Multi-wire arc additive manufacturing high-entropy alloy equiaxed crystal organization regulation method based on pulse peak current

Abstract

This invention provides a method for controlling the equiaxed crystal structure of high-entropy alloys using multi-wire arc additive manufacturing based on pulsed peak current, belonging to the field of additive manufacturing technology. This invention uses Fe, Co, Ni, and Al wires as deposition wires, and prepares FeCoNiAl alloy single-pass thin-walled components by synergistically melting four pure metal wires with a single arc. The directional induction and refinement of the equiaxed crystal structure are achieved by precisely controlling the pulsed peak current parameter to 200-250A. This invention features a simple and low-cost process, is compatible with single-arc four-wire equipment, effectively solves the problem of columnar crystal dominance in traditional processes, and significantly improves the microstructure uniformity and comprehensive mechanical properties of FeCoNiAl alloy thin-walled components. It can be widely applied in aerospace, precision machinery, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology, specifically relating to a method for controlling the equiaxed crystal structure of high-entropy alloys based on multi-wire arc additive manufacturing using pulse peak current. Background Technology

[0002] FeCoNiAl alloy, as a novel high-performance multi-principal element alloy, possesses excellent strength, toughness, corrosion resistance, and magnetic properties, and has broad application prospects in high-end fields such as aerospace, precision machinery, and energy equipment. Single-arc four-wire electric arc additive manufacturing technology, with its unique advantage of simultaneous feeding of four wires, features high deposition efficiency, precise composition control, high material utilization, flexible forming, and strong equipment integration adaptability, making it the preferred technology path for near-net-shape forming of FeCoNiAl alloy components.

[0003] However, in the current process of multi-wire arc additive manufacturing of FeCoNiAl alloys, due to factors such as concentrated heat input from a single arc, uneven distribution of melt pool composition and temperature during simultaneous melting of four wires (Fe, Co, Ni, and Al), and large fluctuations in cooling rate, the volume ratio of columnar crystal structure in the deposited microstructure is ≥80%. Columnar crystal structure suffers from problems such as coarse grains, uniform orientation, and weak grain boundary bonding, leading to significant anisotropy in the mechanical properties of the components, decreased crack resistance, toughness, and fatigue resistance, severely restricting the engineering application of FeCoNiAl high-entropy alloy additively manufactured components in high-end equipment. Summary of the Invention

[0004] The purpose of this invention is to provide a method for controlling the equiaxed grain structure of high-entropy alloys using multi-wire arc additive manufacturing based on pulsed peak current. This invention utilizes the simultaneous melting of four wires (Fe, Co, Ni, and Al) and optimizes key peak current thermal input process parameters to achieve the directional induction formation and grain refinement of the equiaxed grain structure in FeCoNiAl high-entropy alloys.

[0005] To achieve the objectives of this invention, the following technical solutions are provided: A method for controlling the equiaxed grain structure of high-entropy alloys based on multi-wire arc additive manufacturing using pulsed peak current includes the following steps: The FeCoNiAl alloy thin-walled component is obtained by molten deposition of multiple welding wires using a single electric arc. The multiple welding wires include Fe wires, Co wires, Ni wires, and Al wires. The welding wire ends are connected to the molten pool via liquid bridges. The peak current of the single arc is 200~250A, and the peak current accounts for 15~30% of the time. The fused deposition method is a single-pass multi-layer deposition, and the path is as follows: deposit the first thin-walled layer from the starting point to the ending point, and after reaching the ending point, extinguish the arc and stop wire feeding, and return to the starting point; then ignite the arc and feed the wire again, and continue to deposit the next layer above the first thin-walled layer from the starting point to the ending point.

[0006] Preferably, the Fe wire has a diameter of 1.2cm±0.05mm, the Co wire has a diameter of 1.2cm±0.05mm, the Ni wire has a diameter of 1.6cm±0.05mm, and the Al wire has a diameter of 1.0cm±0.05mm.

[0007] Preferably, the feeding speed of the Fe wire is 0.5~0.6 m / min, the feeding speed of the Co wire is 0.5~0.6 m / min, the feeding speed of the Ni wire is 0.6~0.7 m / min, and the feeding speed of the Al wire is 0.4~0.5 m / min.

[0008] Preferably, the molten deposition process further includes auxiliary heating of the Fe wire, Co wire, and Ni wire respectively; The auxiliary heating is achieved by using a hot wire current; the hot wire current is 110~150A.

[0009] Preferably, the pulse frequency of the single electric arc is 0.5~1.0Hz, and the base current is 20~60A.

[0010] Preferably, the moving speed of the welding torch is 100~150mm / min; the distance between the welding torch and the substrate is 5~7mm, and the angle between the welding torch and the substrate is 40°~45°.

[0011] Preferably, the process further includes preheating the substrate before fused deposition; the preheating of the substrate includes the following steps: Turn off the wire feed, start the arc, and preheat from the starting point to the ending point. After reaching the ending point, extinguish the arc and return to the starting point; start the arc again and repeat the preheating process from the starting point to the ending point.

[0012] Preferably, the number of deposition layers in the single-pass multi-layer deposition is 20 to 30, and the thickness of a single layer is 0.1 to 0.2 mm.

[0013] Preferably, the thickness of the FeCoNiAl alloy thin-walled component is 2.9~3.2mm.

[0014] Preferably, the FeCoNiAl alloy thin-walled component has an equiaxed crystal structure and a columnar crystal structure; the content of the equiaxed crystal structure is ≥30%.

[0015] This invention provides a method for controlling the equiaxed crystal structure of high-entropy alloys using multi-wire arc additive manufacturing based on pulsed peak current. This invention utilizes multi-wire arc additive manufacturing and achieves the transformation of FeCoNiAl high-entropy alloys from columnar crystal structure to equiaxed crystal structure by controlling the peak current of a single arc as a heat input parameter. Specifically, this invention sets the peak current to 200-250 A: when the peak current is 250 A, equiaxed crystals appear inside the deposited sample, mainly distributed in the interlayer region, while columnar crystals still dominate in other areas. At this peak current, the melting rate of the four pure wires is moderate, but the heat input is relatively high, resulting in generally uneven composition of the melt pool. An equiaxed crystal structure forms in the region with a relatively fast interlayer cooling rate. As shown in the results of the examples, the proportion of the equiaxed crystal structure is 30.5%. When the peak current is 200A, the number of equiaxed crystals inside the deposited sample increases significantly, the distribution range of equiaxed crystals expands, and the size of equiaxed crystal grains decreases significantly. At this peak current, the four pure wires melt synchronously and uniformly, the heat input of the molten pool is moderate, and compositional segregation is effectively suppressed. As shown in the results of the examples, the proportion of equiaxed crystals is 46.5%. When the peak current is 300A, the arc heat input is too large, the molten pool is severely overheated, the temperature gradient increases significantly, and the interior of the deposited sample is mainly composed of columnar crystals, with the proportion of equiaxed crystals being only 13%.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) The method for controlling the equiaxed crystal structure of FeCoNiAl alloy in multi-wire arc additive manufacturing provided by the present invention is precisely adapted to multi-wire arc additive manufacturing equipment and the synchronous feeding mode of Fe, Co, Ni and Al four wires. By optimizing the peak current at 200~250A, the formation of equiaxed crystal structure in single-pass thin-walled FeCoNiAl alloy samples can be effectively induced.

[0017] 2) The method for controlling the equiaxed crystal structure of FeCoNiAl alloys in multi-wire arc additive manufacturing provided by this invention is simple and low-cost. The equiaxed crystal structure can be controlled by optimizing only the single process parameter of the pulse peak current. It is easy to operate and readily applicable to industrial applications. Furthermore, using pure Fe, pure Co, pure Ni, and pure Al single-wire feeds results in lower raw material costs and more flexible composition control compared to prefabricated alloy wires.

[0018] 3) The method for controlling the equiaxed crystal structure of FeCoNiAl alloy in multi-wire arc additive manufacturing provided by the present invention optimizes the basic process parameters such as wire arrangement and wire feeding speed, which can effectively avoid problems such as deformation, cracking and compositional segregation that are prone to occur in the additive manufacturing process of thin-walled components, while ensuring the forming quality and microstructure properties of the components, and adapting to the high-performance requirements of thin-walled components in high-end fields. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the wire arrangement and welding torch movement direction during the multi-wire arc additive manufacturing process according to an embodiment of the present invention; Figure 2 Macroscopic morphology images of FeCoNiAl alloys fabricated by multi-wire arc additive manufacturing at different peak currents; where (a) is the macroscopic morphology image of the part with a peak current of 200A, (b) is the macroscopic morphology image of the part with a peak current of 250A, and (c) is the macroscopic morphology image of the part with a peak current of 300A. Figure 3 The KAM and IPF spectra of FeCoNiAl alloys manufactured by multi-wire arc additive manufacturing in Examples 1-2 and Comparative Example 1 of this invention are shown below under different peak currents (200A, 250A, 300A); where a1-c1 are the KAM spectra of Examples 1, 2 and Comparative Example 1, respectively; and a2-c2 are the IPF spectra of Examples 1, 2 and Comparative Example 1, respectively. Figure 4 The figures show the grain morphology of FeCoNiAl alloys manufactured by multi-wire arc additive manufacturing in Examples 1-2 and Comparative Example 1 of this invention under different peak currents (200A, 250A, 300A). Detailed Implementation

[0021] This invention provides a method for controlling the equiaxed grain structure of high-entropy alloys using multi-wire arc additive manufacturing based on pulsed peak current, comprising the following steps: The FeCoNiAl alloy thin-walled component is obtained by molten deposition of multiple welding wires using a single electric arc. The multiple welding wires include Fe wires, Co wires, Ni wires, and Al wires. The welding wire ends are connected to the molten pool via liquid bridges. The peak current of the single arc is 200~250A, and the peak current accounts for 15~30% of the time. The fused deposition method is a single-pass multi-layer deposition, and the path is as follows: deposit the first thin-walled layer from the starting point to the ending point, and after reaching the ending point, extinguish the arc and stop wire feeding, and return to the starting point; then ignite the arc and feed the wire again, and continue to deposit the next layer above the first thin-walled layer from the starting point to the ending point.

[0022] Unless otherwise specified, all raw materials used in this invention are commercially available products well known to those skilled in the art.

[0023] In this invention, the Fe wire, Co wire, Ni wire, and Al wire are pure Fe, pure Co, pure Ni, and pure Al, respectively, with a purity greater than 99%; the diameter of the Fe wire is 1.2cm ± 0.05mm, the diameter of the Co wire is 1.2cm ± 0.05mm, the diameter of the Ni wire is 1.6cm ± 0.05mm, and the diameter of the Al wire is 1.0cm ± 0.05mm.

[0024] In this invention, the feeding speed of the Fe wire is 0.5~0.6 m / min, the feeding speed of the Co wire is 0.5~0.6 m / min, the feeding speed of the Ni wire is 0.6~0.7 m / min, and the feeding speed of the Al wire is 0.4~0.5 m / min.

[0025] This invention does not specifically limit the equipment used for multi-wire arc additive manufacturing; conventional additive manufacturing equipment in the field can be used. Specifically, tungsten inert gas (TIG) welding is employed.

[0026] In this invention, the fused deposition process further includes auxiliary heating of Fe wire, Co wire and Ni wire respectively; the auxiliary heating is heating using hot wire current; the hot wire current is 110~150A; the specific steps of the auxiliary heating are as follows: the positive terminal of the hot wire machine is grounded, the negative terminal of the hot wire machine is connected to Fe wire, Co wire and Ni wire, and the hot wire machine starts to work to perform auxiliary heating when the wires contact the molten pool or substrate.

[0027] In this invention, the pulse frequency of the single electric arc is 0.5~1.0Hz, and in a specific embodiment it can be 0.6, 0.8 or 0.9Hz, and the base current is 20~60A, and in a specific embodiment it can be 30 or 50A.

[0028] In this invention, the moving speed of the welding torch is 100~150mm / min, and in a specific embodiment it can be 120 or 130mm / min; the distance between the welding torch and the substrate is 5~7mm, and the angle between the welding torch and the substrate is 40~45°.

[0029] The FeCoNiAl alloy thin-walled components manufactured by multi-wire arc additive manufacturing according to this invention do not require solution heat treatment or aging heat treatment.

[0030] In this invention, the number of layers in the single-pass multilayer deposition is 20 to 30; the thickness of a single layer is 0.1 to 0.2 mm.

[0031] In this invention, the thickness of the FeCoNiAl alloy thin-walled component is 2.9~3.2 mm.

[0032] In this invention, the crystal structure of the FeCoNiAl alloy thin-walled component is equiaxed crystal structure and columnar crystal structure; the content of the equiaxed crystal structure is ≥30%, preferably 30~55%, and in specific implementations it can be 30.5% or 46.5%. This invention controls the peak current to be 200~250A. When the peak current is 250A, equiaxed crystals begin to appear inside the deposited sample. The equiaxed crystals are mainly distributed in the interlayer region, while columnar crystals still dominate in other regions. The equiaxed crystal grain size is relatively large. At this peak current, the melting rate of the four pure wires is moderate, but the heat input is relatively high, the uniformity of the melt pool composition is generally poor, and only a small amount of equiaxed crystals are formed in the region with a relatively fast interlayer cooling rate. When the peak current is 200A, the number of equiaxed crystal structures inside the deposited sample increases significantly, the distribution range of equiaxed crystals expands, and the size of equiaxed crystal grains becomes significantly smaller. Under this peak current, the four pure wires melt synchronously and uniformly, the heat input of the molten pool is moderate, and the compositional segregation is effectively suppressed. When the peak current is 300A, the heat input of the arc is too large, the molten pool is severely overheated, the temperature gradient increases significantly, and the interior of the deposited sample is columnar crystal.

[0033] To further illustrate the present invention, the method for controlling the equiaxed crystal structure of high-entropy alloys based on pulse peak current multi-wire arc additive manufacturing provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1 S1. Select pure Fe wire, pure Co wire, pure Ni wire, and pure Al wire, where the diameter of pure Fe wire and pure Co wire is 1.2cm, the diameter of pure Ni wire is 1.6cm, and the diameter of pure Al wire is 1.0cm, with a diameter deviation ≤ ±0.05mm; use sandpaper to sand the surface of the four wires to remove the oxide scale, wipe them one by one with anhydrous ethanol, and let them dry for later use; Select a TC4 titanium alloy substrate with a composition matching FeCoNiAl alloy. The substrate size is 150mm×150mm×5mm. Sand the surface of the substrate until it is shiny. Clean it with anhydrous ethanol and let it dry. Then fix it on the worktable.

[0035] S2. Adjust the wire feeding speed according to the preset composition of FeCoNiAl alloy. The wire feeding speeds for pure Fe wire, pure Co wire, pure Ni wire, and pure Al wire are 0.5~0.6m / min, 0.5~0.6m / min, 0.6~0.7m / min, and 0.4~0.5m / min, respectively. Use a hot wire machine to assist in the melting of pure Fe wire, pure Co wire, and pure Ni wire. The hot wire current is 150A for all wires.

[0036] S3. Based on multi-wire arc additive manufacturing equipment, the welding torch moves according to the set deposition path. The wire arrangement and welding torch movement direction are as follows: Figure 1As shown; a liquid bridge transition mode is adopted, and the wire is melt-deposited layer by layer to form a final deposition layer. The multi-wire arc additive manufacturing equipment uses a DC pulse arc, and the heat input parameters are: pulse frequency of 1Hz; welding torch moving speed of 100mm / min; peak current of 200A, peak current time percentage of 20%; base current of 50A, 20 layers are deposited, and the single-pass thickness of the obtained FeCoNiAl alloy thin-walled component is 3.2mm. The macroscopic diagram is shown below. Figure 2 As shown in (a).

[0037] Example 2 FeCoNiAl alloy thin-walled components were prepared according to the method for controlling the equiaxed grain structure of FeCoNiAl alloy in multi-wire arc additive manufacturing as described in Example 1. The only difference was that the peak current was 250A and the single-pass thickness of the FeCoNiAl alloy thin-walled component was 2.9mm. The macroscopic image is shown below. Figure 2 As shown in (b).

[0038] Comparative Example 1 FeCoNiAl alloy thin-walled components were prepared according to the method for controlling the equiaxed grain structure of FeCoNiAl alloy in multi-wire arc additive manufacturing as described in Example 1. The only difference was that the peak current was 300A and the single-pass thickness of the FeCoNiAl alloy thin-walled component was 2.5mm. The macroscopic image is shown below. Figure 2 As shown in (c).

[0039] Figure 3 The KAM and IPF spectra of FeCoNiAl alloys fabricated by multi-wire arc additive manufacturing in Examples 1-2 and Comparative Example 1 are shown at different peak currents (200A, 250A, 300A); where a1-c1 are the KAM spectra of Examples 1, 2 and Comparative Example 1, respectively; and a2-c2 are the IPF spectra of Examples 1, 2 and Comparative Example 1, respectively. Figure 4 Statistical graphs of grain morphology of FeCoNiAl alloys manufactured by multi-wire arc additive manufacturing in Examples 1-2 and Comparative Example 1 under different peak currents (200A, 250A, 300A).

[0040] pass Figure 3 and Figure 4The results showed that when the peak current was 250 A, equiaxed crystals began to appear inside the deposited sample. These equiaxed crystals were mainly distributed in the interlayer region, while columnar crystals dominated in other areas. The equiaxed crystal grains were relatively large. At this peak current, the melting rate of the four pure wires was moderate, but the heat input was relatively high, resulting in generally poor compositional uniformity of the melt pool. Only a small number of equiaxed crystals could form in the interlayer region where the cooling rate was relatively fast. When the peak current was 200 A, the number of equiaxed crystal structures inside the deposited sample increased significantly, the distribution range of equiaxed crystals expanded, and the grain size of the equiaxed crystals decreased significantly, resulting in significantly improved grain uniformity. At this peak current, the four pure wires melted synchronously and uniformly, the heat input of the melt pool was moderate, and compositional segregation was effectively suppressed, providing favorable conditions for equiaxed crystal nucleation and refinement. When the peak current was 300 A, the arc heat input was too large, the melt pool overheated severely, the temperature gradient increased significantly, and columnar crystals formed inside the deposited sample.

[0041] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for controlling the equiaxed grain structure of high-entropy alloys in multi-wire arc additive manufacturing based on pulsed peak current, characterized in that, Includes the following steps: The FeCoNiAl alloy thin-walled component is obtained by molten deposition of multiple welding wires using a single electric arc. The multiple welding wires include Fe wires, Co wires, Ni wires, and Al wires. The welding wire ends are connected to the molten pool via liquid bridges. The peak current of the single arc is 200~250A, and the peak current accounts for 15~30% of the time. The fused deposition method is a single-pass multi-layer deposition, and the path is as follows: deposit the first thin-walled layer from the starting point to the ending point, and after reaching the ending point, extinguish the arc and stop wire feeding, and return to the starting point; then ignite the arc and feed the wire again, and continue to deposit the next layer above the first thin-walled layer from the starting point to the ending point.

2. The control method according to claim 1, characterized in that, The Fe wire has a diameter of 1.2cm ± 0.05mm, the Co wire has a diameter of 1.2cm ± 0.05mm, the Ni wire has a diameter of 1.6cm ± 0.05mm, and the Al wire has a diameter of 1.0cm ± 0.05mm.

3. The control method according to claim 1, characterized in that, The feeding speed of the Fe wire is 0.5~0.6 m / min, the feeding speed of the Co wire is 0.5~0.6 m / min, the feeding speed of the Ni wire is 0.6~0.7 m / min, and the feeding speed of the Al wire is 0.4~0.5 m / min.

4. The control method according to claim 1, characterized in that, The molten deposition process also includes auxiliary heating of the Fe wire, Co wire and Ni wire respectively; The auxiliary heating is achieved by using a hot wire current; the hot wire current is 110~150A.

5. The control method according to claim 1, characterized in that, The pulse frequency of the single electric arc is 0.5~1.0Hz, and the base current is 20~60A.

6. The control method according to claim 1, characterized in that, The welding torch moves at a speed of 100-150 mm / min; the distance between the welding torch and the substrate is 5-7 mm, and the angle between the welding torch and the substrate is 40°-45°.

7. The control method according to claim 1, characterized in that, The process includes preheating the substrate before molten deposition; The preheating substrate includes the following steps: Turn off the wire feed, start the arc, and preheat from the starting point to the ending point. After reaching the ending point, extinguish the arc and return to the starting point; start the arc again and repeat the preheating process from the starting point to the ending point.

8. The control method according to claim 1, characterized in that, The number of deposition layers in the single-pass multi-layer deposition is 20 to 30, and the thickness of a single layer is 0.1 to 0.2 mm.

9. The control method according to claim 1, characterized in that, The thickness of the FeCoNiAl alloy thin-walled component is 2.9~3.2mm.

10. The control method according to claim 1, characterized in that, The FeCoNiAl alloy thin-walled component has an equiaxed crystal structure and a columnar crystal structure; the content of the equiaxed crystal structure is ≥30%.

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