Defect control method for selective laser melting manufacturing of eutectic high-entropy alloy AlCoCrFeNi2.1

Abstract

The invention discloses a defect control method for selective laser melting manufacturing of eutectic high-entropy alloy AlCoCrFeNi2.1, and belongs to the technical field of material manufacturing. The invention aims to solve the problem that cracks, warping and interlayer cracking are very easy to generate in the structure of the existing SLM formed high-entropy alloy. The welding method comprises the following steps: 1, preparing AlCoCrFeNi2.1 alloy powder; 2, pretreating the substrate, and preheating the substrate; and thirdly, the alloy powder is deposited on the preheated base plate in a layer-by-layer partitioned laser melting mode. The method is used for defect control of selective laser melting manufacturing of the eutectic high-entropy alloy AlCoCrFeNi2.1.

Description

Technical Field

[0001] The invention belongs to the technical field of material manufacturing. Background Art

[0002] High-entropy alloys (HEAs) have attracted widespread attention due to their excellent mechanical properties, corrosion resistance, and high-temperature resistance. However, the smelting process for preparing HEAs still has some shortcomings. HEAs are typically composed of multiple elements, and the smelting process requires high temperatures and a high vacuum environment, which places high demands on the smelting equipment. Because HEAs are typically composed of five or more metallic elements, uneven distribution of components can occur during smelting and solidification, leading to inconsistent alloy properties and the risk of oxidation and contamination during the smelting process.

[0003] Since its official naming in 2004, high-entropy alloys have attracted widespread attention from scholars at home and abroad. Research on the technology of forming high-entropy alloys by selective laser melting is still in the process of continuous experimental exploration. Domestic and foreign studies have shown that the use of SLM in the preparation of high-entropy alloys can make the alloy elements uniform and without segregation. The density of the sample increases with the increase of VED. It can also make the high-entropy alloys have good mechanical properties, which are superior to high-entropy alloys prepared by traditional methods.

[0004] Due to the compositional characteristics of high-entropy alloys with multiple principal components, complex interactions will occur between the principal components with different physical properties, causing complex physical and chemical metallurgical reactions to occur in the high-entropy alloys during the SLM forming process. Under the action of complex thermal cycles, cracks, warping and interlayer cracking are very likely to occur in the structure of SLM-formed high-entropy alloys. Therefore, SLM still has requirements for powder preparation quality and process optimization, which need to be urgently solved. Summary of the Invention

[0005] The present invention aims to solve the problem that cracks, warping and interlayer cracking are very easy to occur in the structure of existing SLM-formed high-entropy alloys, and further provide a defect control method for the laser selective melting manufacturing of eutectic high-entropy alloy AlCoCrFeNi2.1.

[0006] A defect control method for manufacturing a eutectic high entropy alloy AlCoCrFeNi2.1 by laser selective melting is performed according to the following steps:

[0007] 1. preparing AlCoCrFeNi2.1 alloy powder by a rotating electrode method, and then drying to obtain dried AlCoCrFeNi2.1 alloy powder;

[0008] 2. Pre-treat the substrate, fix it on the workbench of the laser melting system under a protective atmosphere and preheat it;

[0009] III. Set the scanning path and process parameters of the laser melting system. Put the dried AlCoCrFeNi2.1 alloy powder into the powder feeder of the laser melting system, start the laser melting system, and under a protective atmosphere, layer by layer and zone by zone, the alloy powder is laser melted and deposited on the preheated substrate, thus completing the defect control method for the selective laser melting manufacturing of the eutectic high-entropy alloy AlCoCrFeNi2.1;

[0010] During the printing process in the same area, the high and low volume energy densities are alternately set for adjacent layers. The high volume energy density is 120 J / mm 3 ~140 J / mm 3 , and the low volume energy density is 80 J / mm 3 ~100 J / mm 3 ;

[0011] During the printing process in the same layer, the high and low volume energy densities are alternately set for adjacent areas. The high volume energy density is 120 J / mm 3 ~140 J / mm 3 , and the low volume energy density is 80 J / mm 3 ~100 J / mm 3 。

[0012] The beneficial effects of the present invention are as follows:

[0013] 1. The defect control method for the selective laser melting manufacturing of the eutectic high-entropy alloy AlCoCrFeNi2.1 provided by the present invention prepares alloy powder by the rotating electrode method. Compared with inert gas atomization, the rotating electrode can directly disperse the metal liquid stream for atomization without the need for a high-speed inert gas flow. Therefore, the formation of hollow powder particles caused by the "umbrella effect" in gas atomization can be avoided, and the mechanical properties of the material can be improved.

[0014] 2. The defect control method for the selective laser melting manufacturing of the eutectic high-entropy alloy AlCoCrFeNi2.1 provided by the present invention, on the basis of zone scanning, adopts a high-low staggered setting method for the volume energy density (VED value) between adjacent layers and within adjacent areas during printing, effectively reducing the occurrence of cracks, warping, and interlayer cracking that are prone to occur during the printing process; in addition, the alternating setting of the heat input in adjacent areas also weakens the superposition effect of stress inside the specimen, reduces the stress level of alloy preparation, further broadens the preparation process window, and improves the application feasibility.

[0015] 3. The specimens prepared by the method of the present invention have good forming effects, uniform structures, high densities, and excellent mechanical properties and processing properties at room temperature and high temperatures. Description of the Drawings

[0016] Figure 1SEM image of the AlCoCrFeNi2.1 alloy powder prepared in Step 1 of Example 1 at low magnification;

[0017] Figure 2 SEM image of the AlCoCrFeNi2.1 alloy powder prepared in Step 1 of Example 1 at high magnification;

[0018] Figure 3 Schematic diagram of the checkerboard layout for zonal scanning in Step 3 of Example 1;

[0019] Figure 4 Comparison diagram of the upper surface morphologies of the as-formed specimens of the AlCoCrFeNi2.1 high-entropy alloy in Example 1 and the comparative experiment, where a and b are the comparative experiment, and c and d are Example 1;

[0020] Figure 5 Comparison diagram of the side surface morphologies of the as-formed specimens of the AlCoCrFeNi2.1 high-entropy alloy in Example 1 and the comparative experiment, where a and b are the comparative experiment, and c and d are Example 1. Detailed implementation manners

[0021] Detailed implementation manner 1: A method for defect control in the selective laser melting manufacturing of the eutectic high-entropy alloy AlCoCrFeNi2.1 is carried out according to the following steps:

[0022] 1. Prepare the AlCoCrFeNi2.1 alloy powder by the rotating electrode method, and then dry it to obtain the dried AlCoCrFeNi2.1 alloy powder;

[0023] 2. Pretreat the substrate, fix it on the working table of the laser melting system and preheat it under a protective atmosphere;

[0024] 3. Set the scanning path and process parameters of the laser melting system, put the dried AlCoCrFeNi2.1 alloy powder into the powder feeder of the laser melting system, start the laser melting system, and under a protective atmosphere, layer by layer and zone by zone, laser melt and deposit the alloy powder on the preheated substrate, thus completing the method for defect control in the selective laser melting manufacturing of the eutectic high-entropy alloy AlCoCrFeNi2.1;

[0025] During the printing process in the same area, the high volumetric energy density and the low volumetric energy density are alternately set. The high volumetric energy density is 120 J / mm 3 ~140 J / mm 3 and the low volumetric energy density is 80 J / mm 3 ~100 J / mm 3 ;

[0026] During the same-layer printing process, the high volumetric energy density and low volumetric energy density are alternately set in adjacent areas. The high volumetric energy density is 120 J / mm 3 ~140 J / mm 3 , and the low volumetric energy density is 80 J / mm 3 ~100 J / mm 3 .

[0027] In step two of this specific embodiment, the formed substrate is pre-treated, including but not limited to surface treatment, grinding treatment, sandblasting treatment, ultrasonic cleaning, and alcohol cleaning.

[0028] The beneficial effects of this embodiment are as follows:

[0029] 1. The defect control method for selective laser melting manufacturing of eutectic high-entropy alloy AlCoCrFeNi2.1 provided by this embodiment prepares alloy powder by the rotating electrode method. Compared with inert gas atomization, the rotating electrode can directly disperse the metal liquid stream for atomization without a high-speed inert gas flow. Therefore, the formation of hollow powder particles caused by the "umbrella effect" in gas atomization can be avoided, and the mechanical properties of the material can be improved.

[0030] 2. The defect control method for selective laser melting manufacturing of eutectic high-entropy alloy AlCoCrFeNi2.1 provided by this embodiment, on the basis of zonal scanning, adopts a high-low staggered setting method for the volumetric energy density (VED value) of adjacent areas between printing layers and within layers, effectively reducing the occurrence of cracks, warping, and interlayer cracking that are extremely likely to occur during the printing process; in addition, the alternating setting of the heat input in adjacent areas also weakens the superposition effect of stress inside the specimen, reduces the stress level of alloy preparation, further broadens the preparation process window, and improves the application feasibility.

[0031] 3. The specimens prepared by the method of this embodiment have good forming effects, uniform structures, high densities, and excellent mechanical properties and processing properties at room temperature and high temperatures.

[0032] Specific embodiment two: The difference between this embodiment and specific embodiment one is that in step one, the molar ratio of Al:Co:Cr:Fe:Ni in the AlCoCrFeNi2.1 alloy powder is 1:1:1:1:2.1. Others are the same as specific embodiment one.

[0033] Specific Embodiment 3: The difference between this embodiment and either of Specific Embodiments 1 or 2 is as follows: In Step 1, under the conditions that the diameter of the electrode rod is 60 mm to 70 mm and the rotational speed is 1500 r / min to 1800 r / min, the AlCoCrFeNi2.1 alloy powder is prepared by the rotating electrode method, and then dried for 4 h to 8 h under the condition that the temperature is 100 °C to 150 °C to obtain the dried AlCoCrFeNi2.1 alloy powder. Others are the same as in Specific Embodiment 1 or 2.

[0034] Specific Embodiment 4: The difference between this embodiment and any one of Specific Embodiments 1 to 3 is as follows: In Step 1, the particle size range of the AlCoCrFeNi2.1 alloy powder is 15 μm to 53 μm, the median particle size is 28 μm to 33 μm, and the powder Hall flow rate < 35 s / 50 g. Others are the same as in Specific Embodiments 1 to 3.

[0035] Specific Embodiment 5: The difference between this embodiment and any one of Specific Embodiments 1 to 4 is as follows: The substrate described in Step 2 is a stainless steel plate or a zirconium alloy plate. Others are the same as in Specific Embodiments 1 to 4.

[0036] Specific Embodiment 6: The difference between this embodiment and any one of Specific Embodiments 1 to 5 is as follows: Preheat to 100 °C to 150 °C in Step 2. Others are the same as in Specific Embodiments 1 to 5.

[0037] Specific Embodiment 7: The difference between this embodiment and any one of Specific Embodiments 1 to 6 is as follows: In Step 3, the pattern to be formed is partitioned according to a checkerboard layout; in Step 3, under a protective atmosphere, the alloy powder is laser melted and deposited layer by layer on the preheated substrate according to a checkerboard layout. Others are the same as in Specific Embodiments 1 to 6.

[0038] Specific Embodiment 8: The difference between this embodiment and any one of Specific Embodiments 1 to 7 is as follows: In Step 3, under the conditions of a protective atmosphere, a printing layer thickness of 0.027 mm to 0.033 mm, an interlayer rotation angle of 67° or 90°, and an interlayer temperature of 300 °C to 400 °C, the alloy powder is laser melted and deposited layer by layer on the preheated substrate in a partitioned manner, and the laser stays on each layer for 10 s to 15 s. Others are the same as in Specific Embodiments 1 to 7.

[0039] Specific Embodiment 9: The difference between this embodiment and any one of Specific Embodiments 1 to 8 is as follows: The protective atmosphere described in Steps 2 and 3 is argon, nitrogen, or helium. Others are the same as in Specific Embodiments 1 to 8.

[0040] Specific Embodiment 10: The difference between this embodiment and any one of Specific Embodiments 1 to 9 is as follows: The oxygen content of the protective atmosphere described in Steps 2 and 3 is less than 150 ppm. Others are the same as in Specific Embodiments 1 to 9.

[0041] The beneficial effects of the present invention are verified by the following embodiments:

[0042] Embodiment 1:

[0043] A method for controlling defects in the selective laser melting manufacturing of a eutectic high-entropy alloy AlCoCrFeNi2.1 is carried out according to the following steps:

[0044] I. Under the conditions that the diameter of the electrode rod is 60 mm and the rotation speed is 1700 r / min, use the rotating electrode method to prepare AlCoCrFeNi2.1 alloy powder, and then dry it at a temperature of 120 °C for 4 h to obtain the dried AlCoCrFeNi2.1 alloy powder;

[0045] II. Pretreat the substrate, fix it on the workbench of the laser melting system under a protective atmosphere and preheat it to 100 °C;

[0046] III. Set the scanning path and process parameters of the laser melting system, divide the pattern to be formed into zones according to the checkerboard layout, put the dried AlCoCrFeNi2.1 alloy powder into the powder feeder of the laser melting system, start the laser melting system, and under the conditions of a protective atmosphere, a printing layer thickness of 0.03 mm, an interlayer rotation angle of 67 °, and an interlayer temperature of 300 °C, the alloy powder is laser melted and deposited layer by layer in the preheated substrate according to the checkerboard layout zones. The laser stays for 12 s per layer to obtain an AlCoCrFeNi2.1 high-entropy alloy formed specimen;

[0047] During the printing process in the same area, the high volumetric energy density and the low volumetric energy density are alternately set for adjacent layers. The high volumetric energy density is 120 J / mm 3 , and the low volumetric energy density is 80 J / mm 3 ;

[0048] During the printing process in the same layer, the high volumetric energy density and the low volumetric energy density are alternately set for adjacent areas. The high volumetric energy density is 120 J / mm 3 , and the low volumetric energy density is 80 J / mm 3 .

[0049] In step I, the molar ratio of Al:Co:Cr:Fe:Ni in the AlCoCrFeNi2.1 alloy powder is 1:1:1:1:2.1.

[0050] In step I, the particle size range of the AlCoCrFeNi2.1 alloy powder is 15 μm to 53 μm, the median particle size is 29.1 μm, and the powder Hall flow rate is 30 s / 50 g.

[0051] The substrate described in Step 2 is a 304 stainless steel plate; the pretreatment described in Step 2 is to first perform sandblasting on the surface with a sandblaster, and then wipe it clean with anhydrous ethanol to remove surface contaminants.

[0052] The protective atmosphere described in Steps 2 and 3 is argon;

[0053] The printing process is carried out after the oxygen content of the protective atmosphere described in Steps 2 and 3 is reduced to 120 ppm.

[0054] The checkerboard pattern described in Step 3 is 3×3, numbered 1 to 9 from left to right, as Figure 3 shown, Figure 3 is a schematic diagram of the zonal scanning of the checkerboard pattern layout in Step 3 of Example 1; where each layer of the checkerboard pattern is 3×3 and numbered 1 to 9 in sequence; the volume energy density of the regions numbered 1, 3, 5, 7, 9 in the nth layer is 120 J / mm 3 , and the volume energy density of the regions numbered 2, 4, 6, 8 in the nth layer is 80 J / mm 3 ; the volume energy density of the regions numbered 1, 3, 5, 7, 9 in the (n + 1)th layer is 80 J / mm 3 , and the volume energy density of the regions numbered 2, 4, 6, 8 in the (n + 1)th layer is 120 J / mm 3 .

[0055] Comparative experiment: The difference between this comparative experiment and Example 1 is that in Step 3, the pattern to be formed is not arranged in zones according to the checkerboard pattern, and the VED is kept constant at 90 J / mm 3 during the entire printing process. Others are the same as in Example 1.

[0056] Figure 1 is a low-magnification scanning electron micrograph of the AlCoCrFeNi2.1 alloy powder prepared in Step 1 of Example 1; Figure 2 is a high-magnification scanning electron micrograph of the AlCoCrFeNi2.1 alloy powder prepared in Step 1 of Example 1. It can be seen from the figure that the powder has good sphericity, a smooth surface, almost no hollow powder and satellite balls, and good formability.

[0057] Figure 4 is a comparison diagram of the upper surface morphologies of the AlCoCrFeNi2.1 high-entropy alloy formed specimens in Example 1 and the comparative experiment, where a and b are the comparative experiment, and c and d are Example 1. Figure 5Figure for comparing the side morphologies of the as-formed specimens of AlCoCrFeNi2.1 high-entropy alloy in Example 1 and the comparative experiment. a and b are the comparative experiments, and c and d are Example 1. As shown in the figure, serious surface spattering and interlayer cracking occur during conventional printing. However, through the intersection of the volume energy density (VED value) of adjacent checkerboards, obvious improvement is obtained after process optimization, with no cracks, warping, or interlayer cracking, and good forming effect and uniform microstructure.

[0058] For the as-formed specimens c, d of AlCoCrFeNi2.1 high-entropy alloy in Example 1 and the comparative tests a, b, the density test and the elongation measurement in the printing direction were carried out by the Archimedes drainage method. The test results are shown in Table 1. It can be seen from the results that the density of the printed alloy is significantly improved, and the improvement of interlayer cracks greatly enhances the elongation performance of the alloy in the longitudinal direction.

[0059] Table 1

[0060] Number a b c d Density, % 97.5 98.2 99.4 99.6 Elongation, % 9.4 9.7 14.5 13.6

Claims

1. A method for controlling defects in the selective laser melting manufacturing of a eutectic high-entropy alloy AlCoCrFeNi2.1, characterized in that It is carried out according to the following steps:

1. Prepare AlCoCrFeNi2.1 alloy powder by the rotating electrode method, and then dry it to obtain the dried AlCoCrFeNi2.1 alloy powder; 2. Pretreat the substrate, fix it on the working table of the laser melting system and preheat it under a protective atmosphere; 3. Set the scanning path and process parameters of the laser melting system. Put the dried AlCoCrFeNi2.1 alloy powder into the powder feeder of the laser melting system, start the laser melting system, and layer by layer and zone by zone, laser melt and deposit the alloy powder on the preheated substrate under a protective atmosphere, thus completing the defect control method for selective laser melting manufacturing of the eutectic high-entropy alloy AlCoCrFeNi2.1; During the printing process in the same area, the volumetric energy density of adjacent layers is alternately set between high and low values. The high volumetric energy density is 120 J / mm 3 ~140 J / mm 3 , and the low volumetric energy density is 80 J / mm 3 ~100 J / mm 3 ; During the same-layer printing process, the high volumetric energy density and the low volumetric energy density are alternately set in adjacent regions. The high volumetric energy density is 120 J / mm 3 ~140 J / mm 3 , and the low volumetric energy density is 80 J / mm 3 ~100 J / mm 3 .

2. The defect control method for selective laser melting of the eutectic high-entropy alloy AlCoCrFeNi2.1 according to claim 1, characterized in that In the AlCoCrFeNi2.1 alloy powder described in step 1, the molar ratio of Al:Co:Cr:Fe:Ni is 1:1:1:1:2.

1.

3. The defect control method for selective laser melting of the eutectic high-entropy alloy AlCoCrFeNi2.1 according to claim 1, characterized in that In step 1, under the conditions that the diameter of the electrode rod is 60 mm to 70 mm and the rotation speed is 1500 r / min to 1800 r / min, prepare AlCoCrFeNi2.1 alloy powder by the rotating electrode method, and then dry it for 4 h to 8 h under the condition that the temperature is 100 °C to 150 °C to obtain the dried AlCoCrFeNi2.1 alloy powder.

4. A method for controlling defects in the selective laser melting manufacturing of a eutectic high-entropy alloy AlCoCrFeNi2.1 according to claim 3, characterized in that In the AlCoCrFeNi2.1 alloy powder described in step 1, the particle size range is 15 μm to 53 μm, the median particle size is 28 μm to 33 μm, and the powder Hall flow rate is < 35 s / 50 g.

5. The defect control method for selective laser melting manufacturing of eutectic high-entropy alloy AlCoCrFeNi2.1 according to claim 1, characterized in that The substrate described in step 2 is a stainless steel plate or a zirconium alloy plate.

6. The defect control method for selective laser melting manufacturing of eutectic high-entropy alloy AlCoCrFeNi2.1 according to claim 1, characterized in that In step 2, preheat it to 100 °C to 150 °C.

7. A method for controlling defects in the selective laser melting manufacturing of a eutectic high-entropy alloy AlCoCrFeNi2.1 according to claim 1, characterized in that In step 3, partition the pattern to be formed according to a checkerboard layout; in step 3, under a protective atmosphere, layer by layer and according to a checkerboard layout, zone by zone, laser melt and deposit the alloy powder on the preheated substrate.

8. The defect control method for manufacturing an eutectic high-entropy alloy AlCoCrFeNi2.1 by selective laser melting according to claim 1, characterized in that In step 3, under the conditions of a protective atmosphere, a printing layer thickness of 0.027 mm to 0.033 mm, an interlayer rotation angle of 67° or 90°, and an interlayer temperature of 300 °C to 400 °C, layer by layer and zone by zone, laser melt and deposit the alloy powder on the preheated substrate, and the laser stays for 10 s to 15 s for each layer.

9. A method for controlling defects in the selective laser melting manufacturing of a eutectic high-entropy alloy AlCoCrFeNi2.1 according to claim 1, characterized in that The protective atmosphere described in steps 2 and 3 is argon, nitrogen or helium.

10. A method for defect control in the selective laser melting of a eutectic high-entropy alloy AlCoCrFeNi2.1 according to claim 1, characterized in that The oxygen content of the protective atmosphere described in steps 2 and 3 is less than 150 ppm.

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