CN117483799A - Powder bed electron beam additive manufacturing method of aluminum alloy - Google Patents
Powder bed electron beam additive manufacturing method of aluminum alloy Download PDFInfo
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- CN117483799A CN117483799A CN202311842243.5A CN202311842243A CN117483799A CN 117483799 A CN117483799 A CN 117483799A CN 202311842243 A CN202311842243 A CN 202311842243A CN 117483799 A CN117483799 A CN 117483799A
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- 239000000843 powder Substances 0.000 title claims abstract description 182
- 229910000838 Al alloy Inorganic materials 0.000 title claims abstract description 118
- 238000010894 electron beam technology Methods 0.000 title claims abstract description 111
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 39
- 239000000654 additive Substances 0.000 title claims abstract description 33
- 230000000996 additive effect Effects 0.000 title claims abstract description 33
- 238000002844 melting Methods 0.000 claims abstract description 65
- 230000008018 melting Effects 0.000 claims abstract description 65
- 239000000758 substrate Substances 0.000 claims abstract description 46
- 239000011261 inert gas Substances 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 239000001307 helium Substances 0.000 claims description 4
- 229910052734 helium Inorganic materials 0.000 claims description 4
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 4
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 238000000034 method Methods 0.000 abstract description 50
- 230000008569 process Effects 0.000 description 21
- 238000005516 engineering process Methods 0.000 description 12
- 238000010586 diagram Methods 0.000 description 8
- 238000007639 printing Methods 0.000 description 8
- 238000003892 spreading Methods 0.000 description 7
- 239000000956 alloy Substances 0.000 description 6
- 230000000630 rising effect Effects 0.000 description 6
- 238000005054 agglomeration Methods 0.000 description 5
- 230000002776 aggregation Effects 0.000 description 5
- 238000005245 sintering Methods 0.000 description 5
- 230000007480 spreading Effects 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000005266 casting Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000010309 melting process Methods 0.000 description 2
- 238000013021 overheating Methods 0.000 description 2
- 238000010146 3D printing Methods 0.000 description 1
- 229910001008 7075 aluminium alloy Inorganic materials 0.000 description 1
- 229910003407 AlSi10Mg Inorganic materials 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- WYTGDNHDOZPMIW-RCBQFDQVSA-N alstonine Natural products C1=CC2=C3C=CC=CC3=NC2=C2N1C[C@H]1[C@H](C)OC=C(C(=O)OC)[C@H]1C2 WYTGDNHDOZPMIW-RCBQFDQVSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 239000003870 refractory metal Substances 0.000 description 1
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- 238000010079 rubber tapping Methods 0.000 description 1
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- 230000000087 stabilizing effect Effects 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/20—Direct sintering or melting
- B22F10/28—Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/30—Process control
- B22F10/32—Process control of the atmosphere, e.g. composition or pressure in a building chamber
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/30—Process control
- B22F10/36—Process control of energy beam parameters
- B22F10/362—Process control of energy beam parameters for preheating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y10/00—Processes of additive manufacturing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
- B33Y40/10—Pre-treatment
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Abstract
The embodiment of the application relates to a powder bed electron beam additive manufacturing method of an aluminum alloy. Comprising the following steps: preheating a substrate in a forming chamber to a preset temperature; laying aluminum alloy powder on the preheated substrate, and carrying out powder preheating on the aluminum alloy powder on the substrate by utilizing defocused electron beams; carrying out local preheating on a local preheating area where the preheated aluminum alloy powder is located by utilizing defocused electron beams so as to further sinter the aluminum alloy powder in a part melting area; the area of the local preheating area is larger than that of the part melting area, and the shape of the local preheating area is the same as that of the part melting area; carrying out selective melting forming on the aluminum alloy powder after local preheating by utilizing the focused electron beam; repeating the steps of laying powder, local preheating and selective melting forming until the target part is obtained. The method can solve the contradiction that aluminum alloy powder is easy to agglomerate at high temperature and easy to push powder at low temperature, and realizes high-quality forming of the electron beam selective melting aluminum alloy.
Description
Technical Field
The embodiment of the application relates to the technical field of additive manufacturing, in particular to a powder bed electron beam additive manufacturing method of aluminum alloy.
Background
The additive manufacturing technology is also called 3D printing technology, and has the characteristics of short production period, low cost and the like compared with the traditional technology. The aluminum alloy has the advantages of low density, high specific strength, good plasticity, strong corrosion resistance and the like, and has wide application prospect in the fields of aerospace, transportation and the like. With the continuous improvement of the technical level of products and the continuous shortening of the development period, higher requirements are put on the manufacturing technology of the complex precise aluminum alloy components, so that the manufacturing efficiency is high, the rapid response capability which changes along with the design change of equipment is also required, and the flexible adaptability to the production and the manufacture of the complex precise aluminum alloy components is also required. It is apparent that conventional manufacturing techniques are difficult to meet the above requirements, and thus development of additive manufacturing techniques for aluminum alloys is one of the hot spots of research.
Among the mainstream additive manufacturing techniques in the related art, the powder-spreading type additive manufacturing technique has the advantages of high dimensional accuracy, good surface quality, excellent mechanical properties and the like, can be formed in a vacuum or protective gas environment, and is an ideal additive manufacturing technique for small-sized aluminum alloy components. Depending on the source of the heat, powder additive manufacturing techniques can be categorized into selective laser melting (Selective laser melting, SLM) techniques and electron beam selective melting (Electron Beam Selective Melting, SEBM) techniques. The most widely used selective laser melting technology at present, however, the wide application of laser additive manufacturing on aluminum alloy is affected due to the fact that part of aluminum alloy has a larger refractive index to laser. The technology for researching the additive manufacturing of the aluminum alloy by using the laser as a heat source at home and abroad is limited to casting aluminum alloy series or aluminum alloy with better weldability, such as AlSi10Mg casting aluminum alloy, 7075 aluminum alloy and the like.
The electron beam selective melting technology is not limited in this way, and almost all metal materials including refractory metals such as tungsten, molybdenum, tantalum and the like can be easily melted due to high energy density of the electron beam. However, the electron beam selective melting technology has the technical problems in the process of forming aluminum alloy, such as serious vaporization and volatilization of elements such as Mg, zn and the like, easy overheating and skinning of a powder bed in the preheating process, easy agglomeration and agglomeration of powder, and the phenomenon of 'pushing powder' that the powder is pushed to advance by electron beams and the like in the melting process. This results in a wire feed rather than a powder lay-up mainly in the manufacture of aluminium alloy additive materials by means of electron beams. However, the powder-spreading type electron beam additive manufacturing technology has the advantages of high dimensional accuracy, high forming speed, good mechanical property and the like, and the powder-spreading type electron beam additive manufacturing technology can control the dimensional accuracy of the part within +/-0.3 mm. Therefore, the technical problem of electron beam selective melting technology in the process of forming aluminum alloy is solved, compact forming of aluminum alloy is realized, and the method is very important for promoting development of the additive manufacturing industry of small-sized aluminum alloy components.
When overcoming the technical problem of electron beam selective melting technology in the process of forming aluminum alloy, the powder of the aluminum alloy material is easy to agglomerate at 500-600 ℃ because the melting point of the aluminum alloy material is lower (less than or equal to 660 ℃). In the powder bed electron beam additive manufacturing process, the temperature of the powder bed can be quickly increased due to the scanning preheating process after powder is paved, and the phenomena of peeling and caking of aluminum alloy powder scraped by a scraper are easy to occur in the process, so that poor forming quality and even printing failure are caused. Secondly, aluminum alloy powder is light in weight, if the sintering degree among the powder is insufficient, the powder is easy to move along with the electron beam under the bombardment of the electron beam, and the forming quality is reduced in the process.
Accordingly, there is a need to improve one or more problems in the related art as described above.
It is noted that this section is intended to provide a background or context for the technical solutions of the present application as set forth in the claims. The description herein is not admitted to be prior art by inclusion in this section.
Disclosure of Invention
It is an aim of embodiments of the present application to provide a powder bed electron beam additive manufacturing method of an aluminium alloy, which overcomes, at least to some extent, one or more of the problems due to the limitations and disadvantages of the related art.
According to the powder bed electron beam additive manufacturing method of the aluminum alloy, which is provided by the embodiment of the application, the method comprises the following steps:
preheating a substrate in a forming chamber to a preset temperature;
paving aluminum alloy powder on the preheated substrate, and carrying out powder preheating on the aluminum alloy powder on the substrate by utilizing defocused electron beams;
carrying out local preheating on a local preheating area where the preheated aluminum alloy powder is located by utilizing the defocused electron beam so as to further sinter the aluminum alloy powder in a part melting area; the area of the local preheating area is larger than that of the part melting area, the shape of the local preheating area is the same as that of the part melting area, and the center of the local preheating area is coincident with the center of the part melting area;
carrying out selective melting forming on the aluminum alloy powder after local preheating by utilizing the focused electron beam;
repeating the steps of laying powder, local preheating and selective melting forming until the target part is obtained.
In an embodiment of the present application, the preset temperature is 360 to 400 ℃.
In an embodiment of the present application, when the aluminum alloy powder on the substrate is subjected to powder preheating, a control voltage of a first defocus amount of the defocused electron beam is-1 to-0.6V or 0.6 to 1V, and a first defocus current is 3 to 10ma.
In an embodiment of the present application, a preset distance is provided between an outer contour of the local preheating region and an outer contour of the part melting region.
In an embodiment of the present application, the preset distance is in the range of (0, 10), and the preset distance is in mm.
In an embodiment of the present application, when the local preheating area where the preheated aluminum alloy powder is located is locally preheated, the control voltage of the second defocusing amount of the defocused electron beam is-1 to-0.6V or 0.6 to 1V, and the second defocusing current is 16 to 20ma.
In an embodiment of the present application, before preheating the substrate in the forming chamber to a predetermined temperature includes:
and vacuumizing the forming chamber and the gun chamber respectively, and filling inert gas so that the vacuum degree of the forming chamber reaches a first preset vacuum degree, and the vacuum degree of the gun chamber reaches a second preset vacuum degree.
In an embodiment of the present application, the first preset vacuum degree is 1×10 -1 ~2×10 -1 Pa, the second preset vacuum degree is 4 multiplied by 10 -4 ~9×10 -4 Pa。
In one embodiment of the present application, the inert gas is helium or argon.
The technical scheme provided by the embodiment of the application can comprise the following beneficial effects:
according to the embodiment of the application, through the method, the defocused electron beam is utilized to preheat the aluminum alloy powder on the substrate, so that not only can the powder bed be firmly acted, but also the temperature rising speed of the powder bed can be reduced, and the overheat agglomeration of the powder bed is restrained. The defocused electron beam is utilized to locally preheat the local preheating area where the preheated aluminum alloy powder is located, so that the binding force between the aluminum alloy powder is enhanced, the phenomenon that the electron beam impacts a powder bed too much in the selective melting stage is avoided, and the powder pushing phenomenon occurs, thereby improving the internal quality of the target part.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application. It is apparent that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.
FIG. 1 shows a flow chart of steps of a powder bed electron beam additive manufacturing method of an aluminum alloy in an exemplary embodiment of the present application;
FIG. 2 shows a schematic view of the state of an electron beam during powder preheating, partial preheating and selective melting phases in an exemplary embodiment of the present application;
FIG. 3 illustrates a schematic view of three shapes of a localized pre-heat region and a part melt region in an exemplary embodiment of the present application;
FIG. 4 shows a schematic diagram of a method of the present application in comparison to a conventional powder bed e-beam printing process in an exemplary embodiment of the present application;
FIG. 5 is a schematic diagram showing a powder bed during tapping of an aluminum alloy printed by a conventional electron beam selective melting method in an exemplary embodiment of the present application;
FIG. 6 shows a metallographic structure diagram of an aluminum alloy sample printed using a conventional electron beam selective melting method in an exemplary embodiment of the present application;
FIG. 7 shows a state of a powder bed when aluminum alloy is discharged by printing using the method of the present application in an exemplary embodiment of the present application;
fig. 8 shows a metallographic structure diagram of an aluminum alloy sample printed using the method of the present application in an exemplary embodiment of the present application.
Description of the embodiments
Example embodiments will now be described more fully with reference to the accompanying drawings. However, the exemplary embodiments may be embodied in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
Furthermore, the drawings are only schematic illustrations of embodiments of the present application and are not necessarily drawn to scale.
Because the melting point of the aluminum alloy material is lower (less than or equal to 660 ℃), the powder is easy to agglomerate at 500-600 ℃. In the powder bed electron beam additive manufacturing process, the temperature of the powder bed can be quickly increased due to the scanning preheating process after powder is paved, and the phenomena of peeling and caking of aluminum alloy powder scraped by a scraper are easy to occur in the process, so that poor forming quality and even printing failure are caused. Secondly, because the aluminum alloy powder is light in weight, if the sintering degree among the aluminum alloy powder is insufficient, the phenomenon of powder pushing of the aluminum alloy powder moving along with the electron beam easily occurs under the bombardment of the electron beam, and the forming quality is also reduced in the process.
In order to solve the technical problems, electron beam selective melting compact forming of the aluminum alloy is realized. In the example embodiment, a powder bed electron beam additive manufacturing method of an aluminum alloy is provided. Referring to what is shown in fig. 1, the method may include: steps S101 to S105.
Step S101: the substrate in the forming chamber is preheated to a preset temperature.
Step S102: and paving aluminum alloy powder on the preheated substrate, and carrying out powder preheating on the aluminum alloy powder on the substrate by utilizing defocused electron beams.
Step S103: carrying out local preheating on a local preheating area where the preheated aluminum alloy powder is located by utilizing defocused electron beams so as to further sinter the aluminum alloy powder in a part melting area; the area of the local preheating area is larger than that of the part melting area, the shape of the local preheating area is the same as that of the part melting area, and the center of the local preheating area is coincident with that of the part melting area.
Step S104: and carrying out selective melting forming on the aluminum alloy powder after the partial preheating by utilizing the focused electron beam.
Step S105: repeating the steps of laying powder, local preheating and selective melting forming until the target part is obtained.
By the method, the defocused electron beam is utilized to preheat the aluminum alloy powder on the substrate, so that not only can the powder bed be firmly acted, but also the temperature rising speed of the powder bed can be reduced, and the overheat agglomeration of the powder bed is restrained. The defocused electron beam is utilized to locally preheat the local preheating area where the preheated aluminum alloy powder is located, so that the binding force between the aluminum alloy powder is enhanced, the phenomenon that the electron beam impacts a powder bed too much in the selective melting stage is avoided, and the powder pushing phenomenon occurs, thereby improving the internal quality of the target part.
Next, respective portions of the powder bed electron beam additive manufacturing method of the above-described aluminum alloy in the present exemplary embodiment will be described in more detail with reference to fig. 2 to 3.
In step S101, the substrate in the forming chamber is preheated to a preset temperature of 360-400 ℃. The preset temperature may be 360 ℃, 380 ℃, 390 ℃ or 400 ℃, and the specific value of the preset temperature may be set according to practical conditions, which is not limited in this application.
When preheating and heating the substrate in the forming chamber, the preheating and heating may be performed in stages. For example, the substrate may be preheated in three stages. A first stage of preheating a substrate to an initial temperature using a focused electron beam; the second stage, carrying out heat preservation for a preset time period on the basis of the initial temperature; and thirdly, preheating the substrate again to enable the substrate to be raised to a preset temperature from the initial temperature. By preheating the substrate in stages, the occurrence of powder bed overheat sintering caused by too high preset temperature of the substrate or loosening of aluminum alloy powder caused by too low preset temperature of the substrate can be avoided, and the powder bed overheat sintering is easy to collapse when impacted by focused electron beams.
Before preheating the substrate in the forming chamber, the forming chamber and the gun chamber are vacuumized, and then inert gas is filled in to ensure that the vacuum degree of the forming chamber reaches a first preset vacuum degree and the vacuum degree of the gun chamber reaches a second preset vacuum degree, so that the vacuum environment of aluminum alloy forming is ensured. In the process of making the vacuum degree of the forming chamber reach the first preset vacuum degree, the forming chamber needs to be initially vacuumized so as to make the vacuum degree of the forming chamber reach the initial vacuum degree, and the initial vacuum degree of the forming chamber is 9 multiplied by 10 -3 ~2×10 -2 Pa; then filling inert gas to make the vacuum degree of the forming chamber reach the first preset vacuum degree. Wherein the inert gas is preferably helium or argon, and the first preset vacuum degree is 1×10 -1 ~2×10 -1 Pa, a second preset vacuum degree of 4×10 -4 ~9×10 -4 Pa. Specific values of the first preset vacuum degree and the second preset vacuum degree can be set according to actual conditions, and the application is not limited thereto.
In step S102, after the substrate is preheated to a preset temperature, aluminum alloy powder is laid on the preheated substrate by using a powder extractor, and then the defocused electron beam is used to perform powder preheating on the aluminum alloy powder on the substrate.
In one embodiment, when the aluminum alloy powder on the substrate is subjected to powder preheating, the control voltage of the first defocusing amount of the defocused electron beam is-1 to-0.6V or 0.6 to 1V, and the first defocusing current is 3 to 10mA.
It can be understood that when the control voltage of the defocus amount of the electron beam is within the range of-0.5 v to 0.5v, the electron beam is in a focusing state; when the absolute value of the control voltage of the defocusing amount of the electron beam is larger than 0.5V, or when the control voltage of the defocusing amount of the electron beam is-1 to-0.6V or 0.6-1V, the electron beam is in a defocusing state. A schematic diagram of the defocusing state of the electron beam in the powder preheating stage and the partial preheating stage and the focusing state of the electron beam in the selective melting stage in the present application is shown in fig. 2.
The defocused electron beam is adopted to preheat the aluminum alloy powder on the substrate, so that the powder bed is stabilized, the thermal stress in the forming process of the target part is reduced, and the phenomenon of powder pushing caused by overlarge impact of the focused electron beam on the powder bed in the powder preheating process is avoided. And the powder is preheated by using small current of the first defocusing current, so that the temperature rising speed of the powder bed can be greatly reduced, and the powder bed is prevented from overheating and caking. The specific value of the control voltage of the first defocus amount of the defocused electron beam and the specific value of the first defocus current may be set according to the actual situation, which is not limited in this application.
Referring to fig. 2, in step S103, the local preheating region where the preheated aluminum alloy powder is located is locally preheated by using the defocused electron beam to achieve further sintering of the aluminum alloy powder in the part melting region. The area of the local preheating area is larger than that of the part melting area, the shape of the part melting area is the same as that of the local preheating area, and the center of the part melting area is coincident with that of the local preheating area. By the arrangement, the aluminum alloy powder in the part melting area can be further sintered. As shown in fig. 3, the part melting area and the partial preheating area have the same shape, and may be square, regular pentagon, circular, or the like, which is not limited in this application.
In one embodiment, the outer contour of the partial warm-up region is a predetermined distance from the outer contour of the part melt region. Further, the preset distance is (0, 10), the preset distance is mm., and the preset distance can be 2mm, 3mm, 5mm, 8mm or 10mm, and the specific value of the preset distance can be set according to practical situations, which is not limited in the application.
In one embodiment, when the local preheating area where the preheated aluminum alloy powder is located is locally preheated, the control voltage of the second defocusing amount of the defocused electron beam is-1 to-0.6V or 0.6 to 1V, and the second defocusing current is 16 to 20mA.
It can be understood that when the local preheating area where the preheated aluminum alloy powder is located is locally preheated, the control voltage of the second defocusing amount of the defocused electron beam used is-1 to-0.6V or 0.6-1V, and meanwhile, the local preheating is performed by the large current of the second defocusing current, so that the aluminum alloy powder in the part melting area is further sintered. It should be noted that, here, use the heavy current to carry out local preheating, can effectively strengthen the cohesion between the aluminum alloy powder, avoid selecting the electron beam that the district melts stage focus to the excessive impact of powder bed, cause "pushing away the emergence of powder" phenomenon to the internal quality of target part has been promoted. The specific value of the control voltage of the second defocus amount of the defocused electron beam and the specific value of the second defocus current may be set according to the actual situation, which is not limited in this application.
Referring to fig. 2, in step S104, the partially preheated aluminum alloy powder is selectively melt-formed using a focused electron beam, and then the substrate is lowered.
In step S105, the steps of laying powder, local preheating and selective melting and forming are repeated until all the layers are processed, and the target part is obtained.
The present application is further illustrated by example 1 below.
The aluminum alloy printed in the embodiment is an AlZnMgCu alloy, the aluminum alloy powder used is spherical alloy powder prepared by a plasma rotary electrode method, and the granularity interval of the aluminum alloy powder is 45-106 mu m. Before printing, enough aluminum alloy powder is placed in the powder bin of the equipment in advance, and then the forming chamber is vacuumized to ensure that the initial vacuum degree of the forming chamber reaches 2 multiplied by 10 -2 Pa, and simultaneously carrying out vacuumizing treatment on the gun chamber. After the forming chamber and the gun chamber are vacuumized, helium is filled in, and finally the first preset vacuum degree of the forming chamber reaches 1.5x10 -1 Pa, a first preset vacuum degree of the gun chamber reaches 4 multiplied by 10 -4 Pa。
When the control voltage of the defocus amount of the electron beam is within the range of-0.5 v to 0.5v, the electron beam is in a focusing state; when the absolute value of the control voltage of the defocusing amount of the electron beam is larger than 0.5V, or when the control voltage of the defocusing amount of the electron beam is-1 to-0.6V or 0.6-1V, the electron beam is in a defocusing state.
Therefore, before printing, the control voltage of the defocus amount in the preheating process, namely the control voltage of the first defocus amount in the powder preheating stage and the control voltage of the second defocus amount in the local preheating stage are set to be 0.8V, so that the electron beam is in a defocused state in both the powder preheating stage and the local preheating stage. The control voltage of the defocus amount of the electron beam in the selective melt forming process stage is adjusted to-0.3V so that the electron beam assumes a focused state in the selective melt forming stage. Wherein the larger the voltage absolute value of the defocus amount of the electron beam, the worse the focusing state. A schematic diagram of the defocusing state of the electron beam in the powder preheating stage and the partial preheating stage and the focusing state of the electron beam in the selective melting stage in the present application is shown in fig. 2.
Step one: the temperature of the substrate is raised. When the substrate in the forming chamber is preheated by using the electron beam, the substrate is preheated to a preset temperature of 370 ℃ through three stages. The first stage, preheating a substrate to an initial temperature by using an electron beam with 8mA focusing current, wherein the initial temperature is 300 ℃; the second stage, using electron beam with 5mA focusing current to keep temperature in a preset time period, wherein the preset time period is 10min; in the third stage, the substrate is raised from the initial temperature to a preset temperature of 370 ℃ by using an electron beam with a focusing current of 10mA. By preheating the substrate in stages, the phenomenon that the powder bed is overheated and sintered due to the fact that the preset temperature of the substrate is too high or the aluminum alloy powder is loose due to the fact that the preset temperature of the substrate is too low can be avoided, and the focused electron beam impact becomes easy to collapse.
Step two: laying powder and preheating. And laying aluminum alloy powder on the preheated substrate by using a powder extractor, and then preheating the aluminum alloy powder on the whole substrate for 7s by adopting an electron beam in a defocused state with a control voltage of 0.8V of a first defocusing amount and a first defocusing current of 8mA, so that the powder bed is slightly sintered. The aluminum alloy powder on the substrate is preheated by using the low current with the first defocusing current of 8mA, so that the effect of stabilizing the powder bed can be achieved, the heating speed of the powder bed can be reduced, and the overheat agglomeration of the powder bed is restrained.
Step three: and carrying out local preheating on a local preheating area where the preheated aluminum alloy powder is located, so that the aluminum alloy powder in the part melting area is further sintered. The partial preheating region was partially preheated for 5s using an electron beam in a defocused state with a control voltage of 0.8V for the first defocus amount and a second defocused current of 17mA, the area of the partial preheating region was larger than that of the part melting region, the shape of the partial preheating region was identical to that of the part melting region, the center of the partial preheating region was coincident with the center of the part melting region, and in addition, a preset distance d was provided between the outer contour of the partial preheating region and the outer contour of the part melting region, the preset distance d being 3mm, as shown in detail in fig. 3.
Step four: and (5) melting and forming the electron beam selected area. The aluminum alloy powder is selectively melted and formed by using a focused electron beam, and the scanning path is in a serpentine scanning strategy and is rotated by 90 degrees layer by layer. The substrate is lowered after each layer is melted.
Step five: and repeating the second step to the fourth step until all the layers are processed, and obtaining the target part. In this example, the scanning current at the time of melting the selected region was 6mA, and the scanning speed was 2.8m/s.
A comparison schematic diagram of the method and a conventional powder bed electron beam printing process is shown in FIG. 4, and the printing process of the conventional method is as follows: spreading powder, presintering after powder spreading, melting in selected areas, thermally compensating before powder spreading, and spreading powder. The presintered powder bed is generally presintered by using an electron beam in a focused state (the control voltage of the defocus amount of the electron beam in the focused state is 0.2V, and the focusing current is more than 12 mA). In the process, the powder bed is easy to overheat, and meanwhile, the electron beam focusing state is good, the impact force is strong, and the powder pushing phenomenon is easy to occur to aluminum alloy powder.
In the method, the powder bed is presintered by using the completely defocused electron beam (the control voltage of the first defocusing amount of the electron beam in a defocused state is 0.8V, and the first defocusing current is 8 mA), so that the temperature rising speed of the powder bed can be greatly reduced, and the powder pushing phenomenon in the preheating stage can be avoided. Subsequently, the application also introduces a local preheating process, and uses a larger second defocusing current (17 mA) to locally preheat a small part of areas containing the aluminum alloy powder, so that the powder can be further sintered, the binding force between the aluminum alloy powder is enhanced, and the powder pushing phenomenon in the melting process is prevented. In addition, the heat compensation process before powder paving is omitted, and the temperature rising speed of the powder bed can be further reduced. Therefore, the method can greatly reduce the temperature rising speed of the powder bed while ensuring the stability of the powder bed, and avoid the occurrence of the phenomenon of powder pushing in the preheating and melting stages, thereby solving the contradiction that the aluminum alloy powder is easy to agglomerate at high temperature and easy to push at low temperature and realizing the high-quality forming of the electron beam selective melting aluminum alloy.
Fig. 5 shows the state of the powder bed when the aluminum alloy is printed and discharged by adopting the conventional electron beam selective melting method, and it can be seen that the powder bed is seriously agglomerated when the method is not used, and part of the powder bed is scraped by the powder extractor due to deformation, so that a large amount of coarse massive powder is accumulated on the right side of the powder bed, and the powder utilization rate is poor. Fig. 6 is a metallographic structure diagram of an aluminum alloy sample printed by a conventional electron beam selective melting method, and it can be seen that the internal defect of the aluminum alloy sample is serious and the forming effect is poor.
Fig. 7 shows the state of the powder bed when the aluminum alloy is printed and discharged by the method, and the powder bed is smooth after the method is used, no caking phenomenon occurs, aluminum alloy powder is not accumulated on the right side of the powder bed, and the utilization rate of the aluminum alloy powder is greatly improved. Meanwhile, as shown in fig. 8, the aluminum alloy sample printed by the method has good internal quality, no holes or unfused defects are generated, and compact forming is realized.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature.
In the description of the present specification, reference to the description of the terms "one embodiment," "some embodiments," "examples," "particular examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, one skilled in the art can combine and combine the different embodiments or examples described in this specification.
Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the application following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the application pertains.
Claims (9)
1. The powder bed electron beam additive manufacturing method of the aluminum alloy is characterized by comprising the following steps of:
preheating a substrate in a forming chamber to a preset temperature;
paving aluminum alloy powder on the preheated substrate, and carrying out powder preheating on the aluminum alloy powder on the substrate by utilizing defocused electron beams;
carrying out local preheating on a local preheating area where the preheated aluminum alloy powder is located by utilizing the defocused electron beam so as to further sinter the aluminum alloy powder in a part melting area; the area of the local preheating area is larger than that of the part melting area, the shape of the local preheating area is the same as that of the part melting area, and the center of the local preheating area is coincident with the center of the part melting area;
carrying out selective melting forming on the aluminum alloy powder after local preheating by utilizing the focused electron beam;
repeating the steps of laying powder, local preheating and selective melting forming until the target part is obtained.
2. The powder bed electron beam additive manufacturing method of an aluminum alloy according to claim 1, wherein the preset temperature is 360-400 ℃.
3. The powder bed electron beam additive manufacturing method of an aluminum alloy according to claim 1, wherein when powder preheating is performed on the aluminum alloy powder on the substrate, a control voltage of a first defocusing amount of the defocused electron beam is-1 to-0.6V or 0.6 to 1V, and a first defocusing current is 3 to 10ma.
4. The powder bed electron beam additive manufacturing method of an aluminum alloy according to claim 1, wherein a preset distance is provided between an outer contour of the partial preheating region and an outer contour of the part melting region.
5. The powder bed electron beam additive manufacturing method of an aluminum alloy according to claim 4, wherein the preset distance ranges from (0, 10], and the preset distance is in mm.
6. The powder bed electron beam additive manufacturing method of an aluminum alloy according to claim 1, wherein when a local preheating area where the preheated aluminum alloy powder is located is locally preheated, a control voltage of a second defocusing amount of the defocused electron beam is-1 to-0.6V or 0.6 to 1V, and a second defocusing current is 16 to 20ma.
7. The powder bed electron beam additive manufacturing method of an aluminum alloy according to claim 1, wherein the preheating the substrate in the forming chamber to a preset temperature comprises:
and vacuumizing the forming chamber and the gun chamber respectively, and filling inert gas so that the vacuum degree of the forming chamber reaches a first preset vacuum degree, and the vacuum degree of the gun chamber reaches a second preset vacuum degree.
8. The powder bed electron beam additive manufacturing method of an aluminum alloy according to claim 7, wherein the first preset vacuum degree is 1 x 10 -1 ~2×10 -1 Pa, the firstTwo preset vacuum degrees are 4 multiplied by 10 -4 ~9×10 -4 Pa。
9. The powder bed electron beam additive manufacturing method of an aluminum alloy according to claim 7, wherein the inert gas is helium or argon.
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