A method for laser additive manufacturing joining of dissimilar titanium alloy components

Abstract

The present application relates to a kind of laser additive manufacturing connection method of different titanium alloy components, belong to metal material laser additive manufacturing technical field, by regulating laser additive manufacturing deposition parameter, obtain the volume fraction of 100%, the width of 0.45~0.55 μm, the dislocation density of greater than 10 ‑19.5 m ‑2 Ultrafine micron flake alpha organization, combined with subsequent special heat treatment regulation method, on the basis of not changing the original component organization performance, additive connection area obtains the volume fraction of 38~55%, the average width of not more than 4.62 μm long strip alpha P Phase and volume fraction of 45~62%, the average width of not more than 2.54 μm alpha S Phase, thereby preparing large different high strength and toughness titanium alloy component.

Description

Technical Field

[0001] This invention belongs to the field of laser additive manufacturing technology for metallic materials, and specifically relates to a laser additive manufacturing connection method for dissimilar titanium alloy components. Background Technology

[0002] As a crucial load-bearing reinforcement frame for the fuselage, the titanium alloy integral load-bearing frame has a significant impact on the structural stability of the aircraft. This structure is generally manufactured by machining large titanium alloy forgings. The integral load-bearing frame structure is relatively complex, has poor machinability, low material utilization, and is extremely difficult to manufacture and machine, making it difficult to meet the requirements of low-cost, high-efficiency manufacturing in the aerospace industry.

[0003] Laser additive manufacturing (LMD) technology, based on a 3D CAD slicing model and following a planned forming path, uses a laser to melt and deposit synchronously fed metal powder onto a substrate point by point, layer by layer, under a sealed atmosphere, ultimately obtaining a near-net-shape dense metal component. This technology enables the high-efficiency, low-cost, and high-quality manufacturing of large and complex titanium alloy components. In recent years, large-scale laser additive manufacturing (LMDed) titanium alloy components have been gradually applied in the aerospace field. As aerospace equipment develops towards larger sizes, higher safety, and longer lifespans, there are urgent requirements for its overall load-bearing frame components to be larger, more complex, and more integrated.

[0004] Compared to TC4 titanium alloy, TC4-DT titanium alloy has lower maximum allowable contents of interstitial elements C, N, O and impurity elements Fe, Si, etc., making smelting control more difficult and manufacturing costs higher. TC4-DT titanium alloy (basket structure) exhibits high fracture toughness, fatigue crack propagation resistance, and fatigue crack propagation threshold, making it the best known damage-tolerant titanium alloy. This alloy has been mass-produced and applied to aircraft outer frame components. LMDed TC11 titanium alloy (elongated primary α phase (α...) P ) and secondary α phase (α S The transverse and longitudinal specimens of the component showed no obvious anisotropy and both exhibited high fatigue crack propagation resistance, comparable to that of TC4-DT titanium alloy (Zhang Jikui et al., Acta Aeronautica Sinica, 2021, 42(10): 525430). LMDed TC11 titanium alloy has been applied to the manufacturing of upper and lower frame components for aircraft. How to achieve the overall connection of key load-bearing components such as outer frame components, upper frame sections, and lower frame sections has become a major challenge in its engineering application. Therefore, it is urgent to propose a laser additive manufacturing connection method for high-strength and high-toughness dissimilar titanium alloy components to achieve excellent comprehensive mechanical properties while realizing a good connection interface. Summary of the Invention

[0005] The purpose of this invention is to provide a laser additive manufacturing method for joining dissimilar titanium alloy components. By adjusting the laser additive manufacturing deposition parameters, an ultrafine nanometer-sized α-structure with a volume fraction of 100% is obtained. Combined with heat treatment control, without changing the microstructure and properties of the original component, the additive bonding region obtains long strips of α-structure with a volume fraction of 38-55% and an average width of no more than 4.62 μm. P The phase and volume fraction are 45-62%, with an average width not exceeding 2.54 μm. S Phase, to prepare the target dissimilar titanium alloy component.

[0006] The above-mentioned objectives of the present invention are mainly achieved through the following technical solutions:

[0007] A laser additive manufacturing method for joining dissimilar titanium alloy components includes the following steps:

[0008] (1) Beveling and cleaning are performed on multiple dissimilar titanium alloy components to be connected;

[0009] (2) Load titanium alloy powder into the powder feeder, and connect and clamp the multiple dissimilar titanium alloy components obtained in step (1) onto the forming chamber workbench base plate.

[0010] (3) The titanium alloy powder is melted and deposited in the bevel to obtain the dissimilar titanium alloy components that are joined together.

[0011] (4) The dissimilar titanium alloy components obtained in step (3) are subjected to heat treatment. The connection positions of the heat-treated dissimilar titanium alloy components include long strips α with a volume fraction of 38-55% and an average width of no more than 4.62 μm. P The phase and volume fraction are 45-62%, with an average width not exceeding 2.54 μm. S Mutually.

[0012] The dissimilar titanium alloy components to be connected are TC4-DT titanium alloy components and LMDed TC11 titanium alloy components.

[0013] In step (2), the forming chamber is filled with argon gas, and the purity of the argon gas in the forming chamber is not less than 99.99%.

[0014] During the deposition process described in step (3), the energy density of the titanium alloy deposition zone is 56–68 J / mm². 2 The overlap ratio is 45-55%, and the cooling rate of the formed solid-liquid molten pool is 10. 4.5 ~10 5 K / s.

[0015] The microstructure at the connection site of the dissimilar titanium alloy component obtained in step (3) is as follows: layer height is 0.3–0.5 mm, volume fraction is 100%, width is 0.45–0.55 μm, and dislocation density is greater than 10.-19.5 m -2 α-organism.

[0016] Step (3) involves a layer-by-layer deposition method with an interlayer interval of 15–25 min.

[0017] The heat treatment method in step (4) is as follows: heat up to 750-800℃ at 25-35℃ / min, keep warm for 2-4 hours, then cool down to 550-650℃ at 30℃ / min, keep warm for 4-6 hours, and then air cool.

[0018] The [Mo] equivalent in the titanium alloy powder is 4.6 to 6.5.

[0019] The titanium alloy powder has a particle size of 75–185 μm and an oxygen content greater than 0.12 wt%.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects:

[0021] (1) This invention lays the foundation for subsequent overall component microstructure and performance control by adjusting the process parameters of the deposition process, and at the same time achieves effective control of deformation and cracking of large titanium alloy integral components.

[0022] (2) The present invention designs a special heat treatment method to obtain a high-performance dual-phase structure without changing the matrix structure characteristics, which can realize the high-performance and rapid manufacturing of large integral components. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the microstructure of a dissimilar titanium alloy component before heat treatment in Embodiment 1 of the present invention, wherein... Figure 1 a is a schematic diagram of the overall sample structure. Figure 1 b is a schematic diagram of the connection area organization. Figure 1 c is a schematic diagram of the microstructure of the connection region;

[0024] Figure 2 This is a schematic diagram of the microstructure of a dissimilar titanium alloy component after heat treatment, as shown in Embodiment 1 of the present invention. Figure 2 a is a schematic diagram of the overall sample structure. Figure 2 b is a schematic diagram of the connection area organization. Figure 2 c is a schematic diagram of the microstructure of the connection region. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments:

[0026] Example 1

[0027] A laser additive manufacturing method for joining dissimilar titanium alloy components includes the following steps:

[0028] (1) The TC4-DT titanium alloy components and LMDed TC11 titanium alloy components are beveled and ground respectively. The connection area is cleaned with acetone to ensure that the bevel surface is free of oil and other impurities.

[0029] (2) Load titanium alloy powder with a particle size of 75μm into the powder feeder. The oxygen content of the powder must be greater than 0.12wt%.

[0030] (3) The cleaned TC4-DT titanium alloy components and LMDed TC11 titanium alloy components are mated and clamped on the base plate of the forming chamber worktable filled with argon gas. The purity of argon gas in the forming chamber is not less than 99.99%.

[0031] (4) When the water and oxygen content in the forming chamber is lower than 50 ppm, the synchronously fed powder is melted and deposited in the bevel using a laser, with an interlayer interval of 15 min; during the deposition process, the energy density of the titanium alloy deposition zone is controlled to be 56 J / mm². 2 The overlap ratio is 46%, resulting in a cooling rate of 10 for the formed solid-liquid molten pool. 4.5 K / s, a layer with a height of 0.31 mm, a volume fraction of 100%, a width of 0.46 μm, and a dislocation density of 10 was prepared. -19.2 m -2 The ultrafine nano-scale α-structure provides a basis for subsequent heat treatment to obtain long α-strips. P Phase and α S Phase provides driving force;

[0032] (5) After the laser additive bonding is completed, the entire component is placed in a heat treatment furnace for heat treatment. The specific process parameters for heat treatment are as follows: the alloy is heated to 750℃ at 25℃ / min in the furnace, held for 2 hours, cooled to 550℃ at 30℃ / min, held for 4 hours, and then the sample is taken out and air-cooled, so that the additive bonding area obtains a strip α with a volume fraction of 38% and an average width of 4.61μm. P The phase and volume fraction of α are 62%, with an average width not exceeding 2.5 μm. S Phase structure was used to obtain large, high-strength and high-toughness dissimilar titanium alloy components.

[0033] like Figure 1 The diagram shown is a schematic representation of the microstructure of the dissimilar titanium alloy component before heat treatment in this embodiment. Figure 1 a is a schematic diagram of the overall sample structure. Figure 1 b is a schematic diagram of the connection area organization. Figure 1 c is a schematic diagram of the microstructure of the connection zone; the overall sample structure consists of fine grains + equiaxed grains + columnar grains, the connection zone structure consists of axial grains, and the microstructure consists of fine lamellar structure.

[0034] like Figure 2The diagram shown is a schematic representation of the microstructure of the dissimilar titanium alloy component after heat treatment in this embodiment. Figure 2 a is a schematic diagram of the overall sample structure. Figure 2 b is a schematic diagram of the connection area organization. Figure 2 c is a schematic diagram of the microstructure of the bonding region. After heat treatment, the overall sample microstructure consists of fine grains + equiaxed grains + columnar grains, while the bonding region microstructure consists of axial grains, and the microstructure consists of elongated α-shaped grains. P +small α S organize.

[0035] Table 1 shows a comparison of the mechanical properties of the laser additive bonding zone of dissimilar titanium alloy components after heat treatment regulation.

[0036] Table 1

[0037]

[0038]

[0039] Example 2

[0040] A laser additive manufacturing method for joining high-strength and high-toughness dissimilar titanium alloy components, the specific steps of which are as follows:

[0041] (1) The TC4-DT titanium alloy components and LMDed TC11 titanium alloy components are beveled and ground respectively. The connection area is cleaned with acetone to ensure that the bevel surface is free of oil and other impurities.

[0042] (2) Load titanium alloy powder with a particle size of 85μm into the powder feeder. The oxygen content of the powder must be greater than 0.12wt%.

[0043] (3) The cleaned TC4-DT titanium alloy components and LMDed TC11 titanium alloy components are mated and clamped on the base plate of the forming chamber worktable filled with argon gas. The purity of argon gas in the forming chamber is not less than 99.99%.

[0044] (4) When the water and oxygen content in the forming chamber is lower than 50 ppm, the synchronously fed powder is melted and deposited in the bevel using a laser, with an interlayer interval of 18 min; during the deposition process, the energy density of the titanium alloy deposition zone is controlled to be 60 J / mm². 2 The overlap ratio is 48%, resulting in a cooling rate of 10 for the formed solid-liquid molten pool. 4.8 K / s, a layer with a height of 0.35 mm, a volume fraction of 100%, a width of 0.51 μm, and a dislocation density of 10 was prepared. -19.2 m -2 The ultrafine nano-scale α-structure provides a basis for subsequent heat treatment to obtain long α-strips. P Phase and α S Phase provides driving force;

[0045] (5) After the laser additive bonding is completed, the entire component is placed in a heat treatment furnace for heat treatment. The specific process parameters for heat treatment are as follows: the alloy is heated to 780℃ at 28℃ / min in the furnace, held for 2.2h, then cooled to 560℃ at 30℃ / min, held for 4.5h, and then the sample is taken out and air-cooled, so that the additive bonding area obtains a strip α with a volume fraction of 40% and an average width of 4.54μm. P The phase and volume fraction were 60%, with an average width of 2.44 μm for α. S Phase structure was used to obtain large, high-strength and high-toughness dissimilar titanium alloy components.

[0046] Example 3

[0047] A laser additive manufacturing method for joining dissimilar titanium alloy components includes the following steps:

[0048] (1) The TC4-DT titanium alloy components and LMDed TC11 titanium alloy components are beveled and ground respectively. The connection area is cleaned with acetone to ensure that the bevel surface is free of oil and other impurities.

[0049] (2) Load titanium alloy powder with a particle size of 95μm into the powder feeder. The oxygen content of the powder must be greater than 0.12wt%.

[0050] (3) The cleaned TC4-DT titanium alloy components and LMDed TC11 titanium alloy components are mated and clamped on the base plate of the forming chamber worktable filled with argon gas. The purity of argon gas in the forming chamber is not less than 99.99%.

[0051] (4) When the water and oxygen content in the forming chamber is lower than 50 ppm, the synchronously fed powder is melted and deposited in the bevel using a laser, with an interlayer interval of 20 min; during the deposition process, the energy density of the titanium alloy deposition zone is controlled to be 65 J / mm². 2 The overlap ratio is 54%, resulting in a cooling rate of 10 for the formed solid-liquid molten pool. 5.0 K / s, a layer with a height of 0.45 mm, a volume fraction of 100%, a width of 0.55 μm, and a dislocation density of 10 was prepared. -19.0 m -2 The ultrafine nano-scale α-structure provides a basis for subsequent heat treatment to obtain long α-strips. P Phase and α S Phase provides driving force;

[0052] (5) After the laser additive bonding is completed, the entire component is placed in a heat treatment furnace for heat treatment. The specific process parameters for heat treatment are as follows: the alloy is heated to 800℃ at a rate of 30℃ / min, held for 4 hours, then cooled to 600℃ at a rate of 30℃ / min, held for 6 hours, and then the sample is taken out and air-cooled, so that the additive bonding area obtains a strip α with a volume fraction of 44% and an average width of 4.35μm. P The phase and volume fraction were 56%, with an average width of 2.36 μm for α. S Phase structure was used to obtain large, high-strength and high-toughness dissimilar titanium alloy components.

[0053] The above description is only the best specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.

[0054] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method of laser additive manufacturing joining of dissimilar titanium alloy components, characterized by: The method comprises the following steps: (1) bevel processing and cleaning of a plurality of titanium alloy components to be connected; (2) loading titanium alloy powder into a powder feeder, and clamping the plurality of cleaned titanium alloy components obtained in step (1) on a forming bin workbench base plate; (3) melting and depositing the titanium alloy powder in the bevel to obtain connected titanium alloy components; (4) subjecting the dissimilar titanium alloy component obtained in step (3) to heat treatment, the connection position of the dissimilar titanium alloy component after heat treatment comprising long strip α P phases with a volume fraction of 38-55% and an average width of not more than 4.62 µm and α S phases with a volume fraction of 45-62% and an average width of not more than 2.54 µm; In the step (3), the energy density of the titanium alloy deposition area is 56-68 J / mm 2 , the lap rate is 45-55%, and the cooling rate of the formed solid-liquid pool is 10 4.5 -10 5 K / s; The deposition method in step (3) is layer-by-layer deposition, and the interval time between layers is 15-25 min; The heat treatment method in step (4) is as follows: heating at 25-35 ℃ / min to 750-800 ℃, holding for 2-4 h, cooling at 30 ℃ / min to 550-650 ℃, holding for 4-6 h, and then air cooling.

2. A method of laser additive manufacturing joining of dissimilar titanium alloy components according to claim 1, wherein: The titanium alloy components to be connected are TC4-DT titanium alloy components and LMDed TC11 titanium alloy components.

3. A method of laser additive manufacturing joining of dissimilar titanium alloy components according to claim 1, wherein: The forming bin in step (2) is filled with argon, and the argon purity in the forming bin is not less than 99.99%.

4. The method of claim 1, wherein: The microstructure of the connection position of the dissimilar titanium alloy component obtained in step (3) is α structure with a layer height of 0.3-0.5 mm, a volume fraction of 100%, a width of 0.45-0.55 µm, and a dislocation density of greater than 10 -19.5 m -2 .

5. The method of claim 1, wherein: The [Mo] equivalent in the titanium alloy powder is 4.6-6.

5.

6. A method of laser additive manufacturing joining of dissimilar titanium alloy components according to claim 1, wherein: The titanium alloy powder has a particle size of 75-185 µm and an oxygen content of more than 0.12 wt%.

7. A dissimilar titanium alloy component, characterized by: The connected components are prepared by the method according to any one of claims 1-6.

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