Method for realizing mechanical property gradient control of Ti-6Al-4V alloy by multi-laser powder bed fusion based on scanning trajectory combination

Abstract

This invention discloses a method for gradient control of mechanical properties of Ti-6Al-4V alloy formed by multi-laser powder bed melting based on scanning trajectory combination, relating to the field of additive manufacturing technology. The method includes: acquiring mechanical property data of Ti-6Al-4V alloy samples formed by multi-laser powder bed melting under different scanning trajectories; constructing a mechanical property control model; determining the height of the influence zone of a single scanning trajectory, and judging whether the interlayer heterogeneous microstructure is retained based on the matching relationship between the height of the influence zone and the alternation height between trajectory layers; when the interlayer heterogeneous microstructure is determined to be retained, selecting at least two different scanning trajectories as target scanning trajectories, and constructing an interlayer scanning trajectory combination scheme; and performing multi-laser powder bed melting according to the interlayer scanning trajectory combination scheme to obtain Ti-6Al-4V alloy formed parts with a gradient distribution of mechanical properties, thereby improving the efficiency and performance of the mechanical property gradient control of the alloy.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and in particular to a method for gradient control of the mechanical properties of Ti-6Al-4V alloy formed by multi-laser powder bed melting based on scanning trajectory combination. Background Technology

[0002] Ti-6Al-4V, as a high-strength, high-corrosion-resistance, and high-fatigue-resistance alloy, is widely used in aerospace, defense, and other fields. However, due to the low thermal conductivity and low bulk heat capacity of Ti-6Al-4V alloy, conventional processing techniques such as casting and forging are difficult to achieve the integral molding of complex structural components. Laser powder bed melting technology, through digital slicing and layer-by-layer printing, solves the problems faced by traditional processing techniques, demonstrating excellent design freedom and good processing accuracy. Furthermore, with technological advancements, multi-laser powder bed melting equipment has significantly improved the processing efficiency of formed parts and overcome the size limitations of single-laser equipment compared to single-laser equipment. However, both existing single-laser and multi-laser powder bed melting of Ti-6Al-4V alloys suffer from the problem of limited forming performance, restricting the further application of Ti-6Al-4V alloys in aerospace and other fields, such as engine turbine blades and aircraft landing gear, which have specific performance requirements. Therefore, it is necessary to develop a method for achieving gradient performance control of Ti-6Al-4V alloys through laser powder bed melting without material replacement or post-heat treatment processes.

[0003] Achieving a balance between strength and ductility in printed Ti-6Al-4V alloys remains challenging. The high cooling rate of laser powder bed fusion molding technology often leads to problems such as a fine needle-like martensite microstructure, high dislocation density, high residual stress, and process defects, all of which affect the mechanical properties of the formed specimens. Currently, domestic and international research mainly focuses on three methods to achieve a synergistic effect between strength and ductility in high-strength, low-ductility alloys. The first method involves modifying the powder raw materials. This is achieved through alloy design, element doping, and adjustment of composition ratios. For example, first-principles calculations can be used to design precipitates to enhance alloy properties; or functionally graded materials can be used to achieve a combination of soft and hard layers, and strong-ductility synergy can be achieved through heterogeneous deformation-induced strengthening. The second method relies on external energy field-assisted manufacturing, that is, combining an external energy field to control the microstructure during the printing process, thereby optimizing mechanical properties, such as ultrasonic fields, magnetic fields, force fields, and thermal fields. Finally, the third strategy involves complex post-heat treatment. Process parameters are changed during the printing process to control dislocation density based on energy density differences, and gradient performance is controlled through post-heat treatment. While existing methods can achieve a synergistic effect of strong and ductile properties by altering phase composition, grain morphology, dislocation density, and other factors, these methods primarily change the overall material. Achieving responsive mechanical properties within a single alloy remains challenging.

[0004] A unique advantage of scanning trajectories is their ability to act as independent variables, allowing for the localized control of the thermal history of printed samples simply by adjusting the laser trajectory, without altering powder, equipment, or process parameters. This holds promise for achieving microstructural control and synergistic effects of strong plasticity between printed layers based on scanning trajectory optimization. Therefore, it is necessary to propose a method for gradient control of the mechanical properties of Ti-6Al-4V alloys formed by multi-laser powder bed melting based on scanning trajectory combinations, filling the current theoretical and technological gap in achieving gradient control of the mechanical properties of Ti-6Al-4V alloys formed by multi-laser powder bed melting using scanning trajectory combinations. Summary of the Invention

[0005] The purpose of this invention is to provide a method for gradient control of mechanical properties of Ti-6Al-4V alloy based on scanning trajectory combination in multi-laser powder bed melting forming, which solves the problem that the mechanical properties of the formed sample are singular and cannot meet the regional performance requirements of complex structural parts during the multi-laser powder bed melting forming of Ti-6Al-4V alloy.

[0006] The first aspect of this invention provides a method for gradient control of the mechanical properties of Ti-6Al-4V alloy formed by multi-laser powder bed melting based on scanning trajectory combination, comprising: Mechanical property data of Ti-6Al-4V alloy samples formed by multi-laser powder bed melting under different scanning trajectories were obtained; Based on the mechanical property data, a mechanical property control model for Ti-6Al-4V alloy specimens was constructed. The mechanical property control model includes at least the influence of the scanning trajectory on the morphology of the molten pool, the height of the affected zone, and the interlayer coupling relationship, and establishes a quantitative relationship between the combination of interlayer scanning trajectories and the yield strength of the formed specimen. Based on the aforementioned mechanical performance control model, the height of the influence zone of a single scanning trajectory is determined, and the interlayer heterogeneous microstructure is judged to be preserved based on the matching relationship between the height of the influence zone and the alternation height between trajectory layers. When determining the retention of interlayer heterogeneous microstructure, at least two different scanning trajectories are selected as target scanning trajectories, and an interlayer scanning trajectory combination scheme is constructed to achieve gradient control of the mechanical properties of Ti-6Al-4V alloy. Multi-laser powder bed melting is performed according to the interlayer scanning trajectory combination scheme to obtain Ti-6Al-4V alloy forming parts with a gradient distribution of mechanical properties.

[0007] Preferably, after constructing the interlayer scanning trajectory combination scheme, the method further includes: A Ti-6Al-4V alloy sample was formed according to the interlayer scanning trajectory combination scheme. The sample was then separated from the substrate and its warpage deformation was measured. If the warping deformation exceeds a preset threshold, the process returns to the construction step of the mechanical performance control model, warping deformation correction parameters are introduced, and the interlayer scanning trajectory combination scheme is reconstructed based on the corrected mechanical performance control model.

[0008] Preferably, the acquisition of mechanical property data of Ti-6Al-4V alloy samples formed by multi-laser powder bed melting under different scanning trajectories includes: Ti-6Al-4V alloy basic samples corresponding to different scanning trajectories were prepared using at least two different scanning trajectories; Tensile tests were performed on the base specimens corresponding to different scanning trajectories along at least two different loading directions to obtain mechanical property data of at least one of yield strength, tensile strength and elongation under different loading directions. The molten pool morphology and microstructure of the base specimens corresponding to different scanning trajectories are characterized, and a mapping relationship between scanning trajectory, microstructure and mechanical properties is established in combination with the mechanical property data.

[0009] Preferably, the construction of the mechanical property control model includes: Based on the correspondence between laser energy density and molten pool morphology, the height of the influence zone for different scanning trajectories is determined; wherein, the laser energy density is determined by laser power, scanning speed, molten pool spacing, and printing layer thickness; Determine the ideal interlayer spacing of the scanning trajectory based on the number of printing layers and the printing layer thickness corresponding to a single scanning trajectory. Based on the ratio of the ideal interlayer spacing to the height of the affected zone, a dimensionless parameter characterizing the interlayer coupling relationship is determined. Based on the dimensionless parameter, it is determined whether the interlayer heterogeneous microstructure is preserved; when the dimensionless parameter is greater than 1, it is determined that the interlayer heterogeneous microstructure is preserved. When the interlayer heterogeneous microstructure is preserved, the true layer height of the scanning trajectory is determined based on the height of the affected area and the number of printed layers. Combined with the yield strength corresponding to each scanning trajectory, a basic quantitative relationship is established between the combination of interlayer scanning trajectories and the equivalent yield strength of the formed specimen. When there is warping deformation in the combination of interlayer scanning trajectories, the warping deformation amount and the strengthening factor of the microstructure of the soft and hard layers in the interlayer are introduced into the basic quantitative relationship for correction, so as to obtain the optimized quantitative relationship of combined yield strength.

[0010] Preferably, the determination of whether the interlayer heterogeneous microstructure is preserved includes: The height of the influence area of ​​a single scan trajectory is compared with the alternation height between trajectory layers, wherein the alternation height between trajectory layers is the ideal interlayer spacing; When the height of the affected area is less than the alternation height between the trajectory layers, the dimensionless parameter is greater than 1, and it is determined that the heterogeneous microstructure between the layers is preserved. When the height of the affected area is equal to the height of the alternation between the trajectory layers, the dimensionless parameter is equal to 1, and the heterogeneous microstructure between the layers is determined to be in a critical coupling state. When the height of the affected area is greater than the alternation height between the trajectory layers, the dimensionless parameter is less than 1, and it is determined that the heterogeneous microstructure between layers is not retained.

[0011] Preferably, the scheme for constructing the interlayer scanning trajectory combination includes: Based on the mechanical property distribution requirements of the target forming area, at least two scanning trajectories capable of forming different microstructure characteristics are selected as the target scanning trajectory. The distribution order of each target scanning trajectory in the forming direction, the number of consecutive printing layers, and the alternation position between layers are determined in order to construct an interlayer scanning trajectory combination structure with heterogeneous microstructure layering characteristics; Based on the mechanical property control model, the equivalent yield strength corresponding to the interlayer scanning trajectory combination structure is predicted, and the prediction result is matched with the target mechanical property distribution requirements. The corresponding inter-layer scanning trajectory combination scheme is determined based on the matching results.

[0012] Preferably, the quantitative relationship between the interlayer scanning trajectory combination and the equivalent yield strength of the formed specimen includes: The basic equivalent yield strength is calculated by summing the products of the yield strength corresponding to each scanning trajectory and the proportion of the actual layer height of the scanning trajectory in the forming direction; When the interlayer scanning trajectories combine to form a heterogeneous microstructure with alternating soft and hard layers, a correction term consisting of the yield strength difference between soft and hard layers, the interface strengthening factor, and microstructure parameters is introduced on the basis of the basic equivalent yield strength to obtain the optimized equivalent yield strength of the shaped specimen.

[0013] A second aspect of the present invention provides a device for gradient control of mechanical properties of Ti-6Al-4V alloy based on scanning trajectory combination in multi-laser powder bed melting, comprising: The data acquisition module is used to acquire mechanical property data of Ti-6Al-4V alloy samples formed by multi-laser powder bed melting under different scanning trajectories; The model building module is used to construct a mechanical property control model for Ti-6Al-4V alloy specimens based on the mechanical property data. The mechanical property control model includes at least the influence of the scanning trajectory on the morphology of the molten pool, the height of the influence zone and the interlayer coupling relationship, and establishes a quantitative relationship between the combination of interlayer scanning trajectories and the yield strength of the formed specimen. The influence zone height determination and judgment module is used to determine the influence zone height of a single scanning trajectory based on the mechanical performance control model, and to determine whether the interlayer heterogeneous microstructure is preserved based on the matching relationship between the influence zone height and the alternation height between trajectory layers. The combined scheme construction module is used to select at least two different scanning trajectories as target scanning trajectories when determining the retention of interlayer heterogeneous microstructure, and to construct a combined scheme of interlayer scanning trajectories to achieve gradient control of the mechanical properties of Ti-6Al-4V alloy. The forming execution module is used to perform multi-laser powder bed melting forming according to the interlayer scanning trajectory combination scheme to obtain Ti-6Al-4V alloy forming parts with a gradient distribution of mechanical properties.

[0014] A third aspect of the present invention provides an electronic device, characterized in that it comprises: The memory is used to store the processing program; A processor, which, when executing the processing program, implements the method for gradient control of mechanical properties of Ti-6Al-4V alloy based on scanning trajectory combination as described in any one of claims 1 to 7.

[0015] A fourth aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, characterized in that, when the computer program is executed by a processor, it implements the steps of the above-described method for gradient control of mechanical properties of Ti-6Al-4V alloy based on a combination of scanning trajectories in multi-laser powder bed melting.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for gradient control of the mechanical properties of Ti-6Al-4V alloy formed by multi-laser powder bed melting based on scanning trajectory combinations. Using the scanning trajectory as an independent control variable, and without the need for material replacement, external energy field introduction, or subsequent heat treatment, gradient control of the mechanical properties of Ti-6Al-4V alloy printed parts can be achieved solely through the combination of interlayer scanning trajectories during the multi-laser powder bed melting process. Simultaneously, a quantitative correlation model is established between scanning trajectory, melt pool morphology, affected zone height, interlayer coupling relationship, and mechanical properties, enabling the determination of whether the interlayer heterogeneous microstructure is preserved. The invention also predicts the equivalent yield strength of the assembled parts and improves the model prediction accuracy and the reliability of the assembly design by introducing warpage correction parameters and heterogeneous interface strengthening factors. In addition, the invention can construct and retain a stable layered heterogeneous microstructure inside the component, achieving synergistic optimization of strength and plasticity. It has universality and can be extended to other alloy systems suitable for multi-laser powder bed melting forming, such as nickel-based alloys, 316L stainless steel, and copper alloys. It can achieve gradient control of the strength of Ti-6Al-4V alloy in the range of over 25% and the elongation in the range of over 100%, promoting its practical application in aerospace, defense and military industries. Attached Figure Description

[0017] Figure 1 This is a schematic diagram illustrating the steps of the method for gradient control of mechanical properties of Ti-6Al-4V alloy based on scanning trajectory combination in an embodiment of the present invention; Figure 2 This is a schematic diagram of the mechanical properties of Ti-6Al-4V alloy samples formed by multi-laser powder bed melting with different scanning trajectories in an embodiment of the present invention; Figure 3 This is a stress-strain curve diagram of Ti-6Al-4V alloy formed by multiple laser scanning trajectories in an embodiment of the present invention; Figure 4 This is a schematic diagram of the microstructure of Ti-6Al-4V alloy formed by combining multiple laser scanning trajectories in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] In this embodiment, Ti-6Al-4V alloy is taken as the research object. On a multi-laser powder bed melting and forming equipment, the mechanical properties of the formed sample are gradient controlled by designing different scanning trajectories and their interlayer combinations.

[0020] like Figure 1 As shown, this embodiment provides a method for gradient control of mechanical properties of Ti-6Al-4V alloy based on scanning trajectory combination in multi-laser powder bed melting. This method can also be extended to the gradient mechanical property control of printed samples of other alloy systems such as nickel-based alloys, 316L, and copper alloys in multi-laser powder bed melting.

[0021] This embodiment, based on the differences in mechanical properties of Ti-6Al-4V alloy samples formed by different scanning trajectories, achieves gradient control of the mechanical properties of Ti-6Al-4V alloy samples through the combination of interlayer scanning trajectories. Specifically, it includes the following steps: Step S1: Obtain mechanical property data of Ti-6Al-4V alloy samples formed by multi-laser powder bed melting under different scanning trajectories; prepare Ti-6Al-4V alloy base samples corresponding to at least two different scanning trajectories, such as the zigzag scanning trajectory H, the zebra-shaped scanning trajectory Z, and the 67° rotating scanning trajectory R. Perform tensile tests on the base samples corresponding to different scanning trajectories along at least two different loading directions (such as the X and Y directions) to obtain mechanical property data such as yield strength, tensile strength, and elongation; simultaneously, characterize the molten pool morphology and microstructure of the base samples corresponding to different scanning trajectories, and establish the mapping relationship between scanning trajectory, microstructure, and mechanical properties based on the mechanical property data.

[0022] Step S2: Based on the mechanical property data, construct a mechanical property control model for Ti-6Al-4V alloy samples. The mechanical property control model includes at least the influence of the scanning trajectory on the morphology of the molten pool, the height of the affected zone, and the interlayer coupling relationship, and establishes a quantitative relationship between the combination of interlayer scanning trajectories and the yield strength of the formed sample. Step S3: Based on the mechanical property control model, determine the height of the influence zone of a single scanning trajectory, and determine whether the heterogeneous microstructure between layers is preserved based on the matching relationship between the height of the influence zone and the alternation height between trajectory layers. Step S4: When determining the retention of the interlayer heterogeneous microstructure, select at least two different scanning trajectories as target scanning trajectories and construct an interlayer scanning trajectory combination scheme to achieve gradient control of the mechanical properties of Ti-6Al-4V alloy; Step S5: Perform multi-laser powder bed melting forming according to the interlayer scanning trajectory combination scheme to obtain Ti-6Al-4V alloy forming parts with a gradient distribution of mechanical properties.

[0023] The interlayer scanning trajectory combination scheme takes the printed layer as a unit and uses at least two different scanning trajectories to alternately combine and / or sequentially combine along the forming direction and / or in a specified area. By controlling the microstructure layering through scanning trajectory combination, and combining it with the mechanical property control model for quantitative prediction, the gradient control of the mechanical properties of the printed Ti-6Al-4V alloy can be achieved without material replacement or post-processing.

[0024] In one embodiment, step S1 involves acquiring mechanical property data of Ti-6Al-4V alloy samples formed by multi-laser powder bed melting under different scanning trajectories, including: Laser powder bed melting forming of Ti-6Al-4V alloy exhibits significant anisotropy, which is essentially influenced by the molten pool morphology and thermal history. Different scanning trajectories, by altering the laser path, create different interlayer thermal histories and temperature gradients, leading to different microstructures and ultimately affecting the macroscopic mechanical properties of the formed specimens. Therefore, it is necessary to first determine the differences in mechanical properties of the formed specimens under different scanning trajectories, specifically including: At least two different scanning trajectories were used to prepare Ti-6Al-4V alloy basic samples corresponding to different scanning trajectories. Specifically, three different scanning trajectories, namely the zigzag scanning trajectory H, the zigzag scanning trajectory Z, and the 67° rotating scanning trajectory R, ​​could be selected for multi-laser powder bed melting forming to construct basic samples with differentiated thermal histories and microstructures. Tensile tests are performed on the base specimens corresponding to different scanning trajectories along at least two different loading directions to obtain mechanical property data of at least one of yield strength, tensile strength, and elongation under different loading directions; to comprehensively characterize the anisotropic features, the different loading directions include loading directions parallel to the forming direction and loading directions perpendicular to the forming direction (such as the X and Y loading directions). Figure 2 As shown, Ti-6Al-4V samples formed by three different scanning trajectories (H, Z, and R) exhibit significant differences in mechanical properties in the X and Y loading directions. The molten pool morphology and microstructure of the base samples corresponding to different scanning trajectories were characterized, and a mapping relationship between scanning trajectory, microstructure, and mechanical properties was established in conjunction with the mechanical property data. By clarifying the geometric morphology and internal microstructure characteristics (such as phase composition and dislocation density) of the molten pool under different scanning trajectories, the intrinsic mechanism by which the scanning trajectory affects the evolution of microstructure and thus determines macroscopic mechanical properties through the regulation of thermal history was revealed, providing solid physical and data support for the subsequent construction of a mechanical property regulation model.

[0025] In one embodiment, the specific process of constructing the mechanical performance control model in step S2 is as follows: Based on the differences in mechanical properties of Ti-6Al-4V alloy samples formed by multi-laser powder bed melting with different scanning trajectories in step 1 and the yield strength obtained experimentally, a mechanical property control model for Ti-6Al-4V alloy samples formed by multi-laser powder bed melting is constructed. Since the scanning trajectory of the printed layer affects the microstructure of the deposited layer, the core of the model construction lies in quantifying the influence of the scanning trajectory on the molten pool morphology, the height of the affected zone, and the interlayer coupling relationship, specifically including: Based on the correlation between laser energy density and molten pool morphology, the height h of the affected region for different scanning trajectories is determined. AZ The height of the affected zone is closely related to the morphology of the molten pool, which is mainly determined by the laser energy density. The laser energy density E is determined by the laser power P, scanning speed v, melt channel spacing h, and printing layer thickness t, and can be calculated using the following formula: , In the formula, E is the laser energy density, P is the laser power, v is the scanning speed, h is the melt channel spacing, and t is the printed layer thickness. The relationship between melt pool morphology and energy density can be obtained by constructing a single-pass melt pool morphology orthogonal experiment based on the laser power and scanning speed process window. A deeper melt pool may lead to repeated thermal cycling, melting and regenerating previously solidified grains, thus changing the grain morphology of the solidified region. Based on this, the height h of the influence zone corresponding to different scanning trajectories can be determined. AZ .

[0026] Determine the ideal interlayer spacing h of the scan trajectory based on the number of printing layers and the printing layer thickness corresponding to a single scan trajectory. theo The ideal interlayer spacing is the theoretical stacking height for continuous printing on a single scan trajectory, and can be calculated using the following formula: Where m is the number of printing layers in a single scan trajectory, and h theo The ideal interlayer spacing for the scanning trajectory is t, where t is the printing layer thickness.

[0027] Based on the ratio of the ideal interlayer spacing to the height of the affected zone, the dimensionless parameter Ψ characterizing the interlayer coupling relationship is determined and calculated using the following formula: In the formula, Ψ is a dimensionless parameter characterizing the interlayer coupling relationship, and h theo h is the ideal interlayer spacing for the scan trajectory. AZ The height of the influence area of ​​a single scan trajectory.

[0028] The dimensionless parameter Ψ is used to describe the degree of interlayer coupling, which is expressed as the height h of the influence region of a single scan trajectory. AZ The ideal interlayer spacing h is the alternation height between trajectory layers. theo Comparison is used to determine whether the interlayer heterogeneous microstructure is preserved: When the height of the affected area is greater than the alternation height between the trajectory layers, the dimensionless parameter Ψ is less than 1. It is determined that the heterogeneous microstructure between the layers is not preserved, which means severe remelting. The microstructure formed by the previous scanning trajectory is completely affected by the next scanning trajectory, forming a relatively uniform microstructure. It is determined that the heterogeneous microstructure between the layers is not preserved, and the combination of scanning trajectories cannot play a gradient adjustment role.

[0029] When the height of the affected area is equal to the alternation height between the trajectory layers, the dimensionless parameter Ψ is equal to 1, and the heterogeneous microstructure between layers is determined to be in a critical coupling state. When the height of the affected area is less than the alternation height between the trajectory layers, the dimensionless parameter Ψ is greater than 1, the height of the affected area is less than the spacing between the scanning trajectories, and it is determined that the heterogeneous microstructure between layers is preserved. The mechanical properties can be effectively controlled by combining the scanning trajectories between layers.

[0030] A basic quantitative relationship is established between the combination of interlayer scanning trajectories and the equivalent yield strength of the formed specimen. This relationship includes: the basic equivalent yield strength is calculated by summing the products of the yield strength corresponding to each scanning trajectory and the proportion of the actual layer height of that trajectory in the forming direction; when the combination of interlayer scanning trajectories forms a heterogeneous microstructure with alternating soft and hard layers, a correction term consisting of the yield strength difference between soft and hard layers, the interface strengthening factor, and microstructure parameters is introduced based on the basic equivalent yield strength to obtain the optimized equivalent yield strength of the formed specimen: when the heterogeneous interlayer microstructure is preserved (i.e., Ψ>1), the height h of the influence zone is considered. AZ The actual layer height h of the scan trajectory real It can be obtained from the following formula: , In the formula, h real,i Let be the actual layer height of the i-th alternating scan trajectory, and let i be the number of scan trajectory alternations. total The total number of alternations is given. Based on this, and combined with the yield strength corresponding to each scanning trajectory, the interlayer scanning trajectory combination forms the basic equivalent yield strength σ of the specimen. y,eq It can be calculated using the following formula: , In the formula, σ y,eq The basic equivalent yield strength is p; p is the summation index, corresponding to the layer number of the soft layer (type A scan trajectory) and the hard layer (type B scan trajectory), respectively. σ represents the true layer height of the p-th soft layer (Class A scan trajectory); y,A This represents the yield strength corresponding to the soft layer (Type A scan trajectory); σ represents the true layer height of the p-th hard layer (Class B scan trajectory); y,B i represents the yield strength corresponding to the hard layer (Type B scan trajectory); total h is the total number of alternations in the inter-slice scan trajectory combination (i.e., the total number of slices); theo The ideal interlayer spacing for the scanning trajectory.

[0031] By introducing warpage correction, an optimized quantitative relationship for the combined yield strength is obtained: When warpage exists in the interlayer scanning trajectory combination, the residual stress release and redistribution are caused by the interlayer soft-hard heterogeneous structure. Therefore, the warpage amount and the strengthening factors of the microstructure of the interlayer soft and hard layers need to be introduced into the basic quantitative relationship for correction, resulting in the optimized combined yield strength σ. y,oq : , In the formula, σ y,o p represents the optimized combined yield strength, and σ y,eq The basic equivalent yield strength, Ω is the warpage correction factor, and σ is the basic equivalent yield strength. y,A and σ y,B These represent the yield strengths corresponding to the microstructures of the soft and hard layers, respectively, where t is the printing layer thickness and h is the yield strength. real Let G be the true layer height, G be the interface strengthening factor of the interlayer soft and hard layer microstructure, σ be the average residual stress of the formed specimen, and L be the characteristic length of the formed specimen. Based on this optimized quantitative relationship, accurate prediction and control of the equivalent yield strength of the composite formed part containing warpage deformation can be achieved. Through the above model, the equivalent yield strength of the composite formed specimen with interlayer scanning trajectory can be predicted, providing a theoretical basis for the subsequent design of interlayer scanning trajectory combination schemes.

[0032] In one embodiment, step S3, based on the mechanical performance control model, determines the height of the influence zone of a single scanning trajectory, and determines whether the interlayer heterogeneous microstructure is preserved based on the matching relationship between the height of the influence zone and the alternation height between trajectory layers, specifically including: The height of the influence zone of a single scan trajectory can be obtained by comparing the theoretical microstructure height printed by the interlayer scan trajectory with the actual microstructure height, and its value can be determined by combining the cross-sectional melt pool morphology characterization, microstructure distribution analysis and the mechanical property control model.

[0033] This step involves determining whether different scanning trajectories can retain the original heterogeneous microstructure after interlayer combination. If the height of the affected region is less than the alternation height between trajectory layers, it indicates that the lower layer structure will not be completely homogenized by subsequent thermal effects, and the layered characteristics of the interlayer structure can be preserved. If the height of the affected region is equal to the alternation height between trajectory layers, it indicates that the layers are in a critical coupling state. If the height of the affected region is greater than the alternation height between trajectory layers, it indicates that the interlayer remelting effect is too strong, and the original interlayer heterogeneous structure is difficult to retain. In this case, the interlayer scanning trajectory combination strategy needs to be redesigned.

[0034] In one embodiment, step S4, which involves constructing an inter-layer scanning trajectory combination scheme, includes: When determining the retention of the interlayer heterogeneous microstructure, at least two different scanning trajectories are selected as target scanning trajectories, and an interlayer scanning trajectory combination scheme is constructed to achieve gradient control of the mechanical properties of the Ti-6Al-4V alloy. The interlayer scanning trajectory combination scheme is based on the printed layer, employing at least two different scanning trajectories in alternating and / or sequential combinations along the forming direction and / or designated areas. Specifically, it includes: Based on the mechanical property distribution requirements of the target forming area, at least two scanning trajectories capable of forming different microstructure characteristics are selected as target scanning trajectories; the distribution order, number of consecutive printing layers, and alternating positions between layers of each target scanning trajectory in the forming direction are determined to construct an interlayer scanning trajectory combination structure with heterogeneous microstructure layering characteristics; based on the mechanical property control model, the equivalent yield strength corresponding to the interlayer scanning trajectory combination structure is predicted, and the prediction results are matched with the target mechanical property distribution requirements; the corresponding interlayer scanning trajectory combination scheme is determined according to the matching results.

[0035] In this embodiment, the mechanical properties of the Ti-6Al-4V alloy sample are graded by changing the number of alternating layers between different scanning trajectories. The stress-strain curves of the sample formed by the combination of interlayer scanning trajectories are shown below. Figure 3 As shown, based on the differences in interlayer microstructure, the gradient control of the mechanical properties of Ti-6Al-4V alloy samples formed by multi-laser powder bed melting can be successfully achieved. Among them, under the L33 combination strategy, the samples exhibit a significant synergistic improvement in strength and plasticity. The enhancement mechanism lies in the alternating distribution of soft and hard layers formed by different scanning trajectories between the layers, thus constituting a heterogeneous microstructure interface. Under external load, this interface strengthening effect can be generated, improving the overall strength-plasticity matching level of the material.

[0036] In one embodiment, after constructing the inter-layer scanning trajectory combination scheme in step S4, a closed-loop correction step for warpage deformation is further included as follows: Due to significant differences in the microstructure formed by different scanning trajectories (such as different dislocation densities and phase compositions, resulting in soft and hard layers), this heterogeneous interlayer microstructure leads to uneven interlayer thermal shrinkage and residual stress distribution during printing. When the formed sample separates from the substrate, the release of residual stress easily causes macroscopic warping deformation, which not only affects the dimensional accuracy of the formed part but also causes deviations in the mechanical properties predicted based on ideal conditions. Therefore, it is necessary to verify and correct the warping deformation of the combined scheme. A Ti-6Al-4V alloy sample was formed according to the interlayer scanning trajectory combination scheme. The sample was then separated from the substrate and its warpage deformation was measured. If the warpage exceeds a preset threshold, it indicates that the residual stress caused by the interlayer soft-hard heterogeneous structure is too large, and the equivalent yield strength predicted by the original basic quantitative relationship can no longer accurately reflect the mechanical properties of the actual formed specimen. Then, return to the mechanical property control model construction step in step S2, and introduce warpage correction parameters and interface strengthening parameters of the microstructure of the interlayer soft layer and hard layer into the basic quantitative relationship of the model for correction (such as introducing warpage δ and strengthening factor G) to obtain the optimized combined yield strength quantitative relationship. At the same time, based on the differences in microstructure and dislocation density between scanning trajectories, the scanning trajectory combination method is redesigned and adjusted (such as adjusting the number of consecutive printing layers, the alternating position between layers, etc.) to balance the interlayer residual stress, and re-predict and match based on the corrected mechanical property control model to construct a new interlayer scanning trajectory combination scheme.

[0037] If the warpage deformation does not exceed a preset threshold, it indicates that the residual stress of the interlayer scanning trajectory combination is within a controllable range, the heterogeneous microstructure is stably preserved without significant deformation, and this combination scheme can be directly used as the final execution scheme, effectively ensuring the gradient mechanical properties and dimensional accuracy of the formed part. Thus, step S4 forms a closed-loop control mechanism of "prediction-forming-measurement-correction-redesign," thereby improving the matching accuracy of the interlayer scanning trajectory combination scheme with the target mechanical properties and forming quality.

[0038] In one embodiment, step S5 performs multi-laser powder bed melting forming according to the interlayer scanning trajectory combination scheme to obtain a Ti-6Al-4V alloy forming part with a gradient distribution of mechanical properties, specifically including: Multi-laser powder bed melting is performed according to the interlayer scanning trajectory combination scheme that has been predicted, matched and verified by warpage correction. The microstructure is controlled by the combination of scanning trajectories, and quantitative prediction is performed by combining the mechanical property control model established in step S2. Gradient control of the mechanical properties of the printed Ti-6Al-4V alloy can be achieved without material replacement, introduction of external energy field and post-processing.

[0039] Microstructure observations were performed on specimens with single scanning trajectories and specimens with combined interlayer scanning trajectories. The results are as follows: Figure 4 As shown, specimens formed by single scanning trajectories such as H and Z exhibit a relatively uniform microstructure, while specimens under the L33 combination strategy show significant microstructure stratification, exhibiting a three-layer sandwich structure. This three-layer sandwich heterogeneous structure demonstrates that by rationally selecting the combination sequence of scanning trajectories and the number of alternating layers, a stable and retained interlayer heterogeneous microstructure can be constructed within Ti-6Al-4V alloy printed components, providing an microstructure basis for achieving gradient mechanical property control and synergistic effects of strength and plasticity.

[0040] Based on the above experimental results, parameters such as the scanning trajectory type, influence zone height, ideal interlayer spacing, actual interlayer height, equivalent yield strength, warpage deformation, and corresponding microstructure characteristics that enable effective mechanical property control will be extracted and recorded in the database for subsequent gradient mechanical property control design of different target components.

[0041] Based on the same concept, this invention provides a device for gradient control of mechanical properties of Ti-6Al-4V alloy formed by multi-laser powder bed melting based on scanning trajectory combination, comprising: The data acquisition module is used to acquire mechanical property data of Ti-6Al-4V alloy samples formed by multi-laser powder bed melting under different scanning trajectories; The model building module is used to construct a mechanical property control model for Ti-6Al-4V alloy specimens based on the mechanical property data. The mechanical property control model includes at least the influence of the scanning trajectory on the morphology of the molten pool, the height of the influence zone and the interlayer coupling relationship, and establishes a quantitative relationship between the combination of interlayer scanning trajectories and the yield strength of the formed specimen. The influence zone height determination and judgment module is used to determine the influence zone height of a single scanning trajectory based on the mechanical performance control model, and to determine whether the interlayer heterogeneous microstructure is preserved based on the matching relationship between the influence zone height and the alternation height between trajectory layers. The combination scheme construction module is used to select at least two different scanning trajectories as target scanning trajectories when determining the retention of interlayer heterogeneous microstructure, and to construct an interlayer scanning trajectory combination scheme to achieve gradient control of the mechanical properties of Ti-6Al-4V alloy. The interlayer scanning trajectory combination scheme is based on the printing layer, and at least two different scanning trajectories are used in alternating and / or sequential combinations along the forming direction and / or in the specified area. The forming execution module is used to perform multi-laser powder bed melting forming according to the interlayer scanning trajectory combination scheme to obtain a Ti-6Al-4V alloy forming part with a gradient distribution of mechanical properties. The implementation principle of the above module has been described in the foregoing embodiments and will not be repeated here.

[0042] Based on the same concept, an electronic device is also provided in some embodiments of this application. This electronic device includes a memory and a processor, wherein the memory stores a processing program, and the processor executes the processing program according to instructions. When the processor executes the processing program, the method for gradient control of the mechanical properties of Ti-6Al-4V alloy based on scanning trajectory combinations in the foregoing embodiments is realized.

[0043] In some embodiments of this application, a readable storage medium is also provided, which can be either a non-volatile or volatile readable storage medium. This readable storage medium stores instructions that, when executed on a computer, cause an electronic device containing such a readable storage medium to perform the aforementioned method for gradient control of the mechanical properties of Ti-6Al-4V alloy based on a combination of scan trajectories obtained by multi-laser powder bed melting.

[0044] It is understood that, regarding the aforementioned method for gradient control of mechanical properties of Ti-6Al-4V alloy based on multi-laser powder bed melting and forming using scanning trajectory combinations, if all of these methods are implemented as software functional modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0045] Computer-readable storage media may include data signals propagated in baseband or as part of a carrier wave, carrying readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A readable storage medium may also be any readable medium other than a readable storage medium that can transmit, propagate, or transfer a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the readable storage medium may be transmitted using any suitable medium, including but not limited to wireless, wired, optical fiber, RF, etc., or any suitable combination thereof.

[0046] The program code for executing the technical solutions disclosed in this application can be written in any combination of one or more programming languages. These programming languages ​​include object-oriented programming languages—such as Java and C++—and conventional procedural programming languages—such as C or similar languages. The program code can be executed entirely on the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server. In cases involving remote computing devices, the remote computing device can be connected to the user's computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for gradient control of mechanical properties of Ti-6Al-4V alloy formed by multi-laser powder bed melting based on scanning trajectory combination, characterized in that, include: Mechanical property data of Ti-6Al-4V alloy samples formed by multi-laser powder bed melting under different scanning trajectories were obtained; Based on the mechanical property data, a mechanical property control model for Ti-6Al-4V alloy specimens was constructed. The mechanical property control model includes at least the influence of the scanning trajectory on the morphology of the molten pool, the height of the affected zone, and the interlayer coupling relationship, and establishes a quantitative relationship between the combination of interlayer scanning trajectories and the yield strength of the formed specimen. Based on the aforementioned mechanical performance control model, the height of the influence zone of a single scanning trajectory is determined, and the interlayer heterogeneous microstructure is judged to be preserved based on the matching relationship between the height of the influence zone and the alternation height between trajectory layers. When determining the retention of interlayer heterogeneous microstructure, at least two different scanning trajectories are selected as target scanning trajectories, and an interlayer scanning trajectory combination scheme is constructed to achieve gradient control of the mechanical properties of Ti-6Al-4V alloy. Multi-laser powder bed melting is performed according to the interlayer scanning trajectory combination scheme to obtain Ti-6Al-4V alloy forming parts with a gradient distribution of mechanical properties.

2. The method for gradient control of mechanical properties of Ti-6Al-4V alloy based on scanning trajectory combination as described in claim 1, characterized in that, The method for constructing the interlayer scanning trajectory combination also includes: A Ti-6Al-4V alloy sample was formed according to the interlayer scanning trajectory combination scheme. The sample was then separated from the substrate and its warpage deformation was measured. If the warping deformation exceeds a preset threshold, the process returns to the construction step of the mechanical performance control model, warping deformation correction parameters are introduced, and the interlayer scanning trajectory combination scheme is reconstructed based on the corrected mechanical performance control model.

3. The method for gradient control of mechanical properties of Ti-6Al-4V alloy based on scanning trajectory combination as described in claim 1, characterized in that, The acquisition of mechanical property data for Ti-6Al-4V alloy samples formed by multi-laser powder bed melting under different scanning trajectories includes: Ti-6Al-4V alloy basic samples corresponding to different scanning trajectories were prepared using at least two different scanning trajectories; Tensile tests were performed on the base specimens corresponding to different scanning trajectories along at least two different loading directions to obtain mechanical property data of at least one of yield strength, tensile strength and elongation under different loading directions. The molten pool morphology and microstructure of the base specimens corresponding to different scanning trajectories are characterized, and a mapping relationship between scanning trajectory, microstructure and mechanical properties is established in combination with the mechanical property data.

4. The method for gradient control of mechanical properties of Ti-6Al-4V alloy based on scanning trajectory combination as described in claim 1, characterized in that, The construction of the mechanical property control model includes: Based on the correspondence between laser energy density and molten pool morphology, the height of the influence zone for different scanning trajectories is determined; wherein, the laser energy density is determined by laser power, scanning speed, molten pool spacing, and printing layer thickness; Determine the ideal interlayer spacing of the scanning trajectory based on the number of printing layers and the printing layer thickness corresponding to a single scanning trajectory. Based on the ratio of the ideal interlayer spacing to the height of the affected zone, a dimensionless parameter characterizing the interlayer coupling relationship is determined. Based on the dimensionless parameter, it is determined whether the interlayer heterogeneous microstructure is preserved; when the dimensionless parameter is greater than 1, it is determined that the interlayer heterogeneous microstructure is preserved. When the interlayer heterogeneous microstructure is preserved, the true layer height of the scanning trajectory is determined based on the height of the affected area and the number of printed layers. Combined with the yield strength corresponding to each scanning trajectory, a basic quantitative relationship is established between the combination of interlayer scanning trajectories and the equivalent yield strength of the formed specimen. When there is warping deformation in the combination of interlayer scanning trajectories, the warping deformation amount and the strengthening factor of the microstructure of the soft and hard layers in the interlayer are introduced into the basic quantitative relationship for correction, so as to obtain the optimized quantitative relationship of combined yield strength.

5. The method for gradient control of mechanical properties of Ti-6Al-4V alloy based on scanning trajectory combination as described in claim 4, characterized in that, The determination of whether the interlayer heterogeneous microstructure is preserved includes: The height of the influence area of ​​a single scan trajectory is compared with the alternation height between trajectory layers, wherein the alternation height between trajectory layers is the ideal interlayer spacing; When the height of the affected area is less than the alternation height between the trajectory layers, the dimensionless parameter is greater than 1, and it is determined that the heterogeneous microstructure between the layers is preserved. When the height of the affected area is equal to the height of the alternation between the trajectory layers, the dimensionless parameter is equal to 1, and the heterogeneous microstructure between the layers is determined to be in a critical coupling state. When the height of the affected area is greater than the alternation height between the trajectory layers, the dimensionless parameter is less than 1, and it is determined that the heterogeneous microstructure between layers is not retained.

6. The method for gradient control of mechanical properties of Ti-6Al-4V alloy based on scanning trajectory combination as described in claim 1, characterized in that, The scheme for constructing interlayer scanning trajectory combinations includes: Based on the mechanical property distribution requirements of the target forming area, at least two scanning trajectories capable of forming different microstructure characteristics are selected as the target scanning trajectory. The distribution order of each target scanning trajectory in the forming direction, the number of consecutive printing layers, and the alternation position between layers are determined in order to construct an interlayer scanning trajectory combination structure with heterogeneous microstructure layering characteristics; Based on the mechanical property control model, the equivalent yield strength corresponding to the interlayer scanning trajectory combination structure is predicted, and the prediction result is matched with the target mechanical property distribution requirements. The corresponding inter-layer scanning trajectory combination scheme is determined based on the matching results.

7. The method for gradient control of mechanical properties of Ti-6Al-4V alloy based on scanning trajectory combination as described in claim 4, characterized in that, The quantitative relationship between the interlayer scanning trajectory combination and the equivalent yield strength of the formed specimen includes: The basic equivalent yield strength is calculated by summing the products of the yield strength corresponding to each scanning trajectory and the proportion of the actual layer height of the scanning trajectory in the forming direction; When the interlayer scanning trajectories combine to form a heterogeneous microstructure with alternating soft and hard layers, a correction term consisting of the yield strength difference between soft and hard layers, the interface strengthening factor, and microstructure parameters is introduced on the basis of the basic equivalent yield strength to obtain the optimized equivalent yield strength of the shaped specimen.

8. A device for gradient control of mechanical properties of Ti-6Al-4V alloy based on scanning trajectory combination in multi-laser powder bed melting, characterized in that, include: The data acquisition module is used to acquire mechanical property data of Ti-6Al-4V alloy samples formed by multi-laser powder bed melting under different scanning trajectories; The model building module is used to construct a mechanical property control model for Ti-6Al-4V alloy specimens based on the mechanical property data. The mechanical property control model includes at least the influence of the scanning trajectory on the morphology of the molten pool, the height of the influence zone and the interlayer coupling relationship, and establishes a quantitative relationship between the combination of interlayer scanning trajectories and the yield strength of the formed specimen. The influence zone height determination and judgment module is used to determine the influence zone height of a single scanning trajectory based on the mechanical performance control model, and to determine whether the interlayer heterogeneous microstructure is preserved based on the matching relationship between the influence zone height and the alternation height between trajectory layers. The combined scheme construction module is used to select at least two different scanning trajectories as target scanning trajectories when determining the retention of interlayer heterogeneous microstructure, and to construct a combined scheme of interlayer scanning trajectories to achieve gradient control of the mechanical properties of Ti-6Al-4V alloy. The forming execution module is used to perform multi-laser powder bed melting forming according to the interlayer scanning trajectory combination scheme to obtain Ti-6Al-4V alloy forming parts with a gradient distribution of mechanical properties.

9. An electronic device, characterized in that, include: The memory is used to store the processing program; A processor, which, when executing the processing program, implements the method for gradient control of mechanical properties of Ti-6Al-4V alloy based on scanning trajectory combination as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for gradient control of mechanical properties of Ti-6Al-4V alloy based on scanning trajectory combination as described in any one of claims 1-7.

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