Interlayer for welding of aluminum matrix composites and method for making and welding thereof

Abstract

This invention discloses an intermediate layer for welding aluminum-based composite materials, its fabrication method, and a welding method, belonging to the field of welding. The welding method includes the following steps: grinding and cleaning the intermediate layer and the base material to be welded. The intermediate layer, except that the particle size of the aluminum powder in the raw material is smaller than that of the base material, has the same composition and content as the base material. The intermediate layer is sandwiched between the surfaces of the base material to be welded, and after clamping, a stirring pin is pressed into the intermediate layer for friction stir welding. This welding method uses an intermediate layer with a small grain size, which can counteract grain growth caused by heat input during welding. Furthermore, the use of small-particle-size aluminum powder can introduce more 3D network Al2O3, which plays a role in load transfer and grain boundary pinning during welding, further inhibiting grain growth and effectively controlling the grain size in the weld area. This solves the problem of reduced joint strength due to grain growth in existing friction stir welding technologies, significantly improving the efficiency of the weld joint.

Description

Technical Field

[0001] This invention relates to an intermediate layer for welding aluminum-based composite materials, its manufacturing method, and welding method, belonging to the field of welding. Background Technology

[0002] Aluminum matrix composites possess the advantages of aluminum matrix, such as light weight, good plasticity, and ease of processing, while also exhibiting the characteristics of reinforcing fillers added to the aluminum matrix. Aluminum matrix composites can have better specific strength, wear resistance, and high-temperature performance than aluminum itself, and are commonly used as structural materials and aircraft components in aerospace, transportation, and energy fields. However, when welding aluminum matrix composites using common fusion welding methods such as laser welding and TIG welding, problems such as interfacial reactions between the filler and the aluminum matrix and particle agglomeration can occur at the weld, making it difficult to achieve good bonding of the materials.

[0003] Among various welding techniques, friction stir welding (FSW) is considered the most promising method for welding aluminum-based composite materials. The principle of FSW is to use a high-speed rotating stirring head to rub against the materials to be welded, thereby raising the temperature of the material at the joint and softening it, resulting in plastic flow and thus achieving joint bonding. The high-speed rotating stirring head can evenly disperse the filler, preventing agglomeration in the weld nugget area. When the stirring head speed is low, the generated frictional heat is insufficient to plasticize the material, resulting in inadequate flow and the formation of voids in the weld, failing to achieve a good bond between the materials. Only at higher speeds, generating sufficient frictional heat, can the materials fully fuse to form a dense weld. However, when applying FSW to aluminum-based composite materials, the high heat input during the process can lead to grain growth in the weld area, reducing the strength of the weld joint to a level far below the original strength of the base material. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides an intermediate layer for welding aluminum-based composite materials and a method for manufacturing the same, and also provides a welding method for aluminum-based composite materials, so that the strength of the welded joint is close to the original strength of the base material.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] In a first aspect, this application provides an intermediate layer for welding aluminum-based composite materials, which is sheet-shaped and has contours on both sides that are consistent with the contours of the base material to be welded. The intermediate layer material is composed of aluminum powder and reinforcing filler, and the ratio of the intermediate layer material is consistent with the ratio of the base material. The specifications of the reinforcing filler in the intermediate layer material are consistent with the specifications of the reinforcing filler in the base material, and the particle size of the aluminum powder in the intermediate layer material is smaller than the particle size of the aluminum powder in the base material.

[0007] The intermediate layer provided in this application for welding aluminum-based composite materials has the same composition and content as the base material, except that the particle size of the aluminum powder in the raw material is smaller than that of the base material. This intermediate layer can offset the grain growth caused by heat input during friction stir welding, effectively control the grain size in the weld area, and thus improve the bonding strength of the weld joint. The use of small-particle-size aluminum powder can introduce more 3D network Al2O3, which plays a role in load transfer and grain boundary pinning during the welding process, further controlling grain growth, achieving good welding of aluminum-based composite materials, and improving the strength of the weld joint.

[0008] Furthermore, the particle size of the aluminum powder in the intermediate layer raw material is 15%-90% of the particle size of the aluminum powder in the parent material raw material.

[0009] Smaller aluminum powder particle sizes increase the difficulty and cost of preparation, and also result in poor dispersibility during intermediate layer fabrication. If the base material's aluminum powder particle size is already very small, the proportion can be increased. Experiments have shown that a particle size of 90% or less of the aluminum powder particle size in the intermediate layer material is sufficient to achieve excellent joint strength enhancement. When two-pass welding is required, smaller aluminum powder particle sizes in the intermediate layer material are preferable, provided good dispersibility is maintained.

[0010] Furthermore, the thickness of the intermediate layer is 10%-150% of the diameter of the stirring pin in friction stir welding. If the thickness of the intermediate layer is too small, it will be difficult to enhance the joint strength; if the thickness of the intermediate layer is too large, the intermediate layer cannot be completely fused with the base material during the friction stir welding process.

[0011] Furthermore, the intermediate layer is suitable for aluminum-based composite materials in which the aluminum powder particle size in the parent material is 1.5μm-30μm.

[0012] Furthermore, the intermediate layer is suitable for aluminum-based composite materials containing 5 wt%-30 wt% reinforcing filler in the parent material.

[0013] Secondly, this application provides a method for fabricating an intermediate layer for welding aluminum-based composite materials, the steps of which include:

[0014] Weigh aluminum powder and reinforcing filler. The amount and specifications of the reinforcing filler are consistent with those of the reinforcing filler in the base material of the aluminum matrix composite material to be welded. The amount of aluminum powder is consistent with the amount of aluminum powder in the base material. The particle size of the aluminum powder is smaller than that of the aluminum powder in the base material.

[0015] The materials are mixed, pressed, and sintered sequentially to obtain a second plate with a cross-sectional shape that matches the shape of the welding surface of the base material; preferably, after sintering, there are also hot working plastic deformations such as extrusion and rolling.

[0016] The second plate is sliced ​​to obtain an intermediate layer for welding aluminum-based composite materials.

[0017] The second sheet is essentially another aluminum-based composite material with properties very similar to the base material. Its properties do not change significantly after being cut into sheets. Furthermore, the grain size in the interlayer is smaller than that of the base material, which can offset grain growth caused by heat input during friction stir welding, effectively controlling the grain size in the weld area and thus improving the bonding strength of the weld joint. In addition, using small-particle-size aluminum powder results in more 3D network Al2O3 in the interlayer, which plays a role in load transfer and grain boundary pinning during welding, further controlling grain growth, achieving good welding of the aluminum-based composite material, and improving joint strength.

[0018] Optionally, the particle size of the aluminum powder is 15%-90% of the particle size of the aluminum powder in the base material. Small-particle-size aluminum powder is difficult and costly to prepare, and its dispersibility is poor when making the second plate. If the particle size of the aluminum powder in the base material is already very small, such as below 5μm, a larger particle size aluminum powder can be appropriately selected as the intermediate layer material, considering the negative consequences of grain growth compared to the negative consequences of poor aluminum powder dispersion. For example, it could be 70%-90% of the particle size of the aluminum powder in the base material. Experiments have shown that as long as the particle size of the aluminum powder in the intermediate layer material reaches 90% or less of the particle size of the aluminum powder in the base material, a good effect on enhancing joint strength can be achieved. Furthermore, when two welding passes are required, the smaller the particle size of the aluminum powder in the intermediate layer material, the better, provided that good dispersibility is maintained.

[0019] Optionally, the thickness of the slice is 10%-150% of the diameter of the stirring pin in friction stir welding. When the base material to be welded is large, the cross-sectional shape of the second plate needs to be consistent with the shape of the base material to be welded, which makes slicing difficult. In this case, the intermediate layer can be cut thicker to reduce the difficulty of slicing. In the subsequent welding, two welding passes are used to ensure that both base materials are tightly bonded to the intermediate layer.

[0020] Thirdly, this application provides a welding method for aluminum-based composite materials, comprising the following steps:

[0021] Grind and clean the intermediate layer and the base material to be welded for welding aluminum-based composite materials prepared according to the manufacturing method described in the second aspect; at least grind and clean the surfaces to be welded, preferably all surfaces that will come into contact with the stirring head.

[0022] The intermediate layer is sandwiched between the welding surfaces of the first base material and the second base material, and the welding surfaces of the first base material and the second base material are aligned with the two sides of the intermediate layer.

[0023] The stirring needle is pressed into the intermediate layer for friction stir welding.

[0024] The stirring pin locally melts the interlayer and the base material. As the welding tool moves forward along the welding interface, the plasticized material flows from the front to the rear of the tool under the rotational friction force, forming a dense solid-phase weld under the pressure of the tool. The small grain size of the interlayer can offset the grain growth caused by heat input during friction stir welding, effectively controlling the grain size in the weld area, thus improving the bonding strength of the weld joint. On the other hand, the use of small-particle aluminum powder can introduce more 3D network Al2O3, which plays a role in load transfer and grain boundary pinning during welding, further controlling grain growth, achieving good welding of aluminum matrix composites, and improving the strength of the weld joint.

[0025] Preferably, in the friction stir welding, if the thickness of the intermediate layer is less than 50% of the diameter of the stirring pin, a single pass welding is performed; if the thickness of the intermediate layer is greater than or equal to 50% of the diameter of the stirring pin and less than 100% of the diameter of the stirring pin, a single pass welding or a two-pass welding is performed; if the thickness of the intermediate layer is greater than 100% of the diameter of the stirring pin, a two-pass welding is performed.

[0026] The two-pass welding involves stirring the gap between the first base material and the intermediate layer of the brazing filler metal during the first pass, and stirring the gap between the second base material and the intermediate layer of the brazing filler metal during the second pass. Preferably, in the friction stir welding, the shoulder pressure is 0.1mm-3mm, the stirring pin tilt angle is 0°-3°, the stirring pin rotation speed is 400rpm-1600rpm, and the travel speed is 50mm / min-400mm / min.

[0027] The beneficial effects of this invention are as follows: The welding method based on the intermediate layer can counteract grain growth caused by heat input during friction stir welding, effectively controlling the grain size in the weld area, thus improving the bonding strength of the weld joint. The use of small-particle aluminum powder can introduce more 3D network Al2O3, which plays a role in load transfer and grain boundary pinning during welding, further controlling grain growth, achieving good welding of aluminum-based composite materials, and improving the strength of the weld joint. The welding method of this invention can solve the problem of reduced joint strength caused by grain growth due to welding heat input in existing friction stir welding technology, control the grain size in the weld area, and achieve good welding of aluminum-based composite material joints with strength comparable to the base material, significantly improving the efficiency of welding joints.

[0028] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the clamping of the intermediate layer and the base material in a welding method for aluminum-based composite materials provided in an embodiment of this application.

[0030] Figure 2 This is a schematic diagram of the weld state after two welding passes in a welding method for aluminum-based composite materials provided in this application embodiment.

[0031] Figure 3 This is a schematic diagram of the cross-sectional state during the first and second welding passes in a welding method for aluminum-based composite materials provided in this application embodiment.

[0032] Figure 4 This is a schematic diagram of the cross-sectional state during a single-pass welding process in a welding method for aluminum-based composite materials provided in this application embodiment.

[0033] Reference numerals: 27, first base material; 28, second base material; 39, intermediate welding layer. Detailed Implementation

[0034] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0035] The following disclosure provides many different embodiments or examples for implementing different structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed.

[0036] When friction stir welding is applied to aluminum-based composite materials, the high heat input during the welding process leads to grain growth in the weld area, resulting in a reduction in joint strength far below the original strength of the base material. This invention uses an aluminum-based composite material made from small-particle-size aluminum powder (compared to the particle size of the aluminum powder in the base material) as an intermediate layer. This material has a small grain size, and the introduction of more 3D network Al2O3 can control the grain size in the weld area of ​​the joint, making the joint strength comparable to that of the base material.

[0037] This embodiment provides an intermediate layer for welding aluminum-based composite materials. The intermediate layer is sheet-like, with its contours on both sides matching the contours of the surfaces to be welded on the base material. The intermediate layer material consists of aluminum powder and reinforcing filler, with the same proportions as the base material. The specifications of the reinforcing filler in the intermediate layer material are the same as those in the base material, and the particle size of the aluminum powder in the intermediate layer material is smaller than that in the base material. To accurately reflect the characteristics of this product, the intermediate layer will be referred to as a "welding interlayer" in some subsequent sections. This welding interlayer is suitable for aluminum-based composite materials containing 5 wt%-30 wt% reinforcing filler in the base material.

[0038] Accordingly, this embodiment provides a method for fabricating a welded interlayer, the steps of which include:

[0039] S11: Weigh aluminum powder and reinforcing filler. The amount and specifications of the reinforcing filler are the same as those of the reinforcing filler in the parent material of the aluminum matrix composite material to be welded. The amount of aluminum powder is the same as that of the aluminum powder in the parent material. The particle size of the aluminum powder is smaller than that of the aluminum powder in the parent material.

[0040] S12: The mixture is mixed, pressed, and sintered sequentially to obtain a second plate with a cross-sectional shape consistent with that of the parent material. Preferably, after sintering, there is further hot working plastic deformation such as extrusion and rolling, which makes the cross-sectional shape of the second plate consistent with that of the parent material and makes the second plate more dense.

[0041] S13: Slice the second plate to obtain the welding interlayer 39.

[0042] The welded interlayer is essentially another aluminum-based composite material with properties very similar to the base material. Its grain size is smaller than that of the base material, which can counteract grain growth caused by heat input during friction stir welding, effectively controlling the grain size in the weld area and thus improving the bonding strength of the weld joint. The small-particle aluminum powder introduced into the interlayer material gives it more 3D network Al2O3, which plays a role in load transfer and grain boundary pinning during welding, further controlling grain growth, achieving good welding of the aluminum-based composite material, and improving joint strength.

[0043] When the aluminum powder particle size in the base material is less than 1.5μm, it is difficult and costly to prepare aluminum powder smaller than 1.5μm, and it is difficult to disperse when making the second plate. Therefore, the welded interlayer 39 is suitable for aluminum-based composite materials with aluminum powder particle size of 1.5μm-30μm in the base material.

[0044] Specifically, the particle size of the aluminum powder in the interlayer material is 15%-90% of the particle size of the aluminum powder in the base material. Smaller aluminum powder particle sizes increase the difficulty and cost of preparation, and also result in poor dispersion during welding interlayer fabrication. If the particle size of the aluminum powder in the base material is already very small, such as below 5μm, a larger particle size can be appropriately selected as the interlayer material, considering the trade-off between the adverse consequences of grain growth and poor aluminum powder dispersion. For example, a particle size of 70%-90% of the aluminum powder in the base material can be used. Experiments have shown that as long as the particle size of the aluminum powder in the interlayer material reaches 90% or less of the particle size of the aluminum powder in the base material, a good effect on enhancing joint strength can be achieved. Furthermore, when two welding passes are required, the grains in the weld interlayer will grow twice. Therefore, provided good dispersion is maintained, the smaller the particle size of the aluminum powder in the interlayer material, the better.

[0045] Preferably, the thickness of the welding interlayer is 10%-150% of the diameter of the stirring pin in friction stir welding. If the thickness is too small, it is difficult to enhance the joint strength; if the thickness is too large, some areas in the welding interlayer will not be stirred by the stirring pin during friction stir welding, making it difficult to ensure complete fusion between the welding interlayer and the base material. In addition, when the base material to be welded is large, the cross-sectional shape of the second plate needs to match the shape of the base material to be welded, which makes slicing difficult and the welding interlayer prone to deformation. For example, if the length is 50 times larger than the width, if the welding interlayer is too thin, it is easy to deform. In this case, the welding interlayer can be cut thicker to reduce the slicing difficulty, and two-pass welding can be used in subsequent welding to ensure that both base materials are tightly bonded to the intermediate layer. When the aspect ratio of the base material to be welded is too large, another approach is to make multiple welding interlayers, and the outline of each segment of the welding interlayer is consistent with the outline of the base material to be welded, which can also reduce the slicing difficulty. It is important to note that the "thickness" mentioned here refers to the thickness at the time of slicing, not the thickness exhibited on the workpiece after the welding interlayer 39 is integrated into the base material. Figure 1 and Figure 2 Describing the thickness direction in terms of orientation, the thickness direction during slicing is from the upper left corner to the lower right corner of the diagram. The thickness direction exhibited on the workpiece after the welded interlayer 39 integrates into the base material is from top to bottom in the diagram. Figure 3 and Figure 4 The direction of the thickness during slicing is described by the left-right direction in the figure, and the direction of the thickness of the welded interlayer 39 after it is integrated into the base material is described by the up-down direction in the figure.

[0046] Based on the same principle, this embodiment provides a welding method for welding two base materials, including the following steps (including the process of creating a welding interlayer). The two base materials to be welded are hereinafter referred to as the first base material 27 and the second base material 28, and the first base material 27 and the second base material 28 are made of the same material.

[0047] S01: Locate or detect the raw material composition and proportions of the base material.

[0048] S11: Weigh aluminum powder and reinforcing filler. The amount and specifications of the reinforcing filler are the same as those of the reinforcing filler in the parent material of the aluminum matrix composite material to be welded. The amount of aluminum powder is the same as that of the aluminum powder in the parent material. The particle size of the aluminum powder is smaller than that of the aluminum powder in the parent material.

[0049] S12: The mixture is mixed, pressed, and sintered in sequence to obtain a second plate with a cross-sectional shape that is consistent with that of the parent material.

[0050] S13: Slice the second plate to obtain the welding interlayer 39.

[0051] S21: Grind and clean the welded interlayer 39, the first base material 27, and the second base material 28. Specifically, use sandpaper or a grinding wheel to mechanically grind them to remove the oxide film on the surface; then use anhydrous ethanol or acetone to clean the treated base material or welded interlayer to remove stains and grease from the material surface.

[0052] S22: The welding interlayer 39 is sandwiched between the welding surfaces of the first base material 27 and the second base material 28, with the contours fitting so that the welding surfaces of the first base material and the second base material abut against the two sides of the intermediate layer, such as... Figure 1 As shown.

[0053] S23: Press the stirring needle into the intermediate layer for friction stir welding. Figure 1 The arrows in the diagram indicate the direction of movement of the stirring head.

[0054] like Figure 3 and Figure 4 As shown, in step S23, if the thickness of the welding interlayer 39 is less than 50% of the diameter of the stirring pin, a single-pass welding is performed; if the thickness of the welding interlayer 39 is greater than or equal to 50% of the diameter of the stirring pin and less than 100% of the diameter of the stirring pin, a single-pass or two-pass welding is performed; if the thickness of the welding interlayer 39 is greater than 100% of the diameter of the stirring pin, two-pass welding is performed. This ensures that every position of the welding interlayer 39 is stirred, resulting in a good bond between the welding interlayer 39 and the base material. When the thickness of the welding interlayer 39 is less than 50% of the diameter of the stirring pin, and when the thickness of the welding interlayer 39 is greater than 100% of the diameter of the stirring pin, the particle size of the aluminum powder in the intermediate layer material can be 60%-90% of the particle size of the aluminum powder in the base material, which helps to reduce costs and simplify the manufacturing of the second plate. When the thickness of the welding interlayer 39 is greater than or equal to 50% of the diameter of the stirring pin and less than 100% of the diameter of the stirring pin, two-pass welding can achieve a better connection effect than single-pass welding. In this case, the particle size of aluminum powder in the intermediate layer material needs to be 15%-30% of the particle size of aluminum powder in the parent material to accommodate the secondary growth of grains in the welding interlayer 39.

[0055] like Figure 2 and Figure 3 As shown, the two welding passes involve stirring the gap between the first base material and the intermediate layer during the first welding pass, and stirring the gap between the second base material and the intermediate layer during the second welding pass.

[0056] The stirring pin locally melts the welding interlayer 39 and the base material. As the welding tool moves forward along the welding interface, the plasticized material flows from the front to the rear of the welding tool under the rotational friction force of the tool, forming a dense solid-phase weld under the pressure of the tool. Although the grains in the base material and the welding interlayer 39 will grow, the small grain size of the intermediate layer can offset the grain growth caused by heat input during friction stir welding, effectively controlling the grain size in the weld area and thus improving the bonding strength of the weld joint. On the other hand, the use of small-particle aluminum powder can introduce more 3D network Al2O3, which plays a role in load transfer and grain boundary pinning during the welding process, further controlling grain growth, achieving good welding of aluminum-based composite materials, and improving the strength of the weld joint.

[0057] Specifically, in friction stir welding, the shoulder pressing amount is 0.1mm-3mm, the stirring pin tilt angle is 0°-3°, the stirring pin rotation speed is 400rpm-1600rpm, and the travel speed is 50mm / min-400mm / min.

[0058] Example 1

[0059] Aluminum-based composite material sheets were prepared by blending aluminum powder with an average particle size of 1.5 mm and 10 wt% boron carbide particles with a particle size of 7 mm using powder metallurgy. The resulting sheets were machined to a size of 150 mm * 85 mm * 6 mm as the base material for welding. Separately, sheets prepared using aluminum powder with an average particle size of 1.3 mm under the same composition and process were machined to a size of 150 mm * 4 mm * 6 mm as the welding interlayer. Both the base material and the interlayer were sanded, and then the treated sheets were cleaned with anhydrous ethanol. Figure 1 The plates are arranged on the worktable and clamped with fixtures. The stirring pin is positioned in the middle of the welding interlayer, rotated and pressed into the plate to be welded, and then welded at a welding speed of 800 rpm and 100 mm / min. The shoulder pressing amount is 0.2 mm, and the stirring pin tilt angle is 2.5°. The stirring pin has a tapered thread, a root diameter of 8 mm, a pin length of 5.7 mm, and a shoulder diameter of 15 mm. The weld joint strength of the plate after welding is tested according to the national standard GB / T 2651-2008 "Tension Test Method for Welded Joints" and compared with the strength of the base material. The weld joint strength obtained using this embodiment can reach 96% of the base material strength.

[0060] Example 2

[0061] Aluminum-based composite material sheets were prepared by blending aluminum powder with an average particle size of 1.5 mm and 10 wt% boron carbide particles with a particle size of 7 mm using powder metallurgy. The resulting sheets were machined to a size of 150 mm * 85 mm * 6 mm as the base material for welding. Separately, sheets prepared using aluminum powder with an average particle size of 1.3 mm under the same composition and process were machined to a size of 150 mm * 6 mm * 6 mm as the welding interlayer. Both the base material and the interlayer were sanded, and then the treated sheets were cleaned with anhydrous ethanol. Figure 1 The plates are arranged on the worktable and clamped with fixtures. The stirring pin is positioned in the middle of the welding interlayer, rotated and pressed into the plate to be welded, and then welded at a welding speed of 800 rpm and 100 mm / min. The shoulder pressure is 0.2 mm, and the stirring pin tilt angle is 2.5°. The stirring pin has a tapered thread, a root diameter of 8 mm, a pin length of 5.7 mm, and a shoulder diameter of 15 mm. The weld joint strength of the plate after welding is tested according to the national standard GB / T 2651-2008 "Tension Test Method for Welded Joints" and compared with the strength of the base material. The weld joint strength obtained using this embodiment can reach 94% of the base material strength.

[0062] Example 3

[0063] Aluminum-based composite material sheets were prepared by blending aluminum powder with an average particle size of 1.5 mm and 10 wt% boron carbide particles with a particle size of 7 mm using powder metallurgy. The resulting sheets were machined to a size of 150 mm * 85 mm * 6 mm as the base material for welding. Separately, sheets prepared using aluminum powder with an average particle size of 1.3 mm under the same composition and process were machined to a size of 150 mm * 6 mm * 6 mm as the welding interlayer. Both the base material and the interlayer were sanded, and then the treated sheets were cleaned with anhydrous ethanol. Figure 1 The components are arranged on a fixture pad and clamped with the fixture for two passes of friction stir welding. First, the stirring pin is positioned 2mm to the left of the center of the welding interlayer for the first pass. Then, the stirring head is positioned 2mm to the right of the center of the welding interlayer for the second pass. The weld condition after both passes is as follows: Figure 2 As shown. The welding process parameters for both passes were identical: welding rotation speed of 800 rpm, welding speed of 100 mm / min, shoulder indentation of 0.2 mm, and stirring pin tilt angle of 2.5°. The stirring pin had a tapered thread with a root diameter of 8 mm, a pin length of 5.7 mm, and a shoulder diameter of 15 mm. The weld joint strength of the plate material after welding was tested according to the national standard GB / T 2651-2008 "Tension Test Method for Welded Joints" and compared with the strength of the base material. The weld joint strength obtained using this embodiment reached 91% of the base material strength.

[0064] Example 4

[0065] Aluminum-based composite material sheets were prepared by blending aluminum powder with an average particle size of 2.5 mm and 10 wt% boron carbide particles with a particle size of 7 mm using powder metallurgy. The resulting sheets were machined to a size of 150 mm * 85 mm * 6 mm as the base material for welding. Separately, sheets prepared using aluminum powder with an average particle size of 1.3 mm under the same composition and process were machined to a size of 150 mm * 4 mm * 6 mm as the welding interlayer. Both the base material and the interlayer were sanded, and then the treated sheets were cleaned with anhydrous ethanol. Figure 1 The plates are arranged on the worktable and clamped with fixtures. The stirring pin is positioned in the middle of the welding interlayer, rotated and pressed into the plate to be welded, and then welded at a welding speed of 800 rpm and 100 mm / min. The shoulder pressing amount is 0.2 mm, and the stirring pin tilt angle is 2.5°. The stirring pin has a tapered thread, a root diameter of 8 mm, a pin length of 5.7 mm, and a shoulder diameter of 15 mm. Tensile tests were conducted on the welded plates according to the national standard GB / T 2651-2008 "Tension Test Method for Welded Joints". It was found that all the specimens fractured at the base material, indicating that the strength of the welded joint obtained by this embodiment exceeds the strength of the base material.

[0066] Comparative Example 1

[0067] Aluminum-based composite material sheets were prepared by blending aluminum powder with an average particle size of 1.5 mm and 7 mm boron carbide particles with a content of 10 wt% using powder metallurgy. The resulting sheets were machined to a size of 150 mm * 85 mm * 6 mm as the base material for welding. The sheets to be welded were directly butted together on a worktable and clamped with fixtures. The stirring head was positioned at the joint, rotated and pressed into the sheets, and welding was performed at a welding speed of 800 rpm and a welding speed of 100 mm / min. The shoulder pressure was 0.2 mm, and the stirring pin tilt angle was 2.5°. The stirring pin had a tapered thread with a root diameter of 8 mm, a pin length of 5.7 mm, and a shoulder diameter of 15 mm. The weld joint strength of the sheets after welding was tested according to the national standard GB / T 2651-2008 "Tension Test Method for Welded Joints" and compared with the strength of the base material. The weld joint strength obtained using this example was 76% of the base material strength, which was worse than that of Examples 1, 2, and 3.

[0068] Comparative Example 2

[0069] Aluminum-based composite material sheets were prepared by blending aluminum powder with an average particle size of 2.5 mm and 7 mm boron carbide particles with a content of 10 wt% using powder metallurgy. The resulting sheets were machined to a size of 150 mm * 85 mm * 6 mm as the base material for welding. The sheets to be welded were directly butted together on a worktable and clamped with fixtures. The stirring head was positioned at the joint, rotated and pressed into the sheets, and welding was performed at a welding speed of 800 rpm and a welding speed of 100 mm / min. The shoulder pressure was 0.2 mm, and the stirring pin tilt angle was 2.5°. The stirring pin had a tapered thread with a root diameter of 8 mm, a pin length of 5.7 mm, and a shoulder diameter of 15 mm. The strength of the welded joint was tested according to the national standard GB / T 2651-2008 "Tension Test Method for Welded Joints" and compared with the strength of the base material. The strength of the welded joint obtained in this embodiment was 79% of the strength of the base material, which was lower than the strength of the welded joint obtained in Example 4.

[0070] Therefore, it can be seen that the present invention uses aluminum-based composite material made of small-particle-size aluminum powder as a welding interlayer. The small grain size of the interlayer and the introduction of more three-dimensional network Al2O3 can control the grain size of the joint weld area, so that the joint strength is comparable to the strength of the base material.

[0071] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0072] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. An interlayer for welding of aluminum matrix composites, characterized in that It is sheet-like, with the contours of both sides consistent with the contours of the base material to be welded. The intermediate layer material is composed of aluminum powder and reinforcing filler, and the ratio of the intermediate layer material is consistent with the ratio of the base material. The specifications of the reinforcing filler in the intermediate layer material are consistent with the specifications of the reinforcing filler in the base material. The particle size of the aluminum powder in the intermediate layer material is smaller than that of the aluminum powder in the base material. The particle size of the aluminum powder in the intermediate layer material is 15%-90% of the particle size of the aluminum powder in the base material.

2. The interlayer for welding of aluminum matrix composites according to claim 1, characterized in that, The thickness of the intermediate layer is 10%-150% of the diameter of the stirring pin in friction stir welding.

3. The intermediate layer for welding aluminum-based composite materials according to claim 1, characterized in that, It is suitable for aluminum-based composite materials in which the aluminum powder particle size in the base material is 1.5μm-30μm.

4. The interlayer for welding of aluminum matrix composites according to claim 1, characterized in that, It is suitable for aluminum-based composite materials in which the base material contains 5 wt%-30 wt% reinforcing filler.

5. A method for making an interlayer for welding of aluminum matrix composites, characterized by the steps of include: Weigh aluminum powder and reinforcing filler, wherein the amount and specifications of the reinforcing filler are consistent with those of the reinforcing filler in the base material of the aluminum matrix composite to be welded, and the amount of aluminum powder is consistent with that of the aluminum powder in the base material. The particle size of the aluminum powder is smaller than that of the aluminum powder in the base material; the particle size of the aluminum powder is 15%-90% of that of the aluminum powder in the base material. The materials are mixed, pressed, and sintered in sequence to obtain a second plate with a cross-sectional shape that matches the shape of the welding surface of the base material. The second plate is sliced ​​to obtain an intermediate layer for welding aluminum-based composite materials.

6. The method for making an interlayer for welding of aluminum matrix composites according to claim 5, wherein The thickness of the slice is 10%-150% of the diameter of the stirring pin in friction stir welding.

7. A method for welding of an aluminum matrix composite material, characterized by Includes the following steps: Grind and clean the intermediate layer for welding aluminum-based composite materials prepared by the manufacturing method according to any one of claims 5 to 6, and grind and clean the first and second base materials to be welded. The intermediate layer is sandwiched between the surfaces to be welded of the first base material and the second base material, with the contours fitting so that the surfaces to be welded of the first base material and the second base material abut against the two sides of the intermediate layer; The stirring needle is pressed into the intermediate layer for friction stir welding.

8. The method for welding aluminum matrix composites according to claim 7, characterized by, In the friction stir welding process, if the thickness of the intermediate layer is less than 50% of the diameter of the stirring pin, a single pass welding is performed; if the thickness of the intermediate layer is greater than or equal to 50% of the diameter of the stirring pin and less than 100% of the diameter of the stirring pin, a single pass welding or a two-pass welding is performed; if the thickness of the intermediate layer is greater than 100% of the diameter of the stirring pin, a two-pass welding is performed. The two welding passes are as follows: during the first welding pass, the gap between the first base material and the intermediate layer is stirred; during the second welding pass, the gap between the second base material and the intermediate layer is stirred.

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