A gamma-TiAl / TC4 bimetallic component and an electron beam melting integrated forming method thereof

Abstract

The present application relates to a kind of γ-TiAl / TC4 bimetallic component and its electron beam melting integrated forming method, belong to metal additive manufacturing and dissimilar material connection technical field.To solve the problem that interface accurate control is difficult to realize in the integrated forming of γ-TiAl / TC4 dissimilar material, high-quality metallurgical bonding cannot be obtained, the present application carries out electron beam forming in the way of gradient energy input, in initial cladding stage, energy input is carried out with gradually increasing or stepped volume energy density to realize component gentle transition, the gradient interface layer construction of controllable thickness, guarantee the stability and reliability of interface bonding, significantly improve the interface bonding strength and overall mechanical properties of bimetallic component, component room temperature tensile strength is stably kept above 300MPa, realize the accurate matching of interface structure and performance, improve the structural reliability and service safety of γ-TiAl / TC4 bimetallic component.

Description

Technical Field

[0001] This invention belongs to the field of metal additive manufacturing and dissimilar material joining technology, and particularly relates to a γ-TiAl / TC4 bimetallic component and its electron beam melting integrated forming method. Background Technology

[0002] The aerospace industry's demand for improved engine thrust-to-weight ratio and fuel efficiency has driven the development of lightweight, high-temperature resistant components. γ-TiAl alloys, with their low density and excellent high-temperature performance, are ideal materials for hot-end components such as turbine blades, but they suffer from high room-temperature brittleness and poor machinability. TC4 alloys, on the other hand, offer excellent comprehensive mechanical and machinability properties, making them suitable for load-bearing structures such as casings. Connecting these two materials to form a bimetallic composite structure, such as an integrated TiAl blade and TC4 disk, can fully leverage the material advantages, achieving structural weight reduction and performance optimization, and holds great application potential. However, the significant differences in their physical and chemical properties make achieving a high-strength, high-reliability metallurgical bond a technical challenge.

[0003] Existing γ-TiAl and TC4 joining technologies have significant limitations: diffusion welding and brazing are post-joining processes, which are complex, inefficient, prone to brittle phase formation at the joint, difficult to achieve complex interface configurations, and cannot be integrated into a single design; traditional fusion welding suffers from large differences in the thermophysical properties of the materials, resulting in an unstable molten pool and the formation of continuous, coarse, brittle intermetallic compound layers at the interface, leading to extremely poor joint toughness; while conventional additive manufacturing direct forming offers the potential for integration, laser technologies such as SLM / DED can easily cause hot cracks in TiAl, and mismatched EBM process parameters can lead to incomplete interface fusion, over-melting of the TC4 substrate, and thermal deformation. Current technologies are caught in a dilemma: post-joining makes it difficult to achieve high-performance interfaces, and conventional additive manufacturing cannot precisely control the interface reaction.

[0004] Recent improvements to the EBM forming process for γ-TiAl alloys are also unsuitable for joining dissimilar materials. For example, the ultra-high energy input strategy employed in patent CN115502412A fails to consider the thermal tolerance limit of the TC4 substrate, potentially leading to substrate damage. Meanwhile, the overall high volumetric energy density cyclic heat treatment strategy used in patent CN117464022A triggers severe interfacial reactions, forming brittle phases and damaging the substrate. Interfacial energy input must simultaneously meet two mutually restrictive conditions: first, sufficient energy to completely melt the γ-TiAl powder and form a metallurgical bond with the TC4 substrate; and second, it must not induce uncontrolled melting, thermal deformation, or excessive formation of harmful brittle phases in the TC4 substrate. Therefore, to address the technological gap in precisely controlling the γ-TiAl / TC4 dissimilar material interface, an integrated forming method that synergistically optimizes energy input, material matching, and forming path is urgently needed to achieve high-quality metallurgical bonding and performance synergy in bimetallic components. Summary of the Invention

[0005] To address the challenges of achieving precise interface control and obtaining high-quality metallurgical bonding in the integrated forming of γ-TiAl / TC4 dissimilar materials, this invention provides a γ-TiAl / TC4 bimetallic component and its integrated forming method using electron beam melting.

[0006] The technical solution of this invention:

[0007] An electron beam melting integral forming method for γ-TiAl / TC4 bimetallic components includes the following steps:

[0008] Step 1: Provide TC4 substrate and γ-TiAl alloy powder:

[0009] Prepare a clean TC4 alloy substrate and spherical γ-TiAl alloy powder;

[0010] Step 2: Equipment and Atmosphere Preparation

[0011] The TC4 substrate is placed in the forming chamber of the electron beam melting equipment to establish the inert protective atmosphere required for forming;

[0012] Step 3: Preheating of TC4 substrate:

[0013] A defocused electron beam is used to preheat the TC4 substrate in a stepped manner, so that the substrate temperature is uniformly raised to 1050℃; Step 4: Gradient energy input integrated molding:

[0014] Under the preheating conditions of the TC4 substrate, powder was laid layer by layer according to the preset three-dimensional model path, and the powder bed was preheated after each layer was laid.

[0015] Electron beam forming is performed at a powder bed preheating temperature using a gradient energy input method. The gradient energy input includes an initial cladding stage and a second cladding stage. The initial cladding stage starts from the first cladding layer and ends at the Nth layer, with energy input using a progressively increasing or stepwise increase in volumetric energy density, increasing the volumetric energy density from an initial value ρ1 to a stable value ρ2, where ρ2 > ρ1. The second cladding stage uses a fixed volumetric energy density ρ2 to complete the remaining layer-by-layer cladding. After all layers are clad, the electron beam is stopped, and the component is cooled to room temperature in a vacuum environment or under a protective atmosphere, resulting in an integrally formed γ-TiAl / TC4 bimetallic component.

[0016] Furthermore, the chemical composition of the spherical γ-TiAl alloy powder in step one, in atomic percentage, is: Al: 45~50 at.%, Cr: 0~4 at.%, Nb: 0~4 at.%, with the balance being Ti and unavoidable impurities; the particle size distribution of the spherical γ-TiAl alloy powder is 50~150 μm.

[0017] Furthermore, the establishment of the inert protective atmosphere in step two involves evacuating the chamber to a vacuum level of 5 × 10⁻⁶. -3 Below Pa, high-purity helium gas with a purity of not less than 99.999% is then refilled into the cavity as a protective gas, and the vacuum level in the forming cavity is stably maintained at 0.5 × 10⁻⁶ Pa. -1 ~1.2×10 -1 Pa.

[0018] Furthermore, the method for step-by-step preheating of the TC4 substrate in step three is as follows: first, a defocused electron beam with a current of 10mA is used to scan the entire substrate in a fast scanning mode for 10 minutes; then, the current is increased to 15mA and scanned for 15 minutes; finally, the current is increased to 20mA and scanned for 5 minutes.

[0019] Furthermore, in step four, the method for preheating the powder bed after each layer of powder is as follows: a defocused electron beam with a current of 30mA is used to scan the powder bed area for 12s; after each layer of cladding is formed in step four, a defocused electron beam with a current of 30mA is used to scan the cladding powder bed area for 10s to homogenize the temperature.

[0020] Furthermore, the initial value of the volumetric energy density ρ1 in the initial cladding stage in step four is set based on the premise of ensuring that the spherical γ-TiAl alloy powder is completely melted and the interface metallurgical bonding is achieved, while controlling the macroscopic warping deformation of the TC4 substrate caused by heat within the threshold X, and controlling the thickness of the brittle intermetallic compound continuous layer at the interface below the threshold Y; the threshold X is 0.1~0.5% of the total length of the substrate, and the threshold Y is ≤300μm.

[0021] Furthermore, the Nth layer mentioned in step four refers to layers 10 to 50; the volumetric energy density is gradually increased by adjusting the electron beam current intensity I, so that I gradually increases from a first value I1 to a second value I2, and I2>I1; the initial value of the volumetric energy density ρ1 in the initial cladding stage is 24~36 J / mm. 3 The volumetric energy density ρ2 in the second cladding stage is a fixed value of 30~60 J / mm². 3 .

[0022] Furthermore, in step four, the initial electron beam current intensity I1 in the initial cladding stage is 12~20mA, and the fixed electron beam current intensity I2 in the second cladding stage is 16~22mA; the accelerating voltage in both the initial cladding stage and the second cladding stage is 60kV, the electron beam moving speed is 3~5m / s, the electron beam scanning spacing is 0.08~0.12mm, and the printing layer thickness is 0.08~0.12mm.

[0023] Furthermore, in step four, the scraper moving speed is 50 mm / s, the electron beam spot radius is ≤100 μm, the powder thickness of each layer is 0.11~0.13 mm, each layer adopts a strip scanning strategy, and the rotation angle of each layer is 90°.

[0024] A TiAl / TC4 bimetallic component prepared by an electron beam melting integral forming method provided by the present invention.

[0025] The beneficial effects of this invention are:

[0026] This invention employs a gradient energy input method in the initial cladding stage of electron beam melting integrated forming of γ-TiAl / TC4 bimetallic components. This allows for precise control of the solidification behavior of the molten pool and the element diffusion process in the interface region, successfully achieving the construction of a gradient interface layer with smooth compositional transition and controllable thickness. It can effectively alleviate the accumulation of thermal mismatch stress between the two materials, while inhibiting the concentrated formation of harmful brittle phases such as Ti3Al, thus ensuring the stability and reliability of the interface bonding from a structural perspective.

[0027] The gradient interface layer formed by the gradient energy input strategy provided by this invention is a dense, defect-free, and fully metallurgically bonded morphology, significantly improving the interfacial bonding strength and overall mechanical properties of bimetallic components. Verification has shown that the room temperature tensile strength of the component remains consistently above 300 MPa, and the fracture mode is optimized to plastic fracture within the gradient intermediate layer, rather than direct separation along the interface. This completely solves the problem of the interface easily becoming a weak point in the component, ensuring uniform stress transmission under load and significantly improving the structural reliability and service safety of the γ-TiAl / TC4 bimetallic component.

[0028] The electron beam melting integrated forming method for γ-TiAl / TC4 bimetals of this invention possesses excellent controllability and engineering application value. By clearly defining the control window and logic of core energy input parameters such as beam intensity and beam velocity in the initial cladding stage, precise matching of interface structure and performance can be achieved, resulting in outstanding process stability and repeatability. Simultaneously, it enables direct integrated manufacturing from digital models to high-performance bimetallic components, significantly shortening the process flow, improving material utilization, and reducing the risk of process fluctuations during production. This provides efficient and reliable technical support for the standardized mass production of γ-TiAl / TC4 bimetallic components. Attached Figure Description

[0029] Figure 1 Photographs of the γ-TiAl / TC4 bimetallic components prepared in Examples 1-3;

[0030] Figure 2 Comparison of metallographic structures at the interface of γ-TiAl / TC4 bimetallic components prepared in Example 1 and Comparative Example 1;

[0031] Figure 3 The elemental surface and line distribution diagrams of the interface region of the γ-TiAl / TC4 bimetallic components prepared in Example 1 and Comparative Example 1 are shown.

[0032] Figure 4 Room temperature engineering stress-strain curves of γ-TiAl / TC4 bimetallic components prepared for Example 1 and Comparative Example 1. Detailed Implementation

[0033] The technical solution of the present invention will be further described below with reference to embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention. In the following embodiments, the process equipment or apparatus not specifically specified are all conventional equipment or apparatus in the art. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commercially available; unless otherwise specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.

[0034] Example 1

[0035] This embodiment provides an integrated forming method for γ-TiAl / TC4 bimetallic components based on electron beam melting technology. The specific steps are as follows:

[0036] Step 1: Provide TC4 substrate and γ-TiAl alloy powder:

[0037] A forged TC4 (Ti-6Al-4V) alloy plate with dimensions of 120mm×120mm×15mm was selected as the substrate. The substrate surface was ultrasonically cleaned for 15 minutes each with anhydrous ethanol and acetone to remove oil and oxides, and then dried in an oven at 80℃.

[0038] The γ-TiAl alloy powder used is a pre-alloyed spherical powder prepared by electrode induction melting gas atomization (EIGA) technology. Its chemical composition, by atomic percentage, is: Al: 48 at.%, Cr: 2 at.%, Nb: 2 at.%, with the balance being Ti and unavoidable impurities. The particle size distribution of the γ-TiAl alloy powder is between 53 and 150 μm, with a D50 of approximately 75 μm. Before use, the γ-TiAl alloy powder is dried in a vacuum oven at 120°C for 4 hours to reduce its moisture content.

[0039] Step 2: Equipment and Atmosphere Preparation

[0040] The processed TC4 substrate was mounted on the forming chamber stage of the electron beam melting (EBM) equipment. After closing the chamber, the vacuum system was activated to evacuate the chamber to a vacuum level of 5 × 10⁻⁶. -3Below Pa. Subsequently, high-purity helium gas with a purity of not less than 99.999% is refilled into the chamber as a protective gas, and the working vacuum is stably maintained at 1.2 × 10⁻⁶ Pa. -1 Pa.

[0041] Step 3: Preheating of TC4 substrate:

[0042] A defocused electron beam was used to preheat the TC4 substrate in a stepped manner to reduce thermal and residual stress. First, a 10mA defocused electron beam was used to scan the entire substrate in a rapid scanning mode for 10 minutes; then the beam current was increased to 15mA for 15 minutes; finally, the beam current was increased to 20mA for 5 minutes. This process uniformly raised the substrate temperature to 1050℃, reaching or approaching the ductile-brittle transition temperature of the TiAl alloy.

[0043] Step 4: Gradient energy input for integrated forming:

[0044] On the preheated TC4 substrate, powder is laid layer by layer according to the preset three-dimensional model path. After each layer of powder is laid, the powder bed is preheated. A defocused electron beam with a beam current of 30mA is used to scan the powder bed area for 12s to make its temperature reach 1050℃. Then, electron beam shaping is performed at the preheated temperature of the powder bed according to the preset gradient energy input.

[0045] In this embodiment, the initial cladding stage covers layers 1 to 20. Energy input is achieved by progressively increasing the volumetric energy density. During the cladding of the first layer, the initial electron beam current I1 is 15 mA, the accelerating voltage U is 60 kV, the electron beam velocity v is 4 m / s, the electron beam scanning interval t is 0.10 mm, and the printed layer thickness h is 0.09 mm. During the layer-by-layer cladding process, the electron beam current intensity linearly increases from 15 mA to 18 mA. That is, when printing the 20th layer, the electron beam current intensity is 18 mA. During this period, the accelerating voltage U, electron beam velocity v, electron beam scanning interval t, and printed thickness h remain constant.

[0046] Starting from the 21st layer, the second cladding stage uses a fixed volumetric energy density for energy input. The electron beam current intensity I2 remains at 18mA, the accelerating voltage U remains at 60kV, the electron beam velocity v remains at 4m / s, the electron beam scanning spacing t remains at 0.10mm, and the printed layer thickness h remains at 0.09mm. The cladding from the 21st layer to the last layer is completed using these parameters.

[0047] Based on the formula VED=(I×U) / (v×t×h), by substituting the accelerating voltage (U), beam current intensity (I), scanning speed (v), scanning spacing (t), and printing layer thickness (h) into the parameters, the initial value of the volumetric energy density ρ1 in the initial cladding stage is calculated to be 25 J / mm². 3The volumetric energy density ρ2 of the second cladding stage is a fixed value of 30 J / mm². 3 .

[0048] During electron beam forming, the scraper moves at a speed of 50 mm / s, the electron beam spot radius is 100 μm, a strip scanning strategy is adopted for each layer, and the rotation angle of each layer is 90°.

[0049] After each layer of cladding is formed, a defocused electron beam with a current of 30mA is used to scan the powder bed area for 10 seconds to homogenize the temperature before the next layer of powder is laid. After all layers of cladding are completed, the electron beam is stopped, and the component is allowed to cool to room temperature in a vacuum environment or under a protective atmosphere, resulting in an integrally formed γ-TiAl / TC4 bimetallic component.

[0050] Example 2

[0051] This embodiment provides a method for integral forming of γ-TiAl / TC4 bimetallic components based on electron beam melting technology. The only difference between this embodiment and Embodiment 1 is the gradient energy input integral forming in step four:

[0052] In this embodiment, the initial cladding stage covers layers 1 to 30. Energy input is achieved by progressively increasing the volumetric energy density. During the cladding of the first layer, the initial electron beam current I1 is 14 mA, the accelerating voltage U is 60 kV, the electron beam velocity v is 3 m / s, the electron beam scanning interval t is 0.10 mm, and the printed layer thickness h is 0.09 mm. During the layer-by-layer cladding process, the electron beam current intensity linearly increases from 14 mA to 20 mA. That is, when printing the 30th layer, the electron beam current intensity is 20 mA. During this period, the accelerating voltage U, electron beam velocity v, electron beam scanning interval t, and printed thickness h remain constant.

[0053] Starting from the 31st layer, the second cladding stage uses a fixed volumetric energy density for energy input. The electron beam current intensity I2 remains at 20mA, the accelerating voltage U remains at 60kV, the electron beam moving speed v remains at 3m / s, the electron beam scanning spacing t remains at 0.10mm, and the printed layer thickness h remains at 0.09mm. The cladding from the 31st layer to the last layer is completed using these parameters.

[0054] Based on the formula VED=(I×U) / (v×t×h), by substituting the accelerating voltage (U), beam current intensity (I), scanning speed (v), scanning spacing (t), and printing layer thickness (h) into the parameters, the initial value of the volumetric energy density ρ1 in the initial cladding stage is calculated to be 31 J / mm². 3 The volumetric energy density ρ2 of the second cladding stage is a fixed value of 44 J / mm². 3 .

[0055] Example 3

[0056] This embodiment provides a method for integral forming of γ-TiAl / TC4 bimetallic components based on electron beam melting technology. The only difference between this embodiment and Embodiment 1 is the gradient energy input integral forming in step four:

[0057] In this embodiment, the initial cladding stage covers layers 1 to 40. Energy input is achieved by progressively increasing the volumetric energy density. During the cladding of the first layer, the initial electron beam current I1 is 15 mA, the accelerating voltage U is 60 kV, the electron beam velocity v is 3 m / s, the electron beam scanning interval t is 0.10 mm, and the printed layer thickness h is 0.09 mm. During the layer-by-layer cladding process, the electron beam current intensity linearly increases from 15 mA to 22 mA. That is, when printing the 40th layer, the electron beam current intensity is 22 mA. During this period, the accelerating voltage U, electron beam velocity v, electron beam scanning interval t, and printed thickness h remain constant.

[0058] Starting from layer 41, the second cladding stage uses a fixed volumetric energy density for energy input. The electron beam current intensity I2 remains at 22 mA, the accelerating voltage U remains at 60 kV, the electron beam velocity v remains at 3 m / s, the electron beam scanning spacing t remains at 0.10 mm, and the printed layer thickness h remains at 0.09 mm. Cladding from layer 41 to the last layer is completed using these parameters.

[0059] Based on the formula VED=(I×U) / (v×t×h), by substituting the accelerating voltage (U), beam current intensity (I), scanning speed (v), scanning spacing (t), and printing layer thickness (h) into the parameters, the initial value of the volumetric energy density ρ1 in the initial cladding stage is calculated to be 33 J / mm². 3 The volumetric energy density ρ2 of the second cladding stage is a fixed value of 48 J / mm². 3 .

[0060] Comparative Example 1

[0061] The difference between the integrated forming method of the γ-TiAl / TC4 bimetallic component in this comparative example and Example 1 lies only in the energy input integrated forming in step four:

[0062] The initial cladding stage of this comparative example consists of layers 1 to 20. Energy input is performed using a fixed volumetric energy density method. The electron beam current intensity I1 is 12mA, the accelerating voltage U is 60kV, the electron beam moving speed v is 4m / s, the electron beam scanning spacing t is 0.10mm, and the printed layer thickness h is 0.09mm.

[0063] Starting from the 21st layer, the second cladding stage also uses a fixed volumetric energy density for energy input, with the electron beam current intensity I2 fixed at 16mA, the accelerating voltage U remaining at 60kV, the electron beam movement velocity v still at 4m / s, the electron beam scanning spacing t still at 0.10mm, and the printed layer thickness h still at 0.09mm. Cladding from the 21st layer to the last layer is completed using these parameters.

[0064] Based on the formula VED=(I×U) / (v×t×h), by substituting the accelerating voltage (U), beam current intensity (I), scanning speed (v), scanning spacing (t), and printing layer thickness (h) into the parameters, the volumetric energy density of the initial cladding stage is calculated to be 20 J / mm². 3 The volumetric energy density of the second cladding stage is 26 J / mm². 3 .

[0065] The volumetric energy density of the initial cladding stage in Comparative Example 1 is 20 J / mm². 3 The initial volumetric energy density is lower than the recommended value, and because it adopts a fixed-value strategy rather than a gradual increase strategy, it remains low, failing to meet the cumulative heat input requirements for good metallurgical bonding at the interface. This indicates that the scope of protection of this invention is the entire process strategy starting from a lower ρ1 and gradually increasing to a higher ρ2, rather than any isolated parameter point within it.

[0066] Metallographic and tensile specimens were prepared by wire cutting of the formed γ-TiAl / TC4 bimetallic components of Example 1 and Comparative Example 1. The interfaces were observed by optical microscopy (OM) and scanning electron microscopy (SEM).

[0067] Figure 2 Comparative images show the metallographic structures at the interface of the γ-TiAl / TC4 bimetallic components prepared in Example 1 and Comparative Example 1; Figure 2 As shown, the bimetallic component in Comparative Example 1 exhibits obvious incomplete fusion defects at its interface. These defects directly lead to insufficient interfacial bonding strength and stress concentration. In contrast, the bimetallic component in Example 1 shows no obvious defects at its interface, achieving a continuous and dense metallurgical bond, thus ensuring the structural stability of the interface at the microstructural level. This demonstrates that the gradient energy input used in the initial cladding stage of this invention can precisely control the fusion process in the interfacial region, significantly improving the quality of the metallurgical bond at the interface.

[0068] Figure 3 The image shows the elemental surface and line distribution of the interface region of the γ-TiAl / TC4 bimetallic components prepared in Example 1 and Comparative Example 1; as shown. Figure 3As shown, Comparative Example 1 formed an extremely thin diffusion layer (approximately 30-50 μm) in a few bonding regions, but the composition changed abruptly. This abrupt composition distribution easily leads to interfacial stress concentration and enrichment of brittle phases. In contrast, Example 1 formed a diffusion layer of moderate thickness (approximately 150-200 μm) in the bonding regions, with a smooth concentration gradient of elemental composition. The thickness (H) of this diffusion layer is positively correlated with the beam energy density ρ applied during the forming process. As ρ increases, H changes accordingly within the range of 50 μm to 300 μm. The interfacial gradient transition layer is mainly composed of α2-Ti3Al phase and B2 phase, moving from the TC4 side to the γ-TiAl side. The Al element content gradually increases from 10 at.% to approximately 48 at.%, while the atomic percentage of Ti element decreases accordingly. The warpage deformation of the TC4 substrate was found to be less than 0.5% of the total length.

[0069] Figure 4 The figures show the room temperature engineering stress-strain curves of the γ-TiAl / TC4 bimetallic components prepared in Example 1 and Comparative Example 1. A1-A5 and C1-C5 in the figures represent parallel samples from multiple experiments. Figure 4 As shown, the tensile strength of the γ-TiAl / TC4 bimetallic component prepared in Comparative Example 1 is approximately 60 MPa, while the tensile strength of the γ-TiAl / TC4 bimetallic component prepared in Example 1 is in the range of approximately 280-320 MPa. This demonstrates that the improved interfacial metallurgical bonding quality achieved by the gradient energy input strategy of this invention directly translates into a significant optimization of the component's mechanical properties, with its tensile strength increasing by more than 366.7% compared to Comparative Example 1. This fully verifies the effectiveness of this forming method in improving the interfacial bonding strength of bimetallic components.

[0070] By comparing Comparative Example 1 and Example 1, it is clear that the energy input strategy in the initial cladding stage is crucial to the success of the interface when directly integrally forming γ-TiAl alloy on a TC4 substrate. Comparative Example 1 used relatively low and insufficiently controlled initial parameters, resulting in poor interface bonding, the formation of harmful brittle phases, and low performance. In contrast, Example 1 of this invention employs an optimized gradient energy input strategy (increasing the initial beam current I1 to 15mA and progressively increasing it in the first 20-30 layers), actively controlling the thermal history of the molten pool and the interfacial metallurgical reaction, forming an intermediate layer with a gradient transition in composition and microstructure and a suitable thickness in situ. This achieves a high-strength and high-reliability metallurgical bond, fully verifying the effectiveness and superiority of the technical solution of this invention.

[0071] In summary, this invention successfully achieved high-quality integrated molding of γ-TiAl / TC4 bimetallic components by precisely controlling the key range of the gradient energy input strategy during the initial cladding stage of the integrated molding process. The interface structure and mechanical properties can be effectively controlled by the beam intensity. This invention provides an innovative and reliable solution for the manufacture of high-performance lightweight composite components in the aerospace field.

Claims

1. A method for integral forming of γ-TiAl / TC4 bimetallic components by electron beam melting, characterized in that, Includes the following steps: Step 1: Provide TC4 substrate and γ-TiAl alloy powder: Prepare a clean TC4 alloy substrate and spherical γ-TiAl alloy powder; Step 2: Equipment and Atmosphere Preparation The TC4 substrate is placed in the forming chamber of the electron beam melting equipment to establish the inert protective atmosphere required for forming; Step 3: Preheating of TC4 substrate: A defocused electron beam was used to preheat the TC4 substrate in a stepped manner, so that the substrate temperature was uniformly raised to 1050℃. Step 4: Gradient energy input for integrated forming: Under the preheating conditions of the TC4 substrate, powder was laid layer by layer according to the preset three-dimensional model path, and the powder bed was preheated after each layer was laid. Electron beam forming is performed at a powder bed preheating temperature using a gradient energy input method. The gradient energy input includes an initial cladding stage and a second cladding stage. The initial cladding stage starts from the first cladding layer and ends at the Nth layer, where the Nth layer is the 10th to the 50th layer. Energy input is performed using a progressively or stepwise increase in volumetric energy density. This progressive increase in volumetric energy density is achieved by adjusting the electron beam intensity I, gradually increasing I from a first value I1 to a second value I2, where I2 > I1; the volumetric energy density is increased from an initial value ρ1 to a stable value ρ2, where ρ2 > ρ1; the second cladding stage uses a fixed volumetric energy density ρ2 to input energy and complete the remaining layer-by-layer cladding. The initial electron beam current intensity I1 during the initial cladding stage is 12~20mA, and the initial volumetric energy density ρ1 is 24~36J / mm². 3 The fixed electron beam current intensity I2 in the second cladding stage is 16~22mA, and the fixed volume energy density ρ2 is 30~60J / mm². 3 ; The accelerating voltage for both the initial cladding stage and the second cladding stage is 60kV, the electron beam moving speed is 3~5m / s, the electron beam scanning spacing is 0.08~0.12mm, and the printing layer thickness is 0.08~0.12mm. After all layers are clad, the electron beam is stopped, and the component is cooled to room temperature in a vacuum environment or under a protective atmosphere to obtain an integrally formed γ-TiAl / TC4 bimetallic component.

2. The electron beam melting integral forming method for a γ-TiAl / TC4 bimetallic component according to claim 1, characterized in that, The chemical composition of the spherical γ-TiAl alloy powder in step one, in atomic percentage, is: Al: 45~50 at.%, Cr: 0~4 at.%, Nb: 0~4 at.%, with the balance being Ti and unavoidable impurities; the particle size distribution of the spherical γ-TiAl alloy powder is 50~150μm.

3. The electron beam melting integral forming method for a γ-TiAl / TC4 bimetallic component according to claim 1 or 2, characterized in that, The establishment of the inert protective atmosphere in step two involves evacuating the chamber to a vacuum level of 5 × 10⁻⁶. -3 Below Pa, high-purity helium gas with a purity of not less than 99.999% is then refilled into the cavity as a protective gas, and the vacuum level in the forming cavity is stably maintained at 0.5 × 10⁻⁶ Pa. -1 ~1.2×10 -1 Pa.

4. The electron beam melting integral forming method for a γ-TiAl / TC4 bimetallic component according to claim 3, characterized in that, Step 3 involves a stepped preheating process for the TC4 substrate. First, a defocused electron beam with a current of 10mA is used to scan the entire substrate in a fast scanning mode for 10 minutes. Then, the current is increased to 15mA and scanned for 15 minutes. Finally, the current is increased to 20mA and scanned for 5 minutes.

5. The electron beam melting integral forming method for a γ-TiAl / TC4 bimetallic component according to claim 4, characterized in that, In step four, the method for preheating the powder bed after each layer of powder is as follows: a defocused electron beam with a current of 30mA is used to scan the powder bed area for 12s; after each layer of cladding is formed in step four, a defocused electron beam with a current of 30mA is used to scan the cladding powder bed area for 10s to homogenize the temperature.

6. The electron beam melting integral forming method for a γ-TiAl / TC4 bimetallic component according to claim 5, characterized in that, The initial value of volumetric energy density ρ1 in the initial cladding stage in step four is set based on the premise of ensuring that the spherical γ-TiAl alloy powder is completely melted and the interface metallurgical bonding is achieved, while controlling the macroscopic warping deformation of the TC4 substrate caused by heat within the threshold X, and controlling the thickness of the brittle intermetallic compound continuous layer at the interface below the threshold Y; the threshold X is 0.1~0.5% of the total length of the substrate, and the threshold Y is ≤300μm.

7. The electron beam melting integral forming method for a γ-TiAl / TC4 bimetallic component according to claim 6, characterized in that, In step four, the scraper moving speed is 50 mm / s, the electron beam spot radius is ≤100 μm, the powder thickness of each layer is 0.11~0.13 mm, each layer adopts a strip scanning strategy, and the rotation angle of each layer is 90°.

8. A γ-TiAl / TC4 bimetallic component prepared by the electron beam melting integral forming method according to any one of claims 1-7.

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