary migration at high temperatures and reduce deformation caused by creep.

[0016] Thermal conductivity balance strategy ① Solid solubility control: Cr, Zr, and Ti all maintain low solid solubility (<1.5% total) to avoid excessive electron scattering.

[0017] ② Second phase optimization: The size of nano-Al2O3 is controlled at 50~100 nm to ensure diffuse distribution without blocking the heat conduction path.

[0018] In summary, the composition of the copper alloy in the present invention is intended to reduce the difference in coefficient of thermal expansion (CTE) between the copper alloy and pure copper, improve the high-temperature strength of the copper alloy, reduce plastic deformation, and maintain good thermal conductivity (>300 W / mK).

[0019] Compared with the prior art, the present invention has the following beneficial effects: The present invention first improves the difference in thermal expansion coefficient between the copper alloy and the pure copper substrate by designing the composition and dosage of the copper alloy material, thereby avoiding the risk of deformation and ensuring good thermal conductivity and mechanical properties of the product; secondly, by improving the printing process, the residual stress is reduced. In the present invention, the method of setting a countersunk screw hole fixing constraint on the substrate is suitable for most scenarios of substrate and fine structure grafting printing, and will not affect the grafting printing process. The fixed constraint can make the positioning of the grafted structure more precise, obtain better dimensional accuracy, and can suppress the stress deformation generated during the scanning process and the deformation of the substrate caused by uneven stress release during the annealing process. There is no need to add additional supports and fixtures, which ensures that the processing time does not increase while effectively reducing the construction cost and will not affect the performance of the final part. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a diagram showing how the base plate is fastened to the print base plate using M3 countersunk screws.

[0021] In the figure: 1 is the printing base plate, 2 is the base plate, and 3 is the countersunk screw on the base plate. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to understand the present invention more clearly and intuitively, the present invention will be further described below with reference to the accompanying drawings.

[0023] Example 1 This embodiment provides a method for reducing deformation of plate-shaped copper alloy parts during grafting printing, comprising the following steps: S1. Prepare pure copper substrates (110 mm long, 60 mm wide, and 3 mm thick). Symmetrically machine four countersunk screw holes on each substrate (the locations of the countersunk screw holes are staggered with the area on the substrate where the grafting printing will be performed. In this embodiment, the four countersunk screw holes are located at the four corners of the substrate). S2. Fix the base plate to the printing base plate with M3 countersunk screws. Figure 1 shown.

[0024] S3. Use Materialise slicing software to slice the model of the grafted part, setting the layer thickness to 0.03mm, and generate the corresponding slice file. Use the upper surface of the substrate as the grafting printing surface for leveling and air cleaning, and then apply copper alloy powder layer by layer on the substrate. Remelt the first layer to increase adhesion and raise the substrate temperature (100-150°C) to avoid local deformation of the substrate due to uneven temperature between the substrate and the printed layer. Use a printing strategy of lower power and higher scanning speed (200W + 1000 mm / s) to reduce heat accumulation; Partition scanning: adopts a checkerboard scanning strategy to avoid local overheating (jumping areas in the same layer to avoid repeated heat input in adjacent areas); Interlayer cooling: Increase the interlayer cooling time (10~20s) to reduce residual stress (by adjusting the software to set the interlayer jump interval time and extend the interlayer cooling time); S4. After printing, the entire part is placed in a vacuum furnace along with the printed base plate for annealing (without removing the fixing screws). The temperature is raised to 600°C at a rate of 10°C / min, held for 2 hours, and then cooled to 80°C with argon gas. Finally, the entire part is taken out and placed in air to cool to room temperature to obtain optimal thermal conductivity and mechanical properties. S5. After the whole body has completely cooled, remove the screws and check the flatness of the parts substrate; In this embodiment, the copper alloy powder includes the following components in percentage by mass: Cr: 1.0%, Zr 0.2%, Ti 0.10%, nano-Al2O3 0.4%, and the balance copper.

[0025] The mechanical properties test standard of the parts substrate refers to GB / T 228.1: (1) Install the sample Clamp the specimen in the testing machine fixture, ensuring axial alignment to avoid eccentric loading.

[0026] The clamping force is moderate to prevent the specimen from slipping or being pinched.

[0027] (2) Preloading Apply a small initial load (e.g. 1% of the expected maximum force) to eliminate the gap and adjust the extensometer zero point.

[0028] (3) Loading test Rate Control: Elastic stage: controlled by stress rate (e.g. 1~10 MPa / s, ISO 6892-1 Method A).

[0029] Plastic stage: switchable strain rate (e.g. 0.0025~0.025 s -1 ).

[0030] Continuous recording: load-displacement data is collected synchronously until the specimen breaks.

[0031] (4) Measurement after fracture Take out the sample, piece together the broken part, and measure the gauge length after fracture (L u ) and minimum diameter / width at the necking point.

[0032] Example 2 This embodiment proposes a method for reducing deformation of plate-shaped copper alloy parts during grafting printing. The difference between this embodiment and embodiment 1 is that: during the annealing process, the cooling rate is 5°C / min; the printing power is 180W, and the scanning speed is 1050 mm / s; In this embodiment, the copper alloy powder includes the following components in percentage by mass: Cr: 0.8%, Zr 0.1%, Ti 0.05%, nano-Al2O3 0.3%, and the balance copper.

[0033] Example 3 This embodiment provides a method for reducing deformation during grafting printing of plate-shaped copper alloy parts. The difference between this embodiment and embodiment 1 is that the substrate has dimensions of 110 mm in length, 60 mm in width, and 2 mm in thickness and is fixed to the printing base plate using M2 countersunk screws. The printing power is 220 W and the scanning speed is 950 mm / s. In this embodiment, the copper alloy powder includes the following components in percentage by mass: Cr: 1.2%, Zr 0.3%, Ti 0.15%, nano-Al2O3 0.5%, and the balance copper.

[0034] Comparative Example 1 The only difference between this comparative example and Example 1 is that Cr is removed from the copper alloy powder, that is, the copper alloy powder includes the following components in percentage by mass: Zr 0.2%, Ti 0.1%, nano-Al2O3 0.4%, balance Cu.

[0035] Judging from the effect of grafting printing using the above-mentioned copper alloy powder on a pure copper substrate, the thermal deformation of the substrate increases, affecting the flatness; at the same time, the mechanical properties are affected, and the lack of Cr reduces the solid solution of the copper alloy powder and improves the thermal conductivity.

[0036] Comparative Example 2 The only difference between this comparative example and Example 1 is that the amount of Cr added to the copper alloy powder is increased, that is, the copper alloy powder includes the following components in percentage by mass: Cr 1.5%, Zr 0.2%, Ti 0.1%, nano-Al2O3 0.4%, balance Cu.

[0037] Judging from the effect of grafting printing using the above-mentioned copper alloy powder on a pure copper substrate, excessive Cr is dissolved in the matrix, increasing the free electron scattering rate, hindering the heat conduction path, and thus affecting the thermal conductivity; and excessive Cr leads to increased brittleness, affecting the mechanical properties.

[0038] Comparative Example 3 The only difference between this comparative example and Example 1 is that Zr and Ti are removed from the copper alloy powder, that is, the copper alloy powder includes the following components in percentage by mass: Cr 1.0%, nano-Al2O3 0.4%, balance Cu.

[0039] Judging from the effect of grafting printing using the above-mentioned copper alloy powder on a pure copper substrate, the lack of Zr and Ti causes residual stress accumulation in the grafted part and the interface adhesion effect deteriorates. The interface bonding quality is significantly reduced due to the coarse grain formation and the accumulation of residual stress on the interface, and the interface is prone to cracking.

[0040] Comparative Example 4 The only difference between this comparative example and Example 1 is that the amount of Zr added to the copper alloy powder is increased, that is, the copper alloy powder includes the following components in percentage by mass: Cr 1.0%, Zr 0.4%, Ti 0.1%, nano-Al2O3 0.4%, balance Cu.

[0041] Judging from the effect of grafting printing using the above-mentioned copper alloy powder on a pure copper substrate, although excessive addition of Zr can slightly improve the strength, it significantly reduces the plasticity and toughness, and forms excessive brittle intermetallic compounds (such as Cu5Zr), which leads to grain boundary stress concentration, especially the elongation is greatly affected.

[0042] Comparative Example 5 The only difference between this comparative example and Example 1 is that the nano-Al2O3 in the copper alloy powder is removed, that is, the copper alloy powder includes the following components in percentage by mass: Cr 1.0%, Zr 0.2%, Ti 0.1%, balance Cu.

[0043] Judging from the effect of grafting printing using the above copper alloy powder on a pure copper substrate, the lack of nano-Al2O3 leads to a lack of stress buffering and strengthening phase, and high-temperature creep is aggravated, resulting in a decrease in the mechanical properties of the molded parts.

[0044] Comparative Example 6 The only difference between this comparative example and Example 1 is that an excessive amount of nano-Al2O3 is added to the copper alloy powder, that is, the copper alloy powder includes the following components in percentage by mass: Cr 1.0%, Zr 0.2%, Ti 0.1%, nano-Al2O3 0.8%, balance Cu.

[0045] Judging from the effect of grafting printing using the above copper alloy powder on a pure copper substrate, excessive nano-Al2O3 particles agglomerate to form local stress concentration points, which promote cracks.

[0046] Comparative Example 7 This comparative example proposes a method for grafting printing onto a substrate. This method differs from Example 1 in that no fixed constraints are added during printing using a copper substrate, and a flat fixture is used to secure the substrate during the annealing process. All other aspects are the same as Example 1. The final results show that the substrate exhibited significant deformation due to the lack of fixed constraints during the printing phase. The use of a flat fixture during the subsequent annealing process failed to fully suppress this deformation tendency or repair any deformation from the printing phase, resulting in severe warping of the final sample.

[0047] Comparative Example 8 This comparative example proposes a method for grafting printing on a substrate. This method differs from Example 1 in that it utilizes a printing strategy with a laser power of 250W. The results of grafting printing using the copper alloy powder on a pure copper substrate show that excessive laser power leads to excessive heat accumulation, which affects the flatness of the copper substrate.

[0048] Comparative Example 9 This comparative example proposes a method for grafting printing on a substrate. This method differs from Example 1 in that it utilizes a printing strategy with a scanning speed of 900 mm / s. Grafting printing using the aforementioned copper alloy powder on a pure copper substrate also demonstrates that the slow scanning speed also leads to excessive heat accumulation, which compromises the copper substrate's flatness.

[0049] Comparative Example 10 This comparative example proposes a method for grafting printing onto a substrate. This method differs from Example 1 in that no remelting is performed during printing, and the copper substrate is not preheated. Grafting printing using the aforementioned copper alloy powder onto a pure copper substrate reveals significant thermal differences between the pure copper substrate and the substrate, leading to inconsistent residual stress release. This results in significant stress differences in the first few layers during printing, resulting in arching in the middle of the base plate and affecting overall mechanical properties.

[0050] The mechanical properties of the products obtained by grafting and printing in each embodiment and comparative example were tested, and the results are shown in Table 2.

[0051] Table 2 Mechanical properties test results of the products printed in various embodiments and comparative examples

[0052] From the results of the examples and comparative examples 1-6 in Table 2, it can be seen that the amount of each component in the copper alloy powder plays an important role in the deformation of the plate-shaped copper alloy parts during grafting printing, especially the influence on the flatness and the mechanical properties. In addition, from the structure of comparative example 7, the present invention adopts the method of countersunk screws to fix the substrate to the printing base plate, which well prevents the thermal stress deformation of the substrate. This method will not affect the printing process and heat treatment process of the parts, and thus will not have a negative impact on the mechanical properties and thermal conductivity of the plate-shaped copper alloy parts. From the results of comparative examples 8-10, by changing the laser power, scanning speed and whether to use remelting, the heat accumulation during the product printing process is too large, which leads to the generation of deformation.

[0053] The present invention combines the thermal deformation law of the plate edge and reduces the possibility of warping of the plate during the heat treatment process through edge and corner constraints, so that the flatness deviation rate of the plate is reduced by 90-95%, and the flatness can be controlled to ≤0.1mm; the present invention maximizes the stability of the final performance of the part through the selection of copper alloy powder and the selection of printing process. After treatment, the density of the part reaches 99.99%, the tensile strength is above 550MPa, the yield strength is above 450MPa, and the thermal conductivity is above 300W / mK, which meets the performance requirements of thermal conductive parts.

[0054] The above description of the embodiments is intended to facilitate understanding and application of the present invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the embodiments described herein, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for reducing deformation of plate-shaped copper alloy parts during grafting and printing, characterized in that: The steps include: S1. Prepare a pure copper substrate. Each substrate is symmetrically machined with at least four countersunk screw holes. The positions of the countersunk screw holes are staggered with the area to be grafted and printed. S2. Fix the base plate to the printing base plate with countersunk screws; S3. Use Materialise slicing software to slice the model of the grafted part, set the layer thickness to 0.03mm, and generate the corresponding slice file. Use the upper surface of the substrate as the grafting printing surface for leveling and air washing. Then, apply copper alloy powder layer by layer on the substrate for printing, and remelt the first printed layer. The copper alloy powder comprises the following components in percentage by mass: Cr: 0.8-1.2%, Zr 0.1-0.3%, Ti 0.05-0.15%, nano-Al2O3 0.3-0.5%, and the balance copper; The printing laser power was 180-220 W, the scanning speed was 950-1050 mm / s, a checkerboard scanning strategy was used, and the inter-layer cooling time was set to 10-20 s; S4. After printing, the entire part is sent into a vacuum furnace along with the printed base plate for annealing. The temperature is raised to 600°C ± 3°C at a rate of 5-10°C / min, kept at this temperature for 2 hours, then cooled to 70°C ± 10°C with argon gas, and finally taken out and placed in air to cool to room temperature. S5. After the entire part has completely cooled, remove the screws to obtain the plate-shaped copper alloy part.

2. A method for reducing deformation of plate-shaped copper alloy parts during grafting and printing according to claim 1, characterized in that: The copper alloy powder includes the following components in percentage by mass: Cr: 1.0%, Zr 0.2%, Ti 0.10%, nano-Al2O3 0.4%, and the balance copper.

3. A method for reducing deformation of plate-shaped copper alloy parts during grafting and printing according to claim 1, characterized in that: The countersunk screw holes are located at the four corners of the base plate.

4. A method for reducing deformation of plate-shaped copper alloy parts during grafting and printing according to claim 1, characterized in that: When the substrate thickness is 1.5mm<3mm, use M2 countersunk screws.

5. The method for reducing deformation of plate-shaped copper alloy parts during grafting and printing according to claim 1, wherein: When the substrate thickness is 3mm≤4mm, use M3 countersunk screws.

6. A method for reducing deformation of plate-shaped copper alloy parts during grafting and printing according to claim 1, characterized in that: Remelting causes the substrate temperature to rise to 100~150°C.

7. Use of the method according to any one of claims 1 to 6 in preparing a liquid cooling radiator.

8. The use according to claim 7, characterized in that The liquid-cooled radiator includes a copper substrate and a copper alloy heat dissipation structure, and the copper alloy heat dissipation structure is constructed by grafting printing.

9. The product prepared by the method according to any one of claims 1 to 6.

10. The product according to claim 9, characterized in that The product is a liquid-cooled radiator with a density of 99.99%, a tensile strength of over 550MPa, a yield strength of over 450MPa, and a thermal conductivity of over 300W / mK.

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