A method and apparatus for shape and property control in additive manufacturing based on directed energy deposition

Abstract

The application discloses a kind of additive manufacturing shape and property control methods based on directional energy deposition, belong to the field of additive manufacturing.The method in the process of directional energy deposition, using active cooling mode, deposition process in situ real-time cooling, to change cooling rate, control the temperature of molten pool, affect the surface tension and viscosity of molten pool, improve the flowability of molten pool, and the expected physical wettability is obtained to improve the apparent quality;It also includes active cooling cooperates with in-situ ultrasonic vibration and / or interlayer ultrasonic impact, provides in-situ ultrasonic vibration field in the process of directional energy deposition;Provide interlayer ultrasonic impact field on the solidification surface after deposition is completed;Through the assistance of active cooling cooperates with in-situ ultrasonic vibration field and / or interlayer ultrasonic impact field, control the structure and performance of additive part.The application improves and optimizes the structure and performance in the process of deposition and solidification, improves the apparent quality and mechanical properties, and improves the forming efficiency.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of additive manufacturing, and particularly relates to a method and device for controlling shape and properties of additive manufacturing based on directional energy deposition. BACKGROUND

[0002] Additive manufacturing (AM), also known as 3D printing, is considered one of the twelve disruptive technologies that constitute the fourth industrial revolution. With the advent of new manufacturing technologies, AM-based repair technologies are expected to become a practical application. Among them, the directed energy deposition technology (DED) is a kind of AM, which adds materials while inputting heat, melts and deposits materials according to the planned path to form three-dimensional parts. The heat input can be an electric arc, a laser, an electron beam or a plasma arc. DED has the characteristics of high material utilization, high deposition efficiency and low cost, and has significant advantages in rapid prototyping and manufacturing of large-scale workpieces, and has broad application prospects in the fields of aerospace, energy, medical treatment, etc.

[0003] In recent years, with the rapid development of industrial automation and intelligent manufacturing, the demand for DED technology in manufacturing industry has been increasing. According to market research data, the global DED equipment market size was about 650 million US dollars in 2022, and is expected to reach 1.85 billion US dollars by 2030, with a compound annual growth rate of about 13.8%. This is mainly due to the wide use of DED technology in the aerospace, automotive, medical and other industries.

[0004] However, compared with other AM technologies such as powder bed fusion technology, DED parts, especially electric arc additive parts, have lower dimensional accuracy, higher surface roughness, lower apparent quality, and larger subsequent machining amount, which increases the manufacturing cost; in addition, DED parts, especially electric arc additive parts, have lower microstructure refinement degree, and due to the directionality of deposition, DED samples usually exhibit anisotropy in microstructure and mechanical properties, which affects the mechanical properties and service reliability of the parts. Therefore, external field assisted methods are usually used to improve the apparent quality, microstructure and mechanical properties of additive parts.

[0005] Chinese invention patent with publication number CN111215898A discloses a kind of electric arc additive synchronous ultrasonic hot rolling and rapid cooling compound processing device and method, and the device uses ultrasonic impact special-shaped roller and liquid nitrogen cooling device to assist electric arc additive manufacturing synchronously. However, the ultrasonic impact has little effect on the molten pool liquid phase, and the use of liquid nitrogen cooling cannot control the cooling speed, and cannot improve the apparent quality of the additive parts.

[0006] Chinese invention patent publication number CN117102501A discloses a high-strength aluminum alloy ultrasonic-assisted laser directed energy deposition manufacturing device. This device features a water-cooling plate fixed to an ultrasonic vibrator, and an additive substrate fixed to the water-cooling plate. However, as the number of additive layers increases, the water cooling and ultrasonic effects decrease and eventually disappear. Heat from the top molten pool must be transferred layer by layer through the deposited portion downward to the substrate and water-cooling plate. The water-cooling plate's cooling effect is poor, making it difficult to completely resolve the heat accumulation issue and unable to control the temperature and cooling rate of each molten pool layer.

[0007] Chinese invention patent publication number CN110484843A discloses a method for improving grain size in additive manufacturing. This involves ultrasonically impacting a substrate during CMT additive manufacturing, and then impacting the surface of the solidified component after CMT manufacturing. However, this method achieves ultrasonic vibrations by impacting the substrate, which always acts on the substrate. This has a long range, resulting in weak acoustic streaming and cavitation in the molten pool. The effect decreases with increasing deposition depth, leading to poor dendrite fragmentation and microstructure refinement. Furthermore, the different distances from the ultrasonic impact point on the two sides of the additive component lead to different microstructures.

[0008] Obviously, none of the above existing technologies can effectively improve the surface quality, microstructure and mechanical properties of additive parts at the same time. Moreover, they have a narrow scope of application and cannot be applied to all directed energy deposition additive manufacturing. In addition, they are costly. Summary of the Invention

[0009] In response to the above-mentioned defects, an embodiment of the present invention provides a method and device for shape and property control in additive manufacturing based on directed energy deposition. Through active cooling and coordinated ultrasonic vibration and / or ultrasonic impact, it assists the solidification during the directed energy deposition process and improves the structure after solidification, thereby improving the apparent quality, structure and performance of the additive parts.

[0010] In order to achieve the above objectives, the embodiments of the present invention adopt the following technical solutions:

[0011] In the first aspect, an embodiment of the present invention provides a shape and property control method for additive manufacturing based on directed energy deposition, the method comprising: in the directed energy deposition process, using active cooling to perform in-situ real-time cooling of the deposition process, thereby changing the cooling rate, controlling the molten pool temperature, thereby affecting the surface tension and viscosity of the molten pool, improving the fluidity of the molten pool, and obtaining the expected physical wettability of the molten pool to improve the apparent quality; at the same time, refining the structure and reducing segregation.

[0012] In the embodiment, the active cooling can reduce the spreading degree of the molten droplets by increasing the cooling rate, improve the apparent quality, refine the structure, and obtain a lower interlayer temperature, reduce the influence of heat accumulation and repeated heat input on the forming quality and structure performance, so as to obtain good apparent quality and mechanical properties; meanwhile, the interlayer waiting time is reduced, and the forming efficiency is improved.

[0013] Preferably, the active cooling adopts one or more of near-submerged active cooling, arc following cooling, and interlayer forced cooling. The active cooling intervention temperature is 500-900℃; the cooling temperature interval is 25-900℃, the cooling rate is 1-20℃ / s, and the interlayer temperature is 20-30℃. In the near-submerged active cooling, the substrate and the solidified additive part are completely immersed in the cooling liquid; the cooling liquid surface is 0.5-2mm lower than the current additive working surface.

[0014] The directed energy deposition described herein can adopt electric arc additive manufacturing or laser deposition additive manufacturing.

[0015] As a preferred embodiment of the embodiment of the present application, the material used in the additive manufacturing process includes one or more of steel, aluminum alloy, titanium alloy, cobalt-based alloy, nickel-based alloy, high-entropy alloy, intermetallic compound, shape memory alloy, ceramic, composite material, and functional gradient material.

[0016] As a preferred embodiment of the present application, the method further comprises: the active cooling and the in-situ ultrasonic vibration field cooperatively assist the additive manufacturing process; wherein the in-situ ultrasonic vibration field is applied in the directed energy deposition process, and with the movement of the deposition device, the ultrasonic vibration field influences the molten pool by acoustic streaming and cavitation effect, mechanically vibrates the material, influences the liquid phase solidification behavior, and directly improves the solidification structure; the in-situ ultrasonic vibration field can break dendrites, refine grains, and convert columnar crystals into equiaxed crystals.

[0017] In a specific embodiment, the ultrasonic parameters of the in-situ ultrasonic vibration field are ultrasonic frequency 5-50kHz, and the distance between the vibration action position and the deposition device is 0-50mm. In specific operation, the ultrasonic parameters are selected according to different materials and directed energy deposition parameters.

[0018] As a preferred embodiment of the present application, the method further comprises: the active cooling and the interlayer ultrasonic impact field cooperatively assist the additive manufacturing process; wherein the interlayer ultrasonic impact field acts on the solidified surface structure, and directly impacts the deposited layer surface in a mechanical contact manner, so that the solidified surface structure is plastically deformed, the geometry of the deposited layer is shaped, a large number of substructures are generated within a predetermined depth from the surface of the deposited layer, and good structure is left for the additive part, so as to control the structure and performance through work hardening and recrystallization. Preferably, the predetermined depth is 1-3mm.

[0019] Among them, the plastic deformation produced by the solidified surface organization presents a neat groove-shaped geometric structure along the horizontal length direction of the wall. The groove provides guidance for the next layer of additive manufacturing, which is beneficial to the expected spreading of the next molten pool, not only making the interlayer bonding closer, but also improving the neatness of the two layers and between layers, obtaining a smoother surface, improved dimensional accuracy and excellent surface quality; at the same time, a large number of substructures produced by ultrasonic impact plastic deformation will not be completely remelted in the subsequent additive process, and the retained substructures can undergo recrystallization.

[0020] In a specific embodiment, the ultrasonic parameters used in the interlayer ultrasonic impact field are an ultrasonic frequency of 5-50 kHz and an impact amplitude of 10-120 μm. In a specific embodiment, the ultrasonic parameters are selected according to different materials and directed energy deposition parameters.

[0021] As a preferred embodiment of the present invention, the method also includes: active cooling and in-situ ultrasonic vibration field, interlayer ultrasonic shock field composite ultrasonic synergistic assistance additive manufacturing process; wherein, in the directed energy deposition process, an in-situ ultrasonic vibration field is provided; on the solidification surface after deposition is completed, an interlayer ultrasonic shock field is provided; through the composite ultrasonic assistance of the in-situ ultrasonic vibration field and the interlayer ultrasonic shock field, the structure and performance of the additive part are controlled; the in-situ ultrasonic vibration field and the interlayer ultrasonic shock field appear alternately; at the same time, active cooling is used to accelerate heat dissipation in the directed energy deposition process, and cooperates with the composite ultrasonic assistance to jointly complete the structure and performance control of the additive part.

[0022] The difference between the in-situ ultrasonic vibration field and the interlayer ultrasonic impact field is that they use different ultrasonic transmission methods. When providing the in-situ ultrasonic vibration field, a vibration head with a large contact area is used, such as a hemispherical, arc-shaped, square, roller-shaped, etc., so that the material and the ultrasound can resonate more easily and the ultrasonic field can be better transmitted; when providing the interlayer ultrasonic impact field, a vibration head with a small contact area is used, such as a needle-shaped, cone-shaped, etc., so that the ultrasound can more easily cause plastic deformation on the surface of the material. In addition, the ultrasonic parameters used in the in-situ ultrasonic vibration field and the interlayer ultrasonic impact field can be different. For example, the ultrasonic parameters used in the in-situ ultrasonic vibration field are an ultrasonic frequency of 5-50kHz, and the distance between the vibration action position and the deposition equipment is 0-50mm; the ultrasonic parameters used in the interlayer ultrasonic impact field are an ultrasonic frequency of 5-50kHz and an impact amplitude of 10-120μm; among them, the in-situ ultrasonic vibration field uses 25kHz, and the interlayer ultrasonic impact field uses 20kHz, etc.

[0023] In a preferred embodiment, the in-situ ultrasonic vibration field and the interlayer ultrasonic impact field are controlled by two ultrasonic generators respectively.

[0024] In another preferred specific embodiment, the in-situ ultrasonic vibration field and the interlayer ultrasonic shock field are controlled by the same ultrasonic generator. When the directed energy is deposited on the current layer of material, an in-situ ultrasonic vibration field is provided to mechanically vibrate the material; after the current layer is solidified, an interlayer ultrasonic shock field is provided to mechanically impact the surface of the material; after completion, it is converted into an in-situ ultrasonic vibration field to enter the next layer of deposition.

[0025] In the second aspect, an embodiment of the present invention also provides an additive manufacturing shape and property control device based on directed energy deposition, the device comprising: an active cooling tank; the active cooling tank is used to use active cooling to perform in-situ real-time cooling of the deposition process during the directed energy deposition process, thereby changing the cooling rate, controlling the molten pool temperature, affecting the surface tension and viscosity of the molten pool, improving the fluidity of the molten pool, and obtaining the expected physical wettability of the molten pool to improve the apparent quality; at the same time, refining the structure and reducing segregation.

[0026] In a preferred embodiment, the device also includes a controller and an ultrasonic generator; the ultrasonic generator is used to generate an in-situ ultrasonic vibration field and / or an interlayer ultrasonic shock field; the controller is used to control the timing of two different ultrasonic occurrences; wherein, the in-situ ultrasonic vibration field occurs during the directed energy deposition process; the interlayer ultrasonic shock field occurs on the solidification surface after the deposition is completed.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The embodiment of the present invention provides a method and apparatus for controlling shape and properties of additive manufacturing based on directed energy deposition. During the directed energy deposition process, active cooling is used, or active cooling is combined with an in-situ ultrasonic vibration field and / or an interlayer ultrasonic impact field to improve the surface quality, structure, and performance of the additive part. Active cooling improves the spread of the molten droplets by regulating the cooling rate, improves the surface quality, refines the structure, and obtains a lower interlayer temperature, thereby improving production efficiency and reducing the effects of heat accumulation and repeated heat input on the forming quality and structure performance. Active cooling is combined with an in-situ ultrasonic vibration field and / or an interlayer ultrasonic impact field. Through in-situ ultrasonic vibration technology, acoustic streaming and cavitation are used to affect the molten pool, affecting the liquid phase solidification behavior, directly improving the solidification structure, breaking up dendrites, refining grains, and converting columnar crystals into equiaxed crystals. Through interlayer ultrasonic impact technology, the solidified surface is acted on and plastic deformation is generated, which can shape the geometric structure of the deposited layer, improve the surface quality, and generate substructures of a certain depth, leaving a good structure for the additive part, thereby improving the structure and performance through work hardening and recrystallization. Through active cooling, or the synergistic effect of active cooling in situ ultrasonic vibration field and / or interlayer ultrasonic impact field, the problems caused by their independent use are effectively overcome, the apparent quality, organization and performance are effectively improved, and the waiting time between layers is reduced, thereby improving the forming efficiency, which is of great significance for the further promotion of directed energy deposition. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0030] Figure 1 This is a schematic diagram of the process of near-immersion active cooling in conjunction with in-situ ultrasonic vibration field and interlayer ultrasonic impact field combined with ultrasonic-assisted arc additive manufacturing of austenitic stainless steel in Example 1 of the present invention;

[0031] Figure 2 This is the macroscopic morphology of the cross section of an austenitic stainless steel thin-walled part produced by composite ultrasonic-assisted arc additive manufacturing using near-immersion active cooling, in-situ ultrasonic vibration field, and interlayer ultrasonic impact field in Example 1 of the present invention;

[0032] Figure 3 This is a comparison diagram of the electron backscatter diffraction (EBSD) inverse pole figure (IPF) of the austenitic stainless steel thin-walled part prepared by near-immersion active cooling in conjunction with in-situ ultrasonic vibration field and interlayer ultrasonic shock field composite ultrasonic-assisted arc additive manufacturing in Example 1 of the present invention;

[0033] Figure 4 This is a comparison diagram of the electron backscatter diffraction (EBSD) grain boundary (GB) structure of an austenitic stainless steel thin-walled part prepared by near-immersion active cooling in conjunction with in-situ ultrasonic vibration field and interlayer ultrasonic shock field composite ultrasonic-assisted arc additive manufacturing in Example 1 of the present invention;

[0034] Figure 5 This is a comparison diagram of the electron backscatter diffraction (EBSD) local average orientation error (KAM) of the austenitic stainless steel thin-walled part prepared by near-immersion active cooling in conjunction with in-situ ultrasonic vibration field and interlayer ultrasonic shock field composite ultrasonic-assisted arc additive manufacturing in Example 1 of the present invention;

[0035] Figure 6 This is a bar graph comparing the mechanical properties of austenitic stainless steel thin-walled parts prepared by composite ultrasonic-assisted arc additive manufacturing using near-immersion active cooling, in-situ ultrasonic vibration field, and interlayer ultrasonic impact field in Example 1 of the present invention. DETAILED DESCRIPTION

[0036] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0037] Example 1

[0038] This embodiment provides a method for controlling shape and properties of additive manufacturing based on directed energy deposition. The method includes: actively cooling the directed energy deposition process; at the same time, providing an in-situ ultrasonic vibration field during the directed energy deposition process; providing an interlayer ultrasonic shock field on the solidified surface after deposition is completed; and controlling the morphology and properties of the additive part through active cooling combined with a composite ultrasonic assistance of the in-situ ultrasonic vibration field and the interlayer ultrasonic shock field. The metal material used in this embodiment is SUS321 austenitic stainless steel wire. Directed energy deposition adopts arc additive manufacturing, and the equipment is CMT Advanced4000R, using CMT mode.

[0039] like Figure 1 As shown, the additive manufacturing shape and property control method is specifically operated as follows:

[0040] First, each layer in the arc additive process combines near-immersion active cooling and in-situ ultrasonic vibration to achieve directional deposition of the wire. After the deposition of the previous layer is completed, the in-situ ultrasonic vibration field is converted to an interlayer ultrasonic shock field, and the surface of the deposited layer is optimized using interlayer ultrasonic shock. After the previous layer is completed, the next layer is deposited in a directional manner, and then converted to an in-situ ultrasonic vibration field. This auxiliary deposition and shock treatment are repeated to finally produce a thin-walled sample11. The above-mentioned conversion of different ultrasonic fields is achieved by replacing the vibration head. When providing the in-situ ultrasonic vibration field, a hemispherical vibration head with a larger diameter is used; when providing the interlayer ultrasonic shock field, a needle-shaped vibration head is used.

[0041] Among them, the near-immersion active cooling method immerses the deposited portion of the substrate and structural components in a coolant, maintaining a distance of 3 mm between the liquid surface and the arc. After deposition is completed, the coolant removes residual heat, increasing the cooling rate. The cooling rate is controlled by adjusting the distance between the coolant and the deposited layer, the coolant temperature, and the type of coolant. The auxiliary cooling equipment corresponding to the near-immersion active cooling method includes a water tank, a water pool, a lifting platform, a circulating water pump, a water temperature gauge, and corresponding piping. The ultrasonic frequency of the composite ultrasonic assistance is 20 kHz, the ultrasonic amplitude is 80 μm, and the distance between the ultrasonic impact head and the welding torch during in-situ ultrasonic vibration is 15 mm.

[0042] Comparative Example 1

[0043] A comparative example was prepared using the same directed energy deposition parameters as example 1, except that no active cooling and combined ultrasonic assistance were used, to produce thin-walled sample 12.

[0044] Thin-walled sample 11 and thin-walled sample 12 were compared in terms of apparent quality, microstructure and properties. As shown in Table 1: Figure 2-Figure 6

[0045] The combined ultrasonic assistance of near-submerged active cooling, in-situ ultrasonic vibration and interlayer ultrasonic impact helped to improve dimensional accuracy, with the ratio of effective width to maximum full width increasing from 65.24% to 72.00%, a 10% increase in dimensional accuracy; transformed columnar grains into equiaxed grains, while refining the grain size, with the average grain size of the thin-walled sample decreasing from 54±17 μm to 33±9 μm, the dislocation density increasing from 4.4 × 10 13 m -2 to 46.57 × 10 13 m -2 , the proportion of small-angle grain boundaries (2°≤θ≤15°) increasing from 26.97% to 57.24%; the yield strength increasing from 308 MPa to 442 MPa, the tensile strength increasing from 631 MPa to 687 MPa, a 43.5% increase.

[0046] Example 2

[0047] This example also provides a method for controlling shape and properties in additive manufacturing based on directed energy deposition. The method is basically the same as example 1, except that only the combined ultrasonic assistance of in-situ ultrasonic vibration and interlayer ultrasonic impact is used, without active cooling. The ultrasonic frequency for in-situ ultrasonic vibration field assisted deposition is 25 kHz, the ultrasonic amplitude is 60 μm, and the distance between the ultrasonic impact head and the welding torch is 10 mm; the ultrasonic frequency for interlayer ultrasonic impact field assisted deposition is 20 kHz, and the ultrasonic amplitude is 80 μm. When providing the in-situ ultrasonic vibration field, a circular arc vibration head is used; when providing the interlayer ultrasonic impact field, a conical vibration head is used. Thin-walled sample 21 was produced.

[0048] Comparative Example 2

[0049] A comparative example was prepared using the same directed energy deposition parameters as example 2, except that no combined ultrasonic assistance was used, to produce thin-walled sample 22.

[0050] Thin-walled sample 21 and thin-walled sample 22 were compared in terms of apparent quality, microstructure and properties, with the results as follows:

[0051] ​The composite ultrasonic assisted method of in-situ ultrasonic vibration and interlayer ultrasonic impact was used to improve the dimensional accuracy of the sample by 5%. From top to bottom, the average grain size ranged from 44 μm to 62 μm, and the dislocation density increased from 4.4 × 10 13 m -2 Increased to 38.24 × 10 13 m -2 The proportion of small-angle grain boundaries (2°≤θ≤15°) increased from 26.97% to 49.92%; the yield strength increased from 308MPa to 383MPa, and the tensile strength increased from 631MPa to 655MPa, an increase of 24.4%.

[0052] Example 3

[0053] This example also provides a method for controlling shape and properties in additive manufacturing based on directed energy deposition. The method is essentially the same as that in Example 1, except that the wire used in the experiment is IN718 nickel-based high-temperature alloy welding wire, and the VP-CMT+P mode is used. Arc-following chilling is the active cooling method. A square vibrating head is used to provide the in-situ ultrasonic vibration field. A thin-walled sample 31 is produced.

[0054] The specific operation of the additive manufacturing shape and property control method is as follows:

[0055] First, during the arc additive process, each layer combines arc-following active cooling with in-situ ultrasonic vibration to achieve directional deposition of the wire. After the deposition of the previous layer is completed, the in-situ ultrasonic vibration field is transformed into an interlayer ultrasonic shock field, which is used to optimize the surface of the deposited layer. After the current layer is completed, the next layer is deposited in a directional manner, and then the process is transformed into an in-situ ultrasonic vibration field. This assisted deposition and shock treatment is repeated to finally produce a thin-walled sample11.

[0056] The arc-following active cooling method places a liquid nitrogen cooling device on a trolley behind the ultrasonic vibration device. The welding torch pulls the liquid nitrogen into the device during the additive process at a rate of 10 mL / s, maintaining a distance of 100 mm between the liquid nitrogen cooling position and the arc. After deposition is complete, the liquid nitrogen removes residual heat, increasing the cooling rate. The ultrasonic frequency of the hybrid ultrasonic-assisted method is 20 kHz, the ultrasonic amplitude is 80 μm, and the distance between the ultrasonic impact tip and the welding torch during in-situ ultrasonic vibration is 15 mm.

[0057] Comparative Example 3

[0058] This comparative example uses the same directed energy deposition parameters as Example 3, and the same solution aging post-treatment process is used for comparison. The difference is that active cooling and composite ultrasonic assistance are not used to produce the thin-walled sample 32.

[0059] The apparent quality, structure and performance of thin-walled sample 31 and thin-walled sample 32 were compared, and the results are as follows:

[0060] Active cooling with arc-chilling, coupled with in-situ ultrasonic vibration and interlayer ultrasonic impact, improved dimensional accuracy by 2.4%. Coarse columnar grains were transformed into alternating equiaxed and short columnar grains, which were fully equiaxed after solution treatment. The anisotropy of the thin-walled structure was significantly reduced, with the as-deposited texture strength dropping from 21.96 to 4.60. After solution aging, the strength further decreased to 1.49, indicating isotropy. After solution aging, the room temperature tensile strength increased by 19.9% ​​to 1395 MPa, the elongation increased by 39.0% to 25.3%, the tensile strength increased by 14.8% to 1111 MPa at 650°C, the longitudinal elongation increased by 64.0% to 12.3%, and the fatigue life increased by 5.0 times.

[0061] Example 4

[0062] This embodiment also provides a method for controlling shape and properties in additive manufacturing based on directed energy deposition. This method is essentially the same as that in Example 1, except that only active cooling is employed, without the combined ultrasonic assistance of in-situ ultrasonic vibration and interlayer ultrasonic impact. Active cooling involves forced interlayer cooling. After each layer of deposition in the arc additive process is completed and the molten pool of the current deposited layer has solidified, argon gas is used to force cool the deposited layer. This produces a thin-walled sample 41.

[0063] The interlayer forced active cooling method uses argon gas at a flow rate of 15 L / min. Argon gas is blown until the temperature of the deposited layer drops to 400°C, at which point the next layer is deposited. This removes residual heat and increases the cooling rate.

[0064] Comparative Example 4

[0065] This comparative example uses the same directed energy deposition parameters as Example 4, except that active cooling is not used to produce a thin-walled sample 42.

[0066] The apparent quality, structure and performance of thin-walled sample 41 and thin-walled sample 42 were compared, and the results are as follows:

[0067] With the assistance of interlayer forced active cooling method, the dimensional accuracy of the sample was improved by 6%; from top to bottom, the average grain size ranged from 18.6 μm to 25.7 μm, which was reduced by 15.1%-19.8% compared with the unassisted sample; the yield strength increased from 308 MPa to 324 MPa, and the tensile strength increased from 631 MPa to 639 MPa, an increase of 5.2%.

[0068] Example 5

[0069] This embodiment also provides a method for controlling shape and properties in additive manufacturing based on directed energy deposition. The method is essentially the same as that in Example 1, except that only active cooling and an in-situ ultrasonic vibration field are used in conjunction with each other, and no interlayer ultrasonic shock field is used. Active cooling uses near-immersion and arc-following cooling. During near-immersion active cooling, liquid nitrogen is contained in the water tank. The ultrasonic frequency of the in-situ ultrasonic vibration-assisted deposition is 20 kHz, and the distance between the ultrasonic vibration head and the welding gun is 10 mm. A thin-walled sample 51 is produced.

[0070] Comparative Example 5

[0071] This comparative example uses the same directed energy deposition parameters as Example 5, except that active cooling and in-situ ultrasonic vibration field synergistic assistance are not used to produce the thin-walled sample 52.

[0072] The apparent quality, structure and performance of thin-walled sample 51 and thin-walled sample 52 were compared, and the results are as follows:

[0073] By adopting the collaborative assistance of near-immersion active cooling, arc-following active cooling and in-situ ultrasonic vibration, the dimensional accuracy of the sample was improved by 6%; the average grain size ranged from 22.3 μm to 23.3 μm, which was reduced by 16.9%-27.2% compared with the unassisted sample; the yield strength increased from 308 MPa to 350 MPa, and the tensile strength increased from 631 MPa to 639 MPa, an increase of 13.6%.

[0074] Example 6

[0075] This example also provides a method for controlling shape and properties in additive manufacturing based on directed energy deposition. The method is essentially the same as that in Example 1, differing in that only active cooling and an interlayer ultrasonic shock field are used for synergistic assistance, rather than an in-situ ultrasonic vibration field. Active cooling employs near-immersion and interlayer forced cooling. A thin-walled sample 61 was produced.

[0076] The specific operation of the additive manufacturing shape and property control method is as follows:

[0077] First, near-immersion active cooling is used during each deposition of the arc additive process. After the previous layer is deposited, interlayer forced cooling is used. Argon gas is blown through the deposited layer at a flow rate of 15 L / min until the temperature of the deposited layer drops to 400°C. Interlayer ultrasonic impact is then applied to optimize the surface of the deposited layer. After the previous layer is completed, the next layer is deposited in a directional manner, and near-immersion active cooling is used again. The ultrasonic frequency of the interlayer ultrasonic impact-assisted deposition is 20 kHz, and the ultrasonic amplitude is 80 μm. This assisted deposition and impact treatment are repeated to finally produce a thin-walled sample11.

[0078] Comparative Example 6

[0079] A comparative example 6 was prepared using the same directed energy deposition parameters as example 6, except that no active cooling and no interlayer ultrasonic impact assistance were used.

[0080] The apparent quality, microstructure and properties of the thin-walled sample 61 and the thin-walled sample 62 were compared, and the results were as follows:

[0081] Using near-submerged active cooling, interlayer forced cooling active cooling and interlayer ultrasonic impact synergistic assistance, the dimensional accuracy was improved by 5%; the microstructure was partially recrystallized, the grains were refined, and from top to bottom, the average grain size ranged from 17.5 μm to 21.9 μm, which was 20.1%-31.6% lower than that of the sample without assistance, the top and bottom had a higher proportion of low-angle grain boundaries (60.8% and 19.9%), the average KAM values were 1.4° and 1.1°, respectively, and the dislocation density at the top was 8.21×10 13 / m 2 , which was 2.3 times that of the sample without composite ultrasonic assistance; the yield strength increased from 308 MPa to 362 MPa, and the tensile strength increased from 631 MPa to 642 MPa, an increase of 17.5%.

[0082] Example 7

[0083] The example also provides a directed energy deposition-based additive manufacturing method for shape and property control. The method is basically the same as example 1, except that the active cooling uses arc-following cooling and interlayer forced cooling. A thin-walled sample 71 is prepared.

[0084] The additive manufacturing method for shape and property control is specifically operated as follows:

[0085] First, the arc-following cooling and in-situ ultrasonic vibration are combined in each layer during the arc additive process to realize the directed deposition of the wire; after the deposition of the previous layer is completed, the interlayer forced cooling is used to blow argon gas to the deposited layer, and when the temperature of the deposited layer is reduced to 400°C, the in-situ ultrasonic vibration field is changed to an interlayer ultrasonic impact field for interlayer ultrasonic impact to optimize the surface of the deposited layer; after the previous layer is completed, the directed deposition of the next layer is entered again, and the in-situ ultrasonic vibration field is changed to continue using arc-following cooling. The assisted deposition and impact treatment are repeatedly performed in this way, and finally the thin-walled sample 71 is prepared.

[0086] Comparative example 7

[0087] A comparative example 7 was prepared using the same directed energy deposition parameters as example 7, except that no active cooling and no composite ultrasonic assistance were used. A thin-walled sample 72 was prepared.

[0088] The apparent quality, microstructure and properties of the thin-walled sample 71 and the thin-walled sample 72 were compared, and the results were as follows:

[0089] The use of arc-following quenching, interlayer forced cooling active cooling and composite ultrasonic assisted dimensional accuracy increased by 10%; columnar crystals were transformed into equiaxed crystals, and the grain size was refined. The average grain size of the thin-walled sample was reduced from 54±17μm to 34±8μm, and the dislocation density was reduced from 4.4×10 13 m -2 Increased to 45.56 × 10 13 m -2 , the proportion of small-angle grain boundaries (2°≤θ≤15°) increased from 26.97% to 58.32%; the yield strength increased from 308MPa to 445MPa, and the tensile strength increased from 631MPa to 678MPa, an increase of 44.5%.

[0090] Example 8

[0091] This example also provides a method for controlling shape and properties in additive manufacturing based on directed energy deposition. The method is essentially the same as that in Example 1, except that active cooling utilizes near-immersion active cooling, arc-following quenching, and interlayer forced cooling. A thin-walled sample 81 was produced.

[0092] The specific operation of the additive manufacturing shape and property control method is as follows:

[0093] First, each layer of the arc additive process combines near-immersion active cooling, arc-following quenching, and in-situ ultrasonic vibration to achieve directional deposition of the wire. Liquid nitrogen is used in the near-immersion active cooling tank. After the deposition of the previous layer is completed, interlayer forced cooling is used, and argon gas is blown into the deposited layer at a flow rate of 15 L / min. When the temperature of the deposited layer drops to 400°C, the in-situ ultrasonic vibration field is converted to an interlayer ultrasonic shock field for interlayer ultrasonic shock, which optimizes the surface of the deposited layer. After the completion of the previous layer, directional deposition of the next layer is initiated, and then the in-situ ultrasonic vibration field is converted to the in-situ ultrasonic vibration field, continuing with near-immersion active cooling and arc-following quenching. This auxiliary deposition and shock treatment is repeated to finally produce a thin-walled sample 81.

[0094] Comparative Example 8

[0095] This comparative example uses the same directed energy deposition parameters as Example 8, except that active cooling and composite ultrasonic assistance are not used to produce the thin-walled sample 82.

[0096] The apparent quality, structure and performance of thin-walled sample 81 and thin-walled sample 82 were compared, and the results are as follows:

[0097] By adopting near-immersion active cooling, arc-following quenching, interlayer forced cooling and composite ultrasonic assisted synergy, the dimensional accuracy was improved by 11%; the columnar crystals were transformed into equiaxed crystals, and the grain size was refined. The average grain size of the thin-walled sample was reduced from 54±17μm to 32±9μm, and the dislocation density was reduced from 4.4×10 13 m -2 Increased to 45.22 × 10 13 m -2 The proportion of small-angle grain boundaries (2°≤θ≤15°) increased from 26.97% to 55.48%; the yield strength increased from 308 MPa to 444 MPa, and the tensile strength increased from 631 MPa to 685 MPa, an increase of 44.2%.

[0098] Example 9

[0099] This example also provides a method for controlling shape and properties in additive manufacturing based on directed energy deposition. The method is essentially the same as that in Example 1, except that the wire used in the experiment is ZL205A aluminum alloy; the arc additive manufacturing equipment is a CMT Advanced 4000R, operating in VP-CMT mode; and only composite ultrasonic assistance is employed, without active cooling. The ultrasonic frequency of composite ultrasonic-assisted deposition is 20 kHz, the ultrasonic amplitude is 60 μm, and the distance between the ultrasonic impact head and the welding torch is 10 mm. A thin-walled sample 91 was produced.

[0100] Comparative Example 9

[0101] This comparative example uses the same directed energy deposition parameters as Example 9, except that composite ultrasonic assistance is not used to produce the thin-walled sample 92.

[0102] The apparent quality, structure and performance of thin-walled sample 91 and thin-walled sample 92 were compared, and the results are as follows:

[0103] The ratio of effective width to maximum full width increased from 74% to 79% using the combined ultrasonic assisted method of in-situ ultrasonic vibration and interlayer ultrasonic impact, and the dimensional accuracy was improved by 7%. The microstructure underwent partial recrystallization and grain refinement. The average grain size from top to bottom ranged from 17.5 μm to 21.9 μm, which was 20.1%-31.6% lower than that of the unassisted sample. The top and bottom samples had higher proportions of low-angle grain boundaries (61.7% and 21.4%), with average KAM values ​​of 1.38° and 0.84°, respectively. The top dislocation density was 8.33×10 13 / m 2The tensile strength of the sample deposited with the aid of the composite ultrasonic is 2.3 times that of the sample deposited without the aid of the composite ultrasonic; the mechanical properties of the deposited layer are effectively improved by the aid of the composite ultrasonic, the highest tensile strength is 511 MPa, the yield strength is 461 MPa, and the elongation reaches 12.19%, the tensile strength and elongation are increased by 12.2% and 12.9% respectively compared with the sample deposited without the aid of the composite ultrasonic.

[0104] The composite ultrasonic aid is the synergistic effect of in-situ ultrasonic vibration and interlayer ultrasonic impact. The in-situ ultrasonic vibration improves the solidification of the molten pool, reduces pores and refines the structure through cavitation and acoustic streaming; the interlayer ultrasonic impact acts on the surface of the deposited layer, improves the stability of the molten pool, promotes the overflow of hydrogen atoms, closes the pores that do not escape through plastic deformation and further refines the structure, and at the same time, plastic deformation occurs on the surface of the material to form a geometric structure of grooves, which provides a guiding effect for the deposition of the next layer. The synergistic effect of the two reduces defects in the deposited layer, refines the structure and improves the mechanical properties.

[0105] It should be noted that, in the present application, relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element preceded by "comprises... " does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the recited element.

[0106] The above description is merely one specific implementation of the present application, which enables a person skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for controlling shape and properties of additive manufacturing based on directed energy deposition, characterized in that: The method comprises: in a directed energy deposition process, using active cooling to perform in-situ real-time cooling of the deposition process, thereby changing the cooling rate, controlling the molten pool temperature, affecting the surface tension and viscosity of the molten pool, improving the molten pool fluidity, and obtaining the desired physical wettability of the molten pool to improve the surface quality; at the same time, refining the structure and reducing segregation; Active cooling and an in-situ ultrasonic vibration field synergistically assist the additive manufacturing process. The in-situ ultrasonic vibration field, applied during the directed energy deposition process, influences the molten pool through acoustic streaming and cavitation as the deposition equipment moves, mechanically vibrating the material, affecting the liquid-phase solidification behavior and directly improving the solidification structure. The in-situ ultrasonic vibration field can break up dendrites, refine grains, and transform columnar crystals into equiaxed crystals. Active cooling and interlayer ultrasonic shock field cooperate to assist the additive manufacturing process; wherein, the interlayer ultrasonic shock field acts on the solidified surface structure, directly impacts the surface of the deposited layer by mechanical contact, causes the solidified surface structure to produce plastic deformation, shapes the geometric structure in the deposited layer, and produces substructure within a predetermined depth from the surface of the deposited layer, leaving a good structure for the additive part, thereby controlling the structure and performance through work hardening and recrystallization; wherein, the plastic deformation produced by the solidified surface structure presents a neat groove-shaped geometric structure along the horizontal length direction of the wall, which provides guidance for the next layer of additive, is conducive to the expected spread of the next molten pool, not only making the interlayer bonding tighter, but also improving the neatness of the two layers and between layers, obtaining a smoother surface, improving dimensional accuracy, and excellent surface quality; Active cooling and in-situ ultrasonic vibration field, interlayer ultrasonic shock field composite ultrasonic synergistically assist the additive manufacturing process; wherein, in the directed energy deposition process, an in-situ ultrasonic vibration field is provided; and an interlayer ultrasonic shock field is provided on the solidified surface after deposition is completed; the structure and performance of the additive parts are controlled by the composite ultrasonic assistance of the in-situ ultrasonic vibration field and the interlayer ultrasonic shock field; the in-situ ultrasonic vibration field and the interlayer ultrasonic shock field appear alternately; at the same time, active cooling is used to control heat dissipation during the directed energy deposition process, and synergistically works with the composite ultrasonic assistance to jointly complete the structure and performance control of the additive parts.

2. The shape and property control method for additive manufacturing based on directed energy deposition according to claim 1, characterized in that: The active cooling adopts one or more of near-immersion active cooling, arc-following quenching, and interlayer forced cooling.

3. The shape and property control method for additive manufacturing based on directed energy deposition according to claim 2, characterized in that: The near-immersion active cooling completely immerses the substrate and the solidified additive part in the coolant; the coolant level is 0.5-2 mm below the current additive work surface.

4. The shape and property control method for additive manufacturing based on directed energy deposition according to claim 1, characterized in that: The ultrasonic parameters used in the in-situ ultrasonic vibration field are an ultrasonic frequency of 5-50kHz, and the distance between the vibration action position and the deposition equipment is 0-50mm.

5. The shape and property control method for additive manufacturing based on directed energy deposition according to claim 1, characterized in that: The ultrasonic parameters used in the interlayer ultrasonic impact field are ultrasonic frequency 5-50kHz and impact amplitude 10-120μm.

6. A device for implementing the shape and property control method for additive manufacturing based on directed energy deposition according to any one of claims 1 to 5, characterized in that: The device includes an active cooling tank; the active cooling tank is used to perform in-situ real-time cooling of the deposition process in the directed energy deposition process by active cooling, thereby changing the cooling rate, controlling the molten pool temperature, affecting the surface tension and viscosity of the molten pool, improving the molten pool fluidity, and obtaining the desired physical wettability of the molten pool to improve the surface quality; at the same time, the structure is refined and segregation is reduced; The device also includes: a controller and an ultrasonic generator; The ultrasonic generator is used to generate an in-situ ultrasonic vibration field and / or an interlayer ultrasonic shock field; the controller is used to control the timing of the generation of two different ultrasonic fields; wherein, the in-situ ultrasonic vibration field occurs during the directed energy deposition process; and the interlayer ultrasonic shock field occurs on the solidification surface after deposition is completed.

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