Internal micropore preparation method based on powder feeding additive manufacturing

Abstract

The invention provides an internal micropore preparation method based on powder feeding additive manufacturing, and belongs to the technical field of aircraft structure testing, the method comprises the following steps: obtaining an additive manufacturing base material or a forge piece base material through an additive manufacturing or forging mode, and treating the surface of the base material to enable the base material to be in a light state; fixing the base material, and drilling the surface of the base material in a light state by adopting a spherical milling cutter to obtain a prefabricated hole with a specified size; then marking the reverse side of the surface of the substrate in a light state by using an auxiliary positioning technology; determining process parameters of additive manufacturing single-layer deposition, carrying out additive manufacturing single-layer deposition on the surface of the substrate in a light state based on the process parameters, obtaining a closed micropore defect at the prefabricated hole, and continuing to carry out additive manufacturing layer-by-layer deposition on the additive manufacturing single-layer deposition to obtain a structural member with the same size as the test piece; and machining the obtained structural member to obtain a test piece containing the specified micropore defect size.

Description

Technical Field

[0001] This application belongs to the field of aircraft structural testing technology, and specifically relates to a method for preparing internal micropores based on powder feeding additive manufacturing. Background Technology

[0002] With the rapid development of aviation technology, future advanced aircraft must meet requirements such as long endurance, lightweight design, large payload, and high reliability. This not only increases the demand for high-strength alloy materials such as titanium alloys, high-temperature alloys, high-strength aluminum alloys, and ultra-high-strength steel, but also greatly accelerates the application of large and complex integral structural components in key load-bearing components of aviation equipment (such as fuselage joints, wing spars, and engine frames). However, the precision manufacturing of large and complex integral structural components for aircraft poses a challenge to the existing manufacturing capabilities in China, and their quality directly affects the overall level and reliability of the equipment.

[0003] Additive manufacturing (ADM) technology uses 3D model data as a basis and employs a high-energy laser heat source to scan point by point and deposit material layer by layer to create parts. It eliminates the need for molds, significantly reducing manufacturing steps and shortening processing cycles, making it particularly suitable for the rapid prototyping of difficult-to-machine materials such as titanium alloys. Furthermore, additive manufacturing results in significant weight reduction for structural components, providing greater flexibility for the overall structural design and optimization of advanced aircraft, and enabling further optimization and improvement of overall aircraft performance.

[0004] However, compared to traditional manufacturing processes, laser additive manufacturing of structural components features integrated material-process-structure forming, making their mechanical properties subject to the coupled influence of structural details, microstructure characteristics, and internal defects. Experimental studies have shown that additively manufactured structures contain unavoidable forming defects such as irregular unmelted pores, unmelted particles, keyholes, and porosity, which have a significant impact on mechanical properties (especially fatigue performance). The formation of these internal defects is influenced by additive manufacturing process parameters, exhibiting characteristics such as random distribution, varying sizes, and difficulty in control. Currently, although existing research has accumulated some mechanical property data, it still cannot clearly and systematically elucidate the influence of internal porosity defects (especially those with sizes in the range of 0.2 mm to 1.2 mm) on the mechanical properties of additively manufactured structures, limiting the application of this technology in the fabrication of critical aircraft structural components.

[0005] Therefore, how to introduce internal micropores with controllable size and location into additive manufacturing structural parts, and then quantitatively evaluate the impact of internal porosity defects on the mechanical properties of additive manufacturing structural parts, is a technical problem that urgently needs to be solved. Summary of the Invention

[0006] The purpose of this application is to provide a method for preparing internal micropores based on powder feeding additive manufacturing, so as to solve or alleviate at least one of the problems in the prior art.

[0007] The technical solution of this application is: a method for preparing internal micropores based on powder feeding additive manufacturing, comprising:

[0008] An additive manufacturing substrate or forging substrate is obtained by additive manufacturing or forging, and the surface of the additive manufacturing substrate or forging substrate is treated to make it visible to light.

[0009] The additive manufacturing substrate or forging substrate is fixed, and a ball end mill is used to drill holes in the exposed surface of the substrate to obtain pre-drilled holes of a specified size. Then, auxiliary positioning technology is used to mark the reverse side of the exposed surface of the substrate to indicate the processing position of the test piece.

[0010] Determine the process parameters for additive manufacturing single-layer deposition, and perform additive manufacturing single-layer deposition on the light-exposed surface of the substrate based on these process parameters to obtain closed micropore defects at the pre-made holes. Continue to perform additive manufacturing layer-by-layer deposition on the single-layer deposition to obtain a structural part with a size not smaller than the test piece.

[0011] The obtained structural component is machined to obtain an additive manufacturing test piece containing a specified micropore defect size inside.

[0012] Preferably, the additive manufacturing substrate or forging substrate is made of the same material as the test piece, and the additive manufacturing substrate or forging substrate is not less than half the length of the test piece.

[0013] Preferably, the surface of the additive manufacturing substrate or forging substrate is treated by machining to expose the substrate surface to light.

[0014] Preferably, the process parameters for additive manufacturing single-layer deposition are: spot diameter 3mm~10mm, scanning speed 6mm / s~15mm / s, lateral and longitudinal overlap rate 50%, laser power 1000W~3000W, and powder feeding rate 2g / min~10g / min.

[0015] Preferably, the additive manufacturing layer-by-layer deposition process parameters are: spot diameter 3mm~10mm, scanning speed 4mm / s~15mm / s, lateral and longitudinal overlap rate 50%, laser power 1000W~3000W, and powder feeding rate 5g / min~30g / min.

[0016] The method for preparing internal micropores based on powder feeding additive manufacturing provided herein can successfully prepare additive manufacturing test pieces with internal micropores that are controllable in size, location, and shape. This solves the problem in the prior art that it is impossible to quantitatively evaluate the impact of 0.2mm~1.2mm pore defects in the additive manufacturing structure on its mechanical properties. Attached Figure Description

[0017] To more clearly illustrate the technical solutions provided in this application, the accompanying drawings will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application.

[0018] Figure 1 This is a flowchart of the internal micropore preparation method based on powder feeding additive manufacturing in this application.

[0019] Figure 2 This is a schematic diagram of the test specimen preparation process for this application.

[0020] Figure 3 This is a schematic diagram of the metallographic structure of an additively manufactured TC11 titanium alloy test piece according to an embodiment of this application. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings.

[0022] This application proposes a method for preparing internal micropores based on powder feeding additive manufacturing, applicable to existing additive manufacturing high-performance alloy systems, to obtain additive manufacturing structural parts with controllable internal micropore size (0.2mm~1.2mm). The additive manufacturing structural parts can be subjected to mechanical property tests to solve the problem that the random distribution and inconsistent size of internal defects in additive manufacturing structures make it difficult to evaluate their impact on mechanical properties.

[0023] like Figure 1 As shown, the method for preparing internal micropores based on powder feeding additive manufacturing provided in this application includes the following steps:

[0024] Step S1: Obtain an additive manufacturing substrate or forging substrate (hereinafter referred to as substrate) by additive manufacturing or forging, and treat the surface of the substrate to expose it to light.

[0025] Reference Figure 2 As shown, the additive manufacturing substrate or forging substrate is first prepared by additive manufacturing or forging. The substrate and the test piece should be made of the same material. The size of the substrate is selected according to the specifications of the test piece, and it is generally not less than half the length of the test piece. The surface of the substrate is treated by machining to expose it to light, and then cleaned with acetone and dried for later use.

[0026] Step S2: Fix the substrate and use a ball end mill to drill holes in the exposed surface of the substrate to obtain pre-made holes of a specified size. Then, use auxiliary positioning technology to mark the reverse side of the substrate to indicate the processing position of the test piece.

[0027] Specifically, the substrate to be additively manufactured is fixed on a worktable and leveled. Based on relevant technical acceptance standards or specifications, the micropore size of the internal defects to be evaluated is determined. Using a ball end mill adapted to this micropore size, pre-drilled holes are created on the exposed surface of the substrate. After determining the location of the defective micropores using infrared positioning or wire cutting techniques, marks are made on the reverse side of the substrate to indicate the extraction position of the test piece during processing. For example, markings can be made on the reverse side of the substrate with a marker or by drilling with a ball end mill, thereby controlling the position of the micropores inside the test piece.

[0028] In this application, the pre-formed holes prepared on the light-exposed surface of the substrate are typically shallow holes, and the depth of the pre-formed holes can be determined based on the additive manufacturing equipment, process parameters, and remelting depth.

[0029] For example, in this application Figure 2 In the illustrated embodiment, the nominal dimensions of the internal micropore defects to be evaluated are φ0.4mm, φ0.6mm, and φ0.8mm. Ball end mills of the above three sizes can be customized by cutting tools. The ball end mills are used to drill holes in the exposed surface of the substrate to obtain pre-made holes of the three sizes. Then, the ball end mills are also used to drill holes in the substrate on the reverse side of the exposed surface to mark the center position of the test piece.

[0030] Step S3: Determine the process parameters for additive manufacturing single-layer deposition. Based on these process parameters, perform additive manufacturing single-layer deposition on the light-exposed surface of the substrate. Remelt at the pre-made holes to obtain closed micropore defects. Continue additive manufacturing layer-by-layer deposition on the single-layer deposition to obtain a structural part with a size not smaller than the test piece.

[0031] In this application, the process parameters of the additive manufacturing equipment are determined based on the characteristics of the additive manufacturing alloy and the target requirements of additive deposition. Preferably, for single-layer additive deposition, the process parameters are: spot diameter 3mm~10mm, scanning speed 6mm / s~15mm / s, lateral and longitudinal overlap rate 50%, laser power 1000W~3000W, and powder feed rate 2g / min~10g / min. For layer-by-layer additive deposition, the process parameters differ from those for single-layer deposition, and are: spot diameter 3mm~10mm, scanning speed 4mm / s~15mm / s, lateral and longitudinal overlap rate 50%, laser power 1000W~3000W, and powder feed rate 5g / min~30g / min.

[0032] Step S4: Machining the structural component obtained in step S3 to obtain a test piece containing a specified micropore defect size.

[0033] In this application, the structural component obtained in step S3 is extracted from the marked area on the reverse side of the substrate in step S2 by means of wire cutting or machining, thereby preparing a cylindrical test piece containing a specified micropore defect size (the cylinder shown by the dashed line in the figure).

[0034] This application takes an additively manufactured TCl1 titanium alloy structural component test piece (or test bar) as an example. The final length of the test piece is 100mm. First, a TC11 titanium alloy substrate is prepared based on additive manufacturing. The substrate has length, width, and height dimensions of 200mm*50mm*50mm. The powder raw material uses TC11 titanium alloy powder with a particle size range of 45μm~150μm, prepared by plasma rotating electrode method. An inert gas (argon) is used as the protective gas to prepare the additive manufacturing test piece containing internal micropores. The specific process is as follows:

[0035] 1) Perform surface mechanical treatment on the additive manufacturing TC11 titanium alloy substrate until it is in a light-exposed state, and clean the light-exposed surface with acetone solution;

[0036] 2) Fix the substrate on the worktable and use a ball end mill with a diameter of φ0.4mm to drill holes in the exposed surface to a depth of 0.6mm. Then, use an infrared positioning instrument to determine the coordinates of the drilling defect location to ensure that the drilling position is at the center of the test piece. Drill holes on the other side of the substrate using the same ball end mill to a depth of 0.3mm, and use an acrylic marker to draw circles for subsequent sampling and positioning of the test piece.

[0037] 3) Re-fix the substrate and clean the surface with acetone solution. Perform additive manufacturing monolayer deposition on the surface under light to obtain closed micropore defects. The main process parameters for laser additive manufacturing monolayer deposition are spot diameter 3mm, scanning speed 6mm / s, laser power 1200W, and powder feed rate 5.74g / min. Then, continue additive manufacturing layer-by-layer deposition on the same monolayer deposition. Additive manufacturing monolayer deposition and multilayer deposition 50mm, with a substrate height of 50mm, can obtain a block or structural part with the same size as the test piece. The main process parameters for laser additive manufacturing layer-by-layer deposition are spot diameter 3mm, scanning speed 12mm / s, laser power 2400W, and powder feed rate 11.5g / min.

[0038] 4) Test specimens (i.e., test bars) are extracted from the structural components using wire cutting and machining methods to obtain test specimens containing micropore defects of specified sizes. For example... Figure 3 The image shown is a metallographic diagram of the test piece prepared in this embodiment of the application and its internal micropore defects.

[0039] It should be noted that in step 2 above, the substrate can be pre-cut and sampled using wire cutting technology, with the drilling position located at the center of the sample. The sample is then stuffed back into the substrate. After the additive forming is completed in step 4, the block or structural part is flipped over, and the test piece is sampled according to the wire cutting marks left in step 2. The sample is then machined to obtain a test piece (test bar) containing a specified micropore defect size.

[0040] The method for preparing internal micropores based on powder feeding additive manufacturing provided herein can successfully prepare additive manufacturing test pieces with internal micropores that are controllable in size, location, and shape. This solves the problem in the prior art that it is impossible to quantitatively evaluate the impact of 0.2mm~1.2mm pore defects in the additive manufacturing structure on its mechanical properties.

[0041] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for making an internal microcellular structure based on powder-fed additive manufacturing, characterized in that, The application relates to a method for manufacturing a test piece of additive manufacturing, and belongs to the technical field of additive manufacturing. An additive manufacturing base material or a forging base material is obtained by additive manufacturing or forging, and the surface of the additive manufacturing base material or the forging base material is treated to be in a light-seeing state; The additive manufacturing base material or the forging base material is fixed, and a spherical milling cutter is used to drill a preformed hole of a specified size on the light-seeing surface of the base material, and then an auxiliary positioning technology is used to mark the opposite surface of the light-seeing surface of the base material, which is used to indicate the machining position of the test piece; Process parameters of additive manufacturing single-layer deposition are determined, additive manufacturing single-layer deposition is carried out on the light-seeing surface of the base material based on the process parameters, so that a closed micro-hole defect is obtained at the preformed hole, additive manufacturing layer-by-layer deposition is continuously carried out on the additive manufacturing single-layer deposition, and a structural part not smaller than the size of the test piece is obtained; The obtained structural part is machined to obtain an additive manufacturing test piece containing a specified micro-hole defect size.

2. The internal microcellular fabrication method based on powder-fed additive manufacturing of claim 1, wherein, The additive manufacturing base material or the forging base material is the same as the material of the test piece, and the additive manufacturing base material or the forging base material is not less than half the length of the test piece.

3. The internal microcellular fabrication method based on powder-fed additive manufacturing of claim 1, wherein, The surface of the additive manufacturing base material or the forging base material is treated by a mechanical machining method, so that the surface of the base material is in a light-seeing state.

4. The internal microcellular fabrication method based on powder-fed additive manufacturing of claim 1, wherein, The process parameters of the additive manufacturing single-layer deposition are as follows: a spot diameter of 3mm-10mm, a scanning speed of 6mm / s-15mm / s, a transverse and longitudinal lap rate of 50%, a laser power of 1000W-3000W, and a powder feeding rate of 2g / min-10g / min.

5. The internal microporous fabrication method based on powder-fed additive manufacturing of claim 1, wherein, The process parameters of the additive manufacturing layer-by-layer deposition are as follows: a spot diameter of 3mm-10mm, a scanning speed of 4mm / s-15mm / s, a transverse and longitudinal lap rate of 50%, a laser power of 1000W-3000W, and a powder feeding rate of 5g / min-30g / min.

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