Additive manufacturing shape and property control method and device based on directional energy deposition

Abstract

The invention discloses an additive manufacturing shape and property control method based on directional energy deposition, and belongs to the field of additive manufacturing. According to the method, in the directional energy deposition process, an active cooling mode is adopted, and in-situ real-time cooling is conducted in the deposition process, so that the cooling speed is changed, the temperature of a molten pool is controlled, the surface tension and viscosity of the molten pool are affected, the liquidity of the molten pool is improved, and the molten pool obtains expected physical wettability to improve the apparent mass; meanwhile, the structure is refined, and segregation is reduced; the method further comprises the steps that active cooling cooperates with in-situ ultrasonic vibration and / or interlayer ultrasonic peening, and in the directional energy deposition process, an in-situ ultrasonic vibration field is provided; providing an interlayer ultrasonic impact field on the solidified surface after deposition is completed; and the structure and performance of the additive part are controlled through assistance of active cooling cooperating with an in-situ ultrasonic vibration field and / or an interlayer ultrasonic impact field. According to the method, the structure form and performance are improved and optimized in the deposition process and the solidification process, the apparent quality and the mechanical property are improved, and the forming efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the field of additive manufacturing, and in particular relates to a shape and property control method and device for additive manufacturing based on directed energy deposition. Background Art

[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 emergence of new manufacturing technologies, AM-based maintenance technology is expected to become a practical application. Among them, Directed Energy Deposition (DED) is a type of AM that adds material while inputting heat, and melts the deposited material according to the planned path to form a three-dimensional part. The heat input can be an arc, laser, electron beam or plasma arc. DED has the characteristics of high material utilization, high deposition efficiency and low cost. It has significant advantages in the rapid prototyping and manufacturing of large-scale workpieces, and has broad application prospects in aerospace, energy, medical and other fields.

[0003] In recent years, with the rapid development of industrial automation and intelligent manufacturing, the demand for the application of DED technology in the manufacturing industry has been growing. According to market research data, the global DED equipment market size will be approximately US$650 million in 2022 and is expected to reach US$1.85 billion by 2030, with a compound annual growth rate of approximately 13.8%. This is mainly due to the widespread adoption of DED technology in industries such as aerospace, automotive, and medical.

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

[0005] The Chinese invention patent with publication number CN111215898A discloses an arc additive synchronous ultrasonic hot rolling and rapid cooling composite processing device and method, which uses ultrasonic impact special-shaped rollers and liquid nitrogen cooling devices to synchronously assist arc additive manufacturing. However, its ultrasonic impact has almost no effect on the liquid phase of the molten pool, and the use of liquid nitrogen cooling cannot control the cooling rate, and cannot improve the apparent quality of the additive parts.

[0006] The Chinese invention patent with publication number CN117102501A discloses a high-strength aluminum alloy ultrasonic-assisted laser directional energy deposition manufacturing device, in which a water-cooling plate is fixed on an ultrasonic vibrator, and an additive substrate is fixed on a water-cooling plate. However, as the number of additive layers increases, the water cooling and ultrasonic effects of the device decrease until they disappear. The heat of the top molten pool needs to be transferred layer by layer through the deposited part to the substrate and the water-cooling plate. The cooling effect of the water-cooling plate is very poor, and it is difficult to completely solve the problem of heat accumulation, and it is impossible to control the temperature and cooling rate of each molten pool.

[0007] The Chinese invention patent with publication number CN110484843A discloses a method for improving the grain size of additive manufacturing, which uses ultrasonic impact on the substrate in CMT additive manufacturing, and ultrasonic impact on the surface of the solidified component after CMT additive manufacturing. However, the ultrasonic vibration effect of this method is achieved by ultrasonic impact on the substrate, and the ultrasonic vibration always acts on the substrate. The ultrasonic vibration has a long action distance, and the acoustic flow and cavitation of the molten pool are weak. The effect becomes worse and worse with the increase of the deposition layer height, and the dendrite crushing and organization refinement effects are very poor; and the two sides of the additive part have different organizations due to the different distances from the ultrasonic impact position.

[0008] Obviously, none of the above existing technologies can effectively improve the surface quality, organizational structure and mechanical properties of additive parts at the same time, and the scope of application is narrow and cannot be applied to all directed energy deposition additive manufacturing; and the cost is high. 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, which assists in solidification during directed energy deposition and improves the structure after solidification through active cooling and coordinated ultrasonic vibration and / or ultrasonic impact, thereby improving the apparent quality, structure and performance of 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 method for controlling shape and properties of 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 this embodiment, active cooling can reduce the spreading degree of the molten droplets by increasing the cooling rate, improve the surface quality, refine the structure, and obtain a lower interlayer temperature, thereby reducing the influence of heat accumulation and repeated heat input on the forming quality and organizational properties, thereby obtaining good surface quality and mechanical properties; at the same time, it reduces the waiting time between layers and improves the forming efficiency.

[0013] Preferably, the active cooling adopts one or more of near-immersion active cooling, arc-following quenching, and interlayer forced cooling. The active cooling intervention temperature is 500℃-900℃; the cooling temperature range is 25℃-900℃, the cooling rate is 1℃ / s-20℃ / s, and the interlayer temperature is 20℃-30℃. Among them, the near-immersion active cooling completely immerses the substrate and the solidified additive parts in the coolant; the coolant level is 0.5-2mm lower than the current additive working surface.

[0014] The directed energy deposition described herein may be manufactured using arc additive manufacturing or laser deposition additive manufacturing.

[0015] As a preferred embodiment of the present invention, the materials used in the additive manufacturing process include 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 invention, the method also includes: active cooling and in-situ ultrasonic vibration field to coordinately assist the additive manufacturing process; wherein, the in-situ ultrasonic vibration field is applied during the directed energy deposition process, and as the deposition equipment moves, the molten pool is affected by acoustic flow and cavitation, the material is mechanically vibrated, the liquid phase solidification behavior is affected, and the solidification structure is directly improved; the in-situ ultrasonic vibration field can break up dendrites, refine grains, and transform columnar crystals into equiaxed crystals.

[0017] In a specific embodiment, the ultrasonic parameters used in 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 operations, the ultrasonic parameters are selected according to different materials and directed energy deposition parameters.

[0018] As a preferred embodiment of the present invention, the method further includes: active cooling and interlayer ultrasonic shock field 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 a large number of substructures 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. Preferably, the predetermined depth is 1-3 mm.

[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, 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 the 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 be recrystallized.

[0020] In a specific embodiment, the ultrasonic parameters used in the interlayer ultrasonic impact field are ultrasonic frequency 5-50 kHz and impact amplitude 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 assisted additive manufacturing process; wherein, in the directional energy deposition process, an in-situ ultrasonic vibration field is provided; on the solidified surface after deposition is completed, an interlayer ultrasonic shock field is provided; 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 accelerate heat dissipation in the directional energy deposition process, and cooperates with the composite ultrasonic assistance to jointly complete the structure and performance control of the additive parts.

[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 an 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 ultrasound can resonate more easily and the ultrasonic field can be better transmitted; when providing an interlayer ultrasonic impact field, a vibration head with a small contact area is used, such as a needle-shaped, cone-shaped, etc., so that 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 specific 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 deposition is performed on the current layer of material, an in-situ ultrasonic vibration field is provided to mechanically vibrate the material. After the solidification of the current layer is completed, an interlayer ultrasonic shock field is provided to mechanically impact the surface of the material. After completion, it is transformed 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 groove; the active cooling groove is used to use active cooling to perform in-situ real-time cooling on 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; and 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 shape and property control method and device for additive manufacturing based on directed energy deposition provided by the embodiment of the present invention use active cooling, or active cooling in conjunction with an in-situ ultrasonic vibration field and / or an interlayer ultrasonic impact field, during the directed energy deposition process, to improve the apparent quality, organization and performance of the additive parts. Active cooling improves the spreading degree of the molten droplets by regulating the cooling rate, improves the apparent quality, refines the organization, and obtains a lower interlayer temperature, improves production efficiency, and reduces the influence of heat accumulation and repeated heat input on the forming quality and organizational performance; active cooling cooperates with an in-situ ultrasonic vibration field and / or an interlayer ultrasonic impact field, and uses an in-situ ultrasonic vibration technology to affect the molten pool through acoustic flow and cavitation, affects the liquid phase solidification behavior, directly improves the solidification organization, can break up dendrites, refine grains, and transform columnar crystals into equiaxed crystals; through the interlayer ultrasonic impact technology, the solidified surface is acted on and plastic deformation is generated, and the geometric structure can be shaped in the deposited layer, which is beneficial to improving the surface quality, and produces a substructure with a certain action depth, leaving a good organization for the additive parts, thereby improving the organization 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 surface quality, organization and performance are effectively improved, the waiting time between layers is reduced, and the forming efficiency is improved, 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 drawings required for use in the description of the embodiments will be briefly introduced below. 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 creative work.

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

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

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

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

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

[0036] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0037] Example 1

[0038] This embodiment provides a shape and property control method for 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 the deposition is completed; and controlling the morphology and performance of the additive parts through active cooling, coordinated in-situ ultrasonic vibration field and interlayer ultrasonic shock field composite ultrasonic assistance. The metal material used in this embodiment is SUS321 austenitic stainless steel wire. Directed energy deposition adopts arc additive manufacturing, the equipment is CMT Advanced4000R, and the CMT mode is used.

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

[0040] First, in the arc additive process, each layer 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 transformed into an interlayer ultrasonic shock field, and the surface of the deposited layer is optimized by using interlayer ultrasonic shock; after the previous layer is completed, the directional deposition of the next layer is started, and then transformed into an in-situ ultrasonic vibration field. Auxiliary deposition and shock treatment are repeated in this way, and finally a thin-walled sample is made11. The above-mentioned conversion of different ultrasonic fields is achieved by replacing the vibration head. When providing an in-situ ultrasonic vibration field, a hemispherical vibration head with a larger diameter is used; when providing an interlayer ultrasonic shock field, a needle-shaped vibration head is used.

[0041] Among them, the near-immersion active cooling method immerses the deposited part of the substrate and the structural parts in the coolant, so that the distance between the liquid surface and the arc is maintained at 3mm. When the deposition is completed, the coolant takes away the residual heat to increase 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 is a water tank, a pool, a lifting platform, a circulating water pump, a water thermometer, and corresponding pipelines. The ultrasonic frequency of the composite ultrasonic assisted method is 20kHz, the ultrasonic amplitude is 80 μm, and the distance between the ultrasonic impact head and the welding gun is 15 mm during in-situ ultrasonic vibration.

[0042] Comparative Example 1

[0043] This comparative example uses the same directed energy deposition parameters as Example 1, except that active cooling and composite ultrasonic assistance are not used to produce the thin-walled sample 12.

[0044] The apparent quality, organization and performance of thin-walled sample 11 and thin-walled sample 12 were compared. Figure 2-Figure 6 As shown:

[0045] The composite ultrasonic assistance of near-immersion active cooling, in-situ ultrasonic vibration and interlayer ultrasonic impact helps to improve the dimensional accuracy. The ratio of effective width to maximum full width is increased from 65.24% to 72.00%, and the dimensional accuracy is improved by 10%. The columnar crystals are transformed into equiaxed crystals, and the grain size is refined. The average grain size of the thin-walled sample is reduced from 54±17μm to 33±9μm, and the dislocation density is reduced from 4.4 × 10 13 m -2 Increased to 46.57 × 10 13 m -2 , the proportion of small-angle grain boundaries (2°≤θ≤15°) increased from 26.97% to 57.24%; the yield strength increased from 308MPa to 442MPa, and the tensile strength increased from 631MPa to 687MPa, an increase of 43.5%.

[0046] Example 2

[0047] This embodiment also provides a shape and property control method for additive manufacturing based on directed energy deposition. The method is basically the same as that in Example 1, except that only composite ultrasonic assistance of in-situ ultrasonic vibration and interlayer ultrasonic impact is used, and active cooling is not used. The ultrasonic frequency of the in-situ ultrasonic vibration field assisted deposition is 25kHz, the ultrasonic amplitude is 60 μm, and the distance between the ultrasonic impact head and the welding gun is 10mm; the ultrasonic frequency of the interlayer ultrasonic impact field assisted deposition is 20kHz, and the ultrasonic amplitude is 80 μm. When providing an in-situ ultrasonic vibration field, an arc-shaped vibration head is used; when providing an interlayer ultrasonic impact field, a conical vibration head is used. A thin-walled sample 21 is obtained.

[0048] Comparative Example 2

[0049] This comparative example uses the same directed energy deposition parameters as Example 2, except that composite ultrasonic assistance is not used to produce the thin-walled sample 22.

[0050] The apparent quality, organization and performance of thin-walled sample 21 and thin-walled sample 22 were compared, and the results are as follows:

[0051] The composite ultrasonic assistance 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 embodiment also provides a shape and property control method for additive manufacturing based on directed energy deposition. The method is basically the same as that in Example 1, except that the wire used in the experiment is IN718 nickel-based high-temperature alloy welding wire; the experiment uses the VP-CMT+P mode. Among them, the active cooling method is arc-following quenching. When providing an in-situ ultrasonic vibration field, a square vibration head is used. A thin-walled sample 31 is obtained.

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

[0055] First, each layer in the arc additive process combines arc-following 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 transformed into an interlayer ultrasonic shock field, and the surface of the deposited layer is optimized by using interlayer ultrasonic shock; after the previous layer is completed, the directional deposition of the next layer is started, and then transformed into an in-situ ultrasonic vibration field. Auxiliary deposition and shock treatment are repeated in this way, and finally a thin-walled sample is made11.

[0056] Among them, the arc-chilled active cooling method places the liquid nitrogen cooling device on a trolley behind the ultrasonic vibration device, and the welding gun pulls the liquid nitrogen to be poured synchronously during the additive process. The pouring speed is 10mL / s, so that the liquid nitrogen cooling position is kept 100mm away from the arc. After the deposition is completed, the residual heat is taken away by liquid nitrogen to increase the cooling rate. The ultrasonic frequency of the composite ultrasonic-assisted method is 20kHz, the ultrasonic amplitude is 80 μm, and the distance between the ultrasonic impact head and the welding gun is 15 mm during in-situ ultrasonic vibration.

[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 obtain the thin-walled sample 32.

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

[0060] The composite ultrasonic assistance of arc-chilled active cooling, in-situ ultrasonic vibration and interlayer ultrasonic impact improves the dimensional accuracy by 2.4%, and the coarse columnar crystals are transformed into equiaxed crystals and short columnar crystals with alternating distribution. The solution treatment can make them completely equiaxed. The anisotropy of the thin-walled structure is significantly reduced, and the texture strength of the deposited state is reduced from 21.96 to 4.60. After solution aging, it is further reduced to 1.49, showing isotropy. After solution aging treatment, the tensile strength at room temperature increases by 19.9% ​​to 1395MPa; the elongation increases by 39.0% to 25.3%; at 650 ℃, the tensile strength increases by 14.8% to 1111 MPa; the longitudinal elongation increases by 64.0% to 12.3%; and the fatigue life increases by 5.0 times.

[0061] Example 4

[0062] This embodiment also provides a shape and property control method for additive manufacturing based on directed energy deposition. The method is basically the same as that in Example 1, except that only active cooling is used, and the composite ultrasonic assistance of in-situ ultrasonic vibration and interlayer ultrasonic impact is not used. The active cooling method is interlayer forced cooling. After each layer of deposition in the arc additive process is completed, the molten pool of the current deposition layer has solidified, and the deposition layer is forced to cool by blowing argon. A thin-walled sample 41 is obtained.

[0063] Among them, the interlayer forced active cooling method uses an argon gas flow rate of 15 L / min, and the deposition of the next layer begins when the temperature of the deposited layer drops to 400°C. The argon gas removes the 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, organization and performance of thin-walled sample 41 and thin-walled sample 42 were compared, and the results are as follows:

[0067] With the aid of interlayer forced active cooling, 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 15.1%-19.8% lower than that of 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 shape and property control method for additive manufacturing based on directed energy deposition. The method is basically the same as that in Example 1, except that only active cooling and in-situ ultrasonic vibration field are used in a coordinated manner, and no interlayer ultrasonic impact field is used. Active cooling adopts near-immersion and arc-following cooling. During near-immersion active cooling, liquid nitrogen is contained in the water tank. The ultrasonic frequency of in-situ ultrasonic vibration-assisted deposition is 20kHz, and the distance between the ultrasonic vibration head and the welding gun is 10mm. A thin-walled sample 51 is obtained.

[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, organization and performance of thin-walled sample 51 and thin-walled sample 52 were compared, and the results are as follows:

[0073] By adopting near-immersion active cooling, arc-quenching active cooling and in-situ ultrasonic vibration synergistic assistance, the dimensional accuracy of the sample is improved by 6%; the average grain size ranges from 22.3 μm to 23.3 μm, which is 16.9%-27.2% lower than that of the unassisted sample; the yield strength is increased from 308 MPa to 350 MPa, and the tensile strength is increased from 631 MPa to 639 MPa, an increase of 13.6%.

[0074] Example 6

[0075] This embodiment also provides a shape and property control method for additive manufacturing based on directed energy deposition. The method is basically the same as that in Example 1, except that only active cooling and interlayer ultrasonic shock field assisted synergy are used, and no in-situ ultrasonic vibration field is used. Active cooling uses near-immersion and interlayer forced cooling. A thin-walled sample 61 is obtained.

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

[0077] First, near-immersion active cooling is used for each layer deposition in the arc additive process; after the deposition of the previous layer is completed, interlayer forced cooling is used to blow argon gas to the deposited layer with an argon flow rate of 15 L / min until the temperature of the deposited layer drops to 400°C, and interlayer ultrasonic impact is performed to optimize the surface of the deposited layer; after the previous layer is completed, the directional deposition of the next layer is performed, and near-immersion active cooling is used again. Among them, the ultrasonic frequency of interlayer ultrasonic impact assisted deposition is 20kHz, and the ultrasonic amplitude is 80 μm. The auxiliary deposition and impact treatment are repeated in this way, and finally a thin-walled sample 11 is made.

[0078] Comparative Example 6

[0079] This comparative example uses the same directed energy deposition parameters as Example 6, except that active cooling and interlayer ultrasonic impact assistance are not used to produce the thin-walled sample 62.

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

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

[0082] Example 7

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

[0084] The specific operation of the additive manufacturing shape and property control method is as follows:

[0085] First, in the arc additive process, each layer combines arc cooling and in-situ ultrasonic vibration to achieve directional deposition of the wire; after the deposition of the previous layer is completed, interlayer forced cooling is used to blow argon gas to the deposited layer with an argon 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, and the surface of the deposited layer is optimized; after the previous layer is completed, the directional deposition of the next layer is started, and then the in-situ ultrasonic vibration field is converted to continue with arc cooling. Auxiliary deposition and shock treatment are repeated in this way, and finally a thin-walled sample 71 is made.

[0086] Comparative Example 7

[0087] This comparative example uses the same directed energy deposition parameters as Example 7, except that active cooling and composite ultrasonic assistance are not used to produce the thin-walled sample 72.

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

[0089] The dimensional accuracy was improved by 10% by using arc quenching, interlayer forced cooling active cooling and composite ultrasonic assisted. 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 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 embodiment also provides a shape and property control method for additive manufacturing based on directed energy deposition. The method is basically the same as that in Example 1, except that the active cooling adopts near-immersion active cooling, arc-following quenching and interlayer forced cooling. A thin-walled sample 81 is obtained.

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

[0093] First, in the arc additive process, each layer combines near-immersion active cooling, arc-following quenching, and in-situ ultrasonic vibration to achieve directional deposition of wires. Liquid nitrogen is used in the near-immersion active cooling water tank. After the deposition of the previous layer is completed, interlayer forced cooling is used to blow argon gas to the deposited layer. The argon gas flow rate is 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, and the surface of the deposited layer is optimized. After the previous layer is completed, the directional deposition of the next layer is entered, and then converted to an in-situ ultrasonic vibration field, and near-immersion active cooling and arc-following quenching are continued. Auxiliary deposition and shock treatment are repeated in this way, and finally a thin-walled sample 81 is made.

[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, organization 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 and interlayer forced cooling active cooling and composite ultrasonic synergistic assistance, 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 308MPa to 444MPa, and the tensile strength increased from 631MPa to 685MPa, an increase of 44.2%.

[0098] Example 9

[0099] This embodiment also provides a shape and property control method for additive manufacturing based on directed energy deposition. The method is basically 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 CMT Advanced 4000R, using the VP-CMT mode; only composite ultrasonic assistance is used, and active cooling is not used. Among them, the ultrasonic frequency of the composite ultrasonic assisted deposition is 20kHz, the ultrasonic amplitude is 60 μm, and the distance between the ultrasonic impact head and the welding gun is 10mm. A thin-walled sample 91 was obtained.

[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, organization 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 of the composite ultrasonic-assisted sample by in-situ ultrasonic vibration and interlayer ultrasonic impact was increased from 74% to 79%, and the dimensional accuracy was improved by 7%. The microstructure was partially recrystallized, and the grains were refined. The average grain size ranged from 17.5 μm to 21.9 μm from top to bottom, 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%), respectively. The average KAM values ​​were 1.38° and 0.84°, respectively. The dislocation density at the top was 8.33×10 13 / m 2, which is 2.3 times that of the sample without composite ultrasonic assistance; composite ultrasonic assistance effectively improved the mechanical properties of the deposited layer, with the highest tensile strength of 511 MPa, yield strength of 461 MPa, and elongation of 12.19%. The tensile strength and elongation were increased by 12.2% and 12.9% respectively compared with the unassisted sample.

[0104] Composite ultrasonic assistance is the synergistic effect of in-situ ultrasonic vibration and interlayer ultrasonic impact. In-situ ultrasonic vibration improves the solidification of the molten pool through cavitation and acoustic streaming, reduces pores and refines the structure; interlayer ultrasonic impact acts on the surface of the deposited layer, improves the stability of the molten pool and promotes the overflow of hydrogen atoms, closes the unescaped pores through plastic deformation and further refines the structure, and at the same time causes plastic deformation on the surface of the material to form a groove geometry, providing guidance for the next layer of deposition. The synergistic effect of the two reduces the defects of the deposited layer, refines the structure and improves the mechanical properties.

[0105] It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0106] The above description is only a specific implementation of the present application, so that those skilled in the art can 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 the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A shape and property control method for additive manufacturing based on directed energy deposition, characterized in that: The method comprises: in the process of directed energy deposition, using active cooling to perform in-situ real-time cooling of the deposition process, thereby changing the cooling rate, controlling the temperature of the molten pool, 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 surface quality; at the same time, refining the structure and reducing segregation.

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 of 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 lower than the current additive work surface.

4. The shape and property control method of additive manufacturing based on directed energy deposition according to claim 1, characterized in that: Active cooling and in-situ ultrasonic vibration field cooperate to assist the additive manufacturing process; wherein, the in-situ ultrasonic vibration field is applied in the directed energy deposition process, and as the deposition equipment moves, it affects the molten pool through acoustic streaming and cavitation, mechanically vibrates the material, affects the liquid phase solidification behavior, and directly improves the solidification structure; the in-situ ultrasonic vibration field can break up dendrites, refine grains, and transform columnar crystals into equiaxed crystals.

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

6. The shape and property control method of additive manufacturing based on directed energy deposition according to claim 1, characterized in that: 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 plastic deformation of the solidified surface structure, shapes the geometric structure in the deposited layer, and generates 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; 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. It not only makes the interlayer bonding closer, but also improves the neatness of the two layers and between layers, obtaining a smoother surface, improving dimensional accuracy and excellent surface quality.

7. The shape and property control method for additive manufacturing based on directed energy deposition according to claim 6, characterized in that: The ultrasonic parameters used in the interlayer ultrasonic impact field are ultrasonic frequency 5-50kHz and impact amplitude 10-120μm.

8. The shape and property control method for additive manufacturing based on directed energy deposition according to claim 1, characterized in that: Active cooling and in-situ ultrasonic vibration field, interlayer ultrasonic shock field composite ultrasonic synergistically assist the additive manufacturing process; wherein, in the process of directional energy deposition, an in-situ ultrasonic vibration field is provided; 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 in the process of directional energy deposition, and synergizes with the composite ultrasonic assistance to jointly complete the structure and performance control of the additive parts.

9. A shape-controlling and property-controlling device for additive manufacturing based on directed energy deposition, characterized in that: The device comprises: an active cooling groove; the active cooling groove is used to perform in-situ real-time cooling of the deposition process in the process of directed energy deposition by adopting an active cooling method, thereby changing the cooling rate, controlling the temperature of the molten pool, 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, the structure is refined and segregation is reduced.

10. The device for controlling shape and properties of additive manufacturing based on directed energy deposition according to claim 9, characterized in that: 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 occurrence 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 the deposition is completed.

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