CN117483799B - A powder bed electron beam additive manufacturing method of aluminum alloy - Google Patents

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

A powder bed electron beam additive manufacturing method of aluminum alloy

Technical field

Embodiments of the present application relate to the field of additive manufacturing technology, and in particular, to a powder bed electron beam additive manufacturing method of aluminum alloy.

Background technique

Additive manufacturing technology is also known as 3D printing technology. Compared with traditional processes, additive manufacturing technology has the characteristics of short production cycle and low cost. Aluminum alloy has the advantages of low density, high specific strength, good plasticity and strong corrosion resistance, and has broad application prospects in aerospace, transportation and other fields. With the continuous improvement of product technology and the continuous shortening of development cycle, higher requirements are put forward for the manufacturing technology of complex precision aluminum alloy components. Not only high manufacturing efficiency is required, but also rapid response capabilities that change with equipment design changes, as well as flexible adaptability in the production and manufacturing of complex precision aluminum alloy components. Traditional manufacturing technology is obviously difficult to meet the above requirements. Therefore, the development of additive manufacturing technology for aluminum alloys has become one of the research hotspots.

Among related technologies, among the current mainstream additive manufacturing technologies, powder-laying additive manufacturing technology has the advantages of high dimensional accuracy, good surface quality and excellent mechanical properties, and can be formed in a vacuum or protective gas environment. It is a small Ideal additive manufacturing technology for aluminum alloy components. According to different heat sources, powder-laying additive manufacturing technology can be divided into two categories: Selective laser melting (SLM) technology and Electron Beam Selective Melting (SEBM) technology. At present, the most widely used technology is selective laser melting. However, due to the large refractive index of some aluminum alloys to laser, it affects the wide application of laser additive manufacturing on aluminum alloys. The use of laser as a heat source to study the additive manufacturing technology of aluminum alloys at home and abroad is limited to cast aluminum alloy series or aluminum alloys with better weldability, such as AlSi10Mg cast aluminum alloy and 7075 aluminum alloy.

The electron beam selective melting technology has no such restrictions. Due to the high energy density of the electron beam, it can easily melt almost all metal materials including refractory metals such as tungsten, molybdenum, and tantalum. However, electron beam selective melting technology also has technical problems in the process of forming aluminum alloys. For example, elements such as Mg and Zn are severely vaporized and volatilized. During the preheating process, the powder bed is prone to overheating and peeling. The powder is prone to agglomeration and agglomeration. Powder often appears during the melting process. The "powder pushing" phenomenon caused by being pushed forward by electron beams, etc. Therefore, this results in the use of electron beams for additive manufacturing of aluminum alloys, which is mainly wire feeding rather than powder spreading. However, the powder-laying electron beam additive manufacturing technology has the advantages of high dimensional accuracy, fast forming speed, and good mechanical properties. The powder-laying electron beam additive manufacturing technology can control the dimensional accuracy of parts within ±0.3mm. Therefore, overcoming the technical problems of electron beam selective melting technology in the process of forming aluminum alloys and achieving dense forming of aluminum alloys is very important for promoting the development of the additive manufacturing industry of small aluminum alloy components.

When overcoming the technical difficulties of electron beam selective melting technology in the process of forming aluminum alloys, due to the low melting point of aluminum alloy materials (≤660°C), its powder is easily agglomerated at 500~600°C. In the powder bed electron beam additive manufacturing process, due to the scanning preheating process after powder spreading, the temperature of the powder bed will rise rapidly. During this process, the aluminum alloy powder is prone to peeling, agglomeration and being scraped away by the scraper. phenomenon, resulting in poor forming quality or even printing failure. Secondly, due to the light weight of aluminum alloy powder, if the sintering degree between the powders is insufficient, the "powder pushing" phenomenon in which the powder moves with the electron beam is prone to occur under the bombardment of the electron beam. This process will also lead to a decrease in the forming quality.

Therefore, it is necessary to improve one or more problems existing in the above related technical solutions.

It should be noted that this section is intended to provide a background or context for the technical solutions of the present application stated in the claims. The description herein is not admitted to be prior art by virtue of being included in this section.

Contents of the invention

The purpose of the embodiments of the present application is to provide a powder bed electron beam additive manufacturing method of aluminum alloy, thereby overcoming one or more problems caused by limitations and defects of related technologies, at least to a certain extent.

According to an embodiment of the present application, a powder bed electron beam additive manufacturing method of aluminum alloy is provided, which method includes:

Preheat the substrate in the forming chamber to a preset temperature;

Lay aluminum alloy powder on the preheated substrate, and use a defocused electron beam to preheat the aluminum alloy powder on the substrate;

The defocused electron beam is used to locally preheat the local preheating area where the preheated aluminum alloy powder is located, so that the aluminum alloy powder in the melting area of the part is further sintered; wherein, the local preheating The area of the hot area is larger than the area of the melted area of the part, the shape of the local preheating area is the same as the shape of the melted area of the part, and the center of the local preheating area coincides with the center of the melted area of the part;

Using the focused electron beam to perform selective melting and shaping of the locally preheated aluminum alloy powder;

Repeat the above steps of powder spreading, local preheating and selective melting and forming until the target part is obtained.

In an embodiment of the present application, the preset temperature is 360~400°C.

In an embodiment of the present application, when powder preheating is performed on the aluminum alloy powder on the substrate, the control voltage of the first defocus amount of the defocused electron beam is -1~-0.6V or 0.6 ~1V, the first defocus current is 3~10mA.

In an embodiment of the present application, there is a preset distance between the outer contour of the local preheating area and the outer contour of the part melting area.

In an embodiment of the present application, the range of the preset distance is (0,10], and the unit of the preset distance is 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 defocus amount of the defocused electron beam is -1~ -0.6V or 0.6~1V, the second defocus current is 16~20mA.

In one embodiment of the present application, preheating the substrate in the forming chamber to a preset temperature includes:

The forming chamber and the gun chamber are evacuated and filled with inert gas respectively, so that the vacuum degree of the forming chamber reaches the first preset vacuum degree, and the vacuum degree of the gun chamber reaches the second preset vacuum degree.

In an embodiment of the present application, the first preset vacuum degree is 1×10 ^-1 to 2×10 ^-1 Pa, and the second preset vacuum degree is 4×10 ^-4 to 9×10 ^-4 Pa.

In an embodiment of the present application, the inert gas is helium or argon.

The technical solutions provided by the embodiments of this application may include the following beneficial effects:

In the embodiments of the present application, through the above method, the defocused electron beam is used to preheat the aluminum alloy powder on the substrate, which not only stabilizes the powder bed, but also reduces the heating rate of the powder bed, thereby inhibiting the powder bed. The bed is overheated and caked. The defocused electron beam is used to locally preheat the local preheating area where the preheated aluminum alloy powder is located, which enhances the bonding force between aluminum alloy powders and avoids excessive impact of the electron beam on the powder bed during the selective melting stage. A "push-powder" phenomenon occurs, thereby improving the internal quality of the target part.

Description of drawings

The drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present application, and together with the specification are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

Figure 1 shows a step flow chart of the powder bed electron beam additive manufacturing method of aluminum alloy in an exemplary embodiment of the present application;

Figure 2 shows a schematic diagram of the state of the electron beam in the powder preheating, local preheating and selective melting stages in the exemplary embodiment of the present application;

Figure 3 shows a schematic diagram of three shapes of the local preheating area and the part melting area in the exemplary embodiment of the present application;

Figure 4 shows a schematic diagram comparing the method of the present application and the conventional powder bed electron beam printing process in an exemplary embodiment of the present application;

Figure 5 shows a schematic diagram of the state of the powder bed when the aluminum alloy is printed using a conventional electron beam selective melting method in an exemplary embodiment of the present application;

FIG6 shows a metallographic structure diagram of an aluminum alloy sample printed by a conventional electron beam selective melting method in an exemplary embodiment of the present application;

FIG7 shows the state of the powder bed when the aluminum alloy is printed out of the furnace using the method of the present application in an exemplary embodiment of the present application;

Figure 8 shows the metallographic structure diagram of the aluminum alloy sample printed using the method of the present application in the exemplary embodiment of the present application.

Implementation

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in various 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 concepts 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.

In addition, the accompanying drawings are only schematic illustrations of embodiments of the present application and are not necessarily drawn to scale.

Since aluminum alloy materials have a low melting point (≤660°C), their powders are very easy to agglomerate at 500-600°C. In the powder bed electron beam additive manufacturing process, due to the scanning and preheating process after powder laying, the temperature of the powder bed will rise rapidly. In this process, the aluminum alloy powder is prone to peeling, agglomeration and being scraped away by the scraper, resulting in poor forming quality or even printing failure. Secondly, since aluminum alloy powder is light in weight, if the sintering degree between aluminum alloy powders is insufficient, the aluminum alloy powder is prone to "powder pushing" phenomenon under the bombardment of the electron beam, and this process will also lead to a decrease in forming quality.

In order to solve the above technical problems, electron beam selective melting and dense forming of aluminum alloys is achieved. This example embodiment provides a powder bed electron beam additive manufacturing method of aluminum alloy. Referring to what is shown in Figure 1, the method may include: steps S101 to S105.

Step S101: preheating the substrate in the forming chamber to a preset temperature.

Step S102: laying aluminum alloy powder on the preheated substrate, and preheating the aluminum alloy powder on the substrate using a defocused electron beam.

Step S103: Use the defocused electron beam to locally preheat the local preheating area where the preheated aluminum alloy powder is located, so that the aluminum alloy powder in the melting area of the part is further sintered; wherein the area of the local preheating area is larger than The area of the melted area of the part, the shape of the local preheating area is the same as the shape of the melted area of the part, and the center of the local preheating area coincides with the center of the melted area of the part.

Step S104: Use a focused electron beam to perform selective melting and forming on the locally preheated aluminum alloy powder.

Step S105: Repeat the above steps of powder spreading, local preheating and selective melting and forming until the target part is obtained.

Through the above method, the defocused electron beam is used to preheat the aluminum alloy powder on the substrate, which not only stabilizes the powder bed, but also reduces the heating rate of the powder bed, thereby inhibiting overheating and agglomeration of the powder bed. The defocused electron beam is used to locally preheat the local preheating area where the preheated aluminum alloy powder is located, which enhances the bonding force between aluminum alloy powders and avoids excessive impact of the electron beam on the powder bed during the selective melting stage. A "push-powder" phenomenon occurs, thereby improving the internal quality of the target part.

Hereinafter, various parts of the above-described powder bed electron beam additive manufacturing method of aluminum alloy in this exemplary embodiment will be described in more detail with reference to FIGS. 2 to 3 .

In step S101, the substrate in the forming chamber is preheated to raise the temperature of the substrate to a preset temperature, and the preset temperature is 360~400°C. The preset temperature can be 360°C, 380°C, 390°C or 400°C. The specific value of the preset temperature can be set according to the actual situation. This application does not limit this.

When preheating and raising the temperature of the substrate in the forming chamber, the preheating and temperature raising can be performed in stages. For example, the substrate can be preheated in three stages. In the first stage, the focused electron beam is used to preheat the substrate to the initial temperature; in the second stage, the heat preservation is performed for a preset period of time based on the initial temperature; in the third stage, the substrate is preheated again to ensure that the substrate is The initial temperature is raised to the preset temperature. By preheating the substrate in stages, it is possible to avoid overheated sintering of the powder bed due to the preset temperature of the substrate being too high, or loosening of the aluminum alloy powder caused by the preset temperature of the substrate being too low. The beam becomes prone to collapse upon impact.

Before preheating the substrate in the forming chamber, the forming chamber and the gun chamber need to be evacuated, and then filled with inert gas, so that the vacuum degree of the forming chamber reaches the first preset vacuum degree, and the vacuum degree of the gun chamber Reach the second preset vacuum degree to ensure the vacuum environment for aluminum alloy forming. And in the process of making the vacuum degree of the forming chamber reach the first preset vacuum degree, the forming chamber needs to be preliminarily evacuated first, so that the vacuum degree of the forming chamber reaches the initial vacuum degree. The initial vacuum degree of the forming chamber is 9× 10 ^-3 ~2×10 ^-2 Pa; then fill in inert gas to make the vacuum degree of the forming chamber reach the first preset vacuum degree. Among them, the inert gas is preferably helium or argon, the first preset vacuum degree is 1×10 ^-1 ~ 2×10 ^-1 Pa, and the second preset vacuum degree is 4×10 ^-4 ~ 9×10 ^-4 Pa. The specific values of the first preset vacuum degree and the second preset vacuum degree can be set according to the actual situation, and this application does not limit this.

In step S102, after the substrate is preheated to a preset temperature, aluminum alloy powder is laid on the preheated substrate using a powder taker, and then a defocused electron beam is used to preheat the aluminum alloy powder on the substrate.

In one embodiment, when the aluminum alloy powder on the substrate is powder preheated, the control voltage of the first defocus amount of the defocused electron beam is -1~-0.6V or 0.6~1V, and the first defocus current is 3~10mA.

It can be understood that when the control voltage of the defocus amount of the electron beam is in the range of -0.5V~0.5V, the electron beam is in a focused state; when the absolute value of the control voltage of the defocus amount of the electron beam is greater than 0.5V, or When the control voltage of the defocus amount of the electron beam is -1~-0.6V or 0.6~1V, the electron beam is in a defocused state. The schematic diagram of the defocused state of the electron beam in the powder preheating stage and the local preheating stage in this application, and the focused state of the electron beam in the selective melting stage is shown in Figure 2.

The use of a defocused electron beam to preheat the aluminum alloy powder on the substrate not only stabilizes the powder bed and reduces the thermal stress during the forming process of the target part, but also avoids the focused electron beam from having too much impact on the powder bed during the powder preheating process, causing the "powder pushing" phenomenon. And using a small current of the first defocusing current to preheat the powder can significantly reduce the heating rate of the powder bed, thereby preventing the powder bed from overheating and agglomerating. Among them, the specific value of the control voltage of the first defocusing amount of the defocused electron beam and the specific value of the first defocusing current can be set according to actual conditions, and this application does not impose any restrictions on this.

Referring to Figure 2, in step S103, a defocused electron beam is used to locally preheat the local preheating area where the preheated aluminum alloy powder is located, so as to achieve further sintering of the aluminum alloy powder in the melting area of the part. The area of the local preheating zone is larger than the area within the melting zone of the part, the shape of the melting zone of the part is the same as the shape of the local preheating zone, and the center of the melting zone of the part coincides with the center of the local preheating zone. With this arrangement, the aluminum alloy powder in the melted area of the part can be further sintered. As shown in Figure 3, the shapes of the melting area and the local preheating area of the part are the same, which can be square, regular pentagon or circle, etc. This application does not limit this.

In one embodiment, there is a preset distance between the outer contour of the local preheating zone and the outer contour of the part melting zone. Further, the range of the preset distance is (0,10], and its unit is mm. The preset distance can be 2mm, 3mm, 5mm, 8mm or 10mm, etc. The specific value of the preset distance can be set according to the actual situation. determined, this application does not limit this.

In one embodiment, when locally preheating the local preheating area where the preheated aluminum alloy powder is located, the control voltage of the second defocus amount of the defocused electron beam is -1~-0.6V or 0.6~ 1V, the second defocus current is 16~20mA.

It can be understood that when locally preheating the local preheating area where the preheated aluminum alloy powder is located, the control voltage of the second defocus amount of the defocused electron beam used is -1~-0.6V. Or 0.6~1V, and at the same time, a large current of the second defocusing current is selected for local preheating to achieve further sintering of the aluminum alloy powder in the melting area of the part. It should be noted that the use of large current for local preheating can effectively enhance the bonding force between aluminum alloy powders and avoid the excessive impact of the focused electron beam on the powder bed during the selective melting stage, causing the "powder pushing" phenomenon. , thereby improving the internal quality of the target part. The specific value of the control voltage for the second defocus amount of the defocused electron beam and the specific value of the second defocus current can be set according to the actual situation, and this application does not limit this.

Referring to Figure 2, in step S104, a focused electron beam is used to perform selective melting and forming on the locally preheated aluminum alloy powder, and then the substrate is lowered.

In step S105, the above steps of powder spreading, local preheating, and selective melting and forming are repeated until all layers are processed, and the target part is obtained.

The present application will be further described below through the following Example 1.

The aluminum alloy printed in this embodiment is an AlZnMgCu alloy, and the aluminum alloy powder used is spherical alloy powder prepared by the plasma rotating electrode method. The particle size range of the aluminum alloy powder is 45 to 106 μm. Before printing starts, place a sufficient amount of aluminum alloy powder in the powder bin of the equipment, and then start vacuuming the forming chamber so that the initial vacuum degree of the forming chamber reaches 2×10 ^-2 Pa. At the same time, the gun chamber Carry out vacuum treatment. After vacuuming the forming chamber and the gun chamber, start filling helium gas. Finally, the first preset vacuum degree of the forming chamber reaches 1.5×10 ^-1 Pa, and the first preset vacuum degree of the gun chamber reaches 4×10 ^-4 Pa.

It should be noted that when the control voltage of the defocus amount of the electron beam is in the range of -0.5V~0.5V, the electron beam is in a focused state; when the absolute value of the control voltage of the defocus amount of the electron beam is greater than 0.5V, or When the control voltage of the defocus amount of the electron beam is -1~-0.6V or 0.6~1V, the electron beam is in a defocused state.

Therefore, before printing, adjust the control voltage of the defocus amount in the preheating process, that is, set the control voltage of the first defocus amount in the powder preheating stage and the second defocus amount in the local preheating stage. is 0.8V, which makes the electron beam appear defocused 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 melting and forming process stage is adjusted to -0.3V, so that the electron beam becomes focused in the selective melting and forming stage. Among them, the greater the absolute value of the voltage of the defocus amount of the electron beam, the worse the focus state. The schematic diagram of the defocused state of the electron beam in the powder preheating stage and the local preheating stage in this application, and the focused state of the electron beam in the selective melting stage is shown in Figure 2.

Step 1: Heat up the substrate. When the electron beam is used to preheat the substrate in the forming chamber, the substrate is preheated to a preset temperature through three stages, and the preset temperature is 370°C. In the first stage, an electron beam with a focusing current of 8mA is used to preheat the substrate to the initial temperature, which is 300°C. In the second stage, an electron beam with a focusing current of 5mA is used to maintain the temperature within a preset time period. The preset time period is 10min; in the third stage, an electron beam with a focusing current of 10mA is used to raise the substrate from the initial temperature to the preset temperature, which is 370°C. By preheating the substrate in stages, it is possible to avoid overheating and sintering of the powder bed due to the preset temperature of the substrate being too high, or loosening of the aluminum alloy powder due to the impact of the focused electron beam. It is easy to collapse.

Step 2: Spread powder and preheat. Use a powder taker to lay aluminum alloy powder on the preheated substrate, and then use a defocused electron beam with a control voltage of the first defocus amount of 0.8V and a first defocus current of 8mA to target the entire substrate. The aluminum alloy powder is preheated for 7 seconds to slightly sinter the powder bed. Using a low current with a first defocusing current of 8mA to preheat the aluminum alloy powder on the substrate can stabilize the powder bed, reduce the temperature rise rate of the powder bed, and inhibit overheating and agglomeration of the powder bed.

Step 3: Locally preheat the local preheating area where the preheated aluminum alloy powder is located to further sinter the aluminum alloy powder in the melting area of the part. Use a defocused electron beam with a first defocusing control voltage of 0.8V and a second defocusing current of 17mA to locally preheat the local preheating area for 5s. The area of the local preheating area is larger than the area of the part melting area, and the shape of the local preheating area is the same as the shape of the part melting area. The center of the local preheating area coincides with the center of the part melting area. In addition, there is a preset distance between the outer contour of the local preheating area and the outer contour of the part melting area. The preset distance d is 3mm, as shown in Figure 3 for details.

Step 4: Electron beam selective melting and forming. A focused electron beam is used to selectively melt and shape aluminum alloy powder. The scanning path is a serpentine scanning strategy, rotating 90° layer by layer. The substrate is lowered after each layer is melted.

Step 5: Repeat steps 2 to 4 until all layers are processed and the target part is obtained. In this embodiment, the scanning current when melting the selected area is 6mA, and the scanning speed is 2.8m/s.

A schematic diagram comparing the application method with the conventional powder bed electron beam printing process is shown in Figure 4. The printing process of the conventional method is: powder spreading → pre-sintering after powder spreading → selective melting → thermal compensation before powder spreading → powder spreading. Among them, pre-sintering after powder spreading generally uses a focused electron beam (the control voltage of the defocus amount of the focused electron beam is 0.2V, and the focusing current is greater than 12mA) to pre-sinter the powder bed. During this process, this process can easily cause the powder bed to overheat. At the same time, due to the good focusing state of the electron beam and strong impact force, it is also easy to cause "powder pushing" phenomenon for aluminum alloy powder.

In the method of this application, a completely defocused electron beam is used (the control voltage of the first defocusing amount of the defocused electron beam is 0.8V, and the first defocusing current is 8mA) to pre-sinter the powder bed, which can significantly reduce the amount of powder. The heating speed of the bed can also avoid the "push powder" phenomenon during the preheating stage. Subsequently, this application also introduced a local preheating process, using a larger second defocusing current (17mA) to locally preheat a small area including the aluminum alloy powder, which can further sinter the powder and enhance the strength of the aluminum alloy powder. The bonding force between them prevents the "push powder" phenomenon from occurring during the melting process. In addition, this application eliminates the thermal compensation process before powder spreading, which can further reduce the temperature rise rate of the powder bed. Therefore, this application can greatly reduce the heating rate of the powder bed while ensuring the stability of the powder bed, and avoid the occurrence of "powder pushing" phenomenon in the preheating and melting stages, thereby solving the problem that aluminum alloy powder is easy to agglomerate at high temperatures and "push" at low temperatures. The contradiction of "push powder" realizes high-quality forming of electron beam selective melting of aluminum alloy.

Figure 5 shows the state of the powder bed when the aluminum alloy is printed using the conventional electron beam selective melting method. It can be seen that the powder bed is seriously agglomerated when the method of this application is not used, and part of the powder bed is scraped away by the powder taker due to deformation. A large amount of coarse bulk powder accumulates on the right side of the powder bed, resulting in poor powder utilization. Figure 6 shows the metallographic structure of an aluminum alloy sample printed using the conventional electron beam selective melting method. It can be seen that the aluminum alloy sample has serious internal defects and the forming effect is poor.

Figure 7 shows the state of the powder bed when the aluminum alloy is printed using the method of this application. It can be seen that after using the method of this application, the powder bed is smooth and no agglomeration occurs. There is no accumulation of aluminum alloy powder on the right side of the powder bed. The utilization rate has been greatly improved. At the same time, as shown in Figure 8, the internal quality of the aluminum alloy sample printed using the method of this application is good, there are no more holes and unfused defects, and dense forming is achieved.

In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary technical means in the art that are not disclosed in the present application.

Claims (7)

1. A powder bed electron beam additive manufacturing method for aluminum alloy, characterized in that the method comprises: Preheat the substrate in the forming chamber to a preset temperature; Lay aluminum alloy powder on the preheated substrate, and use a defocused electron beam to preheat the aluminum alloy powder on the substrate; When powder preheating is performed on the aluminum alloy powder on the substrate, the control voltage of the first defocus amount of the defocused electron beam is -1~-0.6V or 0.6~1V, and the first defocus current is 3~8mA; The defocused electron beam is used to locally preheat the local preheating area where the preheated aluminum alloy powder is located, so that the aluminum alloy powder in the melting area of the part is further sintered; wherein, the local preheating The area of the hot area is larger than the area of the melted area of the part, the shape of the local preheating area is the same as the shape of the melted area of the part, and the center of the local preheating area coincides with the center of the melted area of the part; When locally preheating the local preheating area where the preheated aluminum alloy powder is located, the control voltage of the second defocus amount of the defocused electron beam is -1~-0.6V or 0.6~1V, The second defocus current is 16~20mA; Using the focused electron beam to perform selective melting and shaping of the locally preheated aluminum alloy powder; Repeat the steps of powder spreading, powder preheating, local preheating and selective melting until the target part is obtained. 2. The powder bed electron beam additive manufacturing method for aluminum alloy according to claim 1, characterized in that the preset temperature is 360~400℃. 3. The powder bed electron beam additive manufacturing method of aluminum alloy according to claim 1, characterized in that there is a preset distance between the outer contour of the local preheating area and the outer contour of the part melting area. 4. The powder bed electron beam additive manufacturing method of aluminum alloy according to claim 3, characterized in that the range of the preset distance is (0,10], and the unit of the preset distance is mm. 5. The powder bed electron beam additive manufacturing method of aluminum alloy according to claim 1, characterized in that the step of preheating the substrate in the forming chamber to a preset temperature comprises: The forming chamber and the gun chamber are evacuated and filled with inert gas respectively, 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. 6. The powder bed electron beam additive manufacturing method of aluminum alloy according to claim 5, characterized in that the first preset vacuum degree is 1×10 ^-1 ~ 2×10 ^{-1 Pa, and the first preset vacuum degree is 1×10 -1 ~ 2×10 -1} Pa. 2. The preset vacuum degree is 4×10 ^-4 ~9×10 ^-4 Pa. 7. The powder bed electron beam additive manufacturing method of aluminum alloy according to claim 5, wherein the inert gas is helium or argon.