Differential stirring friction welding method for aluminum-based material piece

Abstract

The invention provides a differential friction stir welding method for an aluminum-based material part, and relates to the technical field of friction stir welding of aluminum-based materials. According to the main technical scheme, a set differential friction stir welding tool is adopted, and differential friction stir welding is conducted on an aluminum-based material part to be welded; the differential friction stir welding tool comprises a stirring needle assembly and a shaft shoulder assembly. The stirring needle assembly comprises a stirring needle and a stirring needle connecting handle; the stirring needle is made of tungsten carbide-cobalt alloy; the shaft shoulder assembly comprises a shaft shoulder and a shaft shoulder connecting handle; the shaft shoulder is made of tungsten carbide-cobalt alloy; in the tungsten carbide-cobalt alloy, the content of cobalt is 12-25 wt%. According to the method, the set differential stirring welding tool is utilized, weld nugget reinforced phase particles can be broken, the higher strengthening effect is achieved, coarse grain weld nugget grains are refined, and therefore low-heat-input differential stirring friction welding of the aluminum-based material thick plate can be achieved, coarsening of a weld joint structure is restrained, and the welding quality of the aluminum-based material thick plate is improved. And the mechanical property of the large-thickness structural part joint is obviously improved.

Description

Technical Field

[0001] The invention relates to the technical field of friction stir welding of aluminum-based materials, and in particular to a differential friction stir welding method for aluminum-based material parts. Background Art

[0002] In recent years, with the rapid development of rail transportation and aerospace industries, aluminum alloys and composite materials, mainly aluminum-based materials, have been increasingly used in important large-size structural parts. It is extremely challenging to weld thick plates of aluminum-based composite materials using traditional fusion welding. During welding, there are inevitably fusion welding defects such as cyclic softening caused by multiple passes and welding pores. Friction stir welding (FSW) is considered to be the best means of connecting aluminum alloys.

[0003] However, unlike thin plate welding, the FSW tools used for thick plate welding are larger in size, which makes thick plates extremely sensitive to welding parameters. Even at low speed welding, the temperature can still reach the overburning temperature of certain eutectic structures. Therefore, the parameter window for thick plate welding is very narrow, usually limited to less than 400 rpm. Due to the low welding speed, the oxides on the butt joint surface cannot be fully broken, which will cause the oxides on the butt joint surface to gather inside the weld core and form "S" line defects. On the other hand, when welding at low speed, the flow ability of the material at the bottom of the weld is greatly weakened, which is prone to defects such as incomplete root penetration, loose bottom, tunnels and holes, which seriously affect the welding quality of thick plate aluminum-based composite materials.

[0004] Differential FSW can realize the independent rotation of the shaft shoulder and the stirring needle, and can effectively reduce the welding heat input by reducing the shaft shoulder speed. However, the current differential FSW tools are made of tool steel, which can easily cause serious wear and even breakage of the tools when welding aluminum-based composites. Therefore, the current research on differential FSW is mainly focused on the welding of thin plate materials, and there is no relevant research report on thick plate aluminum-based composites.

[0005] The prior art discloses a tungsten-rhenium alloy differential welding tool that can achieve high-quality welding of titanium alloys. However, the material cost of tungsten-rhenium alloy is as high as 20,000 yuan / kg, and the machining cost is close to 10,000 yuan / piece. The thread processing of this type of tool is difficult, and it is basically in a state of no thread or shallow thread. When welding aluminum-based materials, the tool is basically equivalent to a threadless tool after the material is adhered, which will lead to insufficient material flow and various welding defects, making the tool unsuitable for welding aluminum-based composite materials.

[0006] In addition, the thick aluminum-based composite plate is affected by the reinforcement phase particles. During the friction stir welding process, the material flow ability is very poor and it is extremely sensitive to the welding parameters. During low heat input welding, a large amount of debris is generated in the weld, making it difficult to form. Conventional FSW and thin plate differential FSW process parameters are not suitable for welding thick aluminum-based composite plates.

[0007] In summary, thick aluminum-based structural parts often face various welding defects during FSW welding, which will be a potential hidden danger to the safe operation of equipment. In order to solve the problems of tools and process parameters encountered in the welding of thick aluminum-based plates, it is very necessary to improve the existing FSW process and develop a new differential stir friction welding method. Summary of the invention

[0008] In view of this, the present invention provides a differential friction stir welding method for aluminum-based material parts, the main purpose of which is to improve the mechanical properties of thick aluminum-based material structural parts.

[0009] In order to achieve the above object, the present invention mainly provides the following technical solutions:

[0010] On the one hand, an embodiment of the present invention provides a differential friction stir welding method for aluminum-based material parts, wherein a set differential friction stir welding tool is used to perform differential friction stir welding on the aluminum-based material parts to be welded; wherein the differential friction stir welding tool includes a stirring pin assembly and a shoulder assembly;

[0011] Wherein, the stirring needle assembly includes a stirring needle and a stirring needle connecting handle; wherein, the material of the stirring needle is tungsten carbide-cobalt alloy, and the material of the stirring needle connecting handle is different from that of the stirring needle;

[0012] The shoulder assembly includes a shoulder and a shoulder connecting handle; wherein the shoulder is made of tungsten carbide-cobalt alloy, and the shoulder connecting handle is made of a material different from that of the shoulder;

[0013] Wherein, in the tungsten carbide-cobalt alloy, the content of cobalt is 12-25wt%.

[0014] Preferably, the stirring needle connecting handle is made of tool steel, preferably H13 steel.

[0015] Preferably, the shoulder connecting handle is made of tool steel, preferably H13 steel.

[0016] Preferably, the stirring needle includes a connecting portion, a needle portion, and a transition portion between the connecting portion and the needle portion; wherein, the connecting portion of the stirring needle is connected to the stirring needle connecting handle; one end of the shoulder is the connecting end, and the other end is the stirring end; the connecting end of the shoulder is connected to the shoulder connecting handle; wherein, the shoulder connecting handle is sleeved on the stirring needle connecting handle, so that the stirring end of the shoulder is sleeved on the transition portion of the stirring needle, and the shoulder and the stirring needle can rotate independently of each other.

[0017] Preferably, the connecting portion of the stirring needle and the stirring needle connecting handle are connected by welding; further preferably, the connecting portion of the stirring needle and the stirring needle connecting handle are brazed using brazing filler metal; preferably, the brazing filler metal is nickel-based brazing filler metal; preferably, the brazing temperature is 1000-1200°C.

[0018] Preferably, the connecting end of the shoulder is connected to the shoulder connecting handle by welding; further preferably, the connecting end of the shoulder is brazed to the shoulder connecting handle using brazing filler metal; preferably, the brazing filler metal is nickel-based brazing filler metal; preferably, the brazing temperature is 1000-1200°C.

[0019] Preferably, the needle portion of the stirring needle is a tapered thread structure; preferably, the tapered thread structure has a taper angle of 10-15° and a thread pitch of 1.5-3 mm; preferably, the cross section of the thread is a circle with a diameter of 0.5-1 mm or a square with a side length of 0.7-1.5 mm; and / or

[0020] The surface of the needle portion of the stirring needle is cut with three planes, wherein the three planes are distributed in the circumferential direction of the needle portion; and / or

[0021] The transition portion of the stirring needle is provided with threads; preferably, the pitch of the threads is 1.5-3mm, and preferably, the cross-section of the threads is a circle with a diameter of 0.5-1mm or a square with a side length of 0.7-1.5mm to prevent the stirring needle from being welded to the shoulder plug.

[0022] Preferably, the maximum diameter of the needle portion of the stirring needle is d1, and the inner diameter of the stirring end of the shoulder is d2, wherein s=d2-d1, s is 0.3-0.5 mm; and / or

[0023] The end of the stirring end of the shoulder is in a concave structure or a flat structure, and is provided with an Archimedean spiral guide groove; preferably, the cross-section of the guide groove is a circle with a diameter of 1.5-2.5 mm.

[0024] Preferably, the step of performing differential friction stir welding on the aluminum-based material parts to be welded using a set differential friction stir welding tool comprises:

[0025] 1) The surfaces and butt surfaces of two aluminum-based material parts to be welded are polished and cleaned, and then placed on a workbench in a butt-jointed manner and fixed to obtain fixed parts to be welded;

[0026] 2) Using the set differential friction stir welding tool, differential friction stir butt welding is performed on the fixed parts to be welded, and the welding is advanced along the center line of the butt weld until the welding is completed.

[0027] Preferably, the process parameters of the differential stir friction welding are set as follows:

[0028] The welding pressure is set to 0.1-0.2 mm, the rotation speed of the shoulder is set to 50-300 rpm, the rotation speed of the stirring needle is set to 300-1000 rpm, and the welding speed is set to 50-400 mm / min.

[0029] Preferably, the thickness of the aluminum-based material piece to be welded is ≥ 20 mm; and / or

[0030] The outer diameter of the stirring end of the shoulder is 1.5-2.2 times the thickness of the aluminum-based material piece to be welded; and / or

[0031] The maximum diameter of the needle portion of the stirring needle is 0.8-1.2 times the thickness of the aluminum-based material piece to be welded; and / or

[0032] The needle length of the stirring needle is l1, and the thickness of the aluminum-based material piece to be welded is t, wherein s=t-l1, and s is 0.3-0.5 mm.

[0033] On the other hand, an embodiment of the present invention provides an aluminum-based material welded part, wherein the aluminum-based material welded part is welded by the differential friction stir welding method of the aluminum-based material part described in any one of the above items;

[0034] Preferably, the aluminum-based material weld is an aluminum alloy part; or the aluminum-based material weld is a particle-reinforced aluminum-based material weld, and preferably, the reinforcing particles include one or more of SiC, TiB2, B4C, Al2O3, and TiC. Preferably, the weld is an equiaxed crystal structure with an average grain size of 2-5 μm.

[0035] Compared with the prior art, the differential friction stir welding method for aluminum-based material parts of the present invention has at least the following beneficial effects:

[0036] On the one hand, an embodiment of the present invention provides a differential friction stir welding method for aluminum-based material parts, using a set differential friction stir welding tool to perform differential friction stir welding on the aluminum-based material parts to be welded; wherein, the differential friction stir welding tool includes a stirring needle assembly and a shoulder assembly; the stirring needle assembly includes a stirring needle and a stirring needle connecting handle; the material of the stirring needle is tungsten carbide-cobalt alloy, and the material of the stirring needle connecting handle is different from the material of the stirring needle; the shoulder assembly includes a shoulder and a shoulder connecting handle; wherein, the material of the shoulder is tungsten carbide-cobalt alloy, and the material of the shoulder connecting handle is different from the material of the shoulder; wherein, in the tungsten carbide-cobalt alloy, the cobalt content is 12-25wt%. Here, regarding the above scheme, it should be explained that: the present invention selects tungsten carbide-cobalt alloy (cobalt content is 12-25wt%) as the material of the stirring needle and the shoulder in the differential stir friction welding tool for contacting the aluminum-based material. The tungsten carbide-cobalt alloy with a cobalt content makes the stirring needle and the shoulder have excellent hardness (HRA84-93) and excellent bending strength (>3000MPa·m 1 / 2 ) also has excellent fracture toughness (>9.9MPa·m 1 / 2 ), which can not only realize differential welding of aluminum-based material parts, but also will not cause wear of the stirring needle and the shoulder, thereby avoiding various welding defects and improving the welding quality of aluminum-based material parts. In addition, the embodiment of the present invention sets the stirring needle connecting handle to a material different from the stirring needle, and sets the shoulder connecting handle to a material different from the shoulder. Since the stirring needle connecting handle and the shoulder connecting handle do not contact the aluminum-based material part during the welding process, the stirring needle connecting handle and the shoulder connecting handle can be selected from tool steel (preferably H13 steel), so that the differential stir friction welding tool is easy to process and reduces the cost (the cost is significantly reduced, and the unit cost is reduced by about 80%). Based on the above-mentioned high-strength and wear-resistant welding tools, the weld nugget reinforcement phase particles can be broken to achieve a higher strengthening effect, and the coarse-grained weld nugget grains can be refined. The present invention can realize low-heat input differential stir friction welding of thick plates of aluminum-based materials, inhibit the coarsening of weld structure, and significantly improve the mechanical properties of large-thickness structural parts joints.

[0037] Furthermore, an embodiment of the present invention provides a differential friction stir welding method for aluminum-based material parts, wherein the connection portion of the stirring needle and the stirring needle connecting handle are brazed with a brazing material, so that the stirring needle assembly forms an integral part; and the connection end of the shoulder and the shoulder connecting handle are brazed with a brazing material, so that the shoulder assembly forms an integral part. Here, after brazing, the stirring needle assembly and the shoulder assembly can be used as two integral parts, so that the tool has the advantages of high connection strength, high coaxiality, no eccentricity, etc., and can still have a stable structure under complex welding conditions.

[0038] Furthermore, an embodiment of the present invention provides a differential friction stir welding method for aluminum-based material parts, in which the needle portion of the stirring needle is arranged into a conical threaded structure, and three planes are cut on it, and an Archimedean spiral guide groove is arranged at the stirring end of the shoulder; the above-mentioned structural features combined with the materials of the stirring needle and the shoulder can promote the flow of materials during welding, and can fully stir the aluminum-based composite material containing a high volume fraction reinforcing phase, thereby filling the gap of the lack of differential welding tools for thick plates of aluminum-based materials.

[0039] Further, the embodiment of the present invention provides a differential friction stir welding method for aluminum-based material parts. For aluminum-based material parts, based on the set differential friction stir welding tool, when differential friction stir welding is performed on aluminum-based material parts, the process parameters are set as follows: the welding pressure is set to 0.1-0.2mm to ensure sufficient shoulder forging pressure while avoiding excessive shoulder intrusion into the material and excessive flash; the rotation speed of the shoulder is set to a lower range of 50-300 rpm to reduce welding heat input; the rotation speed of the stirring needle is set to 300-1000 rpm to fully break the oxide on the butt surface and eliminate the bottom defect of the weld core; the welding speed is set to 50-400 mm / min to inhibit the softening of the heat-affected zone. Here, for aluminum-based material parts with a larger thickness, the stirring needle speed can be increased to a maximum of 1000 rpm, which can solve the defect of insufficient bottom material flow during welding, and the shoulder can maintain a low speed (50-300 rpm) to avoid excessive shoulder temperature during welding. Therefore, the above process parameters can avoid common welding defects. In addition, the brazing welding tool has higher coaxiality and strength, which can maintain better structural stability during high welding speed welding to reduce welding heat input, thereby obtaining a joint with better performance.

[0040] In summary, the differential friction stir welding method for aluminum-based material parts provided in an embodiment of the present invention can significantly reduce the temperature of the weld core and the heat-affected zone, inhibit the softening effect of the material, reduce the maximum temperature of the heat-affected zone by more than 50°C, significantly reduce the high-temperature cooling rate, inhibit the growth of the weld core grains, and refine the weld core grain structure to 2-3μm. The stirring needle can further break up the size of the reinforcing phase particles and improve the load transfer effect.

[0041] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a schematic structural diagram of a stirring needle provided by an embodiment of the present invention;

[0043] Figure 2 yes Figure 1a top view of the structure shown;

[0044] Figure 3 is a perspective view of a stirring pin assembly provided by an embodiment of the present invention;

[0045] Figure 4 is a structural schematic diagram of a shaft shoulder provided by an embodiment of the present invention;

[0046] Figure 5 It is a schematic diagram of an end portion of a stirring end of a shaft shoulder provided by an embodiment of the present invention;

[0047] Figure 6 is a structural schematic diagram of a shoulder assembly provided by an embodiment of the present invention;

[0048] Figure 7 is a perspective view of a differential friction stir welding tool provided by an embodiment of the present invention;

[0049] Figure 8 The figures are the cross-sectional metallographic and tensile performance curves of the butt weld of the welding tool of Example 1 of the present invention and the obtained SiC / 6092 aluminum-based composite material weldment; wherein (a) is a hard alloy welding tool, (b) is a cross-sectional metallographic diagram of the butt weld, (c) is a microstructure of the butt weld, and (d) is a tensile performance curve of the butt weld;

[0050] Fig. 9 The morphology of friction stir welding tools of different materials after welding aluminum-based materials: (a) shows the conventional FSW stirring needle of H13 steel used, (b) shows the wear of the stirring needle after conventional FSW of H13 steel tool, (c) shows the conventional H13 steel differential welding tool, and (d) shows the fracture morphology of the stirring needle after H13 steel differential tool welding;

[0051] Fig.10 The cross-sectional metallographic and tensile performance curve diagrams of the butt weld on the SiC / 6092 aluminum-based composite material weldment obtained in Comparative Example 3 of the present invention; wherein (a) is a cross-sectional metallographic diagram of the butt weld; (b) is a tensile performance curve diagram of the butt weld;

[0052] Fig.11 1 is a microstructure analysis diagram of the differential joint of the 7075 aluminum alloy plate weldment obtained in Example 2; wherein (a) is a metallographic diagram of the cross section of the joint, (b) is a microstructure diagram of the shoulder influence zone, and (c) is a microstructure diagram of the stirring needle influence zone;

[0053] Fig.12This is a microstructure analysis diagram of the differential joint of the 7075 aluminum alloy plate weldment obtained in Example 4. Among them, (a) is a metallographic diagram of the cross section of the joint, (b) is a hole defect diagram, and (c) is a microstructure diagram of the stirring needle influence zone. DETAILED DESCRIPTION

[0054] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention application are described in detail below in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

[0055] The invention provides a differential friction stir welding method for aluminum-based material parts, which belongs to a low-heat input and high-performance welding process method and is used to solve the welding problem of aluminum-based material parts with a large thickness.

[0056] In the present invention, the aluminum-based material piece is an aluminum alloy piece or an aluminum-based composite material piece.

[0057] The main scheme of the present invention is as follows:

[0058] An embodiment of the present invention provides a differential friction stir welding method for aluminum-based material parts, wherein a set differential friction stir welding tool is used to perform differential friction stir welding on the aluminum-based material parts to be welded.

[0059] Among them, Figures 1 to 7As shown, the differential friction stir welding tool of the embodiment of the present invention includes a stirring needle assembly and a shoulder assembly; wherein the stirring needle assembly includes a stirring needle 1 and a stirring needle connecting handle 2; wherein the material of the stirring needle 1 is tungsten carbide-cobalt alloy (the content of cobalt is 12-25wt%), and the material of the stirring needle connecting handle 2 is different from the material of the stirring needle 1. The shoulder assembly includes a shoulder 3 and a shoulder connecting handle 4; wherein the material of the shoulder 3 is tungsten carbide-cobalt alloy (the content of cobalt is 12-25wt%), and the material of the shoulder connecting handle 4 is different from the material of the shoulder 3. Here, the embodiment of the present invention selects tungsten carbide-cobalt alloy (the content of cobalt is 12-25wt%) as the material of the stirring needle 1 and the shoulder 3 in the differential friction stir welding tool for contacting the aluminum-based material, so that the stirring needle and the shoulder have excellent hardness and toughness, which can not only realize the differential welding of the aluminum-based material, but also will not cause the wear of the stirring needle and the shoulder, thereby avoiding various welding defects and improving the welding quality of the aluminum-based material. On the other hand, since the stirring needle connecting handle 2 and the shoulder connecting handle 4 do not contact the aluminum-based material during the welding process, the stirring needle connecting handle 2 and the shoulder connecting handle 4 can be made of tool steel (preferably H13 steel), which makes the differential stir friction welding tool easy to process and significantly reduces the cost.

[0060] Preferably, if Figure 1-Figure 7 As shown, the structure and connection relationship of the stirring needle assembly and the shoulder assembly are designed as follows:

[0061] The stirring needle 1 includes a connecting portion 12, a needle portion 11, and a transition portion 13 between the connecting portion 12 and the needle portion 11; wherein the connecting portion 12 of the stirring needle 1 is connected to the stirring needle connecting handle 2. One end of the shoulder 3 is a connecting end 32, and the other end is a stirring end 31; the connecting end 32 of the shoulder 3 is connected to the shoulder connecting handle 4; wherein the shoulder connecting handle 4 is sleeved on the stirring needle connecting handle 2, so that the stirring end 31 of the shoulder 3 is sleeved on the transition portion 13 of the stirring needle 1, and the shoulder 3 and the stirring needle 1 can rotate independently of each other.

[0062] Preferably, the connecting portion 12 of the stirring needle 1 is connected to the stirring needle connecting handle 2 by welding; further preferably, the connecting portion 12 of the stirring needle 1 is brazed to the stirring needle connecting handle 2 using a brazing material; preferably, the brazing material is a nickel-based brazing material (for example, BNi-2, NiCrBSi solder); the preferred brazing temperature is 1000-1200°C.

[0063] Preferably, the connecting end 32 of the shoulder 3 is connected to the shoulder connecting handle 4 by welding; further preferably, the connecting end of the shoulder 3 is brazed to the shoulder connecting handle 4 by using a brazing material; preferably, the brazing temperature is 1000-1200° C. The brazing material is a nickel-based brazing material (for example, BNi-2, NiCrBSi solder);.

[0064] It should be noted here that after brazing, the stirring needle assembly and the shoulder assembly are used as two integral components, so that the tool has the advantages of high connection strength, high coaxiality, and no eccentricity, and can have high structural stability under complex welding conditions.

[0065] Preferably, if Figure 1-Figure 7 As shown, the assembly of the shoulder assembly and the stirring needle assembly is as follows: a first boss structure 21 is provided on the stirring needle connecting handle 2, and a second boss structure 41 is provided on the shoulder connecting handle 4. When assembling the shoulder assembly and the stirring needle assembly, it is only necessary to put the shoulder connecting handle 4 on the stirring needle connecting handle 2 so that the second boss structure 41 is placed on the first boss structure 21.

[0066] Preferably, the needle portion 11 of the stirring needle 1 is in a tapered threaded structure; preferably, the cone angle of the tapered threaded structure is 10-15°, the pitch of the thread is 1.5-3mm; the cross-section of the thread is a circle with a diameter of 0.5-1mm or a square with a side length of 0.7-1.5mm. The surface of the needle portion 11 of the stirring needle 1 is cut with three planes 111, wherein the three planes 111 are distributed in the circumferential direction of the needle portion. The transition portion 13 of the stirring needle 1 is provided with threads as mentioned above; wherein the pitch of the thread is 1.5-3mm, and the cross-section of the thread is a circle with a diameter of 0.5-1mm or a square with a side length of 0.7-1.5mm, so as to prevent the stirring needle 1 from being welded to the shoulder 3.

[0067] Preferably, the maximum diameter of the needle portion 11 of the stirring needle 1 (ie, the root diameter of the needle portion) is d1, and the inner diameter of the stirring end of the shoulder 3 is d2, wherein s=d2-d1, and s is 0.3-0.5 mm.

[0068] Preferably, the end of the stirring end 31 of the shoulder 3 is a concave structure or a flat structure, and is provided with an Archimedean spiral guide groove 311; preferably, the cross-section of the guide groove 311 is a circle with a diameter of 1.5-2.5 mm.

[0069] Preferably, the step of performing differential friction stir welding on the aluminum-based material parts to be welded using the differential friction stir welding tool mentioned above includes:

[0070] 1) The surfaces and butt surfaces of the two aluminum-based material pieces to be welded are polished and cleaned, and then they are placed on a workbench in a butt-jointed manner and fixed to obtain fixed parts to be welded; specifically, the surfaces and butt surfaces of the two aluminum-based material pieces to be welded are mechanically polished and cleaned with alcohol or acetone, and the two aluminum-based material pieces to be welded are butt-jointed and placed on a workbench using a clamp, and the two plates are tightly placed and rigidly fixed to ensure that the assembly gap is less than 0.1 times the thickness of the parts to be welded.

[0071] 2) Using the set differential friction stir welding tool, differential friction stir butt welding is performed on the fixed parts to be welded, and the welding is advanced along the center line of the butt weld until the welding is completed.

[0072] The process parameters of the differential friction stir welding are set as follows: the welding pressure is 0.1-0.2 mm, the shoulder rotation speed is 50-300 rpm, the stirring needle rotation speed is 300-1000 rpm, and the welding speed is 50-400 mm / min.

[0073] The thickness of the aluminum-based material to be welded is ≥20 mm; the diameter of the shaft shoulder is 1.5-2.2 times the thickness of the aluminum-based material to be welded; the maximum diameter of the needle of the stirring needle is 0.8-1.2 times the thickness of the aluminum-based material to be welded; the needle length of the stirring needle is l1, and the thickness of the aluminum-based material to be welded is t, wherein s=t-l1, s is 0.3-0.5 mm. The aluminum-based material to be welded is a plate; the aluminum-based material to be welded is an aluminum alloy or an aluminum-based composite material.

[0074] Here, the above-mentioned solution of the present invention is described as follows:

[0075] For thick aluminum-based materials (especially aluminum-based composite materials), the welding temperature is too high due to the large tool size during FSW, which usually easily leads to defects such as burn holes. If the welding speed is reduced, the welding temperature will be reduced, and the stirring effect of the corresponding tool on the material will be reduced, which is easy to form root weak bonding and incomplete penetration defects.

[0076] Differential friction stir welding can be performed at a low speed of the shoulder and a high speed of the stirring needle, thus solving the defects of over-burning or incomplete welding. However, there is currently no welding tool or matching welding process that can be used for differential welding of thick aluminum-based material parts. For thick aluminum-based material parts, the hardness of the ceramic reinforcement phase particles is extremely high, which can easily cause tool wear, which undoubtedly increases the difficulty of tool design. Wear-resistant cemented carbide and other materials are usually small in size, difficult to machine into complex structural parts, and have high machining costs.

[0077] Based on this, the present invention provides a differential friction stir welding method for aluminum-based material parts, wherein the differential friction stir welding tool used includes four parts: a stirring needle (the material is selected from tungsten carbide-cobalt alloy, and the cobalt content is 12-25wt%) and a stirring needle connecting handle (the material is selected from tool steel), a shoulder (the material is selected from tungsten carbide-cobalt alloy, and the cobalt content is 12-25wt%) and a shoulder connecting handle (the material is selected from tool steel). During the welding process, only the shoulder and the stirring needle need to have friction contact with the aluminum-based composite material, and the materials of these two parts are relatively small; while the shoulder connecting handle and the stirring needle connecting handle do not contact the welding material, but are larger in size and only serve as a connection. In view of the four parts of the welding tool, the stirring needle and the stirring needle connecting handle are welded by brazing, and the shoulder and the shoulder connecting handle are brazed, and then the brazed stirring needle and the shoulder are transferred to the differential welding machine for use.

[0078] The stirring pin and the stirring pin connecting handle in the stirring pin assembly are connected by brazing, and the shaft shoulder and the shaft shoulder connecting handle in the shaft shoulder assembly are connected by brazing. After brazing connection, the stirring pin and the shaft shoulder can be used as two integral parts, and the tool has the advantages of high connection strength, high coaxiality, no eccentricity, etc., and can have a stable structure under complex welding conditions.

[0079] The present invention adopts a composite design method, and only the shaft shoulder and the stirring needle adopt a low-cost tungsten carbide-cobalt alloy (cobalt content is 12-25wt%), which has not only excellent hardness, but also good toughness, thereby avoiding wear and welding defects; in addition, the shaft shoulder connecting handle and the stirring needle connecting handle are selected from a lower-cost tool steel, thereby greatly reducing the processing difficulty, significantly reducing the cost, and reducing the cost of a single piece by about 80%. In addition, the composite welding tool can achieve extremely high assembly accuracy, has high structural strength and rotation concentricity under high welding speed conditions, and the maximum welding speed can reach 400 mm / min.

[0080] For aluminum-based parts, based on the set differential friction stir welding tool, when differential friction stir welding is performed on aluminum-based parts, the process parameters are set as follows: the welding pressure is set to 0.1-0.2mm, the rotation speed of the shoulder is set to 50-300 rpm, the rotation speed of the stirring needle is set to 300-1000 rpm, and the welding speed is set to 50-400 mm / min. Here, for aluminum-based parts with thicker thickness, the stirring needle speed can be increased to a maximum of 1000 rpm, which can solve the defect of insufficient bottom material flow during welding. At the same time, the shoulder can maintain a low speed (50-300 rpm) to avoid excessive shoulder temperature during welding. Therefore, the above process parameters can overcome various welding defects. In addition, the coaxiality and strength of the welding tool after brazing are higher, which can maintain better structural stability during high welding speed welding to reduce welding heat input, thereby obtaining a better performance joint.

[0081] The present invention is further described below by specific experimental examples:

[0082] Example 1

[0083] In this embodiment, differential friction stir welding is performed on two 20 mm thick SiC / 6092 aluminum-based composite material plates to be welded, and the main steps are as follows:

[0084] Two SiC / 6092 aluminum-based composite material plates to be welded are butt-jointed and fixed on a workbench to obtain a fixed part to be welded. The differential friction stir welding tool of the present invention is used to perform differential friction stir welding (advancing along the center line of the butt weld until welding is completed) to obtain a SiC / 6092 aluminum-based composite material welded part.

[0085] Among them, Figures 1 to 7 As shown, the differential friction stir welding tool of the present invention comprises a stirring needle assembly and a shoulder assembly; wherein the stirring needle assembly comprises a stirring needle 1 and a stirring needle connecting handle 2; wherein the stirring needle 1 is made of tungsten carbide-cobalt alloy (cobalt content is 25wt%), and the stirring needle connecting handle 2 is made of H13 steel. The shoulder assembly comprises a shoulder 3 and a shoulder connecting handle 4; wherein the shoulder 3 is made of tungsten carbide-cobalt alloy (cobalt content is 25wt%), and the shoulder connecting handle 4 is made of H13 steel.

[0086] like Figures 1 to 7 As shown, the stirring needle 1 of the present invention includes a connecting portion 12, a needle portion 11, and a transition portion 13 located between the connecting portion 12 and the needle portion 11; wherein, the connecting portion 12 of the stirring needle 1 is connected to the stirring needle connecting handle 2 by brazing. One end of the shoulder 3 is a connecting end 32, and the other end is a stirring end 31; the connecting end 32 of the shoulder 3 is connected to the shoulder connecting handle 4 by brazing; wherein, the shoulder connecting handle 4 is sleeved on the stirring needle connecting handle 2, so that the stirring end of the shoulder 3 is sleeved on the transition portion 13 of the stirring needle 1, so that the shoulder 3 and the stirring needle 1 can rotate independently of each other. The needle portion 11 of the stirring needle 1 is a tapered threaded structure, and the surface of the tapered threaded structure is cut with three planes; wherein, the three planes are distributed in the circumferential direction of the needle portion 11, and the interval angles of any two planes are the same. The end of the stirring end 31 of the shoulder 3 is a planar structure; the end of the stirring end 31 of the shoulder 3 is provided with an Archimedean spiral guide groove 311.

[0087] Among them, the outer ring diameter of the stirring end of the shoulder 3 is 40 mm, the maximum diameter of the needle part 11 of the stirring needle 1 is 16 mm (that is, the root diameter of the needle part), and the length of the needle part 11 of the stirring needle 1 is 19.6 mm (that is, the needle length of the stirring needle).

[0088] Among them, in the differential stir friction welding process: the welding pressure is 0.2 mm, the rotation speed of the shoulder is 200 rpm, the rotation speed of the stirring needle is 500 rpm, and the welding speed is 100 mm / min.

[0089] The microstructure analysis of the butt weld on the SiC / 6092 aluminum-based composite weldment obtained in this embodiment shows that there is no wear on the tool after welding. Figure 8 As shown in Figure (a), there are no defects in the weld area (see Figure 8 As shown in Figure (b), the SiC particles are broken, the weld core area is an equiaxed fine-grained structure with an average grain size of 2.3μm (see Figure 8 (as shown in Figure (c)).

[0090] For the SiC / 6092 aluminum-based composite welded parts obtained in this example, full-thickness tensile specimens were cut using electric spark wire cutting in the vertical welding direction, and the mechanical properties of the butt welds obtained in this example were tested. The test results are shown in Figure 8 As shown in Figure (d), the joint strength of this embodiment can reach 340 MPa, while the joint strength of the control is poor.

[0091] Comparative Example 1

[0092] Comparative Example 1 mainly performs conventional friction stir welding on two 20 mm thick SiC / 6092 aluminum-based composite material plates to be welded, and the main steps are as follows:

[0093] The two SiC / 6092 aluminum-based composite plates to be welded are butt-jointed and fixed on a workbench to obtain the fixed welded parts. A conventional H13 steel friction stir welding tool (both the stirring needle and the shaft shoulder are made of H13 steel, see Fig. 9 As shown in Figure (a) in the figure, conventional friction stir welding (non-differential welding) is performed on the fixed parts to be welded.

[0094] Among them, the diameter of the shaft shoulder is 40 mm, the root diameter of the stirring needle is 16 mm, and the needle length of the stirring needle is 19.6 mm. The welding pressure is 0.2 mm, the rotation speed of the shaft shoulder and the stirring needle is 600 rpm, and the welding speed is 100 mm / min.

[0095] Among them, after friction stir welding, the friction stir welding tool is severely worn and can no longer be used. Fig. 9 As shown in Figure (b), the material at the bottom of the weld cannot be fully stirred, resulting in an incomplete weld at the root and a joint strength of less than 150 MPa.

[0096] Comparative Example 2

[0097] Comparative Example 2: Differential friction stir welding was performed on two 20 mm thick SiC / 6092 aluminum-based composite material plates to be welded, and the main steps were as follows:

[0098] Two SiC / 6092 aluminum-based composite materials to be welded are butt-jointed and fixed on a workbench to obtain a fixed part to be welded. A differential friction stir welding tool is used to perform differential friction stir welding (advancing along the center line of the butt weld until the welding is completed) on the fixed parts to be welded to obtain a SiC / 6092 aluminum-based composite welded part.

[0099] Among them, differential friction stir welding tools, see Fig. 9 As shown in Figure (c) in the figure, the material of the differential friction stir tool is H13 steel.

[0100] Among them, the diameter of the shaft shoulder is 40 mm, the maximum diameter of the needle portion of the stirring needle is 18 mm, and the length of the needle portion of the stirring needle is 19.6 mm (ie, the needle length of the stirring needle).

[0101] Among them, in the differential stir friction welding process, the welding pressure is 0.2 mm, the shoulder speed is 200 rpm, the rotation speed of the stirring needle is 500 rpm, and the welding speed is 100 mm / min.

[0102] After welding, due to insufficient tool strength, the needle breaks after welding, such as Fig. 9 As shown in Figure (d), the welding failed. Therefore, it is impossible to perform differential friction stir welding on thick plate aluminum matrix composites using H13 steel tools.

[0103] Comparative Example 3

[0104] Comparative Example 3 Conventional friction stir welding was performed on two 20 mm thick SiC / 6092 aluminum-based composite material plates to be welded, and the main steps were as follows:

[0105] Two SiC / 6092 aluminum-based composite material plates to be welded are butt-jointed and fixed on a workbench to obtain a fixed part to be welded. A stir friction welding tool is used to perform conventional stir friction welding on the fixed parts to be welded (advance along the center line of the butt weld until the welding is completed) to obtain a SiC / 6092 aluminum-based composite material welded part. The material of the stir friction welding tool is tungsten carbide-cobalt alloy (cobalt content is 25wt%), the shoulder diameter is 40 mm, the maximum diameter of the stirring needle is 18 mm, and the length of the stirring needle is 19.6 mm.

[0106] In the friction stir welding process, the welding pressure is 0.2 mm, the rotation speed of the shaft shoulder and the stirring needle is 200 rpm, and the welding speed is 100 mm / min. After welding, due to the weak stirring effect of the stirring needle on the material under the above process parameters, see Fig.10 As shown in Figure (a), there is an obvious root incomplete penetration defect in the bottom area of ​​the weld. The weld obtained in Example 2 was tested for mechanical properties, and the joint strength was only 280MPa. Fig.10 As shown in Figure (b).

[0107] Therefore, in the conventional friction stir welding mode, even if a welding tool made of tungsten carbide-cobalt is used, low heat input welding cannot be performed in the non-differential mode. Due to the low rotation speed of the stirring needle, the material at the bottom of the weld cannot be driven to flow, which easily leads to root incomplete penetration defects and low joint strength.

[0108] Example 2

[0109] In this embodiment, differential friction stir welding is performed on two 26 mm thick 7055 aluminum alloy plates to be welded. The main steps are as follows:

[0110] Two 7055 aluminum alloy plates to be welded are butt-jointed and fixed on a workbench to obtain a fixed part to be welded. The differential friction stir welding tool of the present invention is used to perform differential friction stir welding (advancing along the center line of the butt weld until welding is completed) on the fixed parts to be welded to obtain a 7075 aluminum alloy plate welded part.

[0111] Among them, Figures 1 to 7 As shown, the differential friction stir welding tool of the present invention comprises a stirring needle assembly and a shoulder assembly; wherein the stirring needle assembly comprises a stirring needle 1 and a stirring needle connecting handle 2; wherein the stirring needle 1 is made of tungsten carbide-cobalt alloy (cobalt content is 12wt%), and the stirring needle connecting handle 2 is made of H13 steel. The shoulder assembly comprises a shoulder 3 and a shoulder connecting handle 4; wherein the shoulder 3 is made of tungsten carbide-cobalt alloy (cobalt content is 12wt%), and the shoulder connecting handle 4 is made of H13 steel.

[0112] like Figures 1 to 7As shown, the stirring needle 1 of the present invention includes a connecting portion 12, a needle portion 11, and a transition portion 13 located between the connecting portion 12 and the needle portion 11; wherein, the connecting portion 12 of the stirring needle 1 is connected to the stirring needle connecting handle 2 by brazing. One end of the shoulder 3 is a connecting end 32, and the other end is a stirring end 31; the connecting end 32 of the shoulder 3 is connected to the shoulder connecting handle 4 by brazing; wherein, the shoulder connecting handle 4 is sleeved on the stirring needle connecting handle 2, so that the stirring end of the shoulder 3 is sleeved on the transition portion 13 of the stirring needle 1, so that the shoulder 3 and the stirring needle 1 can rotate independently of each other. The needle portion 11 of the stirring needle 1 is a tapered thread structure, and the surface of the tapered thread structure is cut with three planes; wherein, the three planes are distributed in the circumferential direction of the needle portion 11, and the interval angles of any two planes are the same. The end of the stirring end 31 of the shoulder 3 is a concave structure; the end of the stirring end 31 of the shoulder 3 is provided with an Archimedean spiral guide groove 311.

[0113] The diameter of the shoulder 3 is 40 mm, the maximum diameter of the needle portion 11 of the stirring needle 1 is 18 mm (ie, the root diameter of the needle portion), and the length of the needle portion 11 of the stirring needle 1 is 25.7 mm (ie, the needle length of the stirring needle).

[0114] Among them, in the differential stir friction welding process: the welding pressure is 0.2 mm, the rotation speed of the shoulder is 100 rpm, the rotation speed of the stirring needle is 300 rpm, and the welding speed is 100 mm / min.

[0115] The microstructure analysis of the butt weld of the 7055 aluminum alloy sheet welded piece obtained in this embodiment is shown in FIG. Fig.11 Said, from Fig.11 Figure (a) shows the macroscopic morphology of the weld without defects, and Figures (b) and (c) show that under low heat input, the weld is a fine equiaxed crystal structure with an average grain size of 5 μm. In addition, the 7055 aluminum alloy sheet welded parts obtained in this embodiment were cut into full-thickness tensile specimens using electric spark wire cutting in the vertical welding direction, and the mechanical properties of the butt welds were tested, and the joint strength could reach 350 MPa.

[0116] Comparative Example 4

[0117] Comparative Example 4: Stir friction welding was performed on two 26 mm thick 7055 aluminum alloy plates to be welded. The main steps are as follows:

[0118] Two 7055 aluminum alloy plates to be welded are butt-jointed and fixed on a workbench to obtain a fixed part to be welded. Conventional friction stir welding is performed on the fixed parts to be welded using an H13 steel welding tool (both the stirring pin and the shaft shoulder are made of H13 steel) to obtain a 7075 aluminum alloy plate welded part.

[0119] Among them, the diameter of the shoulder is 40 mm, the root diameter of the stirring needle is 18 mm, the needle length is 25.7 mm, the downward pressure is 0.2 mm, the rotation speed of the shoulder and the stirring needle is 300 rpm, and the welding speed is 100 mm / min.

[0120] The microstructure of the butt weld of the 7055 aluminum alloy sheet welded part finally obtained in this comparative example was analyzed, and the macroscopic morphology of the weld is shown in Fig.12 As shown in Figure (a), a burnt hole defect appears on the upper part of the weld. Since the tool size used for welding thick plate materials is relatively large, the shaft shoulder and the stirring needle are at the same speed of 300 rpm during conventional friction stir welding. At this time, the heat input in the shaft shoulder affected area is high, resulting in obvious burnt and hole defects in this area. (See the enlarged view for details.) Fig.12 (as shown in Figure (b)).

[0121] For the 7055 aluminum alloy plate welded parts finally obtained in this comparative example, full thickness tensile specimens were cut by electric spark wire cutting in the vertical welding direction, and the mechanical properties of the butt weld were tested, and the joint strength was only 120 MPa.

[0122] Comparative Example 5

[0123] In this comparative example, differential friction stir welding is performed on two 20 mm thick SiC / 6092 aluminum-based composite material plates to be welded. Compared with Example 1, the material of the stirring needle 1 and the shoulder of this example is tungsten carbide-cobalt alloy (the cobalt content is 50wt%), and the other structures are consistent with the welding tool of Example 1.

[0124] In the differential friction stir welding process, the welding pressure was 0.2 mm, the shoulder speed was 200 rpm, the rotation speed of the stirring needle was 500 rpm, and the welding speed was 100 mm / min.

[0125] After welding, it was found that due to the reduced tungsten carbide content in the welding tool used in Comparative Example 4, the wear resistance of the tool was reduced, and thread wear occurred after welding.

[0126] Comparative Example 6

[0127] In this comparative example, differential friction stir welding is performed on two 20 mm thick SiC / 6092 aluminum-based composite material plates to be welded. Compared with Example 1, the material of the stirring needle 1 and the shoulder of this example is tungsten carbide-cobalt alloy (the cobalt content is 3wt%), and the other structures are consistent with the welding tool of Example 1.

[0128] Due to the extremely high tungsten carbide content in the welding tool and the cobalt content of only 3%, the material has a bending strength of 2600MPa and a fracture toughness of about 7.6MPa·m 1 / 2, the tool breaks when processing complex threads, and the tool processing rate is less than 50%.

[0129] In the differential friction stir welding process, the welding pressure was 0.2 mm, the shoulder speed was 200 rpm, the rotation speed of the stirring needle was 500 rpm, and the welding speed was 100 mm / min.

[0130] After welding, it was found that the tool was not tough enough and broke brittlely when subjected to welding stress, making differential welding impossible.

[0131] Comparative Example 7

[0132] In this comparative example, two 20 mm thick SiC / 6092 aluminum-based composite material plates to be welded are subjected to differential friction stir welding. The main steps are different from those of Example 1 in that:

[0133] In Comparative Example 7, the shaft shoulder speed is 50 rpm, the stirring needle speed is 1500 rpm, and the welding speed is 200 mm / min.

[0134] Here, since the rotation speed of the stirring needle is too fast, the welded joint is softened significantly, the strength coefficient is less than 50%, and the strength is less than 220 MPa.

[0135] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A differential friction stir welding method for aluminum-based material parts, characterized in that: A differential friction stir welding tool is used to perform differential friction stir welding on the aluminum-based material parts to be welded; wherein the differential friction stir welding tool includes a stirring pin assembly and a shoulder assembly; Wherein, the stirring needle assembly comprises a stirring needle and a stirring needle connecting handle; wherein, the material of the stirring needle is tungsten carbide-cobalt alloy, and the material of the stirring needle connecting handle is different from that of the stirring needle; The shoulder assembly includes a shoulder and a shoulder connecting handle; wherein the shoulder is made of tungsten carbide-cobalt alloy, and the shoulder connecting handle is made of a material different from that of the shoulder; Wherein, in the tungsten carbide-cobalt alloy, the content of cobalt is 12-25wt%.

2. The differential friction stir welding method for aluminum-based material parts according to claim 1, characterized in that: The material of the stirring needle connecting handle is tool steel, preferably H13 steel; and / or The shoulder connecting handle is made of tool steel, preferably H13 steel.

3. The differential friction stir welding method for aluminum-based material parts according to claim 1 or 2, characterized in that: The stirring needle includes a connecting portion, a needle portion, and a transition portion located between the connecting portion and the needle portion; wherein the connecting portion of the stirring needle is connected to the stirring needle connecting handle; one end of the shoulder is the connecting end, and the other end is the stirring end; the connecting end of the shoulder is connected to the shoulder connecting handle; wherein the shoulder connecting handle is sleeved on the stirring needle connecting handle, so that the stirring end of the shoulder is sleeved on the transition portion of the stirring needle, and the shoulder and the stirring needle can rotate independently of each other.

4. The differential friction stir welding method for aluminum-based material parts according to claim 3, characterized in that: The connecting portion of the stirring needle is connected to the connecting handle of the stirring needle by welding; further preferably, the connecting portion of the stirring needle and the connecting handle of the stirring needle are brazed with a brazing material; preferably, the brazing material is a nickel-based brazing material; preferably, the brazing temperature is 1000-1200°C; and / or The connecting end of the shoulder is connected to the shoulder connecting handle by welding; further preferably, the connecting end of the shoulder is brazed to the shoulder connecting handle using brazing filler metal; preferably, the brazing filler metal is nickel-based brazing filler metal; preferably, the brazing temperature is 1000-1200°C.

5. The differential friction stir welding method for aluminum-based material parts according to any one of claims 1 to 4, characterized in that: The needle portion of the stirring needle is a tapered thread structure; preferably, the tapered thread structure has a taper angle of 10-15° and a thread pitch of 1.5-3 mm; preferably, the cross section of the thread is a circle with a diameter of 0.5-1 mm or a square with a side length of 0.7-1.5 mm; and / or The surface of the needle portion of the stirring needle is cut with three planes, wherein the three planes are distributed in the circumferential direction of the needle portion; and / or The transition portion of the stirring needle is provided with threads; preferably, the pitch of the threads is 1.5-3mm, and preferably, the cross-section of the threads is a circle with a diameter of 0.5-1mm or a square with a side length of 0.7-1.5mm to prevent the stirring needle from being welded to the shoulder plug.

6. The differential friction stir welding method for aluminum-based material parts according to any one of claims 1 to 5, characterized in that: The maximum diameter of the needle portion of the stirring needle is d1, and the inner diameter of the stirring end of the shoulder is d2, wherein s=d2-d1, s is 0.3-0.5 mm; and / or The end of the stirring end of the shoulder is in a concave structure or a flat structure, and is provided with an Archimedean spiral guide groove; preferably, the cross-section of the guide groove is a circle with a diameter of 1.5-2.5 mm.

7. The differential friction stir welding method for aluminum-based material parts according to any one of claims 1 to 6, characterized in that: The steps of performing differential friction stir welding on the aluminum-based material parts to be welded by using a set differential friction stir welding tool include: 1) The surfaces and butt surfaces of two aluminum-based material parts to be welded are polished and cleaned, and then placed on a workbench in a butt-jointed manner and fixed to obtain fixed parts to be welded; 2) Using the set differential friction stir welding tool, differential friction stir butt welding is performed on the fixed parts to be welded, and the welding is advanced along the center line of the butt weld until the welding is completed.

8. The differential friction stir welding method for aluminum-based material parts according to any one of claims 1 to 7, characterized in that: The process parameters of the differential stir friction welding are set as follows: The welding pressure is set to 0.1-0.2 mm, the rotation speed of the shoulder is set to 50-300 rpm, the rotation speed of the stirring needle is set to 300-1000 rpm, and the welding speed is set to 50-400 mm / min.

9. The differential friction stir welding method for aluminum-based material parts according to any one of claims 1 to 8, characterized in that: The thickness of the aluminum-based material to be welded is ≥ 20 mm; and / or The outer diameter of the stirring end of the shoulder is 1.5-2.2 times the thickness of the aluminum-based material piece to be welded; and / or The maximum diameter of the needle portion of the stirring needle is 0.8-1.2 times the thickness of the aluminum-based material piece to be welded; and / or The needle length of the stirring needle is l1, and the thickness of the aluminum-based material piece to be welded is t, wherein s=t-l1, and s is 0.3-0.5 mm.

10. An aluminum-based material welded part, characterized in that: The aluminum-based material welded part is welded by the differential friction stir welding method of the aluminum-based material part according to any one of claims 1 to 9; Preferably, the aluminum-based material welded part is an aluminum alloy part; or the aluminum-based material welded part is a particle-reinforced aluminum-based material welded part, and preferably, the reinforced particles include one or more of SiC, TiB2, B4C, Al2O3, and TiC; Preferably, the weld has an equiaxed crystal structure with an average grain size of 2-5 μm.

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