A low defect alsi10mg alloy direct energy deposition additive manufacturing method

Abstract

The application provides a low-defect AlSi10Mg alloy direct energy deposition additive manufacturing method, and belongs to the field of laser metal additive manufacturing, and aims at solving the problem of high porosity of AlSi10Mg alloy manufactured by using the direct energy deposition technology at present. The method comprises the following steps: material pretreatment and processing environment creation, base material preheating treatment, first layer deposition layer processing, powder blowing and interlayer cooling, deposition layer processing surface preheating and next layer deposition layer processing, multi-layer deposition, deposition of the part to be processed to a predetermined height, and completion of processing. By using the reciprocating scanning, interlayer cooling, interlayer offset and laser scanning preheating mode, the deposition layer collapse is effectively prevented, the porosity of the deposition layer is reduced, and the mechanical properties of the AlSi10Mg product manufactured by the direct energy deposition laser additive manufacturing are improved in a certain processing parameter range.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser metal additive manufacturing, in particular, to a low-defect AlSi10Mg alloy direct energy deposition additive manufacturing method. BACKGROUND

[0002] Aluminum and its alloys are one of the most widely used metal materials in the world due to their low density, high strength, low melting point, good corrosion resistance, and good electrical and thermal conductivity. They are also the preferred materials for lightweight design of transportation equipment, marine vessels, and aerospace. With the increasing demand for lightweight and green manufacturing in the fields of transportation, marine vessels, and aerospace, high-quality and rapid manufacturing of complex components and repair of high-value components have become new challenges. Laser metal additive manufacturing technology, represented by selective laser melting (SLM) and direct energy deposition (DED), has broad application prospects in rapid manufacturing of complex components and repair of high-value components. AlSi10Mg alloy is a near-eutectic Al-Si-Mg alloy. Due to its good weldability and low crack sensitivity, it is one of the most common aluminum alloys for additive manufacturing.

[0003] For SLM manufacturing of aluminum alloys, the development is relatively mature and there are some application cases. For direct energy deposition technology, current research is mainly focused on iron-based, titanium-based, and nickel-cobalt-based high-temperature alloys. The development of aluminum alloy DED manufacturing technology is relatively slow. This is because aluminum alloy powder has poor flowability and is sensitive to oxygen. In addition, aluminum and its alloys have low laser absorption rate, so a large laser power is required during DED laser additive manufacturing. Low-melting-point elements such as Mg and Zn in the alloy will evaporate during processing. Metal vapor and gas in the processing environment are drawn into the molten pool under the action of the laser, forming pores and other defects after solidification. These defects often serve as the source of fracture failure, leading to a decrease in strength and poor mechanical properties. According to existing literature reports, the porosity of SLM-manufactured AlSi10Mg alloy can reach 0.2%, while the porosity of DED-manufactured AlSi10Mg alloy is usually above 1%. In order to solve the problem of high porosity of DED-manufactured AlSi10Mg alloy, a low-defect AlSi10Mg alloy direct energy deposition additive manufacturing method is needed to achieve low-defect DED laser additive manufacturing of AlSi10Mg alloy by using appropriate process parameters and processing strategies. SUMMARY

[0004] The technical problem to be solved by the present application is:

[0005] The existing AlSi10Mg alloy has a high porosity problem manufactured by the direct energy deposition technology.

[0006] The present application adopts the technical scheme to solve the above technical problems:

[0007] The present application provides a low-defect AlSi10Mg alloy direct energy deposition additive manufacturing method, comprising the following steps:

[0008] S1, material preprocessing and processing environment: pretreat AlSi10Mg powder and substrate, and the processing environment is inert gas atmosphere processing environment;

[0009] S2, substrate preheating treatment: using 40-60% of the laser power in the proposed processing parameters to scan and preheat the substrate;

[0010] S3, first layer deposition layer processing: using reciprocating scanning to process the first layer deposition layer, and the interpass overlap rate is 40%;

[0011] S4, powder blowing and interlayer cooling: using inert gas to blow off the excess floating powder on the surface of the previous deposition layer which does not participate in melting, and plays a role in interlayer cooling;

[0012] S5, deposition layer processing surface preheating: using laser power lower than the laser power of substrate preheating by 10-15% to scan and preheat the surface of the previous deposition layer;

[0013] S6, next layer deposition layer processing: using reciprocating scanning to process the deposition layer, and the offset between adjacent deposition layers is 30% of the single-track cladding layer fusion width in the proposed processing parameters;

[0014] S7, step seven: repeating S4, S5 and S6 for multi-layer deposition, until the deposition of the part to be processed reaches the predetermined height, and the processing is completed.

[0015] Further, the inert gas in S1 is at least one of argon and nitrogen, and the oxygen content of the inert gas atmosphere processing environment is less than 100ppm.

[0016] Further, the processing parameters are: laser power is 1800-2000W, scanning speed is 480-600mm / min, powder feeding rate is 1.6-2.0g / min, powder feeding gas flow is 3.0-3.5L / min, and spot diameter is 2800-3200μm.

[0017] Further, the processing parameters are: laser power is 1800W, scanning speed is 480-500mm / min, powder feeding speed is 1.6g / min, powder feeding gas flow is 3.0-3.5L / min, and spot diameter is 3000μm.

[0018] Further, the substrate preheating treatment is to use 50% of the laser power in the designed processing parameters to perform scanning preheating treatment on the substrate.

[0019] Further, the deposited layer processing surface preheating is to use laser power 10% lower than that of the substrate preheating to perform scanning preheating treatment on the surface of the previous deposited layer.

[0020] Further, the parameters of powder blowing and interlayer cooling in S4 are: blowing gas flow is 8-11L / min, and scanning speed is 480mm / min.

[0021] Further, the particle size of the AlSi10Mg alloy powder is 40-90μm, and the substrate material is ZL105 or Al-Si series aluminum alloy plate.

[0022] Further, the pretreatment of the AlSi10Mg alloy powder in S1 is to use a vacuum drying box to dry the alloy powder at 120-130℃ for 2-4h.

[0023] Further, the pretreatment of the substrate in S1 is to polish the substrate to remove the surface oxide layer, clean the substrate with anhydrous ethanol or acetone, immerse the substrate in a 5% NaOH solution for 5-7min, then immerse it in a 20% HNO3 solution for 5-7min, and finally wash it with deionized water and alcohol and dry it, and the treated substrate needs to be used within 12h.

[0024] Compared with the prior art, the present application has the following advantages:

[0025] The present application is directed to the defect of high porosity rate in the process of direct energy deposition laser additive manufacturing of AlSi10Mg alloy, and proposes a low-defect AlSi10Mg alloy direct energy deposition additive manufacturing method. By using reciprocating scanning, interlayer cooling, interlayer offsetting and laser scanning preheating, the AlSi10Mg alloy deposited layer collapse can be effectively prevented within a certain processing parameter range, the porosity of the AlSi10Mg alloy deposited layer is effectively controlled, and the reduction of porosity defects can achieve the purpose of improving the mechanical properties of the direct energy deposition laser additive manufacturing AlSi10Mg product, expanding the application range of the direct energy deposition laser additive manufacturing AlSi10Mg alloy, and at the same time, the method can also provide technical reference for the control of porosity in the direct energy deposition additive manufacturing process of other alloys. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 This is a flowchart of the direct energy deposition additive manufacturing method for low-defect AlSi10Mg alloy in this embodiment of the invention;

[0027] Figure 2 This is a comparison diagram showing the impact of the preheating scanning processing method on the deposition layer forming effect in the embodiments of the present invention;

[0028] Figure 3 This is a schematic diagram of the overlapping portion of the deposition layer in an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of interlayer offset in an embodiment of the present invention;

[0030] Figure 5 This is a cross-sectional view of the AlSi10Mg sample in an embodiment of the present invention. Detailed Implementation

[0031] In the description of this invention, it should be noted that the terms "first," "second," and "third" mentioned in the embodiments of this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," and "third" may explicitly or implicitly include one or more of that feature.

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0033] like Figure 1 As shown, this invention provides a method for direct energy deposition additive manufacturing of low-defect AlSi10Mg alloy, comprising the following steps:

[0034] S1. Pre-treatment of processing materials to create a suitable processing environment

[0035] AlSi10Mg alloy powder (40-90μm) was dried in a vacuum drying oven at 120℃ for 2 hours to ensure the powder was dry, non-caking, and had good flowability. Removing moisture from the powder helps reduce porosity in the processed samples. ZL105 substrate was polished with 180-grit and 400-grit sandpaper to remove the oxide layer. After cleaning with anhydrous ethanol (99.7%), the substrate was immersed in a 5% NaOH aqueous solution for 5 minutes, followed by an immersion in a 20% HNO3 aqueous solution for 5 minutes. It was then washed with deionized water and alcohol, and finally dried. The chemically treated substrate must be used within 12 hours to avoid re-oxidation. The treated substrate was placed in a molding chamber, which was then evacuated and purged with argon gas to create an inert gas atmosphere for processing. The oxygen content in the molding chamber was below 100ppm.

[0036] S2, Substrate preheating treatment

[0037] When initially depositing layers on the substrate, the substrate is at room temperature, resulting in low internal energy. Even after powder cooling following the first deposition layer, the substrate's internal energy remains significantly higher than it would have been at room temperature before processing. Because the substrate's internal energy is low at the start of processing, some laser energy is input into the substrate during the first deposition layer, increasing its internal energy. This leads to a shallower molten pool on the substrate surface when the alloy powder melts. The energy accumulation from previous deposition layers causes subsequent deposition layers to have a greater melting depth than the previous layer. This difference becomes increasingly pronounced with multiple deposition layers, ultimately resulting in poor overall forming quality of the molded part. Figure 2 As shown in (a).

[0038] To improve the forming effect described above, preheating scanning of the substrate is required. Preheating scanning refers to using 40-50% of the laser power in the planned processing parameters, with the same scanning rate, no powder feed, and no protective gas. Before processing the deposited layer, the substrate or the surface of the previous deposited layer is preheated by laser scanning to ensure similar internal energy before each deposited layer is prepared. When processing the first deposited layer on the substrate surface, because the substrate itself contains very little heat, 50% of the planned laser power is used for scanning preheating. For other deposited layers, the laser energy stored from the processing of the previous deposited layer is used, so 40% of the laser power is used for scanning preheating before processing. Excessive power will lead to over-melting and collapse of the deposited layer. The deposited layer processing effect after scanning preheating is as follows: Figure 2 As shown in (b), the forming effect has been significantly improved.

[0039] The substrate was preheated and scanned using the following parameters: laser power of 900W, scanning rate of 480mm / min, and spot diameter of 3000μm.

[0040] S3, Processing of the first deposition layer

[0041] The first deposition layer was processed using a reciprocating scanning method. The processing parameters were: laser power 1800W, scanning rate 480mm / min, powder feed rate 1.6g / min, powder gas flow rate 3.0-3.5L / min, spot diameter 3000μm, and overlap rate 40%. The overlap portion of the deposition layer is shown below. Figure 3 As shown.

[0042] S4, Powder blowing and interlayer cooling

[0043] After each layer of processing, a layer of unmelted powder accumulates on the surface of the deposited layer. If this is not cleaned in time, the actual powder feed will be too large, easily leading to unmelted inclusion defects. Furthermore, if the next layer is processed immediately after each layer is completed, the accumulated energy within the deposited layer will be too high, causing the deposited layer to collapse. Therefore, interlayer cooling is necessary. Inert gas is used to blow away the excess unmelted powder from the surface of the previous deposited layer, thus achieving interlayer cooling. The parameters for powder blowing and interlayer cooling are: purge gas flow rate of 8-10 L / min and scanning rate of 480 mm / min.

[0044] S5, Preheating of the deposited layer processing surface

[0045] The surface of the previous deposition layer was preheated and scanned using the following parameters: laser power of 720W, scanning rate of 480mm / min, and spot diameter of 3000μm.

[0046] S6, Processing of the next deposition layer

[0047] The deposited layer was processed using a reciprocating scanning method with the following parameters: laser power of 1800W, scanning rate of 480mm / min, powder feed rate of 1.6g / min, powder gas flow rate of 3.0-3.5L / min, spot diameter of 3000μm, overlap ratio of 40%, and layer height from the substrate bonding surface to the apex of the cladding layer in a single pass. To avoid unmelted inclusion defects, interlayer offset was applied to adjacent deposited layers, with the offset amount being 30% of the weld width of the single pass under the proposed processing parameters. A schematic diagram of the interlayer offset is shown below. Figure 4 As shown.

[0048] S7. Repeat S4, S5 and S6 to perform multi-layer deposition until the part to be processed is deposited to the predetermined height, and the processing ends.

[0049] like Figure 5As shown, the porosity of the AlSi10Mg alloy sample obtained by the direct energy deposition additive manufacturing method of the present invention is 0.09%, which is far lower than the porosity level of AlSi10Mg manufactured by DED reported in existing literature.

[0050] The challenge of this invention lies in the need to conduct energy analysis to determine the reasons for the high porosity and poor forming effect of AlSi10Mg alloy direct energy deposition additive manufacturing. Through a large number of processing experiments and the detection and analysis of the experimental results, the processing process and processing parameters were continuously optimized and adjusted. Finally, the processing method of reciprocating scanning, interlayer cooling, interlayer offset, and laser scanning preheating was determined. The optimal processing parameters, substrate preheating parameters, powder blowing and interlayer cooling parameters, and preheating parameters of the deposited layer processing surface were selected, ultimately achieving a porosity level far lower than that of the existing ones.

[0051] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for direct energy deposition additive manufacturing of low-defect AlSi10Mg alloy, characterized in that... Includes the following steps: S1. Pretreatment of processing materials and creation of processing environment: AlSi10Mg powder and substrate are pretreated, and the processing environment is an inert gas atmosphere. S2. Substrate preheating treatment: The substrate is preheated by scanning using 40-60% of the laser power in the planned processing parameters. S3, Processing of the first deposition layer: The first deposition layer is processed using a reciprocating scanning method, with an inter-pass overlap rate of 40%; S4. Powder blowing and interlayer cooling: Inert gas is used to blow away excess powder that has not participated in melting from the surface of the previous deposit layer, and it also serves as interlayer cooling. S5. Preheating of the deposited layer surface: The surface of the previous deposited layer is scanned and preheated using a laser with a power 10-15% lower than that used for preheating the substrate. S6. Processing the next deposition layer: The deposition layer is processed using a reciprocating scanning method, with the offset between adjacent deposition layers being 30% of the single-pass cladding width under the proposed processing parameters; S7, Step Seven: Repeat S4, S5 and S6 to perform multi-layer deposition until the part to be processed is deposited to the predetermined height, and the processing is completed.

2. The method for direct energy deposition additive manufacturing of low-defect AlSi10Mg alloy according to claim 1, characterized in that... The inert gas mentioned in S1 is at least one of argon and nitrogen, and the oxygen content in the inert gas atmosphere processing environment is less than 100 ppm.

3. The method for direct energy deposition additive manufacturing of low-defect AlSi10Mg alloy according to claim 1, characterized in that... The processing parameters are as follows: laser power of 1800-2000W, scanning rate of 480-600mm / min, powder feeding rate of 1.6-2.0g / min, powder feeding gas flow rate of 3.0-3.5L / min, and spot diameter of 2800-3200μm.

4. The method for direct energy deposition additive manufacturing of low-defect AlSi10Mg alloy according to claim 3, characterized in that... The processing parameters are as follows: laser power is 1800W, scanning rate is 480mm / min, powder feeding rate is 1.6g / min, powder feeding gas flow rate is 3.0-3.5L / min, and spot diameter is 3000μm.

5. The method for direct energy deposition additive manufacturing of low-defect AlSi10Mg alloy according to claim 1, characterized in that... The substrate preheating treatment involves scanning and preheating the substrate using 50% of the laser power in the planned processing parameters.

6. The method for direct energy deposition additive manufacturing of low-defect AlSi10Mg alloy according to claim 1, characterized in that... The surface preheating of the deposited layer is performed by scanning the surface of the previous deposited layer with a laser power 10% lower than that used for preheating the substrate.

7. The method for direct energy deposition additive manufacturing of low-defect AlSi10Mg alloy according to claim 1, characterized in that... The parameters for powder blowing and interlayer cooling in S4 are: purge gas flow rate of 8-11 L / min and scanning rate of 480-500 mm / min.

8. The method for direct energy deposition additive manufacturing of low-defect AlSi10Mg alloy according to claim 1, characterized in that... The particle size of AlSi10Mg alloy powder is 40-90μm, and the substrate material is ZL105 or Al-Si aluminum alloy plate.

9. The method for direct energy deposition additive manufacturing of low-defect AlSi10Mg alloy according to claim 1, characterized in that... The pretreatment of AlSi10Mg alloy powder in S1 is as follows: the alloy powder is dried in a vacuum drying oven at 120-130℃ for 2-4 hours.

10. The method for direct energy deposition additive manufacturing of low-defect AlSi10Mg alloy according to claim 1, characterized in that... The pretreatment of the substrate in S1 is as follows: the substrate is polished to remove the oxide layer on the surface of the substrate, the substrate is cleaned with anhydrous ethanol or acetone, the substrate is immersed in a 5% NaOH solution for 5-7 minutes, and then immersed in a 20% HNO3 solution for 5-7 minutes. After washing with deionized water and alcohol, the substrate is dried. The treated substrate must be used within 12 hours.

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