Laser energy balancing method for reducing stress and cracking in additively manufactured high-strength aluminum alloy specimens

Abstract

The application discloses a method for reducing stress cracking of a laser additive manufacturing high-strength aluminum alloy test piece by means of laser energy balance, and aims at the problem that a complex high-strength aluminum alloy component manufactured by means of laser additive manufacturing is prone to deformation cracking due to stress concentration, and faces a trace rare earth element modified aluminum alloy system, reduces laser energy, especially laser power and laser scanning speed in cooperation, ensures sufficient melting, wetting and spreading of powder, reduces stress of an original deposited test piece by means of reducing a molten pool temperature and a temperature gradient, and reduces the number of precipitated primary precipitated phases caused by in-situ heat treatment to inhibit stress, and simultaneously, a medium-temperature short-time post-treatment is used to reduce stress, so that stress cracking of a laser additive manufacturing high-strength aluminum alloy test piece is effectively inhibited. The application solves the problem of stress concentration cracking of a complex high-strength aluminum alloy component manufactured by means of laser additive manufacturing, and widens the application range of the laser additive manufacturing high-strength aluminum component.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing, specifically relating to a process method for suppressing stress deformation cracking in high-strength aluminum alloys formed by laser additive manufacturing. Background Technology

[0002] Additive manufacturing (AM) technology, especially laser additive manufacturing (LAM), has been widely used in the aerospace industry due to its ability to directly manufacture complex parts from digital models in a short time. This technology can effectively shorten product development cycles, reduce material waste, and allow the design and manufacture of complex structures that are difficult to achieve using traditional methods. Especially for high-strength aluminum alloys, additive manufacturing technology provides a unique way to produce lightweight structural components, which is particularly important for weight-sensitive complex components in the aerospace field. Currently, high-strength aluminum alloy systems modified with trace elements such as Sc and Zr using laser additive manufacturing have become a research hotspot worldwide. Firstly, additive manufacturing technology is expected to overcome the bottlenecks in lightweighting and integration technologies of traditional manufacturing techniques, enabling lightweight design and integrated manufacturing of complex components. Secondly, the trace element-modified high-strength aluminum alloy systems developed for additive manufacturing overcome the problem of insufficient strength (<400MPa) caused by the single strengthening mechanism of conventional Al-Si alloys, meeting high load-bearing requirements while further promoting lightweight design. Therefore, high-strength aluminum alloys formed by laser additive manufacturing have significant application prospects in the fields of aerospace, automotive, and other complex components.

[0003] However, a series of technical challenges remain when using additive manufacturing technology to form complex high-strength aluminum alloy parts. Due to the high thermal conductivity and large coefficient of thermal expansion of aluminum alloys, significant thermal stress is easily generated during rapid laser melting and solidification. The uneven distribution of these thermal stresses within the material often leads to stress cracking and deformation of the finished product during manufacturing or use, especially when manufacturing complex or large-scale structures. Stress concentration not only affects the mechanical properties and precision of the parts but can also lead to low production efficiency and material waste. Currently, some post-processing methods (such as heat treatment and stress relief) have been attempted to address these problems, but in actual production, stress deformation often causes cracking and failure immediately after printing, making repair difficult using post-processing or straightening techniques. Therefore, developing a new method to effectively control stress generation and distribution during additive manufacturing is of significant practical importance for improving the manufacturing quality and reliability of high-strength aluminum alloy parts.

[0004] In summary, laser additive manufacturing technology for forming high-strength aluminum alloys has significant advantages in forming complex aerospace structural components, but challenges remain, such as difficulty in controlling stress deformation and cracking failure. Currently, there is no effective process method to achieve stress deformation control in additive manufacturing of complex high-strength aluminum alloy components. Summary of the Invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is that the stress deformation and cracking failure of high-strength aluminum alloys formed by laser additive manufacturing are difficult to control. The invention proposes a method of reducing stress cracking of high-strength aluminum alloy specimens formed by additive manufacturing by laser energy balance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for reducing stress cracking in additively manufactured high-strength aluminum alloy specimens using laser energy balancing includes the following steps:

[0008] S1. Optimization of conventional laser forming process parameters:

[0009] For rare earth element modified Al-Mg / Mn alloy systems, the range of conventional laser forming processes is determined;

[0010] Forming experiments were conducted on the test parts within the defined conventional laser forming process range to obtain optimized laser forming process parameters, and the corresponding laser energy density η was calculated based on the optimized laser forming process parameters.

[0011] Optimized laser forming process parameters include optimized laser power, optimized scanning speed, optimized layer thickness, and optimized scanning spacing.

[0012] S2. Adjusting laser forming process parameters using the laser energy balance method:

[0013] The optimized laser forming process parameters obtained in step S1 are adjusted using the laser energy balance method. Under the premise of ensuring that the difference in laser energy density before and after adjustment is not significant, the optimized laser power is first reduced to the target range, and then the other parameters included in the optimized laser forming process parameters are adjusted.

[0014] S3. Integrated molding of complex components:

[0015] Based on the adjusted laser forming process parameters obtained in step S2, complex component additive manufacturing integrated forming is carried out to obtain complex component formed parts.

[0016] S4, Medium-temperature short-time heat treatment:

[0017] The complex component formed in step S3 is subjected to medium-temperature short-time heat treatment to further remove internal stress, complete the stress relief process of the complex component formed as a whole, and obtain the heat-treated complex component.

[0018] Preferably, in step S1, the rare earth element modified Al-Mg / Mn alloy system is any one of rare earth element modified Al-Mg alloy, rare earth element modified Al-Mn alloy, or rare earth element modified Al-Mn-Mg alloy.

[0019] Preferably, the rare earth element is any one or a combination of two or more of Sc, Zr, Er, and Ti.

[0020] Preferably, in step S1, the rare earth element modified Al-Mg / Mn alloy system is a rare earth element modified Al-Mn-Mg alloy, comprising the following components: Mg 7-9wt.%, Si 0.4-1.2wt%, Mn 0.3-0.8wt.%, Sc 0.5-0.7wt.%, Zr 0.2-0.5wt.%, with the balance being Al; in the conventional laser forming process range, the laser power is 350-450W, the scanning speed is 800mm / s-1600mm / s, the layer thickness is 30μm, and the scanning spacing is 120μm.

[0021] Preferably, in step S1, the laser energy density η is calculated according to the following formula:

[0022] η = P / (v*h*t);

[0023] In step S2, the adjusted laser forming process parameters satisfy:

[0024] δ1≤η' / η≤δ2 and P01≤P'≤P02 <P;

[0025] In the formula: η' represents the laser energy density of the adjusted laser forming process parameters; η represents the laser energy density corresponding to the optimized laser forming process parameters in step S1; δ1 represents the preset minimum allowable energy density; δ2 represents the preset maximum allowable energy density; P' represents the adjusted laser power; P01 represents the preset minimum laser power; P02 represents the preset maximum laser power; P represents the optimized laser power in step S1.

[0026] In step S2, the preset minimum allowable energy density δ1 is 0.85, the preset maximum allowable energy density δ2 is 1.0; the preset minimum laser power P01 is 200W; the preset maximum laser power P02 is 250W; and the optimized laser power P is greater than 350W.

[0027] Preferably, in step S4, the aging temperature of the medium-temperature short-time heat treatment is controlled at 280-300℃, and the time is 2-4h.

[0028] Preferably, in step S1, the optimized laser forming process parameters include an optimized laser power of 440W and an optimized laser scanning speed of 1350mm / s; the adjusted laser forming process parameters have a laser energy density η' = 90.19, an adjusted laser power P' = 230W, an adjusted laser scanning speed of 850mm / s, a layer thickness of 30μm, and a scanning spacing of 100μm.

[0029] Preferably, in step S4, the heat treatment heating rate is 5K / min, the heat treatment temperature is 300℃, and the heat treatment time is 2h.

[0030] Beneficial effects:

[0031] This invention focuses on controlling stress cracking in additively manufactured high-strength aluminum alloys. Under conventional optimized process range, an isodense process control strategy is introduced to ensure that the powder is fully melted, wetted and spread. At the same time, the internal stress of the original deposited specimen is reduced by lowering the molten pool temperature and temperature gradient to reduce the participating stress and suppress the amount of primary precipitates induced by in-situ heat treatment.

[0032] From a physical mechanism perspective, the internal stress and cracking of high-strength aluminum alloy specimens formed by laser additive manufacturing mainly originate from two aspects. First, laser additive manufacturing has the characteristic of localized rapid melting and solidification. High temperature gradients and solidification rates cause the atomic crystal arrangement to deviate from equilibrium, inducing the initiation of internal stress—an inherent characteristic of additive manufacturing. Second, high-strength aluminum alloys modified by trace elements all employ precipitation strengthening mechanisms. During the forming process, high energy input (generally indicating high laser power) easily promotes the precipitation of primary precipitates such as Al3(Sc, Zr). Simultaneously, high energy input also leads to increased overall heat accumulation in the specimen during forming. The layering effect of additive manufacturing itself and the in-situ heat treatment effect further promote the coarsening of precipitates. These precipitates, formed during solidification and subsequent layering, are mainly distributed at grain boundaries. On the one hand, they weaken grain boundary strength, creating localized stress concentration; on the other hand, the precipitates also hinder dislocation movement, reducing the plasticity and toughness of the specimen. Therefore, under the internal stress caused by the inherent characteristics of additive manufacturing, additively manufactured trace element modified high-strength aluminum alloys are prone to deformation and cracking failure due to internal stress concentration.

[0033] Therefore, to reduce the internal stress and cracking phenomenon in additively manufactured trace element modified high-strength aluminum specimens, the following two aspects need to be addressed: First, minimize the inherent internal stress level during the additive manufacturing process; second, suppress the precipitation and coarsening of primary precipitates during the forming process.

[0034] This invention proposes an isodensity process control strategy (i.e., laser energy balance method) under the premise of optimizing the conventional laser forming process range. By synergistically reducing the optimized laser power and the optimized scanning speed, the temperature gradient of the laser additive manufacturing molten pool is reduced without significant change in laser energy density. This aims to reduce the internal stress of trace element modified high-strength aluminum specimens and suppress cracking. Specifically, this invention reduces the optimized laser power while ensuring that there is no significant difference in laser energy density before and after adjusting the optimized laser forming process parameters. The reduced laser power input is sufficient to melt and wet the molten pool. Thus, on the one hand, reducing the laser power can reduce the temperature gradient and inherent residual stress within the molten pool. On the other hand, reducing the laser power reduces the heat input to the molten pool, which can suppress the coarsening and growth of primary precipitates, thereby suppressing intergranular cracking caused by local stress concentration. Simultaneously, the "medium-temperature, short-time" process strategy is adopted in the post-processing stress relief to avoid cracking caused by significant coarsening of precipitates at grain boundaries.

[0035] The laser energy balance method proposed in this invention reduces stress cracking in additively manufactured high-strength aluminum alloy specimens. It can effectively suppress internal stress levels and cracking tendency in situ during the forming process of high-strength aluminum alloys modified by trace elements, ensuring that the formed parts do not undergo deformation cracking in the original deposition state. This broadens the application of laser additive manufacturing of complex high-strength aluminum alloy structures and is highly operable. Attached Figure Description

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0037] Figure 1 This is a process flow diagram of the method of the present invention.

[0038] Figure 2 This is a schematic diagram illustrating the impact of isodensity process control on microstructure.

[0039] Figure 3 This is a macroscopic image of the formed component in Example 3 of the specific implementation.

[0040] Specific implementation methods combined Figure 1 The present invention discloses a method for reducing stress cracking in additively manufactured high-strength aluminum alloy specimens using a laser energy balancing method, comprising the following steps:

[0041] S1. Optimization of conventional laser forming process parameters:

[0042] For rare earth element modified Al-Mg / Mn alloy systems, the range of conventional laser forming processes is determined;

[0043] Conduct forming tests on the test forming parts within the determined conventional laser forming process range to obtain optimized laser forming process parameters, and calculate the corresponding laser energy density η based on the optimized laser forming process parameters;

[0044] The optimized laser forming process parameters include optimized laser power, optimized scanning speed, optimized layer thickness, and optimized scanning spacing. Generally, however, when conducting forming tests on the test forming parts in a wide process range, optimization is carried out for the laser power and scanning speed, while the layer thickness and scanning spacing are generally selected as fixed values.

[0045] In the present invention, for the laser additive manufacturing forming process, its laser energy density η is calculated according to the following formula: η = P / (v * h * t), where: P represents the laser power; v represents the scanning speed; h represents the scanning spacing; t represents the layer thickness.

[0046] S2. Adjust the laser forming process parameters by the laser energy balance method:

[0047] Use the laser energy balance method to adjust the optimized laser forming process parameters obtained in step S1. On the premise of ensuring that the difference in laser energy density before and after adjustment is not significant, first reduce the optimized laser power to the target range, and then adjust other parameters included in the optimized laser forming process parameters.

[0048] In fact, in this step, it is necessary to协同 reduce the optimized laser power and optimized scanning speed determined in step S1, and based on the calculation formula of laser energy density, adjust the optimized layer thickness and optimized scanning spacing determined in step S1.

[0049] The adjusted laser forming process parameters need to meet two conditions. One condition is the condition of no significant difference in laser energy density (that is, the laser energy density before and after adjustment needs to be maintained in a "balanced" state): δ1 ≤ η' / η ≤ δ2. Another condition is that the heat provided by the adjusted laser power only needs to satisfy melting and wetting the molten pool: P01 ≤ P' ≤ P02 < P. Where: η' represents the laser energy density of the adjusted laser forming process parameters; η represents the laser energy density corresponding to the optimized laser forming process parameters in step S1; δ1 represents the preset minimum allowable value of energy density, and the value can be 0.85; δ2 represents the preset maximum allowable value of energy density, and the value can be 1.0; P' represents the adjusted laser power; P01 represents the preset minimum value of laser power, and the value can be 200W; P02 represents the preset maximum value of laser power, and the value can be 250W; P represents the optimized laser power in step S1, and the value is generally greater than 350W.

[0050] S3. Integral forming of complex components:

[0051] Based on the adjusted laser forming process parameters obtained in step S2, complex component additive manufacturing integrated forming is carried out to obtain complex component formed parts.

[0052] S4, Medium-temperature short-time heat treatment:

[0053] The complex component formed in step S3 is subjected to medium-temperature short-time heat treatment to further remove internal stress, complete the stress relief process of the complex component formed as a whole, and obtain the heat-treated complex component.

[0054] The present invention can be better understood from the following embodiments.

[0055] Example 1

[0056] Step 1: Optimization of conventional laser forming process parameters:

[0057] This embodiment preferably uses an alloy system with precipitation strengthening properties and good laser powder bed melting formability. The rare earth element modified Al-Mg / Mn alloy system is selected as an Al-Mg-Mn-Si alloy, wherein the alloy composition is Mg 7-9 wt.%, Si 0.4-1.2 wt%, Mn 0.3-0.8 wt.%, Sc 0.5-0.7 wt.%, Zr 0.2-0.5 wt.%, with the balance being Al. The raw material is spherical alloy powder with a particle size of 15-45 μm and D... 50 ≥25μm. The powder is dry and has good flowability.

[0058] In this embodiment, for the Al-Mg-Mn-Si alloy mentioned above, process experiments were carried out using laser additive manufacturing forming equipment to determine the process window. Forming experiments were conducted within a wide process range using laser power of 350-450W, scanning speed of 800mm / s-1600mm / s, layer thickness of 30μm, and scanning spacing of 120μm.

[0059] The density of the molded specimen was tested using the Archimedes drainage method. The optimized process parameters were a laser power of 440W and a laser scanning speed of 1350mm / s, resulting in a molding density greater than 99.5%.

[0060] In other words, this step first determined the conventional laser forming process range for Al-Mg-Mn-Si alloys: laser power 350-450W, scanning speed 800mm / s-1600mm / s, layer thickness 30μm, and scanning spacing 120μm. Then, forming experiments were conducted on the test parts within this conventional laser forming process range to optimize the laser power and scanning speed, obtaining the corresponding optimized laser power value of 440W and the optimized scanning speed value of 1350mm / s. The laser energy density was then calculated as η=P / (v*h*t)=440 / (1.35*10^6)^2. 3 *30*10 -6 *120*10 -6 = 90.53 J / m 2 .

[0061] Step 2: Adjusting laser forming process parameters using the laser energy balance method:

[0062] The laser energy balance method is used for parameter scaling calculations. Specifically, since the adjusted laser power P' needs to satisfy 200≤P'≤250, the laser power can be adjusted to 230W, considering an energy density ratio of 0.85≤η. 后 / η 前 ≤1.0, with the laser scanning speed set to 850 mm / s, layer thickness 30 μm, and scanning spacing 100 μm, η 后 =230 / (850*10) 3 *30*10 -6 *100*10 -6 = 90.19 J / m 2 Then η 后 / η 前 =0.996, which satisfies the aforementioned condition that there is no significant difference in laser energy density.

[0063] Therefore, this step is based on the laser energy balance method, which synergistically reduces the laser power optimization value and scanning speed optimization value obtained in step two, and supplements it with the adjustment of the scanning spacing, so that the laser forming process parameters before and after the adjustment basically meet the "equal density scaling" principle.

[0064] Step 3: Based on the process parameters after isodensity scaling, conduct laser additive manufacturing forming experiments. Test the density of the formed specimens and the cracking of large-size specimens. The density of the formed specimens can be referred to Table 1.

[0065] Step 4: Perform medium-temperature short-time heat treatment on the formed specimens using an atmosphere heat treatment furnace. The heat treatment heating rate is 5K / min, the heat treatment temperature is 300℃, and the heat treatment time is 2h. After treatment, test the mechanical properties and cracking of the formed specimens. Specific details can be found in Table 1.

[0066] Figure 2 This is a schematic diagram illustrating how the laser energy balance method of this invention reduces the impact of additive manufacturing on the microstructure of high-strength aluminum alloys. Through isodense process adjustments, the size and quantity of primary precipitates inside the formed specimen are significantly reduced, which can significantly suppress stress concentration and cracking behavior caused by grain boundary precipitates. No deformation or cracking is observed after forming and processing. Stress and deformation are significantly suppressed in laser additive manufacturing of trace element-modified high-strength aluminum alloys.

[0067] Example 2

[0068] The difference between this embodiment and Embodiment 1 is that the control ratio η is adjusted in step two. 后 / η 前 =0.982; The laser forming parameters after isodense scaling are: laser power 200W, scanning speed 750mm / s, layer thickness 30μm, scanning spacing 100μm, at which point η 后 =88.88, otherwise the same as in Example 1.

[0069] The laser forming parameters were scaled down to equal density to form the component. The resulting laser-formed component underwent density testing, and the test results can be found in Table 1.

[0070] The mechanical properties and cracking of the laser-formed components after medium-temperature short-time heat treatment are detailed in Table 1.

[0071] Example 3

[0072] The difference between this embodiment and Embodiment 1 is that the control ratio η is adjusted in step two. 后 / η 前 =0.85; The laser forming parameters after isodense scaling are: laser power 200W, scanning speed 1150mm / s, layer thickness 30μm, scanning spacing 100μm, at which point η 后 =76.95, otherwise the same as in Example 1.

[0073] The laser forming parameters were scaled down to equal density to form the component. The resulting laser-formed component underwent density testing, and the test results can be found in Table 1.

[0074] The mechanical properties and cracking of the laser-formed components after medium-temperature short-time heat treatment are detailed in Table 1.

[0075] Example 4

[0076] The difference between this embodiment and Embodiment 1 is that the control ratio η is adjusted in step two. 后 / η 前=0.90; The laser forming parameters after isodense scaling are: laser power 230W, scanning speed 1350mm / s, layer thickness 30μm, scanning spacing 47.8μm, at which point η 后 =81.47, otherwise the same as in Example 1.

[0077] The laser forming parameters were scaled down to equal density to form the component. The resulting laser-formed component underwent density testing, and the test results can be found in Table 1.

[0078] The mechanical properties and cracking of the laser-formed components after medium-temperature short-time heat treatment are detailed in Table 1.

[0079] Example 5

[0080] The difference between this embodiment and embodiment 1 is that step one involves forming the specimen, without the subsequent isodense process adjustment in steps two and three, and step four involves the same heat treatment process as in embodiment 1.

[0081] Figure 3 The specimen formed in Example 5 was found to have cracked after forming and processing. Therefore, we can conclude that, using conventional forming parameters, laser additive manufacturing of trace element modified high-strength aluminum alloy specimens exhibits significant internal stress and a tendency to crack.

[0082] Example 6

[0083] The difference between this embodiment and Embodiment 1 is that the control ratio η is adjusted in step two. 后 / η 前 =1.1, and the laser process forming parameters after equal density scaling are: laser power of 240W, laser scanning speed of 800mm / s, layer thickness of 30μm, scanning spacing of 100μm, and others are the same as in Example 1.

[0084] The laser forming parameters were scaled down to equal density to form the component. The resulting laser-formed component underwent density testing, and the test results can be found in Table 1.

[0085] The mechanical properties and cracking of the laser-formed components after medium-temperature short-time heat treatment are detailed in Table 1.

[0086] Figure 3 The specimen formed in Example 3 was found to have cracked after forming and processing. Using conventional forming parameters, laser additive manufacturing of trace element modified high-strength aluminum alloy specimens showed significant internal stress and a tendency to crack.

[0087] Example 7

[0088] The difference between this embodiment and Embodiment 1 is that the control ratio η is adjusted in step two.后 / η 前 =0.81. The laser forming parameters after isodense scaling are: laser power 220W, laser scanning speed 1000mm / s, layer thickness 30μm, scanning spacing 100μm, and η = 0.81. 后 =73.33, otherwise the same as in Example 1.

[0089] The laser forming parameters were scaled down to equal density to form the component. The resulting laser-formed component underwent density testing, and the test results can be found in Table 1.

[0090] The mechanical properties and cracking of the laser-formed components after medium-temperature short-time heat treatment are detailed in Table 1.

[0091] Example 8

[0092] The difference between this embodiment and Embodiment 1 is that the heat treatment temperature in step four is 350°C, while the rest is the same as in Embodiment 1.

[0093] Example 9

[0094] The difference between this embodiment and Embodiment 1 is that the heat treatment time in step four is 6 hours, while the rest is the same as in Embodiment 1.

[0095] Density, mechanical properties, and complex component forming tests were conducted on the molded specimens under different embodiments. The test results for different embodiments are shown in Table 1.

[0096] Table 1. Mass of high-strength aluminum alloy specimens formed in different embodiments

[0097]

[0098]

[0099] As can be seen from Table 1:

[0100] Comparing Examples 1-4 with Example 5, conventional process methods show that this method has a good effect on internal stress control and crack suppression of trace element modified high-strength aluminum alloys formed by laser additive manufacturing.

[0101] Comparing Examples 1 and 6, when the process is scaled up, excessively high energy density easily leads to a decrease in density and a significant reduction in tensile strength. This is because high energy density causes Mg evaporation and an increase in the number of pores, resulting in a decrease in the density and mechanical properties of the molded specimen.

[0102] Comparing Examples 1 and 7, when the energy density is too low after process scaling, it also leads to a decrease in density and a significant decrease in tensile strength. This is because the low energy density causes an increase in interlayer unfused porosity, resulting in a decrease in the density and mechanical properties of the formed specimen.

[0103] Comparing Examples 1 and 8, when the heat treatment temperature was too high (350°C), the formed specimens exhibited good density but reduced strength, and cracking also occurred. This is because the excessively high heat treatment temperature led to significant coarsening of the precipitates at the grain boundaries, thereby inducing localized stress concentration and cracking.

[0104] Comparing Examples 1 and 9, when the heat treatment temperature was extended to 6 hours, the formed specimens exhibited good density but reduced strength, and cracking also occurred. This is because the excessively long heat treatment time led to significant coarsening of the precipitates at the grain boundaries, thereby inducing local stress concentration and cracking.

[0105] This invention provides a method for controlling the stress and cracking of high-strength aluminum alloys modified by trace elements through laser additive manufacturing processes. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method of reducing stress cracking in a high strength aluminum alloy test piece formed by additive manufacturing using a laser energy balance method, the method comprising: Comprising the following steps: S1, optimization of conventional laser forming process parameters: For the rare earth element modified Al-Mg / Mn alloy system, the conventional laser forming process interval is determined; perform a forming test on the test forming piece in the determined conventional laser forming process range to obtain optimized laser forming process parameters, and calculate corresponding laser energy density based on the optimized laser forming process parameters η ; Laser energy density η was calculated to be obtained according to the following formula: η= P / (v* h * t) ； The optimized laser forming process parameters include optimized laser power, optimized scanning speed, optimized layer thickness, and optimized scanning spacing. S2, adjusting laser forming process parameters by laser energy balance method: The optimized laser forming process parameters obtained in step S1 are adjusted by laser energy balance method, under the premise of ensuring that the difference of laser energy density before and after adjustment is not significant, the optimized laser power is reduced to the target interval, and then the other parameters included in the optimized laser forming process parameters are adjusted; The adjusted laser forming process parameters satisfy: δ1≤ η’ / η ≤δ2 and P01≤P ’ ≤P02<P; In the formula: η’ represents the laser energy density of the adjusted laser forming process parameter; η represents the laser energy density corresponding to the laser forming process parameter optimized in step S1; δ1 represents a preset minimum value of the energy density allowance, and is 0.85; δ2 represents a preset maximum value of the energy density allowance, and is 1.0; P ’ represents the adjusted laser power; P01 represents a preset minimum value of the laser power, and is 200 W; P02 represents a preset maximum value of the laser power, and is 250 W; P represents the optimized laser power in step S1, and is greater than 350 W; S3, integrated forming of complex components: Based on the adjusted laser forming process parameters obtained in step S2, the integrated forming of complex components is carried out for additive manufacturing, to obtain a complex component forming piece. S4, medium temperature short time heat treatment: The complex component forming piece obtained in step S3 is subjected to medium temperature short time heat treatment, to further remove internal stress, complete the stress relief process of the complex component forming piece as a whole, and obtain a heat treated complex component.

2. The method of reducing stress cracking in a high strength aluminum alloy test piece formed by additive manufacturing using a laser energy balance method according to claim 1, wherein, In step S1, the rare earth element modified Al-Mg / Mn alloy system is any one of rare earth element modified Al-Mg alloy, rare earth element modified Al-Mn alloy or rare earth element modified Al-Mn-Mg alloy.

3. The method of claim 2, wherein the laser energy balance method is used to reduce stress cracking of the additively manufactured high strength aluminum alloy test piece, and wherein the laser energy balance method is used to reduce stress cracking of the additively manufactured high strength aluminum alloy test piece by balancing the laser power and the laser scanning speed to achieve a laser energy density of 0.5 to 5 J / mm2. The rare earth element is any one or a combination of two or more of Sc, Zr, Er and Ti.

4. The method of claim 2, wherein the laser energy balance method is used to reduce stress cracking of the additively manufactured high strength aluminum alloy test piece, and wherein the laser energy balance method is used to reduce stress cracking of the additively manufactured high strength aluminum alloy test piece by balancing the laser power and the laser scanning speed to achieve a laser energy density of 0.5 to 5 J / mm2. In step S1, the rare earth element modified Al-Mg / Mn alloy system is rare earth element modified Al-Mn-Mg alloy, which comprises the following components: Mg 7-9 wt.%, Si 0.4-1.2 wt%, Mn 0.3-0.8 wt.%, Sc 0.5-0.7 wt.%, Zr 0.2-0.5 wt.%, and the balance is Al; in the conventional laser forming process interval, the laser power is 350-450 W, the scanning speed is 800 mm / s-1600 mm / s, the layer thickness is 30 μm, and the scanning spacing is 120 μm.

5. The method for reducing stress cracking in additively manufactured high-strength aluminum alloy specimens using laser energy balancing according to claim 4, characterized in that, In step S4, the aging temperature of the medium temperature short time heat treatment is controlled at 280-300℃, and the time is 2-4h.

6. The method of claim 5, wherein the laser energy balance method is used to reduce stress cracking of the additively manufactured high strength aluminum alloy test piece. In step S1, in the optimized laser forming process parameters, the optimized laser power is 440 W, and the optimized laser scanning speed is 1350 mm / s; the laser energy density of the adjusted laser forming process parameters η’ = 90.19, the adjusted laser power P’ = 230 W, the adjusted laser scanning speed is 850 mm / s, the layer thickness is 30 μm, and the scanning interval is 100 μm.

7. The method of claim 6, wherein the laser energy balance method is used to reduce stress cracking of the additively manufactured high strength aluminum alloy test piece, and wherein the laser energy balance method is used to reduce stress cracking of the additively manufactured high strength aluminum alloy test piece by balancing the laser power and the laser scanning speed to achieve a laser energy density of 0.5 to 5 J / mm2. In step S4, the heat treatment heating rate is 5K / min, the heat treatment temperature is 300℃, and the heat treatment time is 2h.

Images