Device and method for preparing magnesium / aluminum dissimilar metal joint

Abstract

The invention relates to a device and method for preparing a magnesium / aluminum dissimilar metal joint, and relates to the technical field of welding metallurgy technology and material scientificity, the device comprises a welding table, a plate fixing assembly, a magnetic field assembly and a welding tool, a sealing plate is arranged on the welding table in a surrounding mode, and cooling water is poured into the sealing plate; the plate fixing assembly, the magnetic field assembly and a working head of the welding tool are all located below the liquid level. Trapezoid grooves are formed in the welding positions of the magnesium alloy and the aluminum alloy and filled with mixed powder of the magnesium alloy and the aluminum alloy according to a certain proportion, and component optimization is conducted on welding seams; the welding process is carried out underwater, a copper base plate is adopted, the temperature of a weld joint area in the welding process can be rapidly reduced and dispersed, a magnetic field is applied, under the stirring effect of electromagnetic force, molten plastic flowing metal has a better mass transfer effect on the microscale, element segregation is reduced, and therefore generation of magnesium-aluminum intermetallic compounds is restrained; and the cracking behavior in the welding process is reduced, so that the strength and the preparation efficiency of the magnesium / aluminum dissimilar metal joint are improved.

Description

Technical Field

[0001] The invention relates to the fields of welding metallurgy technology and material science technology, and in particular to a device and method for preparing a magnesium / aluminum dissimilar metal joint. Background Art

[0002] Aluminum alloy has a series of advantages such as low density, high specific stiffness and specific strength, good thermal and electrical conductivity, excellent corrosion resistance and good processing performance, and is widely used in aerospace, transportation and other fields. Magnesium is a metal lighter than aluminum, with a density of only 1.74×103kg / m3. Magnesium alloy also has a series of advantages such as high specific strength and high specific stiffness, good casting performance, thermal performance, good electromagnetic shielding and seismic resistance, and has become another important structural material. Magnesium alloy and aluminum alloy have relatively certain special properties, such as the damping capacity of Mg and the creep resistance of aluminum. When used in combination, they can give full play to the different excellent properties of the two metals, play to their strengths and avoid their weaknesses, and have a very good market prospect. With the increasing use of aluminum and magnesium, there is an urgent need for a technology to produce aluminum / magnesium dissimilar metal joint materials.

[0003] Magnesium and aluminum have large differences in physical and chemical properties, which leads to poor compatibility between magnesium and aluminum. When welding using traditional fusion welding methods, it is easy to produce pores, cracks, inclusions, element burnout, and softening of the weld zone and heat-affected zone in the weld joint, which significantly reduces the mechanical properties of the weld joint and limits the in-depth cross-application of magnesium and aluminum alloys as structural materials. At the same time, aluminum alloys and magnesium alloys are very easy to form intermetallic compounds during the welding process, thereby reducing the strength of aluminum / magnesium dissimilar metal joints, and even directly cracking behavior, significantly reducing the mechanical properties and yield rate of magnesium / aluminum dissimilar metals. Therefore, in the process of welding magnesium alloys and aluminum alloys, controlling the content and distribution of magnesium-aluminum intermetallic compounds directly determines the performance and yield rate of magnesium / aluminum dissimilar metals.

[0004] The series of welding processes currently used to produce aluminum / magnesium dissimilar metal joints all have the problems of low strength, easy cracking, and low yield rate. Therefore, the development of a cheap and efficient method for preparing high-strength aluminum / magnesium dissimilar metal joints remains a key issue that needs to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to provide a device and method for preparing magnesium / aluminum dissimilar metal joints in view of the above problems. First, a series of small grooves are processed on the welds of aluminum alloy and magnesium alloy weldments, and magnesium alloy and aluminum alloy powders with the same composition as the matrix of the magnesium alloy and aluminum alloy weldments and in a certain ratio are filled and compacted to improve the uniformity of the composition during the welding process and inhibit the formation of aluminum-magnesium intermetallic compounds. Then, the weldment is implanted into an underwater copper pad to reduce the welding temperature of the weld zone during welding and dissipate heat quickly, thereby significantly reducing the formation of magnesium-aluminum dissimilar metal compounds. At the same time, the welding process is carried out under the water surface, further reducing the welding process temperature and inhibiting the formation of magnesium-aluminum intermetallic compounds. With the external enhanced magnetic field, the molten plastic flowing metal has a better mass transfer effect on the microscopic scale, reducing element segregation, and promoting a more dispersed distribution of magnesium-aluminum intermetallic compound particles, which can significantly reduce component segregation, thereby improving the yield rate of magnesium / aluminum dissimilar metal joints and improving the strength of aluminum / magnesium dissimilar metal joints.

[0006] In order to achieve its purpose, the present invention adopts the following technical solution:

[0007] The first aspect of the present invention provides a device for preparing magnesium / aluminum dissimilar metal joints, adopting the following technical scheme: comprising a welding table, a plate fixing component arranged on the welding table, a magnetic field component and a welding tool arranged on the welding table, the plate fixing component is used to position the magnesium alloy plate and the aluminum alloy plate, the magnetic field component is used to generate a magnetic field, the welding tool is used to stir friction welding the magnesium alloy plate and the aluminum alloy plate, a sealing plate is provided around the welding table, during welding, cooling water is poured into the sealing plate, and the working heads of the plate fixing component, the magnetic field component and the welding tool are all located below the liquid surface.

[0008] By adopting the above technical solution, the plate fixing assembly fixes the plate to be welded, applies a magnetic field, and pours cooling water into the sealing plate. The welding tool is started to weld the plate. The high temperature is beneficial to the Mg2Al3 and Mg 17 Al 12 The formation of intermetallic compounds such as magnesium and aluminum can be inhibited by underwater welding, which can reduce the temperature of the weld zone to inhibit the formation of intermetallic compounds. At the same time, due to the presence of plastically flowing metal bodies in the stirring welding process, there is a vertical component with the applied magnetic field, which generates the Lorentz force and electromagnetic stirring force, so that the molten plastically flowing metal has better mass transfer on a microscopic scale, reduces element segregation, inhibits magnesium-aluminum intermetallic compounds, and also promotes a more dispersed distribution of the formed magnesium-aluminum intermetallic compound particles, thereby improving the strength of magnesium / aluminum dissimilar metal joints.

[0009] Optionally, the plate fixing assembly includes:

[0010] A mold, wherein two molds are provided, and the two molds are both provided on the welding table and arranged opposite to each other, and mounting grooves are provided on the opposite side walls of the two molds, and the two mounting grooves are connected, and one of the mounting grooves is used to install a magnesium alloy plate, and the other mounting groove is used to install an aluminum alloy plate, and a gasket is provided in the mounting groove;

[0011] A clamp, wherein two clamps are provided and correspond to the molds one by one, and the clamps are arranged on the welding table and are used to position the magnesium alloy plate and the aluminum alloy plate.

[0012] By adopting the above technical solution, the two molds are respectively installed with corresponding welding plates, the stability of the plate installation is increased by the gasket, and the plate is positioned with the help of the clamp to improve the stability of the plate during the welding process, thereby improving the welding quality.

[0013] Optionally, the clamp includes a fixing rod, a chuck and a fixing bolt, the fixing rod is arranged on the welding table and abuts against the outer wall of the mold at one end away from the mounting groove, the chuck abuts against the upper surface of the corresponding magnesium alloy plate or aluminum alloy plate, the fixing bolt is threadedly connected to the top of the fixing rod, and the chuck is connected to the fixing bolt at one end close to the fixing rod.

[0014] By adopting the above technical solution, before installation, the fixing bolt is rotated to drive the chuck away from the mold, the plate is placed in the installation groove, the chuck is pushed against the upper surface of the plate, and then the chuck is pressed at one end and the fixing bolt is rotated at the other end, so that the chuck is pressed against the upper surface of the plate after releasing the hand, thereby realizing the positioning of the plate.

[0015] Optionally, the magnetic field component includes:

[0016] A mounting member, wherein two mounting members are provided and are respectively located on both sides of the clamp, a mounting bolt is passed through the two mounting members, and a mounting nut for positioning the mounting member is threadedly connected to the mounting bolt;

[0017] The magnetic parts are provided in two groups and correspond to the mounting parts one by one. The magnetic parts are arranged on the corresponding mounting parts. During welding, the aluminum alloy plate and the magnesium alloy plate are located between the magnetic fields generated by the two groups of magnetic parts.

[0018] By adopting the above technical solution, the position between the two mounting parts is moved, and the mounting nuts are rotated to position the mounting parts, so as to adjust the magnetic field strength during plate welding.

[0019] Optionally, each group of the magnetic parts includes a plurality of magnets, and the plurality of magnets are separated by magnet separation belts.

[0020] By adopting the above technical solution, redundant magnets are separated according to the magnet separation belt, and the magnetic field strength is adjusted by adjusting the number of magnets, thereby improving the convenience of adjusting the magnetic field strength.

[0021] Optionally, a copper pad is provided on the welding table, and the mold is arranged on the copper pad.

[0022] By adopting the above technical solution, the copper backing plate is located on the welding table to reduce and disperse the temperature of the weld zone, further inhibiting the formation of magnesium-aluminum metal compounds, thereby improving the strength of the magnesium / aluminum dissimilar metal joint.

[0023] The second aspect of the present invention provides a method for preparing a magnesium / aluminum dissimilar metal joint, comprising the following steps: S1, preparing filling powder: selecting blocks with the same composition as the magnesium alloy plate and the aluminum alloy plate to be welded for ball milling, respectively, obtaining corresponding powders and drying them, and mixing the dried powders in different proportions and evenly obtaining filling powders 1 and 2;

[0024] S2. Plate processing: determine the weld area of ​​the magnesium alloy plate and the aluminum alloy plate to be welded, process small trapezoidal grooves on the weld area, remove the oxide layer of the weld area, and perform surface degreasing treatment;

[0025] S3, powder filling: filling the filling powder 1 prepared in S1 into the small trapezoidal grooves on the magnesium alloy plate, and filling the filling powder 2 prepared in S1 into the small trapezoidal grooves on the aluminum alloy plate, and performing compaction treatment;

[0026] S4. Weldment assembly: Install the welding device as described in claim 6, first install the copper backing plate on the welding table, install the powder-filled magnesium alloy plate and aluminum alloy plate into the mold respectively, and use a clamp to position the plates, then install the two sets of magnetic parts on the mounting parts on both sides of the clamp respectively, adjust the magnetic field gap width and magnetic field strength, and finally pour cooling water into the sealing plate, and the water level is higher than the upper surface of the magnesium alloy plate and the aluminum alloy plate;

[0027] S5. Welding: Welding parameters are set on the welding tool, and the magnesium alloy plate and the aluminum alloy plate are welded underwater. The magnetic parts are started at the same time to complete the welding of the dissimilar metal joints under the magnetic field conditions. After the welding is completed, the welded joint is obtained.

[0028] By adopting the above technical solution, a series of small grooves are processed in the welds of aluminum alloy and magnesium alloy weldments, filled with magnesium alloy and aluminum alloy powders, and subjected to multiple compaction treatments, the dispersion distribution of the components in the weld area during welding is regulated, and the Mg2Al3 and Mg 17 Al 12The formation of magnesium-aluminum intermetallic compounds is then initiated, and the plate is then implanted onto an underwater copper pad for welding, which is used to quickly disperse and reduce the temperature of the weld zone during the welding process. In conjunction with the application of an external magnetic field, the molten plastic flowing metal can have a better mass transfer effect on a microscopic scale, reduce element segregation, and inhibit magnesium-aluminum intermetallic compounds. At the same time, it can also promote a more dispersed distribution of the formed magnesium-aluminum intermetallic compound particles, thereby improving the strength of the magnesium / aluminum dissimilar metal joint.

[0029] Preferably, the welding method comprises the following steps:

[0030] S1. Preparation of filling powder: respectively selecting blocks with the same composition as the magnesium alloy plate and aluminum alloy plate to be welded for ball milling, the particle size of the powder obtained after ball milling is 20-3000 mesh, vacuum drying the powder at 50° C., and mixing the dried powder in different proportions to obtain filling powder 1 and filling powder 2;

[0031] S2. Plate processing: determine the weld area of ​​the magnesium alloy plate and the aluminum alloy plate to be welded, and process a small trapezoidal groove on the weld area. The upper width of the small trapezoidal groove is 3-4 mm, the lower width is 2-2.5 mm, the height is 5-6 mm, and the distance from the welding edge of the plate is 3-4 mm. Then, remove the oxide layer of the weld area and perform surface degreasing treatment;

[0032] S3, powder filling: filling the filling powder 1 prepared in S1 into the small trapezoidal grooves on the magnesium alloy plate, and filling the filling powder 2 prepared in S1 into the small trapezoidal grooves on the aluminum alloy plate, and performing compaction treatment at 0.5-20 MPa for 1-10 times;

[0033] S4. Weldment assembly: Install the welding device, first install the copper backing plate on the welding table, install the powder-filled magnesium alloy plate and aluminum alloy plate into the mold respectively, and use the fixture to position the plates, then install the two sets of magnetic parts on the mounting parts on both sides of the fixture respectively, adjust the magnetic field gap width and magnetic field strength so that the magnetic field strength range is between 0.01T-0.2T, and finally pour cooling water into the sealing plate, and the distance between the water surface and the upper surface of the magnesium alloy plate and the aluminum alloy plate is not less than 5mm;

[0034] S5. Welding: Select a suitable welding tool, the stirring drill bit of which is a threaded drill bit with a trapezoidal cone and an upper diameter of 15-18mm, a lower diameter of 10-12mm, and a height of 12-15mm. Set the welding speed on the welding tool to 50-300mm / min, and perform underwater welding on the magnesium alloy plate and the aluminum alloy plate. Simultaneously start the magnetic parts to complete the welding of dissimilar metal joints under magnetic field conditions, and obtain a welded joint after welding is completed.

[0035] Preferably, in the above-mentioned technical solution of the welding method, S1, preparation of filling powder: respectively select blocks with the same composition as the magnesium alloy plate and aluminum alloy plate to be welded for ball milling, the average particle size of the powder obtained after ball milling is 200 mesh, the powder is vacuum dried at 50°C, the dried powder is configured in different proportions and stirred evenly to obtain filling powder 1 and filling powder 2, the content ratio of magnesium alloy powder to aluminum alloy powder in filling powder 1 is 1:3, and the content ratio of magnesium alloy powder to aluminum alloy powder in filling powder 2 is 3:1;

[0036] In the preferred embodiment S2, the upper width of the trapezoidal small groove is 3 mm, the lower width is 2 mm, the height is 5 mm, and the distance from the welding edge of the plate is 3 mm.

[0037] Preferably, in the above-mentioned welding method technical scheme, in S4, the magnetic field gap width between the two groups of magnetic parts is 60 mm, the magnetic field strength is 0.2 T, and the distance between the water surface and the upper surface of the magnesium alloy plate and the aluminum alloy plate is 20 mm; in S5, the stirring drill bit of the welding tool is a trapezoidal cone with an upper diameter of 15 mm, a lower end diameter of 10 mm, and a threaded drill bit with a height of 12 mm. The welding speed is 100 mm / min and the rotation speed is 700 r / min.

[0038] The strength of magnesium / aluminum dissimilar metal joints can be improved by optimizing various parameter conditions in the welding method.

[0039] In summary, the present application includes at least one of the following beneficial technical effects:

[0040] 1. A series of small trapezoidal grooves are cut at the welds of magnesium alloy and aluminum alloy plates to fill the welds with aluminum alloy and magnesium alloy powders to optimize the composition of the welds, thereby reducing the formation of aluminum-magnesium intermetallic compounds.

[0041] 2. In the underwater welding cooling process, it is used to reduce the welding temperature of the weld area during welding. At the same time, the copper backing plate is used to significantly inhibit the formation of magnesium-aluminum metal compounds.

[0042] 3. Applying an external magnetic field during the welding process, under the stirring action of electromagnetic force, enables the molten plastic flowing metal to have better mass transfer effect on the micro scale, reduces element segregation, and promotes a more dispersed distribution of aluminum-magnesium intermetallic compound particles, which can significantly reduce component segregation and thus inhibit the formation of magnesium-aluminum metal compounds.

[0043] 4. The device provided by the present invention is easy to load and unload, and the welding method provided by the present invention is easy to operate, which improves the welding strength and reduces the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a top view of the overall structure of the welding device in Example 1 of the present application;

[0045] Figure 2 is a side view of the overall structure of the welding device in Example 1 of the present application;

[0046] Figure 3 : is an operation schematic diagram of the welding method in Example 2 of the present application, wherein the horizontal arrow indicates the welding direction, the rotating arrow indicates the rotation direction of the stirring drill bit of the welding tool, and the vertical arrow indicates the orientation of the stirring drill bit;

[0047] Figure 4 It is the element spectrum detection diagram and macroscopic morphology diagram at the weld interface in Example 2 of the present application;

[0048] Figure 5 This is the finished product test diagram in Comparative Example 3 of this application, where Figure 5 (a) is the element spectrum detection diagram at the weld interface. Figure 5 (b) is the macroscopic morphology of the weld interface.

[0049] Figure numerals: 1. welding table; 11. sealing plate; 111. welding pool; 12. copper pad; 13. water inlet pipe; 14. water outlet pipe; 2. plate fixing assembly; 21. mold; 211. mounting groove; 212. gasket; 22. clamp; 221. fixing rod; 222. chuck; 223. fixing bolt; 224. protruding end; 3. magnetic field assembly; 31. mounting part; 32. magnetic part; 321. magnet; 322. magnet separation belt; 33. mounting bolt; 331. mounting nut; 4. welding tool; 41. stirring drill bit; 5. plate; 6. weld area; 61. small trapezoidal groove. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with examples and drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Those skilled in the art will make modifications or equivalent substitutions based on the understanding of the technical scheme of the present invention, without departing from the spirit and scope of the technical scheme of the present invention, and all should be included in the protection scope of the present invention. The experimental methods in the following embodiments, unless otherwise specified, are conventional methods, and other unspecified specific conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments that do not indicate the manufacturer are all conventional products that can be purchased commercially.

[0051] Example 1

[0052] Reference Figure 1 and Figure 2A device for preparing a magnesium / aluminum dissimilar metal joint comprises a welding table 1, a plate fixing component 2 arranged on the welding table 1, a magnetic field component 3 and a welding tool 4 arranged on the welding table 1, the plate fixing component 2 is used to position the magnesium alloy plate and the aluminum alloy plate, the magnetic field component 3 is used to generate a magnetic field, the welding tool 4 is used to stir friction welding the magnesium alloy plate and the aluminum alloy plate, a sealing plate 11 is arranged around the welding table 1, during welding, cooling water is poured into the sealing plate 11, and the working heads of the plate fixing component 2, the magnetic field component 3 and the welding tool 4 are all located below the liquid surface.

[0053] Reference Figure 1 and Figure 2 The “plate 5” mentioned in this embodiment refers to the parent plate to be welded, which is a magnesium alloy plate or an aluminum alloy plate in this embodiment.

[0054] Reference Figure 1 and Figure 2 A copper pad 12 is provided on the upper surface of the welding table 1. The copper pad 12 can be a pure copper plate or a copper alloy plate. In this embodiment, a pure copper plate is used. A sealing plate 11 is fixedly arranged on the welding table 1. A sealed welding pool 111 is formed between the bottom end of the sealing plate 11 and the welding table 1. The pure copper plate is located in the welding pool 111. A water inlet pipe 13 is provided at the bottom end of the sealing plate 11, and a water outlet pipe 14 is provided on the outer wall of the top end of the sealing plate 11.

[0055] Reference Figure 1 and Figure 2 The plate fixing assembly 2 includes a mold 21 and a clamp 22. There are two molds 21. In this embodiment, the material of the mold 21 is copper (copper or brass). In other feasible embodiments, the material of the mold 21 can be replaced according to needs and is not a limitation to the present application. The two molds 21 are fixed on the copper pad 12 and arranged opposite to each other. There are mounting grooves 211 on the two opposite side walls of the two molds 21. The two mounting grooves 211 are connected, one of the mounting grooves 211 is used to install a magnesium alloy plate, and the other mounting groove 211 is used to install an aluminum alloy plate. A gasket 212 is provided in the mounting groove 211. In this embodiment, a copper gasket 212 is used.

[0056] Reference Figure 1 and Figure 2There are two clamps 22 and they correspond to the mold 21 one by one. The clamps 22 are arranged on the copper pad 12 and are used to position the magnesium alloy plate and the aluminum alloy plate. For the convenience of explanation, only one clamp 22 is used for explanation in this embodiment. The clamp 22 includes a fixing rod 221, a clamp 222 and a fixing bolt 223. The fixing rod 221 is fixed on the copper pad 12 and extends upward. The fixing rod 221 is located on the side of the mold 21 away from the mounting groove 211. The clamp 222 is located above the fixing rod 221 and extends horizontally. One end of the clamp 222 has a downward protruding end 224, and the protruding end 224 is against the upper surface of the plate 5. The other end of the clamp 222 is threadedly connected to the fixing bolt 223, and the lower end of the fixing bolt 223 is threadedly connected to the fixing rod 221.

[0057] Reference Figure 1 and Figure 2 Before installation, rotate the fixing bolt 223 to drive the chuck 222 away from the mold 21, put the plate 5 into the installation groove 211, rotate the chuck 222 so that the protruding end 224 is against the upper surface of the plate 5, then press the chuck 222 with one end and rotate the fixing bolt 223 with the other end, so that the chuck 222 can be tightly against the upper surface of the plate 5 after releasing the hand, so as to realize the positioning of the plate 5.

[0058] Reference Figure 1 and Figure 2 The magnetic field component 3 is arranged on the copper pad 12. The magnetic field component 3 includes a mounting part 31 and a magnetic part 32. Two mounting parts 31 are provided and are respectively located on both sides of the clamp 22. The mounting part 31 is L-shaped, and the vertical surface of the mounting part 31 is in contact with the outer surface of the end of the fixing rod 221 away from the mold 21. The horizontal surface of the mounting part 31 extends in a direction away from the mounting groove 211. Two mounting bolts 33 are horizontally penetrated between the vertical surfaces of the two mounting parts 31. The two mounting bolts 33 are located at both ends of the plate 5. Four mounting nuts 331 are threadedly connected to each mounting bolt 33. When positioning, the mounting nuts 331 are pressed against the opposite side walls of the vertical surface. The mounting bolts 33 and the mounting nuts 331 are both made of plastic.

[0059] Reference Figure 1 and Figure 2 There are two groups of magnetic parts 32 and they correspond to the mounting parts 31 one by one. The magnetic parts 32 are arranged on the corresponding mounting parts 31. During welding, the aluminum alloy plate and the magnesium alloy plate are located between the magnetic fields generated by the two groups of magnetic parts 32. The following only takes one group of magnetic parts 32 as an example for explanation. The magnetic part 32 includes a plurality of magnets 321. The plurality of magnets 321 are sequentially arranged on the horizontal plane of the mounting part 31. The plurality of magnets 321 are separated by a magnet separation belt 322. The magnet separation belt 322 is any accessory in the prior art that can separate the magnetic field. The magnet separation belt 322 is used to separate unnecessary magnets 321 according to the required magnetic field strength.

[0060] Reference Figure 1 and Figure 2 In this embodiment, the magnet 321 adopts a permanent magnet. In other feasible embodiments, the magnet adopted may be a permanent magnet, or an electromagnet, or a magnet, a superconducting magnet, or a hybrid magnet of a magnet and a superconducting magnet. The generated magnetic field may be a steady magnetic field, an alternating magnetic field, a gradient magnetic field, or a pulsed magnetic field.

[0061] Example 2

[0062] Reference Figure 1 , Figure 2 and Figure 3 A method for preparing a magnesium / aluminum dissimilar metal joint comprises the following steps: S1, filling powder preparation: respectively select blocks with the same composition as the magnesium alloy plate and aluminum alloy plate to be welded for ball milling, dry the corresponding powders after obtaining them, mix the dried powders according to different proportions and stir them evenly to obtain filling powder one and filling powder two.

[0063] Specifically, commercially available AZ91 magnesium alloy plates with a thickness of 15 mm and 6061 aluminum alloy plates were selected, and the two plates 5 were ball-milled to obtain powders with an average particle size of 200 meshes. The powders were vacuum-dried at 50°C. After drying, the magnesium alloy powder and the aluminum alloy powder were uniformly mixed together in a ratio of 1:3 to obtain filling powder one, and the magnesium alloy powder and the aluminum alloy powder were uniformly mixed together in a ratio of 3:1 to obtain filling powder two.

[0064] S2. Plate processing: determine the weld area 6 of the magnesium alloy plate and the aluminum alloy plate to be welded, process the small trapezoidal groove 61 on the weld area 6, remove the oxide layer of the weld area 6, and perform surface degreasing treatment.

[0065] Specifically, commercially available AZ91 magnesium alloy sheet and 6061 aluminum alloy sheet are selected as welding sheets, the thickness of sheet 5 is 15 mm, the length of sheet 5 is 150 mm, and the width is 50 mm. The weld area 6 is determined. The weld area 6 is obtained according to actual needs or conventional experience. In this embodiment, the area extending 9-10 mm inward from the adjacent length sides of the two sheets 5 is the weld area 6, and a trapezoidal small groove 61 is processed in the weld area 6. The trapezoidal small groove 61 is wide at the top and narrow at the bottom, and the upper width is 3 mm, the lower width is 2 mm, and the height is 5 mm. The distance between the trapezoidal small groove 61 on the magnesium alloy sheet and the welding edge of the magnesium alloy sheet is 3 mm, and the distance between the trapezoidal small groove 61 on the aluminum alloy sheet and the welding edge of the aluminum alloy sheet is 3 mm. Then, the oxide layer of the weld area 61 is removed, and the surface is rinsed with acetone degreasing tap water for 3 minutes.

[0066] S3, powder filling: filling the filling powder 1 obtained in S1 into the trapezoidal small groove 61 on the magnesium alloy plate, filling the filling powder 2 obtained in S1 into the trapezoidal small groove 61 on the aluminum alloy plate, and performing compaction treatment.

[0067] Specifically, filling powder 1 and filling powder 2 are respectively filled into the corresponding trapezoidal small grooves 61, and compaction treatment is performed three times under 10 MPa, each time for 2 minutes.

[0068] S4. Weldment assembly: Install the welding device, first install the copper pad 12 on the welding table 1, install the powder-filled magnesium alloy plate and aluminum alloy plate into the mold 21 respectively, and use the clamp 22 to position the plate 5, then install the two groups of magnetic parts 32 on the mounting parts 31 on both sides of the clamp 22 respectively, adjust the magnetic field gap width and magnetic field strength, and finally pour cooling water into the sealing plate 11, and the water level is higher than the upper surface of the magnesium alloy plate and the aluminum alloy plate.

[0069] Specifically, the welding device in Example 1 is used to install the magnesium alloy plate and the aluminum alloy plate obtained in S3 into the corresponding mold 21, and the plate 5 is clamped using the clamp 22, and then the magnetic part 32 is installed. The distance between the two mounting parts 31 is adjusted by the mounting bolts 33 and the mounting nuts 331, so that the spacing between the gaps of the two groups of magnets 321 is 60 mm, the magnetic field strength is 0.2 T, and cooling water is poured through the water inlet pipe 13, and the distance between the water surface and the upper surface of the magnesium alloy plate and the aluminum alloy plate is 20 mm.

[0070] S5, welding: setting welding parameters on the welding tool 4, and performing underwater welding on the magnesium alloy plate and the aluminum alloy plate, while starting the magnetic member 32 to complete the welding of the dissimilar metal joint under the magnetic field condition, and obtaining a welded joint after the welding is completed.

[0071] Specifically, a suitable welding tool 4 is selected, and the stirring drill bit 41 of the welding tool 4 is a threaded drill bit with a trapezoidal cone and an upper diameter of 15 mm, a lower diameter of 10 mm, and a height of 12 mm. The welding speed is set to 100 mm / min and the rotation speed is set to 700 r / min on the welding tool 4. Underwater welding is performed on the magnesium alloy plate and the aluminum alloy plate. At the same time, the magnetic part 32 that has been installed in S4 is started to realize the welding of dissimilar metal joints under magnetic field conditions, and a welded joint is obtained after welding is completed.

[0072] Example 3

[0073] Reference Figure 1 , Figure 2 and Figure 3 , a method for preparing a magnesium / aluminum dissimilar metal joint, which is different from Example 2 in that:

[0074] In S1, commercially available AZ91 magnesium alloy plates with a thickness of 15 mm and 6061 aluminum alloy plates are selected, and the two plates 5 are ball-milled to obtain powders with an average particle size of 20 meshes. The magnesium alloy powder and the aluminum alloy powder are uniformly mixed together in a ratio of 1:3 to obtain filling powder 1, and the magnesium alloy powder and the aluminum alloy powder are uniformly mixed together in a ratio of 3:1 to obtain filling powder 2.

[0075] In S2, the trapezoidal small groove 61 is wide at the top and narrow at the bottom, with an upper width of 4 mm, a lower width of 2.5 mm, and a height of 6 mm. The trapezoidal small groove 61 located on the magnesium alloy plate is 4 mm away from the welding edge of the magnesium alloy plate, and the trapezoidal small groove 61 located on the aluminum alloy plate is 4 mm away from the welding edge of the aluminum alloy plate. Then, the oxide layer of the weld area 6 is removed, acetone is used for degreasing, and tap water is rinsed for 3 minutes.

[0076] In S3, the filling powder 1 and the filling powder 2 are respectively filled into the corresponding trapezoidal small grooves 61, and compaction treatment is performed 10 times under 0.5 MPa, each time for 2 minutes.

[0077] In S4, the welding device in Example 1 is used to install the magnesium alloy plate and the aluminum alloy plate obtained in S3 into the corresponding mold 21, and the plate 5 is clamped by the clamp 22, and then the magnetic part 32 is installed. The distance between the two mounting parts 31 is adjusted by the mounting bolts 33 and the mounting nuts 331, so that the spacing of the gaps of the magnets 321 is 200 mm, the magnetic field strength is 0.01 T, and cooling water is poured through the water inlet pipe 13. The distance between the water surface and the upper surface of the magnesium alloy plate and the aluminum alloy plate is 5 mm.

[0078] In S5, the stirring drill bit 41 of the welding tool 4 is a threaded drill bit with a trapezoidal cone and an upper diameter of 18 mm, a lower diameter of 12 mm, and a height of 15 mm. The welding speed is set to 50 mm / min and the rotation speed is set to 700 r / min on the welding tool. Underwater welding is performed on the magnesium alloy plate and the aluminum alloy plate, and the magnetic part 32 that has been installed in S4 is started at the same time.

[0079] Example 4

[0080] Reference Figure 1 , Figure 2 and Figure 3 , a method for preparing a magnesium / aluminum dissimilar metal joint, which is different from Example 2 in that:

[0081] In S1, commercially available AZ91 magnesium alloy plates with a thickness of 15 mm and 6061 aluminum alloy plates are selected, and the two plates 5 are ball-milled to obtain powders with an average particle size of 3000 meshes. The magnesium alloy powder and the aluminum alloy powder are uniformly mixed together at a ratio of 1:100 to obtain filling powder 1, and the magnesium alloy powder and the aluminum alloy powder are uniformly mixed together at a ratio of 100:1 to obtain filling powder 2.

[0082] In S3, the filling powder 1 and the filling powder 2 are respectively filled into the corresponding trapezoidal small grooves 61, and a compaction treatment is performed once under the condition of 20 MPa for 2 minutes.

[0083] In S4, the welding device in Example 1 is used to install the magnesium alloy plate and the aluminum alloy plate obtained in S3 into the corresponding mold 21, and the plate 5 is clamped by using the clamp 22, and then the magnetic part 32 is installed. The distance between the two mounting parts 31 is adjusted by the mounting bolts 33 and the mounting nuts 331, so that the spacing between the gaps of the two groups of magnets 321 is 60 mm, the magnetic field strength is 0.01 T, and cooling water is poured through the water inlet pipe 13, and the distance between the water surface and the upper surface of the magnesium alloy plate and the aluminum alloy plate is 200 mm.

[0084] In S5, the stirring drill bit 41 of the welding tool 4 is a threaded drill bit with a trapezoidal cone and an upper diameter of 16 mm, a lower diameter of 11 mm, and a height of 12 mm. The welding speed is set to 300 mm / min and the rotation speed is set to 700 r / min on the welding tool. Underwater welding is performed on the magnesium alloy plate and the aluminum alloy plate, and the magnetic part 32 that has been installed in S4 is started at the same time.

[0085] Comparative Example 1

[0086] A method for preparing a magnesium / aluminum dissimilar metal joint, which is different from Example 2 in that no external magnetic field is applied.

[0087] Comparative Example 2

[0088] A method for preparing a magnesium / aluminum dissimilar metal joint, which is different from Example 2 in that no external magnetic field is applied and no cooling water is added during the welding process.

[0089] Comparative Example 3

[0090] A method for preparing a magnesium / aluminum dissimilar metal joint, which is different from Example 2 in that: the plate is not processed with small trapezoidal grooves, filling powder is not used, and no external magnetic field is applied, and welding is directly performed using a welding tool.

[0091] Finished product testing

[0092] The magnesium / aluminum dissimilar metal joints prepared by the methods of Examples 2-4 and Comparative Examples 1-3 were tested respectively, and the cracking behavior was observed by a metallographic microscope; the appearance morphology of the joint was observed by naked eye; the intermetallic compounds at the weld were analyzed by energy spectrum surface scanning test, and the tensile strength test was tested according to GB / T 228.

[0093] The test results are shown in Table 1 and Appendix Figure 4-5 As shown:

[0094] Table 1 Test results

[0095]

[0096] Combined with Table 1 and Appendix Figure 4-5 It can be seen that the preparation method provided in Example 2 is the optimal embodiment of the present invention. Compared with Comparative Examples 1-3, this method optimizes the composition of the weld by opening a series of trapezoidal small grooves at the welds of the magnesium alloy and aluminum alloy base materials to fill the welds with aluminum alloy and magnesium alloy powders, thereby reducing the formation of aluminum-magnesium intermetallic compounds. In the underwater welding cooling process, the step of reducing the welding temperature of the weld area during welding is used. At the same time, a copper pad is used as the pad to further inhibit the formation of magnesium-aluminum metal compounds. In addition, an external magnetic field is applied during the welding process. Under the stirring action of the electromagnetic force, the molten plastic flowing metal has a better mass transfer effect on a microscopic scale, reduces element segregation, and promotes a more dispersed distribution of aluminum-magnesium intermetallic compound particles, which can significantly reduce component segregation. The finished product prepared by this method has no cracking phenomenon, and the maximum tensile strength is 98.3Mpa, which is significantly better than the existing preparation method and improves the preparation efficiency. The device and welding method provided by this method can obtain a high-strength magnesium / aluminum dissimilar metal joint, and the device is simple to load and unload, easy to operate, and reduces the cost while improving the welding strength.

Claims

1. A device for preparing magnesium / aluminum dissimilar metal joints, characterized in that: The invention comprises a welding platform (1), a plate fixing component (2) arranged on the welding platform (1), a magnetic field component (3) arranged on the welding platform (1), and a welding tool (4); the plate fixing component (2) is used to position a magnesium alloy plate and an aluminum alloy plate; the magnetic field component (3) is used to generate a magnetic field; the welding tool (4) is used to stir friction welding the magnesium alloy plate and the aluminum alloy plate; a sealing plate (11) is arranged around the welding platform (1); during welding, cooling water is poured into the sealing plate (11); and the working heads of the plate fixing component (2), the magnetic field component (3) and the welding tool (4) are all located below the liquid surface.

2. The device according to claim 1, characterized in that: The plate fixing assembly (2) comprises: A mold (21), wherein two molds (21) are provided, and the two molds (21) are both provided on the welding platform (1) and arranged opposite to each other, and the two molds (21) have mounting grooves (211) on opposite side walls, and the two mounting grooves (211) are connected, and one of the mounting grooves (211) is used to install a magnesium alloy plate, and the other mounting groove (211) is used to install an aluminum alloy plate, and a gasket (212) is provided in the mounting groove (211); A clamp (22), wherein two clamps (22) are provided and correspond one to one with the mold (21), and the clamps (22) are arranged on the welding table (1) and are used to position the magnesium alloy plate and the aluminum alloy plate.

3. The device according to claim 2, characterized in that: The clamp (22) comprises a fixing rod (221), a clamp (222) and a fixing bolt (223); the fixing rod (221) is arranged on the welding table (1) and abuts against the outer wall of the mold (21) at one end away from the mounting groove (211); the clamp (222) abuts against the upper surface of the corresponding magnesium alloy plate or aluminum alloy plate; the fixing bolt (223) is threadedly connected to the top of the fixing rod (221); and the end of the clamp (222) close to the fixing rod (221) is connected to the fixing bolt (223).

4. The device according to claim 3, characterized in that: The magnetic field component (3) comprises: A mounting member (31), wherein two mounting members (31) are provided and are respectively located on both sides of the clamp (22), a mounting bolt (33) is passed through the two mounting members (31), and a mounting nut (331) for positioning the mounting member (31) is threadedly connected to the mounting bolt (33); The magnetic members (32) are provided in two groups and correspond one to one with the mounting members (31). The magnetic members (32) are arranged on the corresponding mounting members (31). During welding, the aluminum alloy sheet and the magnesium alloy sheet are located between the magnetic fields generated by the two groups of magnetic members (32).

5. The device according to claim 4, characterized in that: Each group of magnetic members (32) comprises a plurality of magnets (321), and the plurality of magnets (321) are separated by magnet separation belts (322).

6. The welding device according to claim 5, characterized in that: A copper backing plate (12) is provided on the welding platform (1), and the mold (21) is provided on the copper backing plate (12).

7. A method for preparing a magnesium / aluminum dissimilar metal joint, characterized in that: The following steps are involved: S1. Preparation of filling powder: respectively select blocks with the same composition as the magnesium alloy plate and aluminum alloy plate to be welded for ball milling, obtain corresponding powders and then dry them, mix the dried powders in different proportions and evenly stir them to obtain filling powder 1 and filling powder 2; S2, plate processing: determining the weld area (6) of the magnesium alloy plate and the aluminum alloy plate to be welded, processing a small trapezoidal groove (61) on the weld area, removing the oxide layer of the weld area (6), and performing surface degreasing treatment; S3, powder filling: filling the filling powder 1 obtained in S1 into the trapezoidal small groove (61) on the magnesium alloy plate, and filling the filling powder 2 obtained in S1 into the trapezoidal small groove (61) on the aluminum alloy plate, and performing compaction treatment; S4. Weldment assembly: Install the welding device as described in claim 6, first install the copper backing plate (12) on the welding table (1), install the powder-filled magnesium alloy plate and aluminum alloy plate into the mold (21) respectively, and use the clamp (22) to position the plate (5), then install the two sets of magnetic parts (32) on the mounting parts (31) on both sides of the clamp (22), adjust the magnetic field gap width and magnetic field strength, and finally pour cooling water into the sealing plate (11), and the water level is higher than the upper surface of the magnesium alloy plate and the aluminum alloy plate; S5, welding: setting welding parameters on the welding tool (4), and performing underwater welding on the magnesium alloy plate and the aluminum alloy plate, while starting the magnetic component (32) to complete the welding of the dissimilar metal joint under the magnetic field condition, and obtaining a welded joint after the welding is completed.

8. The method according to claim 7, characterized in that: S1. Preparation of filling powder: respectively selecting blocks with the same composition as the magnesium alloy plate and aluminum alloy plate to be welded for ball milling, the particle size of the powder obtained after ball milling is 20-3000 mesh, vacuum drying the powder at 50° C., and mixing the dried powder in different proportions to obtain filling powder 1 and filling powder 2; S2, plate processing: determining the weld area (6) of the magnesium alloy plate and the aluminum alloy plate to be welded, processing a small trapezoidal groove (61) on the weld area (6), wherein the upper width of the small trapezoidal groove (61) is 3-4 mm, the lower width is 2-2.5 mm, the height is 5-6 mm, and the distance from the welding edge of the plate (5) is 3-4 mm, then removing the oxide layer of the weld area (6) and performing surface degreasing treatment; S3, powder filling: filling the filling powder 1 obtained in S1 into the trapezoidal small groove (61) on the magnesium alloy plate, and filling the filling powder 2 obtained in S1 into the trapezoidal small groove (61) on the aluminum alloy plate, and performing compaction treatment for 1 to 10 times under the condition of 0.5 to 20 MPa; S4, weldment assembly: installing a welding device, first installing a copper pad (12) on a welding table (1), installing the powder-filled magnesium alloy sheet and aluminum alloy sheet into a mold (21) respectively, and using a fixture (22) to position the sheet (5), then installing two sets of magnetic parts (32) on the mounting parts (31) on both sides of the fixture (22), adjusting the magnetic field gap width and magnetic field strength so that the magnetic field strength ranges from 0.01T to 0.2T, and finally pouring cooling water into the sealing plate (11), with the distance between the water surface and the upper surface of the magnesium alloy sheet and the aluminum alloy sheet being not less than 5mm; S5. Welding: Select a suitable welding tool (4), wherein the stirring drill bit (41) of the welding tool (4) is a threaded drill bit with a trapezoidal cone and an upper diameter of 15-18 mm, a lower diameter of 10-12 mm, and a height of 12-15 mm. Set the welding speed on the welding tool (4) to 50-300 mm / min, and perform underwater welding on the magnesium alloy plate and the aluminum alloy plate. Simultaneously, start the magnetic part (32) to complete the welding of the dissimilar metal joint under the magnetic field condition, and obtain a welded joint after the welding is completed.

9. The method according to claim 8, characterized in that: S1. Preparation of filling powder: respectively select blocks with the same composition as the magnesium alloy plate and aluminum alloy plate to be welded for ball milling, the average particle size of the powder obtained after ball milling is 200 mesh, the powder is vacuum dried at 50°C, the dried powder is configured in different proportions and stirred evenly to obtain filling powder 1 and filling powder 2, the content ratio of magnesium alloy powder to aluminum alloy powder in filling powder 1 is 1:3, and the content ratio of magnesium alloy powder to aluminum alloy powder in filling powder 2 is 3:1; In the preferred embodiment S2, the upper width of the trapezoidal small groove (61) is 3 mm, the lower width is 2 mm, the height is 5 mm, and the distance from the welding edge of the plate (5) is 3 mm.

10. The method according to claim 8, characterized in that: In the S4, the width of the magnetic field gap between the two groups of magnetic parts (32) is 60 mm, the magnetic field strength is 0.2 T, and the distance between the water surface and the upper surface of the magnesium alloy plate and the aluminum alloy plate is 20 mm; in the S5, the stirring drill bit (41) of the welding tool (4) is a threaded drill bit with a trapezoidal cone and an upper diameter of 15 mm, a lower diameter of 10 mm, and a height of 12 mm, the welding speed is 100 mm / min, and the rotation speed is 700 r / min.

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