Heterogeneous structure forming method

Abstract

The invention discloses a heterogeneous structure forming method, which is characterized in that interlayer rolling is assisted by displacement magnetic field electric arc material increase, and comprises the following steps: step 1, a displacement magnetic field electric arc material increase process: under the action of a displacement magnetic field, according to a preset material increase manufacturing path, an alloy wire material is melted and deposited to form a deposition layer with a periodic surface profile on the section; and 2, interlayer rolling, specifically, the surface of the deposition layer is rolled through a roller, and the rolling reduction is smaller than or equal to the height difference of the wave crest and the wave trough of the periodic surface profile. According to the method, interlayer rolling is assisted by displacement magnetic field electric arc material increase, the air hole defect generated in the solidification stage of a molten pool can be effectively restrained, and the characteristic of high toughness of a material increase component is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and particularly relates to a method for forming heterogeneous structures. Background Art

[0002] Arc additive manufacturing technology is a technology that uses an arc as a heat source, stacks metal or metal alloys layer by layer based on a set path from bottom to top after melting to obtain parts or components, and has now become a common means of preparing alloy materials.

[0003] Aluminum alloy components manufactured by arc additive manufacturing often have poor mechanical properties and many surface defects. In the process of implementing the present invention, the inventor found that there are at least the following problems in the existing process of arc additive manufacturing of aluminum alloy components: the fluidity of the molten pool affects the pore morphology and porosity in the component. By changing arc pulse parameters, controlling the temperature field, etc., the arc deposition can be adjusted to improve arc deposition defects. However, the obtained aluminum alloy components have tissue defects such as coarse grains and segregation in the solidification state, and often have poor strength and plasticity. Providing a method that can effectively inhibit pore defects during the solidification stage of the molten pool while enhancing the strength and plasticity of the component is one of the key ways to solve the above problems. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for forming heterogeneous structures in view of the above-mentioned deficiencies of the prior art.

[0005] The present invention has the following advantages compared with the prior art:

[0006] 1. The present invention provides a method for forming heterogeneous structures, which uses a variable magnetic field arc additive manufacturing to assist in interlayer rolling, can effectively inhibit pore defects generated during the solidification stage of the molten pool, and has the characteristics of high strength and toughness of the additive component.

[0007] 2. Preferably, in the heterogeneous forming method of the present invention, by controlling the variable magnetic field, the arc morphology and the magnetic field stirring of the molten pool are controlled, the convection of the molten pool is accelerated, the pore size and content in the deposition layer are reduced, and the inhibition of pore defects is achieved.

[0008] 3. Preferably, the heterogeneous forming method of the present invention includes rolling the surface of the deposition layer by a roller, so that the peak is a large deformation area and the valley is a small deformation area, which can "weld" the pores in the deposition layer and further reduce pore defects.

[0009] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Brief Description of the Drawings

[0010] Figure 1 It is a schematic diagram of the mechanism of variable magnetic field generation;

[0011] Figure 2 Schematic structural diagram of the variable magnetic field arc additive manufacturing device for Example 1;

[0012] Figure 3 Variable magnetic field alternating current signal for Example 1;

[0013] Figure 4 Schematic diagram of the principle of variable magnetic field arc additive manufacturing and in - layer rolling process;

[0014] Figure 5 Schematic diagram of the heterogeneous structure of the heterogeneous - structure aluminum alloy additive manufacturing in Example 1;

[0015] Figure 6 Grain morphology and grain shape of the coarse - grain zone and fine - grain zone of the heterogeneous - structure aluminum alloy additive manufacturing in Example 1;

[0016] Figure 7 Average value of the height difference between the appearance and the large and small deformation zones of the heterogeneous - structure aluminum alloy additive manufacturing in Examples 1 - 3;

[0017] Figure 8 Schematic diagram of the morphology of the heterogeneous - structure aluminum alloy additive manufacturing in Comparative Example 1. Detailed implementation manners

[0018] Next, the technical solutions will be described clearly and completely in conjunction with the drawings and examples. Obviously, the described examples are part of the embodiments of this application, rather than all of them. All other examples obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the scope of protection of this application.

[0019] In the following description, the term "and / or" is used to describe the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, B exists alone, and both A and B exist simultaneously. Where A and B can be singular or plural.

[0020] In the following description, terms such as "include", "comprise", "have" and "contain" are all open - ended terms, that is, they are intended to mean including but not limited to.

[0021] Those skilled in the art should understand that in the following description of the embodiments of this application, the sequence numbers do not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0022] Those skilled in the art should understand that the numerical ranges in the embodiments of this application should be understood as specifically disclosing each intermediate value between the upper and lower limits of the range. Intermediate values within any stated value or stated range, as well as each smaller range between any other stated value or intermediate values within the stated range, are also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0023] Unless otherwise specified, the technical / scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this application belongs. Although this application only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of this application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0024] The technical principle adopted by the present invention: Utilize the "point loading" characteristic of the externally applied variable magnetic field to control the arc morphology and movement trajectory, prepare a deposition layer with a periodic surface profile of "quasi-sine wave" on the cross-section, and then roll it to deform it into a plastic body with non-uniform energy storage. The variable magnetic field arc additive manufacturing and interlayer rolling cooperate with each other to obtain a heterogeneous structure with high strength and toughness, coordinated coarse and fine grains and hard and soft phases.

[0025] In some embodiments, a method for forming a heterogeneous structure is provided, with variable magnetic field arc additive manufacturing assisting interlayer rolling, including:

[0026] Step 1, the process of variable magnetic field arc additive manufacturing, including:

[0027] 101. After cleaning the substrate, fix it on the workbench; install the arc welding gun and the variable magnetic field generating device on the workbench, make the gun head of the arc welding gun vertically face the substrate, with the advancing direction of the arc welding gun as the front, and the variable magnetic field generating device is located behind the arc welding gun and the included angle with the arc welding gun is 45°;

[0028] 102. Under the action of the variable magnetic field, according to the preset additive manufacturing path, melt and deposit the alloy wire to form a deposition layer with a periodic surface profile of "quasi-sine wave" on the cross-section; As a charged particle, the arc will change its morphology under the action of the variable magnetic field. By adjusting the included angle between the arc welding gun and the variable magnetic field, the variable magnetic field displacement angle, and the variable magnetic field intensity, the action exerted by the variable magnetic field on the arc can be changed.

[0029] The variable magnetic field intensity will affect both the heat transfer and flow of the arc and the molten pool. When the angle between the variable magnetic field and the welding gun remains unchanged, both the arc and the molten pool morphology have an eccentric and flowing trend.

[0030] The variable magnetic field is a variable magnetic field generated by an alternating current signal, and the waveform of the alternating current signal is a sine wave, a square wave, a positive sawtooth wave or a triangular wave; in some specific embodiments, the waveform of the alternating current signal is a sine wave type, and the upper and lower amplitudes of the sine wave are 30-80 Gs; a schematic diagram of the mechanism of the variable magnetic field generation is as Figure 1 shown;

[0031] Step 2, interlayer rolling, specifically including: using a roller to roll the surface of the deposited layer, and the rolling reduction ≤ Hp - Ht;

[0032] Plastic deformation of the arc deposition additive can promote an increase in the dislocation density inside the deposited layer, and recrystallization occurs under the action of subsequent heat treatment or additive deposition, further reducing the grain size to obtain a plastically deformed body with non-uniform energy storage;

[0033] Step 3, selectively performing heat treatment on the rolled deposited layer; specifically, when the alloy wire is a high stacking fault energy metal material, control the annealing temperature to be 510 °C and the annealing time to be 10 min, and perform heat treatment on the rolled deposited layer; when the alloy wire is a low stacking fault energy metal material, no annealing treatment is required.

[0034] A series of experiments were carried out before the application of the present invention. Now, a part of the test results are listed to further describe the invention in detail, and the following is a detailed description in combination with embodiments.

[0035] Example 1

[0036] This embodiment provides a method for forming an aluminum alloy heterogeneous structure, which uses variable magnetic field arc additive manufacturing to assist interlayer rolling, including:

[0037] Step 1, variable magnetic field arc additive manufacturing process:

[0038] Step 101, after cleaning the aluminum alloy substrate, fix it on the workbench, install the arc welding gun on the workbench, make the tip of the arc welding gun perpendicular to the aluminum alloy substrate, and the height of the tip of the gun from the aluminum alloy substrate is 12 mm. Taking the advancing direction of the arc welding gun as the front, install the variable magnetic field generating device behind the arc welding gun, and make the included angle between the variable magnetic field generating device and the arc welding gun 45°, and the distance between the tip of the welding wire and the center of the end face of the electromagnet is about 25 mm; a schematic diagram of the device structure is as Figure 2 shown;

[0039] Step 102, the wire diameter is 1.2 mm, and the wire is fed at a speed of 7 m / min. The arc melts and deposits the wire under the action of the variable magnetic field to obtain a deposited layer with a periodic surface profile of "quasi-sine wave" in cross-section; among them, the welding current is 131 A, the arc voltage is 15.5 V, and the welding speed is 5 mm / s; according to Figure 3Adjust the input signal of the variable-position magnetic field generating device to make the magnetic field strength in the molten pool area change periodically; among them, the upper and lower amplitude A of the sine wave in the AC section is 30 Gs, the frequency f is 100 Hz, and the phase φ is 0; the thickness of the aluminum alloy substrate is 15 mm; the height difference between the wave crest and the wave trough of the deposition layer is about 1.15 mm;

[0040] Step 2, interlayer rolling, specifically including: Place the roller on the deposition layer, and use the roller to roll the surface of the deposition layer to obtain a plastic body with a flat surface; the starting position for calculating the rolling reduction during the rolling process is the horizontal plane of the upper tangent line at the wave crest, displacement control mode, and the rolling reduction at the wave crest is 1.6 mm; The schematic diagram of the principle of variable-position magnetic field arc additive manufacturing and interlayer rolling process is as Figure 4 shown;

[0041] Step 3, repeat Step 1 to Step 2 according to the preset number of layers;

[0042] Step 4, anneal the plastic body to obtain an aluminum alloy additive with a heterogeneous structure; among them, the annealing temperature is 510 °C and the annealing time is 10 min; The schematic diagram of its heterogeneous structure is as Figure 5 shown, and the grain morphology and grain shape of the coarse grain area and the fine grain area are as Figure 6 shown, where Figure 6 a is the coarse grain area at the wave trough, Figure 6 b is the fine grain area at the wave crest. Based on Figure 5 and Figure 6 it can be seen that the aluminum alloy additive with a heterogeneous structure in this embodiment shows a complex phase heterogeneous configuration with large deformation areas and small deformation areas alternating both between layers and within layers. Among them, the coarse grain area at the wave trough shows thick columnar grains with a long axis size of about 500 μm and a short axis size of about 200 μm, and there are obvious as-deposited pores, maintaining more initial circular shapes, indicating that it has not undergone sufficient deformation; the fine grain area at the wave crest shows recrystallized fine grains with a grain size distribution of 20 - 40 μm, and the pores are significantly reduced compared to the coarse grain area, and all show irregular morphologies, indicating that the initial as-deposited pores in the fine grain area have been effectively welded.

[0043] Example 2

[0044] This example is the same as Example 1, except that in Step 101, the upper and lower amplitude A of the sine wave in the AC section is 50 Gs.

[0045] Example 3

[0046] This example is the same as Example 1, except that in Step 101, the upper and lower amplitude A of the sine wave in the AC section is 80 Gs.

[0047] The deposition layer morphology with a "quasi-sine wave" periodic surface profile and the average value of the height difference in the small deformation area of the cross-section in Step 1 of Examples 1 to 3 are as Figure 7As shown, when the amplitude of the sine wave is 30 - 80 Gs, a complex phase with significantly staggered large and small deformation zones can be obtained. When the amplitude of the sine wave is larger, the height difference of the staggered deformation zones is greater, and the distribution of the large and small deformation zones is more uniform.

[0048] Comparative Example 1

[0049] This comparative example provides a method for forming an aluminum alloy heterogeneous structure. It is the same as Example 1, except that in step one, arc additive manufacturing is carried out under a non-displaced magnetic field. Specifically, a 2319 aluminum alloy wire with a diameter of 1.2 mm is used for additive manufacturing in the CMT mode, with a wire feeding speed of 7 m / min, a traveling speed of 4.5 mm / s, an interlayer temperature of 100 °C, and an interlayer lift of 4 mm.

[0050] The additive morphology of the aluminum alloy with heterogeneous structure in this comparative example is as Figure 8 shown. According to Figure 8 it can be seen that there are obvious pores in the aluminum alloy additive of this comparative example. Combining Figure 6 and Figure 8 it can be seen that compared with the comparative example, the grains of the aluminum alloy additive prepared by the method of Example 1 of the present invention are more refined, and the pore content is significantly reduced.

Claims

1. A method for forming heterogeneous tissues, characterized in that, Additive manufacturing assisted by variable magnetic field arc and interlayer rolling, including: Step 1, the process of additive manufacturing assisted by variable magnetic field arc, including: under the action of the variable magnetic field, according to the preset additive manufacturing path, melting and depositing the alloy wire to form a deposited layer with a periodic surface profile in cross-section; Step 2, interlayer rolling, specifically including: using a roller to roll the surface of the deposited layer, and the rolling reduction ≤ the height difference between the peak and valley of the periodic surface profile.

2. The heterogeneous tissue forming method according to claim 1, characterized in that The variable magnetic field is the variable magnetic field generated by a variable magnetic field generating device, and the included angle between the variable magnetic field generating device and the arc welding torch is 45°.

3. The heterogeneous tissue forming method according to claim 1, wherein The variable magnetic field is the variable magnetic field generated by an alternating current signal, and the waveform of the alternating current signal is a sine wave, square wave, positive sawtooth wave or triangular wave.

4. The heterogeneous tissue forming method according to claim 3, wherein The waveform of the alternating current signal is of the sine wave type.

5. The heterogeneous tissue forming method according to claim 4, characterized in that, The upper and lower amplitudes of the sine wave are 30 - 80 Gs.

6. The heterogeneous tissue forming method according to claim 1, wherein It also includes selectively heat-treating the deposited layer after interlayer rolling. When the alloy wire is a high stacking fault energy metal material, heat treatment is carried out. When the alloy wire is a low stacking fault energy metal material, annealing treatment is not required.

7. The heterogeneous tissue forming method according to claim 6, wherein During the heat treatment, the annealing temperature is 510 °C and the annealing time is 10 min.

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