Method for reducing anisotropy of titanium alloy by laser additive manufacturing with friction stir processing

Abstract

The present application belongs to the technical field of laser additive manufacturing, in particular to a method for reducing anisotropy of titanium alloy by laser additive manufacturing and friction stir processing. The method comprises the following steps: step one, obtaining TC11 powder and performing drying treatment; step two, using a set laser scanning strategy, laser powder deposition is performed on the dried TC11 powder in a layered form to obtain a first laser cladding layer; step three, friction stirring is performed on the first laser cladding layer according to a set stirring path until the first laser cladding layer is completely processed; and step four, steps two to three are repeated to complete laser cladding and friction stir processing layer by layer to obtain a formed part. The present application combines the forming advantages of laser additive manufacturing and the microstructure modification advantages of friction stir processing, adopts an "interlayer instant compounding" mode, and constructs a composite manufacturing process, thereby efficiently reducing the anisotropy of TC11 titanium alloy components without additional alloying or complex heat treatment.

Description

Technical Field

[0001] This invention belongs to the field of laser additive manufacturing technology, specifically a method for reducing the anisotropy of titanium alloys using laser additive manufacturing combined with friction stir process. Background Technology

[0002] TC11 titanium alloy refers to a Ti-6.5Al-3.5Mo-1.5Zr-0.3Si series α+β type titanium alloy. It possesses high specific strength, good corrosion resistance, and formability, making it a core structural material for laser additive manufacturing in high-end fields such as aerospace. Laser additive manufacturing technology, with its advantages of near-net-shape forming and integrated manufacturing of complex components, has become the core manufacturing technology for TC11 titanium alloy components in high-end fields such as aerospace, effectively overcoming the traditional processing difficulties of TC11 titanium alloy. However, the "instant heating and cooling" thermal cycling characteristic of this technology easily causes TC11 titanium alloy to form coarse, directionally grown β-columnar crystals, resulting in significant anisotropy in the mechanical properties of the components (up to 15%-70%), seriously affecting its reliable application under complex load scenarios.

[0003] Existing technologies address the significant anisotropy of titanium alloys through alloying modification, subsequent heat treatment, or optimization of laser process parameters. However, these solutions have the following limitations:

[0004] (1) Alloying modification may disrupt the stability of the matrix composition of TC11 titanium alloy and increase costs;

[0005] (2) Subsequent heat treatment is prone to causing component deformation and prolonging the production cycle;

[0006] (3) Simply optimizing the laser process parameters has limited effect on the breakage of columnar crystals and it is difficult to fundamentally eliminate anisotropy. Summary of the Invention

[0007] The purpose of this invention is to provide a method for reducing the anisotropy of titanium alloys using a laser additive manufacturing and friction stir composite process. By adopting an "interlayer instant composite" mode, the forming advantages of laser additive manufacturing and the microstructure modification advantages of friction stir processing are combined to construct a composite manufacturing process. This process can efficiently reduce the anisotropy of TC11 titanium alloy components without the need for additional alloying or complex heat treatment, perfectly solving the current technical bottleneck and having significant engineering application value.

[0008] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0009] This invention provides a method for reducing the anisotropy of titanium alloys using a laser additive manufacturing process combined with friction stir, comprising the following steps:

[0010] Step 1: Obtain TC11 powder and dry it;

[0011] Step 2: Using the set laser scanning strategy, laser powder deposition is performed on the dried TC11 powder in a layered manner to obtain the first laser cladding layer;

[0012] Step 3: Perform stirring and friction on the first laser cladding layer according to the set stirring path until the first laser cladding layer is completely processed;

[0013] Step 4: Repeat steps 2 to 3 above to complete the laser cladding and friction stir composite processing layer by layer to obtain the shaped part.

[0014] As an alternative technical solution, when performing the drying process:

[0015] The TC11 powder was dried in a vacuum environment at a temperature of 120 degrees Celsius for 4 to 8 hours.

[0016] As an optional technical solution, the laser scanning strategy specifically includes:

[0017] When performing laser scanning on each layer, a serpentine scanning method is used without scanning the edges. The first scanning trajectory passes through the serpentine track to the second scanning trajectory, and so on, to complete the scanning of each layer.

[0018] The scanning directions between layers are arranged at 90° intersections: if the first scan track of the first layer is at 45° to the edge of the substrate, then the first scan track of the second layer is at 135° to the edge of the substrate.

[0019] As an alternative technical solution, a laser additive manufacturing device is used to perform laser powder deposition on TC11 powder. The parameters of the laser additive manufacturing device are set as follows: power 2000 watts, spot size 3 mm, scanning speed 960 mm / min, powder feeding speed 1.2 rpm, overlap 2.0 mm, and layer thickness 1 mm.

[0020] As an alternative technical solution, a stirring head is used to perform stirring friction on the first laser cladding layer according to a set stirring path. The stirring friction process parameters are set as follows: stirring head rotation speed 450 rpm, forward speed 150 mm / min, stirring head tilt 3°, downward pressure 0.1 mm into the surface, and overlap 80%.

[0021] As an optional technical solution, the set stirring path is a straight path.

[0022] As an alternative technical solution, after obtaining the first laser cladding layer, the process involves holding the layer for a first set time, and then performing stirring and friction on the first laser cladding layer according to a set stirring path.

[0023] As an alternative technical solution, in step three:

[0024] The first laser cladding layer is subjected to friction stirring with a straight-line stirring path to complete the first pass, and then remains for a second set time.

[0025] The second pass of friction mixing is completed with an overlap rate of 80% with the first pass, and then the process is paused for the second set time.

[0026] This process is repeated until the entire area of ​​the first laser cladding layer is covered.

[0027] As an alternative technical solution, the dried TC11 powder is laser clad under inert gas protection.

[0028] As an alternative technical solution, the particle size of TC11 powder is 50–150 micrometers.

[0029] The present invention has the following beneficial effects:

[0030] Traditional processes often employ the approach of "concentrated friction processing after overall additive forming" or rely solely on optimizing a single process parameter. This approach fails to fundamentally prevent the directional continuation of coarse β-columnar crystals between layers, resulting in a high level of anisotropy in the components (typically above 15%). This invention provides a method for reducing anisotropy in titanium alloys using a laser additive manufacturing combined with friction stir processing. It innovatively adopts an "instantaneous interlayer composite" mode, simultaneously performing friction stir processing during the high-temperature, fresh microstructure stage of each laser additive forming layer. Leveraging the good plasticity and low deformation resistance of the microstructure at this stage, the process efficiently breaks up the newly formed columnar crystals and promotes equiaxed grains through intense plastic deformation and dynamic recrystallization. Ultimately, this controls the anisotropy of key mechanical properties such as yield strength and tensile strength to within 3.5%, achieving a control effect far exceeding that of traditional methods.

[0031] Meanwhile, existing technologies, when combined with subsequent heat treatment or alloying modifications, not only increase production cycles and raw material costs but also easily lead to new problems such as component deformation and insufficient microstructure uniformity. This method requires no additional processes. Through the integrated design of interlayer processes, it ensures the forming efficiency of complex components while simultaneously eliminating defects such as intralayer porosity and incomplete fusion through friction stir processing. This not only improves the density of components but also takes into account the adaptability and performance stability of complex structures, effectively solving the technical pain point in the industry of the difficulty in balancing "complex component forming" and "high-performance, low-anisotropy control".

[0032] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is an overall flowchart of Embodiment 1 of the present invention.

[0035] Figure 2 This is a schematic diagram of the laser scanning strategy for the additive manufacturing process in Embodiment 1 of the present invention.

[0036] Figure 3 This is a schematic diagram showing the relative position and orientation of the stirring head and the deposited layer in the stirring friction process of Embodiment 1 of the present invention.

[0037] Figure 4 This is a schematic diagram of the rotation direction and processing path of the stirring head in the friction stirring process of Embodiment 1 of the present invention.

[0038] Figure 5 This is a schematic diagram of the microscopic characterization of a portion of the cross section parallel to the BD direction in Embodiment 1 of the present invention, magnified 40 times under an electron microscope.

[0039] Figure 6 for Figure 5 A schematic diagram of the microscopic characterization of a portion of region a under an electron microscope, magnified 100 times.

[0040] Figure 7 for Figure 5 A schematic diagram of the microscopic characterization of a portion of region b under an electron microscope, magnified 100 times.

[0041] Figure 8 for Figure 5 A schematic diagram of the microscopic characterization of a portion of region c under an electron microscope, magnified 100 times.

[0042] Figure 9 This is a schematic diagram of the microscopic characterization of a portion of the cross section perpendicular to the BD direction in Embodiment 1 of the present invention, magnified 40 times under an electron microscope.

[0043] Figure 10 for Figure 9 A schematic diagram of the microscopic characterization of a portion of region d under an electron microscope at 100x magnification.

[0044] Figure 11 for Figure 9 A schematic diagram of the microscopic characterization of a portion of region e under an electron microscope, magnified 100 times.

[0045] Figure 12for Figure 9 A schematic diagram of the microscopic characterization of a portion of region f under an electron microscope, magnified 100 times.

[0046] The attached diagram lists the components represented by each number as follows:

[0047] 1. First laser cladding layer; 2. Second laser cladding layer; 3. Nth laser cladding layer; 4. First scanning trajectory; 5. Second scanning trajectory; 6. Deposition layer; 7. Stirring head; 8. Rotation direction; 9. Processing direction; 10. First pass; 11. Second pass; 12. Third pass. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] This invention provides a novel method for reducing the anisotropy of TC11 titanium alloy produced by laser additive manufacturing through a combined process of laser additive manufacturing and friction stirring. This method can eliminate or effectively suppress the coarse β-columnar grains in titanium alloys produced by laser additive manufacturing, refine the grain size of TC11 titanium alloy produced by laser additive manufacturing, reduce the anisotropy of the titanium alloy, and control the anisotropy of the conventional mechanical properties of the titanium alloy to within 2%.

[0050] The method for reducing the anisotropy of titanium alloys using laser additive manufacturing combined with friction stir composite process provided by this invention includes the following steps:

[0051] Step 1: Obtain TC11 powder and dry it;

[0052] Step 2: Using the set laser scanning strategy, laser powder deposition is performed on the dried TC11 powder in a layered manner to obtain the first laser cladding layer 1;

[0053] Step 3: Perform stirring and friction on the first laser cladding layer 1 according to the set stirring path until the first laser cladding layer 1 is completely processed;

[0054] Step 4: Repeat steps 2 to 3 above to complete the laser cladding and friction stir composite processing layer by layer to obtain the shaped part.

[0055] like Figure 1As shown, a more generalized expression is used, with the current layer being designated as the i-th laser cladding layer, where i represents the i-th layer. After obtaining the i-th laser cladding layer using the set laser scanning strategy and cooling it, the stirring friction head is precisely positioned on the surface of the i-th laser cladding layer according to the set scheme. Finally, the i-th laser cladding layer is stirred and rubbed according to the set stirring strategy until the entire i-th laser cladding layer is processed, at which point the overall processing of the current i-th laser cladding layer is complete.

[0056] Next, continue printing the (i+1)th laser cladding layer and repeat the above steps until the set number of laser cladding layers is completed, and the molded material is obtained.

[0057] Overall, this embodiment incorporates the friction stir method into the additive manufacturing of TC11 titanium alloy, which effectively suppresses the growth of coarse primary columnar crystals, promotes the grains of TC11 titanium alloy to become more equiaxed and refined, and refines the α-lamellae, thereby reducing the anisotropy of the conventional mechanical properties of laser additively manufactured TC11 titanium alloy.

[0058] More detailed:

[0059] In step one, commercial TC11 powder with a particle size of 50-150 μm is selected. The TC11 powder is dried in a vacuum environment at a temperature of 120°C for 4-8 hours to fully remove the adsorbed moisture and impurities from the powder and ensure the quality of subsequent molding.

[0060] In step two, a laser additive manufacturing device is used to deposit TC11 powder using laser powder deposition. The parameters of the laser additive manufacturing device are set as follows: power 2000W, spot size 3mm, scanning speed 960mm / min, powder feed 1.2 rpm, powder density 7g / min, overlap 2.0mm, and layer thickness approximately 1mm.

[0061] Laser additive manufacturing equipment is an industrial device that melts metal powder with a high-energy laser beam and deposits it layer by layer to form parts. Its core consists of modules such as a laser, a CNC machine tool, and a powder feeding system, and it is a mature device in the existing technology.

[0062] It can be understood that in this embodiment, laser powder deposition is performed on the dried TC11 powder in a layered manner, and the layered manner is also a prior art.

[0063] Furthermore, the defined laser scanning strategy specifically includes:

[0064] When performing laser scanning on each layer, a serpentine scanning method is used. The first scanning track 4 passes through the serpentine track to the second scanning track 5, and so on, to complete the scanning of each layer.

[0065] The scanning directions between layers are arranged at 90° intersections: if the first scan track 4 of the first layer is at 45° to the edge of the substrate, then the first scan track 4 of the second layer is at 135° to the edge of the substrate.

[0066] like Figure 2 As shown, the powder dried in step one is deposited using a laser additive manufacturing device with a serpentine reciprocating scanning strategy that does not sweep the edges and crosses the layers at 90°. Each layer is about 1 mm thick, and the layer is left to stand for 60 seconds after each layer is completed.

[0067] Figure 2 In the diagram, the bottom layer shows the first laser cladding layer 1, the middle layer is the second laser cladding layer 2, and the top layer is the Nth laser cladding layer 3, where N represents the Nth layer. The scanning angles of the first laser cladding layer 1 and the second laser cladding layer 2 are intersecting at 90°. A serpentine intra-layer scanning trajectory from the first scanning trajectory 4 to the second scanning trajectory 5 is also shown. Since edge scanning is not performed, the position connecting the first scanning trajectory 4 and the second scanning trajectory 5 is not scanned.

[0068] In step three, the stirring head 7 is used to perform stirring friction on the first laser cladding layer 1 according to the set stirring path. The stirring friction process parameters are set as follows: stirring head rotation speed 450 rpm, forward speed 150 mm / min, stirring head 7 tilt 3°, stirring head 7 diameter 3 mm, effective depth 3 mm, downward pressure 0.1 mm into the surface, and overlap 80%.

[0069] Figure 3 The image clearly shows the relative positional relationship between the deposition layer 6 and the stirring head 7, as well as the orientation of the stirring head 7. The stirring head 7 is tilted at 3° and pressed down 0.1 mm into the surface of the deposition layer 6. The deposition layer 6 is the aforementioned first laser cladding layer 1, second laser cladding layer 2, etc.

[0070] In this embodiment, stirring head 7 is used to perform stirring friction. The stirring head can be a mature device from the existing technology, and the texture adopts an Archimedean spiral. At present, the simple stirring friction process is already mature.

[0071] In this embodiment, the core function of the friction stir process is to contact the deposited laser cladding layer with its high-speed rotation, use frictional heat to locally soften the surface of the cladding layer, and at the same time, use the mechanical stirring action of the stirring head to break the original columnar crystal growth orientation in the cladding layer, thereby inhibiting the continuous growth of columnar crystals. It can also refine the grains, improve the uniformity of the cladding layer structure, and reduce defects such as pores and cracks.

[0072] In step three:

[0073] After obtaining the first laser cladding layer 1, the process is paused for a first set time, and then the first laser cladding layer 1 is stirred and rubbed according to a set stirring path.

[0074] During stirring and friction:

[0075] First, the first laser cladding layer 1 is subjected to friction stirring using a straight-line stirring path to complete the first pass 10, and then remains for a second set time.

[0076] Afterwards, the second pass 11 is completed with an overlap rate of 80% with the first pass 10, and then the process is paused for the second set time.

[0077] This process is repeated until the entire area of ​​the first laser cladding layer 1 is covered.

[0078] The first and second set times mentioned above are both 60 seconds.

[0079] It can be understood that the above-mentioned stirring path is set as a straight path.

[0080] Figure 4 This is a schematic diagram showing the rotation direction of the stirring head and the processing path in the friction stirring process. Figure 4 In the process, the stirring head 7 is fed along a straight line, with the length direction of the deposited layer 6 as the processing direction 9 and the counterclockwise direction as the rotation direction of the stirring head 7 8. The first pass 10, the second pass 11, and the third pass 12 after processing are also shown.

[0081] Friction stir processing can refine the grains and improve the microstructure uniformity of TC11 titanium alloy through intense plastic deformation and dynamic recrystallization, but it cannot directly achieve the forming of complex components. Therefore, this invention combines the forming advantages of laser additive manufacturing with the microstructure modification advantages of friction stir processing to construct a composite manufacturing process. This process can efficiently reduce the anisotropy of TC11 titanium alloy components without the need for additional alloying or complex heat treatment, thus solving the current technical bottleneck and having significant engineering application value.

[0082] In step four, steps two to three are repeated to complete the laser cladding and friction stir composite processing layer by layer, resulting in the shaped part, specifically including:

[0083] After completing the friction stir processing of the first laser cladding layer 1 in step 3, the next cycle begins, and the TC11 powder of the second layer is laser clad as described in step 2 to obtain the second laser cladding layer 2.

[0084] Then, the second laser cladding layer 2 is subjected to friction stirring processing as described in step three until the second laser cladding layer 2 is completely processed.

[0085] The cycle continues until the Nth layer of TC11 powder is laser clad to obtain the Nth laser clad layer 3. The Nth laser clad layer 3 is then subjected to friction stirring. After processing, the shaped part is obtained.

[0086] To better illustrate and compare the solutions of the present invention, the following embodiments and comparative examples are provided.

[0087] Example 1

[0088] This embodiment provides a method for reducing the anisotropy of titanium alloys through a laser additive manufacturing and friction stir composite process. By using a laser additive manufacturing and friction stir composite process, the anisotropy of TC11 titanium alloy in laser additive manufacturing is reduced.

[0089] Step S1: Dry the commercial TC11 powder in a vacuum drying oven at 120°C for at least 4 hours.

[0090] Step S2: Using a laser additive manufacturing apparatus, the TC11 powder dried in step 1 is laser clad under an inert argon protective atmosphere, such as... Figure 2 As shown, the first pass of each layer is at a 45° angle to the edge of the substrate, and passes through a serpentine track to the second pass;

[0091] Step S3: The second laser cladding layer overlaps the first layer by 0.2mm, and this process is repeated until the layer is printed.

[0092] Step S4: After printing the first layer, pause for 60 seconds;

[0093] Step S5: Tilt the stirring head 7 at 3° and press it down 0.1mm into the surface to complete the position and attitude calibration before processing. Figure 3 As shown;

[0094] Step S6: The additive manufacturing layer from step S4 is subjected to a stirring friction process with a straight-to-the-bottom stirring path to complete the first pass 10, with a dwell time of 60s.

[0095] In step S7, the overlap rate between the second pass (11) of the friction stir machining and the first pass (10) is controlled at 80%, and the process is paused for 60 seconds after completion. This process is repeated until the entire area of ​​the cladding layer in step S4 is covered. Figure 4 As shown;

[0096] Step S8: The scanning direction of the second laser cladding layer is arranged at a 90° angle to the scanning direction of the first layer;

[0097] Step S9: Repeat steps S2-S8 to complete the laser cladding and friction stir composite processing layer by layer until a shaped part of the target size is obtained.

[0098] In this embodiment, the commercial TC11 powder selected has a particle size of 50–150 μm. The TC11 powder was dried in a vacuum environment at a temperature of 120°C for 4–8 hours to fully remove adsorbed moisture and impurities from the powder and ensure the quality of subsequent molding.

[0099] Subsequently, the dried TC11 powder was laser powder deposited using a laser additive manufacturing device. The deposition process adopted a serpentine reciprocating scanning strategy with no edge sweeping and 90° interlayer crossover. The core process parameters were set as follows: laser power 2000W, spot diameter 3mm, scanning speed 960mm / min, powder feed rate of about 7g / min (corresponding to a powder feed speed of 1.2 rpm), pass overlap 2.0mm, and deposition thickness of about 1mm per layer. After each layer was scanned, the interlayer dwell time was 60s.

[0100] Finally, the laser additive manufacturing deposited layer 6 was subjected to a friction stir process. The stirring path was designed to be a straight line to the bottom in each pass, with a 60-second pause between each pass. The key parameters of the friction stir process were: stirring head 7 rotation speed 450 rpm, forward speed 150 mm / min, stirring head 7 tilt angle 3°, stirring head 7 diameter 3 mm, effective stirring depth 3 mm, downward pressure 0.1 mm (penetrating to the surface of deposited layer 6), and pass overlap rate 80%. Typical locations were selected, and mechanical property tests and SEM (scanning electron microscope) microscopic characterization were performed at 500℃.

[0101] Comparative Example 1

[0102] Using TC11 pre-alloyed powder with a particle size of 70~150μm as raw material, rolled TA2 (TA2 refers to industrial pure titanium with a titanium content ≥99.0%, which is an α-type titanium alloy) titanium plate as substrate;

[0103] An AGS-TFL-8000 CO2 laser was used, with a laser power of 6kW, a spot diameter of 6mm, a scanning speed of 1200mm / min, and a powder feed rate of 850~900g / h. During the deposition process, the oxygen content in the protective atmosphere was controlled to be below 50ppm (ppm refers to parts per million, which represents the number of a certain component in a mixture per million parts by mass or volume). A unidirectional continuous scanning trajectory was adopted, and the laser moved continuously along the preset direction within the same layer, forming a heterogeneous structure through layer-by-layer deposition.

[0104] No additional heat treatment is required after deposition; samples can be directly cut from the central region of the deposit along the typical orientation.

[0105] Comparative Example 2

[0106] TC11 pre-alloyed powder, prepared by plasma rotating electrode, with a particle size of 50~150μm and an average particle size of 105±25μm, was selected. A 100×100×8mm³ TA1 (TA1 refers to industrial pure titanium with a titanium content ≥99.5%, which is an α-type titanium alloy) pure titanium plate was used as the substrate. Laser cladding was performed using a YLR-1000IPG continuous wave fiber laser (wavelength 1070nm). The laser power was set to 900W, the scanning speed to 4mm / s, the spot diameter to 2.2mm, the powder feed rate to 5.5g / min, the argon gas protection flow rate to 25L / min, and the volumetric energy density to be controlled at 142J / mm³ (joules per cubic millimeter).

[0107] The deposition process employed a special interlayer pause strategy, dividing the deposition process into multiple cycles. Each cycle contained 4 or 6 layers (corresponding to SP4 and SP6 samples, respectively). After each layer was deposited, the deposition was paused for 10 seconds, and the deposited specimens were air-cooled to room temperature after each cycle. Meanwhile, using the conventional interlayer pause process (IP1 sample) with "air-cooling to room temperature after each layer deposition" as a control, flat dog-bone shaped specimens were cut along the horizontal and vertical directions and subjected to room temperature tensile tests at a tensile speed of 0.6 mm / min.

[0108] Finally, the mechanical performance data and anisotropy indices of the vertical BD and parallel BD of the above embodiments and comparative examples are listed in Table 1 for comparison. The meanings of vertical BD and parallel BD are as follows: BD is an abbreviation for Build Direction, which means the direction of construction; parallel BD refers to being parallel to the direction of component manufacturing, and vertical BD refers to being perpendicular to the direction of component manufacturing.

[0109] Table 1: Anisotropy results of tensile tests (including comparative examples)

[0110]

[0111] In Table 1 above, IP1 indicates air cooling to room temperature after each deposition layer; SP4 indicates continuous deposition of 4 layers in each deposition cycle with a 10s pause between each layer, followed by air cooling to room temperature after the entire cycle is completed; SP6 indicates continuous deposition of 6 layers in each deposition cycle with a 10s pause between each layer, followed by air cooling to room temperature after the entire cycle is completed.

[0112] As can be seen from Table 1 above, the present invention, through additive manufacturing processes, can effectively improve the macro- and micro-structure of TC11 produced by laser additive manufacturing, refine the TC11 grains, and eliminate or effectively suppress β-columnar crystals, thereby reducing its anisotropy. Applying the method of the present invention is beneficial for further promoting the application of laser additive manufacturing of TC11 titanium alloys in the defense industry and aerospace fields.

[0113] Figure 5This is a schematic diagram showing the microscopic characterization of a portion of the cross-section parallel to the BD direction in this embodiment, magnified 40 times under an electron microscope. Furthermore, to obtain a clearer demonstration, in... Figure 5 Three regions, a, b, and c, were selected, and portions of each region were magnified 100x under an electron microscope for demonstration. (Specific details are shown below.) Figure 6 , Figure 7 and Figure 8 As shown.

[0114] Figure 9 This is a schematic diagram showing the microscopic characterization of a portion of the cross-section perpendicular to the BD direction in this embodiment, magnified 40 times under an electron microscope. Furthermore, to obtain a clearer demonstration, in... Figure 9 Three regions, d, e, and f, were selected, and portions of each region were magnified 100x under an electron microscope for demonstration. (Specific details are shown below.) Figure 10 , Figure 11 and Figure 12 As shown.

[0115] The above Figures 5-12 In this text, SED stands for Scanning Electron Microscope, kV represents accelerating voltage, WD represents working distance, mm represents millimeter, and μm represents micrometer.

[0116] From the above Figures 5-12 As can be seen, the equiaxed crystal morphology exhibited by the alloy in the direction parallel to BD is highly similar to that in the direction perpendicular to BD. Both not only show a relatively regular equiaxed shape in the overall grain morphology, but also exhibit similar characteristics in grain size distribution, with no significant morphological differences arising from different orientations. This phenomenon indicates that under the conditions of the friction stir process, orientation did not have a significant anisotropic effect on the nucleation and growth process of equiaxed crystals, allowing grains in different directions to develop uniformly, ultimately forming equiaxed crystal structures with similar morphologies.

[0117] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0118] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method of reducing anisotropy in titanium alloys using laser additive manufacturing with friction stir processing, characterized in that, Includes the following steps: Step 1: Obtain TC11 powder and dry it; Step 2: Using the set laser scanning strategy, laser powder deposition is performed on the dried TC11 powder in a layered manner to obtain the first laser cladding layer; The defined laser scanning strategy includes: When performing laser scanning on each layer, a serpentine scanning method is used without scanning the edges. The first scanning trajectory passes through the serpentine track to the second scanning trajectory, and so on, to complete the scanning of each layer. The position connecting the first and second scan tracks was not scanned; The scanning directions between layers are arranged at 90° intersections: if the first scan track of the first layer is at 45° to the edge of the substrate, then the first scan track of the second layer is at 135° to the edge of the substrate. Step 3: Perform stirring and friction on the first laser cladding layer according to the set stirring path until the first laser cladding layer is completely processed; After obtaining the first laser cladding layer, the process is paused for a first set time, and then the first laser cladding layer is stirred and rubbed according to a set stirring path. In step three: the first laser cladding layer is subjected to friction stirring with a straight-line stirring path to complete the first pass, and then remains for the second set time. The second pass of friction mixing is completed with an overlap rate of 80% with the first pass, and then the process is paused for the second set time. This process is repeated until the entire area of ​​the first laser cladding layer is covered. Step 4: Repeat steps 2 to 3 above to complete the laser cladding and friction stir composite processing layer by layer to obtain the shaped part.

2. The method for reducing the anisotropy of titanium alloys using laser additive manufacturing combined with friction stir as described in claim 1, characterized in that, During the drying process: The TC11 powder was dried in a vacuum environment at a temperature of 120 degrees Celsius for 4 to 8 hours.

3. The method of claim 1, wherein the laser additive friction stir processing of titanium alloys to reduce anisotropy is characterized by, Laser powder deposition of TC11 powder was performed using a laser additive manufacturing apparatus. The parameters of the laser additive manufacturing apparatus were set as follows: power 2000 watts, spot size 3 mm, scanning speed 960 mm / min, powder feed speed 1.2 rpm, overlap 2.0 mm, and layer thickness 1 mm.

4. The method of claim 1, wherein the laser additive friction stir processing of titanium alloys to reduce anisotropy is characterized by, The first laser cladding layer is subjected to stirring friction using a stirring head according to a set stirring path. The stirring friction process parameters are set as follows: stirring head rotation speed 450 rpm, forward speed 150 mm / min, stirring head tilt 3°, downward pressure 0.1 mm into the surface, and overlap 80%.

5. The method of claim 1, wherein the laser additive friction stir processing of titanium alloys to reduce anisotropy is characterized by, The set stirring path is a straight path.

6. The method of claim 1, wherein the laser additive friction stir processing of titanium alloys to reduce anisotropy is characterized by, The dried TC11 powder was laser clad under an inert gas atmosphere.

7. The method of claim 1, wherein the laser additive friction stir processing of titanium alloys to reduce anisotropy is characterized by, The particle size of TC11 powder is 50–150 micrometers.

Images