Aluminum alloy coaxial wire feeding laser additive manufacturing method and system

Abstract

The invention discloses an aluminum alloy coaxial wire feeding laser additive manufacturing method and system.The method comprises the steps that a to-be-machined aluminum alloy substrate is placed on a jig, a laser machining head is adjusted to enable light wires to be concentric, so that a laser beam emitted by a single light source can melt the aluminum wires and form a molten pool, and the laser beam is an annular laser beam; technological parameters are set, a machining path is planned, and the moving height of each layer in the Z direction is set; and the jig is controlled to move according to the planned machining path, relative movement between the aluminum wire and the aluminum alloy substrate is caused, and the aluminum wire melted by the laser beam is deposited layer by layer on the scanning path till additive manufacturing is completed. The laser additive manufacturing of the aluminum alloy is carried out by constructing the single-light-source in-light coaxial wire feeding system, accurate coupling of light and wires can be achieved, and the problems of scanning unidirectivity, light-wire interference, aluminum wire spheroidization and the like are solved.

Description

Technical Field

[0001] The present invention relates to the field of additive manufacturing, and in particular to a method and system for coaxial wire feeding laser additive manufacturing of aluminum alloy. Background Art

[0002] Aluminum alloy has low density, high strength, good plasticity, excellent electrical conductivity, thermal conductivity and corrosion resistance. It is the most widely used type of non-ferrous metal structural material in industry and is widely used in aerospace, 3C and chemical industries. As aluminum alloy materials are increasingly used in industrial production, research on additive manufacturing of aluminum alloys has also received widespread attention.

[0003] The wire feeding laser additive manufacturing method has the advantages of high material utilization, low environmental pollution, low material cost, and little impact from the space environment, and has broad development prospects. However, the "optical external lateral wire feeding" laser additive manufacturing method has defects such as poor optical wire coupling accuracy and single scanning directionality; the "multi-light source internal coaxial wire feeding" laser additive manufacturing method consists of multiple laser light sources, and has problems such as large space occupied by the forming system and high use and maintenance costs. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides a coaxial wire feeding laser additive manufacturing method and system for aluminum alloy. By constructing a coaxial wire feeding system in a single light source for laser additive manufacturing of aluminum alloy, precise coupling of light and wire can be achieved, avoiding problems such as unidirectional scanning, light-wire interference, and aluminum wire spheroidization.

[0005] According to one aspect of the present invention, there is provided a method for laser additive manufacturing of aluminum alloy by coaxial wire feeding, comprising: The aluminum alloy substrate to be processed is placed on the jig, and the laser processing head is adjusted to make the light wire concentric, so that the laser beam emitted by the single light source can melt the aluminum wire and form a molten pool, and the laser beam is a ring-shaped beam; Set process parameters and plan processing paths, as well as set the moving height of each layer in the Z direction; The control fixture moves according to the planned processing path, causing relative movement between the aluminum wire and the aluminum alloy substrate, so that the aluminum wire melted by the laser beam is deposited layer by layer on the scanning path until the additive manufacturing is completed.

[0006] As a further technical solution, when adjusting the laser processing head to make the light filaments concentric, it also includes: adjusting the laser processing head to make the light spot energy uniform.

[0007] As a further technical solution, the process parameters include laser power, wire feeding speed, scanning speed and defocus, and the laser power is adjustable within 2400-2600W, the wire feeding speed is adjustable within 1600-1900mm / min, the scanning speed is adjustable within 40-60mm / s, and the defocus is adjustable within 5-6mm.

[0008] As a further technical solution, when it is necessary to reduce the width, height and depth of the cladding layer, the laser power and wire feeding speed are kept unchanged and the scanning speed is increased.

[0009] As a further technical solution, when it is necessary to increase the width of the cladding layer and reduce the height and depth of the cladding layer, the scanning speed and the wire feeding speed are kept unchanged and the laser power is increased.

[0010] As a further technical solution, when it is necessary to increase the height of the cladding layer, reduce the depth of the cladding layer, and allow the width of the cladding layer to fluctuate within a certain range, the laser power and the scanning speed are kept unchanged and the wire feeding speed is increased.

[0011] As a further technical solution, the moving height of each layer in the Z direction is set, including: performing single-pass single-layer additive manufacturing, measuring the first layer forming height with a vernier caliper, and setting the first layer forming height as the moving height of each layer in the Z direction of additive manufacturing.

[0012] As a further technical solution, before setting the moving height of each layer in the Z direction, it also includes: connecting the protective gas and adjusting the flow rate of the protective gas.

[0013] According to one aspect of the present invention, there is provided an aluminum alloy coaxial wire feeding laser additive manufacturing system, comprising: a laser light source, a laser processing head, a wire feeding device, a fixture and a control device, wherein the laser light source is a single light source and provides a laser beam to the laser processing head; the laser processing head shapes the laser beam into an annular beam, and the annular beam is concentrically arranged with the aluminum wire provided by the wire feeding device, so as to melt the aluminum wire and form a molten pool; the fixture is used to place an aluminum alloy substrate; the control device is used to set process parameters and plan a processing path, and control the fixture to move according to the planned processing path, causing relative movement between the aluminum wire and the aluminum alloy substrate, so that the aluminum wire melted by the laser beam is deposited layer by layer on the scanning path until the additive manufacturing is completed.

[0014] As a further technical solution, the wire feeding device is also equipped with a straightener for keeping the aluminum wire concentric with the annular light beam.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention constructs a single-light-source intra-optical coaxial wire feeding system, and realizes the additive manufacturing of aluminum alloy wire by adjusting the four major process parameters of laser power, wire feeding speed, scanning speed, and defocus amount. The additive manufacturing part has good performance as verified by microhardness, which solves the problems of low efficiency, high cost, low density of cladding layer and many defects in powder laser additive manufacturing. At the same time, it solves the problems of poor light-wire coupling accuracy and single scanning directionality in the extra-optical lateral wire feeding laser additive manufacturing method.

[0016] 2. The present invention uses aluminum alloy wire as the raw material for additive manufacturing. Compared with powder laser additive manufacturing, it has high material utilization rate, low cost, higher density of cladding layer and fewer defects.

[0017] 3. The present invention shapes Gaussian light into annular light through a laser processing head, making full use of the energy of the laser beam, so that a single light source laser beam can melt the cold aluminum wire without the need for a composite light source. The annular light reduces the temperature and depth of the molten pool to a certain extent, which not only reduces the deformation of the substrate, but also avoids overheating of the molten pool and the upper deposition layer, and can improve the organization of the deposition layer and improve its performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief introduction is given below to the drawings used in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 A schematic flow chart of a coaxial wire feeding laser additive manufacturing method for aluminum alloy provided in an embodiment of the present invention.

[0020] Figure 2 A schematic structural diagram of a laser additive manufacturing device provided in an embodiment of the present invention.

[0021] Figure 3 A schematic diagram of the light spot shape and size at the processing height provided by an embodiment of the present invention.

[0022] Figure 4 A schematic diagram of a workpiece manufactured by the method provided in an embodiment of the present invention.

[0023] Figure 5 Metallographic diagram of the additively manufactured part after cutting, grinding, polishing and etching provided in an embodiment of the present invention.

[0024] Figure 6 A schematic diagram of microhardness test results provided in an embodiment of the present invention.

[0025] Figure 7A schematic diagram of geometric features of the cladding layer corresponding to different scanning speeds provided in an embodiment of the present invention.

[0026] Figure 8 Schematic diagram of geometric features of cladding layers corresponding to different laser powers provided in an embodiment of the present invention.

[0027] Fig. 9 A schematic diagram of the geometric characteristics of the cladding layer corresponding to different wire feeding speeds provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] For the laser additive manufacturing process, the absorption rate of aluminum alloy to laser is low during the forming process, resulting in serious spheroidization during the forming process and unsatisfactory forming effect. Based on this, the present invention adopts a laser additive manufacturing method with single light source coaxial wire feeding, shapes the Gaussian beam into a ring beam through a laser processing head, and constructs a "single light source coaxial wire feeding" laser additive manufacturing system, which can experiment with the precise coupling of light and wire, and avoid problems such as scanning unidirectionality, light wire interference, and aluminum wire spheroidization.

[0029] Based on the constructed "single light source internal coaxial wire feeding" laser additive manufacturing system, the present invention prepares high-integrity and high-performance formed part specimens by determining the appropriate process window, thereby realizing the laser additive manufacturing of aluminum alloy using the single light source internal coaxial wire feeding system.

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In addition, the technical features in the various embodiments or single embodiments provided by the present invention are arbitrarily combined with each other to form a new technical solution. This combination is not restricted by the sequence of steps and / or the structural composition mode, but must be based on the ability of ordinary technicians in this field to achieve. When the combination of technical solutions is contradictory or cannot be achieved, it should be considered that this combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0031] The embodiment of the present invention provides a coaxial wire feeding laser additive manufacturing method for aluminum alloy, such as Figure 1As shown, the method includes: placing an aluminum alloy substrate to be processed on a fixture, adjusting a laser processing head to make the light wire concentric, so that a laser beam emitted by a single light source can melt the aluminum wire and form a molten pool, wherein the laser beam is a ring-shaped beam; setting process parameters and planning a processing path, and setting a moving height of each layer in the Z direction; controlling the fixture to move according to the planned processing path, causing relative movement between the aluminum wire and the aluminum alloy substrate, so that the aluminum wire melted by the laser beam is deposited layer by layer on the scanning path until additive manufacturing is completed.

[0032] It should be noted that, considering that the absorption rate of aluminum alloy to laser is as low as 10% at room temperature, as the temperature of aluminum alloy increases, especially after the material is melted, its absorption rate will increase to 40%-60%. The present invention adopts an annular light beam for additive manufacturing, and utilizes the annular light beam to heat the aluminum wire as a whole, reducing the temperature gradient to increase its absorption capacity at the laser wavelength.

[0033] The laser additive manufacturing method for aluminum alloy using a single light source coaxial wire feeding system provided in an embodiment of the present invention involves devices including a laser, a laser processing head, a fixture, an air blowing device, a wire feeding device, etc. Figure 2 As shown, the adjustable process parameters include laser power, wire feeding speed, scanning speed and defocusing amount. When the method described in the embodiment of the present invention is implemented, an aluminum substrate is placed on a fixture, appropriate process parameters are given by a computer, a laser beam is used to melt the aluminum wire and form a molten pool, and a scanning path is input to control the movement of the fixture platform, causing relative movement between the aluminum wire and the substrate, so that the aluminum wire melted by the laser beam is deposited layer by layer on the scanning path until the additive manufacturing is completed, and the deposited layer finally obtained is formed uniformly and smoothly.

[0034] The aluminum alloy substrate used in the embodiment of the present invention is grade 7075, and the thickness of the substrate is 3 mm. The aluminum wire used is grade 7075, and the diameter of the aluminum wire is 1.2 mm. The laser wavelength used to complete the aluminum wire additive manufacturing is 1064 nm, the power is 3000 W, and the core diameter is 600 um.

[0035] The embodiment of the present invention adopts a Pretzt coaxial wire feeding welding head to construct a single light source intra-optical coaxial wire feeding system, thereby forming the additive manufacturing method.

[0036] The laser additive manufacturing method for aluminum alloy using a single light source coaxial wire feeding system provided by the embodiment of the present invention also includes: pre-treating the aluminum alloy substrate. Specifically, wiping the surface of the substrate with alcohol to ensure that the surface is free of dirt, and then fixing it on a fixture.

[0037] The laser additive manufacturing method for aluminum alloy using a single light source coaxial wire feeding system provided by the embodiment of the present invention also includes: starting up the equipment for inspection to ensure that the light wire is concentric and the light spot energy is uniform. The light wire concentricity and the light spot energy uniformity can be adjusted by the laser processing head, and the light spot energy uniformity can be measured by a light spot energy analyzer.

[0038] The laser additive manufacturing method for aluminum alloy using a coaxial wire feeding system in a single light source provided by an embodiment of the present invention also includes setting process parameters: laser power, wire feeding speed, scanning speed and defocus. Among them, the laser power can be set within the range of 2400-2600W, the wire feeding speed can be set within the range of 1600-1900mm / min, the scanning speed can be set within the range of 40-60mm / s, and the focal position can be set within the range of negative defocus 5 to 6mm. In addition, the outer ring diameter of the annular spot emitted by the laser processing head is in the range of 2.4-2.6mm.

[0039] The present invention determines a suitable process window for laser additive manufacturing of aluminum alloy by analyzing the influence of laser power, wire feeding speed and scanning speed on additive manufacturing, and can prepare high-integrity and high-performance formed part specimens.

[0040] Table 1 Laser cladding process parameters at different scanning speeds

[0041] See Table 1 and Figure 7 , where Table 1 shows the laser cladding process parameters at different scanning speeds, Figure 7 The geometric characteristics of the cladding layer corresponding to different scanning speeds. It can be seen from the chart that with the increase of scanning speed, the width, height and depth of the cladding layer gradually decrease. This is because under the action of a certain laser power, as the scanning speed increases, the line energy (the energy input per unit length of the melt channel) decreases, the melted metal decreases, and the width, height and depth of the cladding layer decrease.

[0042] Table 2 Laser cladding process parameters under different laser powers

[0043] See Table 2 and Figure 8 , where Table 2 shows the laser cladding process parameters under different laser powers, Figure 8The geometric characteristics of the cladding layer corresponding to different laser powers. It can be seen from the chart that with the increase of laser power, the width of the cladding layer gradually increases and the height of the cladding layer gradually decreases. This is because the actual laser cladding energy is mainly determined by the scanning speed and laser power. When other process parameters remain unchanged, increasing the laser power or reducing the scanning speed can increase the laser radiation energy received by the cladding layer. The increase in energy makes the molten pool convection more sufficient, and the width of the cladding layer also increases accordingly. When the laser power = 2800W, the cross-section of the entire cladding layer is flat; when the laser power is less than 2200W, the laser energy is not enough to completely melt the aluminum wire, making it difficult to continue the cladding layer, and eventually causing wire jams.

[0044] Table 3 Laser cladding process parameters at different wire feeding speeds

[0045] See Table 3 and Fig. 9 , where Table 3 shows the laser cladding process parameters at different wire feeding speeds, Fig. 9 The geometric characteristics of the cladding layer corresponding to different wire feeding speeds. It can be seen from the chart that with the increase of wire feeding speed, the width of the cladding layer fluctuates between 2.5mm and 2.7mm, indicating that the width of the cladding layer is mainly determined by the spot diameter and is less affected by the wire feeding speed. The height of the cladding layer gradually increases. This is because with the increase of wire feeding speed, the mass of the cladding layer per unit time also increases, and the width of the cladding layer changes slowly, which will inevitably lead to an increase in the height of the cladding layer.

[0046] The laser additive manufacturing method for aluminum alloy using a single light source coaxial wire feeding system provided in an embodiment of the present invention also includes planning a processing path and controlling the moving path through coordinates. By controlling the movement of the jig according to the planned processing path, a relative movement between the aluminum wire and the aluminum alloy substrate is caused, so that the aluminum wire melted by the laser beam is deposited layer by layer on the scanning path until the additive manufacturing is completed.

[0047] The laser additive manufacturing method for aluminum alloy using a single light source coaxial wire feeding system provided in an embodiment of the present invention also includes connecting a shielding gas and adjusting the shielding gas flow rate. Specifically, the shielding gas used is argon gas, and the shielding gas flow rate is 5-10 L / min.

[0048] The laser additive manufacturing method for aluminum alloy using a single light source coaxial wire feeding system provided in an embodiment of the present invention also includes setting the moving height of each layer in the Z direction: performing single-pass single-layer additive manufacturing, measuring the first layer forming height with a vernier caliper, and setting this height as the moving height of each layer in the Z direction for additive manufacturing.

[0049] The laser additive manufacturing method for aluminum alloy using a single light source coaxial wire feeding system provided in an embodiment of the present invention performs additive manufacturing layer by layer according to the set moving height of each layer after completing the setting of the moving height of each layer in the Z direction until all are completed.

[0050] Based on the same inventive concept as the method embodiment, the embodiment of the present invention also provides an aluminum alloy coaxial wire feeding laser additive manufacturing system, such as Figure 2 As shown, it includes: a laser light source, a laser processing head, a wire feeding device, a fixture and a control device, wherein the laser light source is a single light source and provides a laser beam to the laser processing head; the laser processing head shapes the laser beam into an annular beam, and the annular beam is concentrically arranged with the aluminum wire provided by the wire feeding device, so as to melt the aluminum wire and form a molten pool; the fixture is used to place the aluminum alloy substrate; the control device (not shown in the figure) is used to set process parameters and plan the processing path, and control the fixture to move according to the planned processing path, causing relative movement between the aluminum wire and the aluminum alloy substrate, so that the aluminum wire melted by the laser beam is deposited layer by layer on the scanning path until the additive manufacturing is completed.

[0051] As a preferred embodiment, the embodiment of the present invention utilizes Figure 2 The aluminum alloy coaxial wire feeding laser additive manufacturing system is used for additive manufacturing. First, the 3mm thick 7075 aluminum alloy substrate is pre-treated, and the substrate surface is wiped with alcohol to ensure that there is no dirt on the surface, and then it is fixed on the fixture workbench; the equipment is turned on, and the concentricity of the light wire and the uniformity of the spot energy are checked. The laser processing head is adjusted to make the light wire concentric and the spot energy uniform. The spot energy uniformity can be measured with a spot energy analyzer. The spot shape and size at the processing height are shown in the attached figure. Figure 3 As shown, the outer ring diameter of the light spot is 2.4-2.6mm, and the energy error value is <2.9%.

[0052] Set the process parameters: set the laser power to 2600W, the wire feeding speed to 1900mm / min, the scanning speed to 60mm / s, and adjust the focus position to negative defocus 5mm. Plan the processing path according to demand. In this embodiment, the path is a 150mm*70mm rectangle with a fillet diameter of 7.5mm. Connect the side-blowing protective gas pipe to argon gas, and adjust the protective gas flow rate to 7L / min. Set the moving height of each layer in the Z direction: perform single-pass single-layer additive manufacturing, measure the forming height of the first layer with a vernier caliper, and set this height as the moving height of each layer in the Z direction of additive manufacturing. Perform additive manufacturing layer by layer until additive manufacturing is completed. Using the method of this embodiment, the forming efficiency of aluminum alloy wire additive manufacturing structural parts is greatly improved, the forming process is stable, the forming effect is good and there is no oxidation phenomenon, and multi-directional additive manufacturing can be achieved. The forming results are as shown in the attached figure. Figure 4 After cutting, grinding, polishing and etching, the formed parts are observed under a microscope for their metallographic structure, as shown in the attached figure. Figure 5As shown; the microhardness test of the parent material and the additive manufacturing part was carried out using a microhardness tester. The test results are shown in the attached Figure 6 shown.

[0053] In summary, the aluminum alloy coaxial wire feeding laser additive manufacturing method provided by the present invention realizes the additive manufacturing of aluminum alloy wire by adjusting the four major process parameters of laser power, wire feeding speed, scanning speed, and defocus amount, and is verified by microhardness. The additive manufacturing part has good performance. The method provided by the present invention can solve the problems of low efficiency, high cost, low density of cladding layer and many defects in powder laser additive manufacturing, and at the same time solves the problems of poor optical wire coupling accuracy and single scanning directionality in the optical outward lateral wire feeding laser additive manufacturing method.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A method for laser additive manufacturing of aluminum alloy by coaxial wire feeding, characterized in that: include: The aluminum alloy substrate to be processed is placed on the jig, and the laser processing head is adjusted to make the light wire concentric, so that the laser beam emitted by the single light source can melt the aluminum wire and form a molten pool, and the laser beam is a ring-shaped beam; Set process parameters and plan processing paths, as well as set the moving height of each layer in the Z direction; The control fixture moves according to the planned processing path, causing relative movement between the aluminum wire and the aluminum alloy substrate, so that the aluminum wire melted by the laser beam is deposited layer by layer on the scanning path until the additive manufacturing is completed.

2. According to claim 1, a method for laser additive manufacturing of aluminum alloy by coaxial wire feeding is characterized in that: When adjusting the laser processing head to make the light filaments concentric, it also includes: adjusting the laser processing head to make the light spot energy uniform.

3. The aluminum alloy coaxial wire feeding laser additive manufacturing method according to claim 1, characterized in that: The process parameters include laser power, wire feeding speed, scanning speed and defocus, and the laser power is adjustable within 2400-2600W, the wire feeding speed is adjustable within 1600-1900mm / min, the scanning speed is adjustable within 40-60mm / s, and the defocus is adjustable within 5-6mm.

4. The aluminum alloy coaxial wire feeding laser additive manufacturing method according to claim 3, characterized in that: When it is necessary to reduce the width, height and depth of the cladding layer, keep the laser power and wire feeding speed unchanged and increase the scanning speed.

5. The aluminum alloy coaxial wire feeding laser additive manufacturing method according to claim 3, characterized in that: When it is necessary to increase the width of the cladding layer and reduce the height and depth of the cladding layer, keep the scanning speed and wire feeding speed unchanged and increase the laser power.

6. The aluminum alloy coaxial wire feeding laser additive manufacturing method according to claim 3, characterized in that: When it is necessary to increase the height of the cladding layer, reduce the depth of the cladding layer, and allow the width of the cladding layer to fluctuate within a certain range, keep the laser power and scanning speed unchanged and increase the wire feeding speed.

7. The aluminum alloy coaxial wire feeding laser additive manufacturing method according to claim 1, characterized in that: The moving height of each layer in the Z direction is set, including: performing single-pass single-layer additive manufacturing, measuring the first-layer forming height with a vernier caliper, and setting the first-layer forming height as the moving height of each layer in the Z direction of the additive manufacturing.

8. The aluminum alloy coaxial wire feeding laser additive manufacturing method according to claim 1, characterized in that: Before setting the moving height of each layer in the Z direction, the process also includes: connecting the shielding gas and adjusting the shielding gas flow rate.

9. An aluminum alloy coaxial wire feeding laser additive manufacturing system, characterized in that: include: A laser light source, a laser processing head, a wire feeding device, a fixture and a control device, wherein the laser light source is a single light source and provides a laser beam to the laser processing head; the laser processing head shapes the laser beam into an annular beam, and the annular beam is concentrically arranged with the aluminum wire provided by the wire feeding device to melt the aluminum wire and form a molten pool; the fixture is used to place an aluminum alloy substrate; The control device is used to set process parameters and plan a processing path, and control the movement of the fixture according to the planned processing path, causing relative movement between the aluminum wire and the aluminum alloy substrate, so that the aluminum wire melted by the laser beam is deposited layer by layer on the scanning path until the additive manufacturing is completed.

10. The aluminum alloy coaxial wire feeding laser additive manufacturing system according to claim 9, characterized in that: The wire feeding device is also provided with a straightener for keeping the aluminum wire concentric with the annular light beam.

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