Heterogeneous alloy additive manufacturing method based on tenon-and-mortise connection

Abstract

The invention provides a heterogeneous alloy additive manufacturing method based on tenon-and-mortise connection, and relates to the technical field of laser additive manufacturing of heterogeneous alloys. The method comprises the following steps: firstly, selecting two alloys as experimental raw materials, and determining brittle phases possibly formed in the additive and smelting processes; a load characteristic and interface failure mode correlation model is established according to the service condition of the heterogeneous component, and the geometrical shape of the heterogeneous interface is designed according to the difference of dominant stress of different structures; a laser additive manufacturing technology is adopted for conducting layer-by-layer printing on the pretreated substrate, a first metal component is obtained, stress relief treatment is conducted on the first metal component, surface texturing treatment is conducted on the first metal component, a textured area is coated with metal B-molding powder, and after the volatilizable solvent is completely volatilized, a second metal component is obtained; and the first metal component is placed in a vacuum heat treatment furnace, a second metal component is manufactured, the laser additive manufacturing technology is continuously used for printing, and a third metal component, namely the needed heterogeneous metal component, is obtained.

Description

Technical Field

[0001] This invention relates to the field of laser additive manufacturing of heterogeneous alloys, and in particular to a heterogeneous alloy additive manufacturing method based on mortise and tenon joints. Background Technology

[0002] With the rapid development of science and technology in my country, the requirements for metallic materials are becoming increasingly stringent. Some single metallic materials can no longer meet the needs of application, while heterojunctions can achieve lightweight, high performance, and low cost while meeting mechanical performance requirements. However, due to the significant differences in melting point, thermal conductivity, and coefficient of linear expansion among most heterojunctions, brittle phase layers are easily formed at the joints, and stress concentration occurs near the brittle phases, leading to cracking at the interface and reducing the bonding strength. Therefore, improving the bonding strength of heterojunction interfaces has become a major research trend.

[0003] Currently, the main methods for improving interfacial bonding strength include: material gradient design, welding, and laser shock blasting. Material gradient design refers to continuously changing the mixing ratio of two materials along the interface normal direction. Its core is to eliminate or reduce abrupt changes in the physical, chemical, or mechanical properties of the material interface, thereby reducing stress concentration, improving load transfer, and inhibiting crack initiation and propagation. Welding mainly includes arc welding, friction welding, and laser welding, but the high temperature during welding can easily lead to grain coarsening and phase transformation, weakening the heat-affected zone. Laser shock blasting uses high-energy short-pulse lasers to bombard the absorption layer covering the material surface, introducing residual compressive stress and dislocation multiplication on the surface. However, excessive energy can lead to micro-craters or micro-cracks, and complex structures such as small holes and deep grooves are difficult to uniformly process. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a heterogeneous alloy additive manufacturing method based on mortise and tenon joints. The aim is to provide an additive manufacturing method that enhances the bonding of brittle heterogeneous metals by controlling interface morphology. This method designs heterogeneous interface bonding forms for different load conditions, optimizes the interface bonding mechanism, and transforms flat, brittle interfaces into mortise and tenon joint interfaces that effectively resist complex loads. It also improves the crack propagation pattern during the cracking process of brittle interfaces, effectively transforming Type I opening cracks propagating along the interface into mixed Type II and Type III cracks, thereby effectively improving the interfacial bonding strength between heterogeneous metal materials. This innovative method establishes a correspondence between stress conditions and interface morphology, achieving directional strengthening design of the interface structure, ultimately achieving a significant improvement in the overall strength of additively manufactured composite structures.

[0005] The technical solution of this invention is as follows:

[0006] A heterogeneous alloy additive manufacturing method based on mortise and tenon joints includes the following steps:

[0007] Step 1: Based on the elemental composition of the heterojunctions to be joined, find the thermodynamic phase diagram. Based on the activation energy of various compounds, select two alloys as experimental raw materials to determine the brittle phases that may be formed during the additive and melting processes. At the same time, based on the melting and boiling points of the two alloys, the alloy with the higher melting point is selected as the first additive part and named Metal A, and the metal with the lower melting point is selected as the pre-melting part and the subsequent additive part. The pre-melting part and the subsequent additive part are named Metal B-melting and Metal B-additive, respectively.

[0008] Step 2: Establish a correlation model between load characteristics and interface failure modes based on the service conditions of heterogeneous components;

[0009] The service conditions of the heterogeneous components include static load and dynamic load;

[0010] The load characteristics and interface failure mode association model includes four modes, specifically (1)-(4):

[0011] (1) Axial tensile stress dominates:

[0012] A crack caused by tensile stress perpendicular to a heterogeneous surface exhibits an opening crack pattern, which can be represented by the following formula for the interfacial stress field:

[0013] ;

[0014] ;

[0015] ;

[0016] In the formula This represents the normal stress along the horizontal x-axis at the crack tip. τ represents the normal stress at the crack tip perpendicular to the y-axis. xy K represents the shear stress in the xy-plane at the crack tip. Ⅰ denoted as Type I stress intensity factor, r represents the distance from the crack tip to a point on the crack, and θ represents the angle of counterclockwise rotation from the crack extension line;

[0017] (2) Shear stress dominates at the heterogeneous interface:

[0018] When shear stress is coupled with local tensile stress, the crack tilts into the material, and the formula for the interfacial stress field is:

[0019] ;

[0020] ;

[0021] ;

[0022] In the formula K ⅡThis indicates the type II stress intensity factor.

[0023] (3) External shear stress dominates at heterogeneous interfaces:

[0024] The heterogeneous interface is subjected to torsional load and interlaminar three-dimensional shear. The stress field formula at the interface is:

[0025] ;

[0026] ;

[0027] In the formula This represents the shear stress at the crack tip in the xz-axis plane of the three-dimensional coordinate system. K represents the shear stress at the crack tip in the yz-axis plane of the three-dimensional coordinate system. Ⅲ This indicates the type III stress intensity factor.

[0028] (4) Mixed mode stress:

[0029] Criteria for determining mixed mode:

[0030] ;

[0031] In the formula G Ⅰ G represents the type I energy release rate. Ⅱ G represents the type II energy release rate. IC G represents the pure type I fracture toughness. IIC This represents pure type II fracture toughness, where α and β are material constants.

[0032] Step 3: Based on the differences in dominant stress of different structures, design the geometry of the heterogeneous interface and perform three-dimensional structural design on the top part of the high melting point alloy, i.e., metal A.

[0033] The three-dimensional structure specifically includes: a dovetail joint interface structure that resists tensile stress, a reverse bracing structure that resists internal shear stress, a biomimetic blade-like structure that resists external shear stress, and a ring-shaped wave structure that resists mixed-mode stress.

[0034] The dovetail joint interface structure that resists tensile stress is specifically designed as follows: based on the existing mortise and tenon structure, the right-angled sides of the mortise and tenon structure are transformed into rounded corners, and the tensile stress at the interface is redistributed through the stress dispersion principle.

[0035] The reverse pseudo-diagonal bracing structure resisting interfacial shear stress is specifically as follows: when the interface of the heterogeneous composite structure is subjected to in-plane unidirectional shear stress, causing directional crack propagation, a diagonal support unit with a set angle is set along the opposite direction of crack propagation, and a multi-directional constraint is formed by using the mechanical interlocking mechanism between adjacent units.

[0036] The set angle is between 75° and 85°;

[0037] The biomimetic blade-like structure resisting external shear stress at the interface is specifically designed as follows: when a helical crack is generated at the interface of the heterogeneous composite structure under external shear stress, a unidirectional array of blades is designed, utilizing the geometric anisotropy of the blade array to change the crack propagation path; wherein the blade thickness t and the number of blades n are determined based on fracture mechanics theory: firstly, through the interfacial shear strength τ... int With external shear stress τ ext The equilibrium relationship n×t×L×τ int ≥τ ext The preliminary estimate of the total blade thickness is n×t, where L is the blade length, A is the interface area, and τ is the total thickness of the blade. int The shear strength of the blade material is given; then, by adjusting the number of blades n=A / (d×L) and the thickness of a single blade layer t, the load is evenly distributed, where d is the center-to-center distance between adjacent blades;

[0038] The aforementioned annular wave structure for resisting mixed-mode stress is specifically designed to address interface failure caused by varying stress fields in heterogeneous composite materials under mixed stress modes. The structural parameters are dynamically adjusted according to the stress level: when local stress decreases, interface failure is suppressed by reducing structural constraints. Specifically, the geometry of the wave interface, i.e., the wave height and the gap between adjacent annular interfaces, is adjusted according to the stress level gradient. Specifically, a stress level is set; for each level decrease in stress, the wave height decreases by 0.2 mm, while the gap between adjacent annular wave interfaces increases by 0.5 mm.

[0039] Step 4: Pre-treat metal A and the substrate;

[0040] Metal A powder was dried in a vacuum environment, the substrate was polished, and the residue left after polishing was removed with organic solvent. The substrate was then fixed and its position was adjusted.

[0041] Step 5: Based on the interface design in Step 3, and combined with the pre-processed metal A and substrate in Step 4, laser additive manufacturing technology is used to print layer by layer on the pre-processed substrate to obtain the first metal component, and stress relief treatment is performed on the first metal component.

[0042] Step 6: The surface of the first metal component is roughened, and the pretreated metal B-melting powder is coated onto the roughened area at a set thickness;

[0043] The pretreatment process of metal B-melting powder is as follows: the metal B-melting powder is immersed in a volatile solvent, and after it has completely settled to the bottom of the solvent, the settled powder is taken out. The settled powder is clean metal B-melting powder after removing impurities.

[0044] Step 7: After the volatile solvent on the surface of the clean metal B-melting powder has completely evaporated, place the first metal component coated with metal B-melting powder in a vacuum heat treatment furnace and heat it for 5 min to 20 min at a temperature higher than the melting point of metal B but lower than the melting point of metal A to obtain the second metal component.

[0045] Step 8: Continue to print metal B-additive powder on the second metal component using laser additive manufacturing technology to obtain a third metal component, which is the desired heterogeneous metal component.

[0046] The beneficial effects of adopting the above technical solution are as follows:

[0047] This invention provides a heterogeneous alloy additive manufacturing method based on mortise and tenon joints. The core innovation lies in introducing and utilizing the mechanical interlocking effect of mortise and tenon-like structures to significantly enhance the connection strength between dissimilar metals. Compared to the traditional method of directly melting and depositing a second low-melting-point metal onto the smooth surface of a first high-melting-point metal, this invention employs a unique three-dimensional structural design at the joint tip of the first high-melting-point metal, pre-constructing mortise and tenon-like geometric features with anchoring properties. Subsequently, when the second low-melting-point metal is melted and printed onto the first metal, the molten low-melting-point metal fully fills, encapsulates, and embeds itself into these pre-designed mortise and tenon structure gaps. After the metal cools and solidifies, these microscopic or macroscopic mortise and tenon structures act like "mechanical latches," forming a strong mechanical fit and interlock at the interface between the two metals. This physical anchoring effect based on geometric morphology fundamentally surpasses traditional methods that rely solely on metallurgical bonding or planar adhesion, thereby greatly strengthening the overall connection strength and structural reliability between two metals with different melting points. Attached Figure Description

[0048] Figure 1 Failure model and interface design diagram dominated by axial tensile stress;

[0049] Where (a) is the tensile stress-dominated failure model, and (b) is the dovetail joint interface connection diagram resisting tensile stress.

[0050] Figure 2 Failure model and interface design diagram dominated by in-plane shear stress;

[0051] Where (a) is the failure model dominated by in-plane shear stress, and (b) is the interface connection diagram of the reverse pseudo-brace resisting in-plane shear stress.

[0052] Figure 3 Failure model and interface design diagram dominated by external shear;

[0053] (a) - Failure model dominated by external shear stress, (b) - Bionic blade interface connection resisting external shear force and local magnified view of the bionic blade interface.

[0054] Figure 4 Failure model and interface design diagram for mixed stress;

[0055] Where (a) is the failure model of mixed stress, and (b) is the connection diagram of the annular wave interface resisting mixed stress.

[0056] Figure 5 This is a detailed flowchart of the hetero alloy additive manufacturing method according to an embodiment of the present invention;

[0057] Figure 6 This is a diagram of a titanium alloy component coated with aluminum alloy powder according to an embodiment of the present invention;

[0058] Figure 7 This is a diagram of the component after melting according to an embodiment of the present invention;

[0059] Figure 8 The diagram shows a composite component made of Tc4 titanium alloy and 7075 aluminum alloy according to an embodiment of the present invention. Detailed Implementation

[0060] The specific implementation methods of this application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0061] A heterogeneous alloy additive manufacturing method based on mortise and tenon joints is proposed. Its core lies in the customized design of different mortise and tenon interface geometries based on the stress distribution characteristics of the heterogeneous material bonding area through microtexture design. High-melting-point metal powder is then layered onto the pre-treated substrate surface using additive manufacturing technology, combined with high-temperature melting technology, ultimately forming a heterogeneous metal component with both high bonding strength and fatigue resistance. The specific process is as follows: Figure 5 As shown, it includes the following steps:

[0062] Step 1: Based on the elemental composition of the heterojunctions to be joined, find the thermodynamic phase diagram. Based on the activation energy of various compounds, select two alloys as experimental raw materials to determine the brittle phases that may be formed during the additive and melting processes. At the same time, based on the melting and boiling points of the two alloys, the alloy with the higher melting point is selected as the first additive part and named Metal A, and the metal with the lower melting point is selected as the pre-melting part and the subsequent additive part. The pre-melting part and the subsequent additive part are named Metal B-melting and Metal B-additive, respectively.

[0063] Step 2: In heterogeneous alloy interfaces, due to differences in material properties (such as elastic modulus, coefficient of thermal expansion, and fracture toughness), the stress distribution at the interface is complex, leading to different cracking modes. First, a correlation model between load characteristics and interface failure modes is established based on the service conditions of heterogeneous components;

[0064] The service conditions of the heterogeneous components include static load and dynamic load;

[0065] The load characteristics and interface failure mode association model includes four modes, specifically (1)-(4):

[0066] (1) Axial tensile stress dominates (similar to type I crack):

[0067] Interfacial cracking caused by thermal expansion mismatch, external tensile load, and phase transformation volume change; cracks caused by tensile stress perpendicular to the surface of the heterogeneous material; cracks exhibiting an opening type; the interfacial stress field formula is expressed as follows:

[0068] ;

[0069] ;

[0070] ;

[0071] In the formula This represents the normal stress along the horizontal x-axis at the crack tip. τ represents the normal stress at the crack tip perpendicular to the y-axis. xy K represents the shear stress in the xy-plane at the crack tip. Ⅰ denoted as Type I stress intensity factor, r represents the distance from the crack tip to a point on the crack, and θ represents the angle of counterclockwise rotation from the crack extension line;

[0072] When subjected to axial tensile stresses F1 and F2, an axial tensile stress field is generated; this type of stress field easily forms straight or wavy crack paths (such as...). Figure 1 As shown in (a), the criterion for judging the propagation of interface cracks is K. I >K IC K IC Indicates the interfacial fracture toughness;

[0073] (2) Shear stress dominates at the heterogeneous interface (similar to type II crack):

[0074] The stress sources between these heterogeneous interfaces are interface slip, interlaminar shear load, and cyclic shear fatigue. When shear stress is coupled with local tensile stress, cracks tilt into the material (hybrid-mode fracture). The formula for the interface stress field is:

[0075] ;

[0076] ;

[0077] ;

[0078] In the formula K Ⅱ This represents the type II stress intensity factor.

[0079] When subjected to external transverse shear forces V1 and V2, an in-plane shear stress field will be generated at the interface. This type of stress field is prone to shear propagation along the interface, resulting in delamination or sheet-like peeling (e.g. Figure 2 As shown in (a), when shear stress is coupled with local tensile stress, the crack may tilt into a certain material (mixed-mode fracture), and the fracture criterion is K. II / K IC +K I / K IC =1.

[0080] (3) External shear stress dominates at the heterogeneous interface (similar to type III crack):

[0081] Heterogeneous interfaces primarily bear torsional loads and interlaminar three-dimensional shear (such as composite laminates). The formula for the interfacial stress field is:

[0082] ;

[0083] ;

[0084] In the formula This represents the shear stress at the crack tip in the xz-axis plane of the three-dimensional coordinate system. K represents the shear stress at the crack tip in the yz-axis plane of the three-dimensional coordinate system. Ⅲ This indicates the type III stress intensity factor.

[0085] When subjected to bidirectional torsional loads T1 and T2, shear stress will be generated outside the interface, and the crack will propagate spirally along the interface (e.g., Figure 3 In (a) ), a spiral or serrated fracture surface is formed, or multi-directional shearing leads to interlayer debonding, which is common in layered heterostructures. Out-of-plane fracture toughness (K IIIC : It is usually much lower than Type I toughness and is prone to tearing.

[0086] (4) Mixed-mode stress (Type I+II+III coupling):

[0087] Since the heterogeneous interface consists of two different alloys, their service conditions and load states are typically vastly different, leading to highly complex actual working conditions and exhibiting a mixed stress mode (such as...). Figure 4In (a), the cracks formed will deviate from the interface and extend along the direction of maximum energy release rate, and may even form bifurcated cracks.

[0088] Criteria for determining mixed mode:

[0089] ;

[0090] In the formula G Ⅰ G represents the type I energy release rate. Ⅱ G represents the type II energy release rate. IC G represents the pure type I fracture toughness. IIC This represents the pure type II fracture toughness, where α and β are material constants.

[0091] Step 3: Based on the differences in dominant stress of different structures, design the geometry of the heterogeneous interface and perform three-dimensional structural design on the top part of the high melting point alloy, i.e., metal A.

[0092] The three-dimensional structure specifically includes: a dovetail joint interface structure that resists tensile stress, a reverse bracing structure that resists internal shear stress, a biomimetic blade-like structure that resists external shear stress, and a ring-shaped wave structure that resists mixed-mode stress.

[0093] The dovetail joint interface structure for resisting tensile stress is specifically designed as follows: To improve the tensile performance of heterogeneous metal composite structures, while traditional dovetail joint structures can effectively resist normal stress perpendicular to the interface through the geometric self-locking effect of trapezoidal bevels, their sharp corner characteristics are not conducive to additive manufacturing processes. Therefore, a rounded dovetail joint structure (such as...) is innovatively designed. Figure 1 As shown in (b), based on the existing mortise and tenon structure, the arc-shaped inclined surface geometric self-locking mechanism is retained. Since the right-angled mortise and tenon structure is not conducive to printing and manufacturing, the right-angled sides of the mortise and tenon structure are transformed into rounded corners. Through the stress dispersion principle, the tensile stress at the interface is redistributed, which significantly enhances the overall tensile bearing capacity of the composite structure.

[0094] The aforementioned reverse-bracing structure resisting interfacial shear stress specifically refers to: when the interface of a heterogeneous composite structure is subjected to in-plane uniaxial shear stress, triggering directional crack propagation, a reverse-bracing structure design is proposed (e.g., Figure 2 As shown in (b), by setting oblique support units at a set angle along the opposite direction of crack propagation, multi-directional constraints are formed by using the mechanical interlocking mechanism between adjacent units. This not only effectively suppresses the unidirectional crack propagation behavior caused by shear stress, but also significantly improves the interface shear strength through stress redistribution.

[0095] The set angle is between 75° and 85°. Too small an angle will reduce the strength, while too large an angle will result in poor self-locking.

[0096] The biomimetic blade-like structure resisting external shear stress at the interface specifically refers to: when a helical crack is generated at the interface of a heterogeneous composite structure under external shear stress, a biomimetic blade-like interface reinforcement structure (such as...) is proposed. Figure 3 As shown in (b), a unidirectional blade array is designed, utilizing the geometric anisotropy of the blade array to alter the crack propagation path; where the blade thickness t and the number of blades n are determined based on fracture mechanics theory: firstly, through the interfacial shear strength τ int With external shear stress τ ext The equilibrium relationship n×t×L×τ int ≥τ ext The preliminary estimate of the total blade thickness is n×t, where L is the blade length, A is the interface area, and τ is the total thickness of the blade. int The shear strength of the blade material is given; by adjusting the number of blades n=A / (d×L) and the thickness of a single blade layer t, the load is evenly distributed, thereby effectively suppressing crack propagation, where d is the center-to-center distance between adjacent blades;

[0097] The aforementioned annular wave structure resisting mixed-mode stress specifically refers to: addressing the interface failure of heterogeneous composite materials under mixed stress modes caused by varying stress fields, a annular wave interface structure designed along the stress boundary is proposed (e.g., Figure 4 (as shown in (b)). This structure is designed to effectively resist dynamically changing stress loads converging from all directions. The structural parameters are dynamically adjusted according to the stress level: when the local stress decreases, the occurrence of interface failure is suppressed by reducing structural constraints; specifically, the geometry of the wave interface, i.e., the wave height and the gap between adjacent annular interfaces, will be adjusted with the stress level gradient. Specifically, for each stress level decrease, the wave height of the interface decreases by 0.2 mm, while the gap between adjacent annular wave interfaces increases by 0.5 mm.

[0098] In this embodiment, the stress level for each stage is 200 Pa;

[0099] Step 4: Pre-treat metal A and the substrate;

[0100] Metal A powder is dried in a vacuum environment, and the substrate is polished. Organic solvent (such as anhydrous ethanol) is used to remove the stains remaining after polishing to ensure material cleanliness and process reliability. The substrate is then fixed and its position is adjusted.

[0101] Step 5: Based on the interface design in Step 3, and combined with the pre-processed metal A and substrate in Step 4, laser additive manufacturing technology is used to print layer by layer on the pre-processed substrate to obtain the first metal component, and stress relief treatment is performed on the first metal component.

[0102] Step 6: Roughen the surface of the first metal component and apply the pretreated metal B-melting powder to the roughened area at a set thickness (0.1-1 mm above the tenon).

[0103] The pretreatment process of metal B-melting powder is as follows: the metal B-melting powder is immersed in a volatile solvent, and after it has completely settled to the bottom of the solvent, the settled powder is taken out. The settled powder is clean metal B-melting powder after removing impurities.

[0104] Step 7: After the volatile solvent on the surface of the clean metal B-melting powder has completely evaporated, place the first metal component coated with metal B-melting powder in a vacuum heat treatment furnace and heat it for 5 min to 20 min at a temperature higher than the melting point of metal B but lower than the melting point of metal A to obtain the second metal component.

[0105] Step 8: Continue to print metal B-additive powder on the second metal component using laser additive manufacturing technology to obtain a third metal component, which is the desired heterogeneous metal component.

[0106] Example 1: The preparation steps are illustrated using the preparation of Ti-Al (Tc4-7075Al) hetero alloy as an example;

[0107] Step 1: Based on the thermodynamic phase diagram, TC4 titanium alloy and 7075 aluminum alloy were selected as research objects. A Ti-Al binary system phase diagram was constructed using thermodynamic software, and the formation rules of the interfacial reaction products were systematically analyzed. It was found that the brittle phase that may be generated in the Ti-Al interfacial reaction is mainly the intermetallic compound Al3Ti. The phase diagram calculation results show that the formation of Al3Ti is inhibited when the temperature is below 750℃. Based on this thermodynamic criterion, to ensure that the formation of brittle phases is effectively avoided during the interfacial reaction, the subsequent experimental temperature should be controlled below the critical temperature of 750℃. Based on the melting points of TC4 titanium alloy (1400℃) and 7075 aluminum alloy (635℃), respectively, TC4 titanium alloy was designated as the first additive part (named Metal A), and 7075 aluminum alloy was designated as the pre-melting part and the subsequent additive part (named Metal B-melting and B-additive, respectively).

[0108] Step 2: Since Ti-Al hetero alloy joints are mainly used in the aerospace field to withstand axial static loads, i.e. tensile stress, a failure model dominated by tensile stress is constructed.

[0109] Step 3: Based on the dominant stress and failure model obtained in Step 2, in order to reduce this type of cracking, a dovetail joint interface structure is selected as the bonding form of the heterogeneous interface. When designing the curved transition slope, the radius of curvature is designed to be 80-85°. This angle range not only ensures the self-locking stability of the tenon and mortise contact surface under axial load, but also effectively reduces the stress concentration factor at the interface tip by optimizing the radius of curvature.

[0110] Step 4: Pre-treat the Tc4 powder and Tc4 substrate; dry the Tc4 powder in a vacuum environment, polish the Tc4 substrate to a smooth surface, and wipe the surface clean with anhydrous ethanol and alcohol cotton. After ensuring that the equipment prints correctly, fix the substrate to the work platform with screws.

[0111] Step 5: Using a laser with a power of 2000W and a scanning speed of 10mm / s, titanium alloy rounded dovetail tenon components are prepared in a pure argon environment by a short-side unidirectional reciprocating scanning method. After the process is completed, the formed parts are cooled to room temperature, removed and placed in a vacuum heat treatment furnace for annealing. The temperature is set at 600℃ and held for 4 hours before being cooled in the furnace to remove residual stress.

[0112] Step 6: Roughen the surface of the titanium alloy component obtained in Step 5, and immerse the B-melting powder in acetone until fully wetted. The powder-to-acetone volume ratio is 1:10. After the powder settles to the bottom of the solution, remove it and evenly brush it onto the surface of the titanium alloy component. Use a scraper to shape the powder, controlling the thickness to about 1 mm. Figure 6 As shown;

[0113] Step 7: After the acetone has completely evaporated, place the titanium alloy component and the pre-placed metal B-melting powder into a vacuum heat treatment furnace. Based on the melting points of TC4 titanium alloy and 7075 aluminum alloy being 1400℃ and 635℃ respectively, and the phase transformation temperature of TC4 titanium alloy being 998℃, the furnace temperature is set to 650℃. After maintaining this temperature for 10 minutes, the vacuum heat treatment furnace is turned off, allowing the component inside the furnace to cool to room temperature, resulting in the structure shown below. Figure 7 As shown;

[0114] Step 8: Continue laser additive manufacturing of the aluminum alloy components on the obtained TC4 titanium alloy and pre-placed aluminum alloy metal layers. Set the parameters as follows: laser power 2000W, scanning speed 8mm / s, scanning spacing 2mm. The final result is a composite structure of TC4 titanium alloy and 7075 aluminum alloy, as shown below. Figure 8 As shown.

[0115] A hetero-alloy additive manufacturing method based on mortise and tenon joints includes, but is not limited to, the joint manufacturing of Ti / Al hetero-alloys. It is applicable to the jointing of hetero-alloy combinations that may precipitate brittle intermetallic compounds during the additive manufacturing process, such as Al / Fe, Al / Cu, Mg / Fe, etc.

[0116] The various embodiments in this application are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0117] The scope of protection of this application is not limited to the embodiments described above. Obviously, those skilled in the art can make various modifications and variations to this disclosure without departing from the scope and spirit of this disclosure. If such modifications and variations fall within the scope of the disclosed solution and its equivalents, then the intent of this disclosure also includes these modifications and variations.

Claims

1. A heterogeneous alloy additive manufacturing method based on mortise and tenon joints, characterized in that, Includes the following steps: Step 1: Based on the elemental composition of the heterojunctions to be joined, find the thermodynamic phase diagram. Based on the activation energy of various compounds, select two alloys as experimental raw materials to determine the brittle phases that may be formed during the additive and melting processes. At the same time, based on the melting and boiling points of the two alloys, the alloy with the higher melting point is selected as the first additive part and named Metal A, and the metal with the lower melting point is selected as the pre-melting part and the subsequent additive part. The pre-melting part and the subsequent additive part are named Metal B-melting and Metal B-additive, respectively. Step 2: Establish a correlation model between load characteristics and interface failure modes based on the service conditions of heterogeneous components; Step 3: Based on the differences in dominant stress of different structures, design the geometry of the heterogeneous interface and perform three-dimensional structural design on the top part of the high melting point alloy, i.e., metal A. Step 4: Pre-treat metal A and the substrate; Metal A powder was dried in a vacuum environment, the substrate was polished, and the residue left after polishing was removed with organic solvent. The substrate was then fixed and its position was adjusted. Step 5: Based on the interface design in Step 3, and combined with the pre-processed metal A and substrate in Step 4, laser additive manufacturing technology is used to print layer by layer on the pre-processed substrate to obtain the first metal component, and stress relief treatment is performed on the first metal component. Step 6: The surface of the first metal component is roughened, and the pretreated metal B-melting powder is coated onto the roughened area at a set thickness; Step 7: After the volatile solvent on the surface of the clean metal B-melting powder has completely evaporated, place the first metal component coated with metal B-melting powder in a vacuum heat treatment furnace and heat it for 5 min to 20 min at a temperature higher than the melting point of metal B but lower than the melting point of metal A to obtain the second metal component. Step 8: Continue to print metal B-additive powder on the second metal component using laser additive manufacturing technology to obtain a third metal component, which is the desired heterogeneous metal component.

2. The heterogeneous alloy additive manufacturing method based on mortise and tenon joints according to claim 1, characterized in that, The service conditions of the heterogeneous components mentioned in step 2 include static load and dynamic load.

3. The heterogeneous alloy additive manufacturing method based on mortise and tenon joints according to claim 2, characterized in that, The load characteristics and interface failure mode association model described in step 2 includes four modes, specifically (1)-(4): (1) Axial tensile stress dominates: A crack caused by tensile stress perpendicular to a heterogeneous surface exhibits an opening crack pattern, which can be represented by the following formula for the interfacial stress field: , , In the formula This represents the normal stress along the horizontal x-axis at the crack tip. τ represents the normal stress at the crack tip perpendicular to the y-axis. xy K represents the shear stress in the xy-plane at the crack tip. Ⅰ denoted as Type I stress intensity factor, r represents the distance from the crack tip to a point on the crack, and θ represents the angle of counterclockwise rotation from the crack extension line; (2) Shear stress dominates at the heterogeneous interface: When shear stress is coupled with local tensile stress, the crack tilts into the material, and the formula for the interfacial stress field is: , , In the formula, K Ⅱ Indicates type II stress intensity factor; (3) External shear stress dominates at heterogeneous interfaces: The heterogeneous interface is subjected to torsional load and interlaminar three-dimensional shear. The stress field formula at the interface is: , In the formula This represents the shear stress at the crack tip in the xz-axis plane of the three-dimensional coordinate system. K represents the shear stress at the crack tip in the yz-axis plane of the three-dimensional coordinate system. Ⅲ Indicates Type III stress intensity factor; (4) Mixed mode stress: Criteria for determining mixed mode: In the formula G Ⅰ G represents the type I energy release rate. Ⅱ G represents the type II energy release rate. IC G represents the pure type I fracture toughness. IIC This represents the pure type II fracture toughness, where α and β are material constants.

4. The heterogeneous alloy additive manufacturing method based on mortise and tenon joints according to claim 1, characterized in that, The three-dimensional structure described in step 3 specifically includes: a dovetail-like interface structure that resists tensile stress, a reverse-brace-like structure that resists internal shear stress, a biomimetic blade-like structure that resists external shear stress, and a ring-shaped wave structure that resists mixed-mode stress. The dovetail joint interface structure that resists tensile stress is specifically designed as follows: based on the existing mortise and tenon structure, the right-angled sides of the mortise and tenon structure are transformed into rounded corners, and the tensile stress at the interface is redistributed through the stress dispersion principle. The reverse pseudo-diagonal bracing structure resisting interfacial shear stress is specifically as follows: when the interface of the heterogeneous composite structure is subjected to in-plane unidirectional shear stress, causing directional crack propagation, a diagonal support unit with a set angle is set along the opposite direction of crack propagation, and a multi-directional constraint is formed by using the mechanical interlocking mechanism between adjacent units. The biomimetic blade-like structure resisting external shear stress at the interface is specifically designed as follows: when a helical crack is generated at the interface of the heterogeneous composite structure under external shear stress, a unidirectional array of blades is designed, utilizing the geometric anisotropy of the blade array to change the crack propagation path; wherein the blade thickness t and the number of blades n are determined based on fracture mechanics theory: firstly, through the interfacial shear strength τ... int With external shear stress τ ext The equilibrium relationship n×t×L×τ int ≥τ ext The preliminary estimate of the total blade thickness is n×t, where L is the blade length, A is the interface area, and τ is the total thickness of the blade. int The shear strength of the blade material is given; then, by adjusting the number of blades n=A / (d×L) and the thickness of a single blade layer t, the load is evenly distributed, where d is the center-to-center distance between adjacent blades; The aforementioned annular wave structure for resisting mixed-mode stress is specifically designed to address interface failure caused by varying stress fields in heterogeneous composite materials under mixed stress modes. The structural parameters are dynamically adjusted according to the stress level: when local stress decreases, interface failure is suppressed by reducing structural constraints. Specifically, the geometry of the wave interface, i.e., the wave height and the gap between adjacent annular interfaces, is adjusted according to the stress level gradient. Specifically, a stress level is set; for each level decrease in stress, the wave height decreases by 0.2 mm, while the gap between adjacent annular wave interfaces increases by 0.5 mm.

5. The heterogeneous alloy additive manufacturing method based on mortise and tenon joints according to claim 4, characterized in that, The set angle is between 75° and 85°.

6. The heterogeneous alloy additive manufacturing method based on mortise and tenon joints according to claim 1, characterized in that, The pretreatment process of the metal B-melting powder in step 6 is as follows: the metal B-melting powder is immersed in a volatile solvent, and after it has completely settled to the bottom of the solvent, the settled powder is taken out. The settled powder is the clean metal B-melting powder after removing impurities.

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