Steel / aluminum dissimilar metal laser welding method based on FeCoCuSiNi / FeCoCuSiNiAl high-entropy alloy transition layer

Abstract

The invention discloses a steel / aluminum dissimilar metal laser welding method based on a FeCoCuSiNi / FeCoCuSiNiAl high-entropy alloy transition layer, and belongs to the technical field of dissimilar metal laser machining. In a FeCoCuSiNi / FeCoCuSiNiAl high-entropy alloy transition layer prepared through a spark plasma sintering process, the Fe content in a FeCoCuSiNi high-entropy alloy is highest and the Al content in the FeCoCuSiNi high-entropy alloy is lowest, the Al content in the FeCoCuSiNiAl high-entropy alloy is highest and the Fe content in the FeCoCuSiNi high-entropy alloy is lowest, during welding, the FeCoCuSiNi high-entropy alloy is in butt joint with stainless steel, the FeCoCuSiNiAl high-entropy alloy is in butt joint with aluminum alloy, laser welding is conducted on the two butt joint faces respectively, and the welding quality of the FeCoCuSiNi / FeCoCuSiNiAl high-entropy alloy is improved. The formation of a brittle Fe-Al intermetallic compound of the steel / aluminum dissimilar metal welding joint is restrained by utilizing the high-entropy effect and the hysteresis diffusion effect of the high-entropy alloy, the structure of the welding interface is improved, the bonding strength of the welding interface is improved, the mechanical property of the welding joint is further improved, the yield strength of the welding joint can reach 57% of that of an aluminum alloy base material, and the welding quality is improved. And the tensile strength can reach 70% of that of an aluminum alloy base material.

Description

Technical Field

[0001] The invention belongs to the technical field of dissimilar metal laser processing, and in particular relates to a steel / aluminum dissimilar metal laser welding method based on a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer. Background Art

[0002] Reasonable use of steel / aluminum dissimilar material structures can effectively reduce weight and greatly reduce energy consumption, and has greater economic and performance advantages compared to traditional steel structures. Among the ways of connecting steel / aluminum dissimilar metals, welding is widely used in the automotive industry. It has high production efficiency and is not affected by the external environment. It is a reliable means of connecting steel / aluminum dissimilar metals. The welding methods that are focused on in the field of steel / aluminum connection include resistance spot welding, laser welding, cold metal transition welding, stir friction welding, and explosion welding. However, due to the different physical and chemical properties of steel / aluminum joints, hard and brittle intermetallic compounds (IMC) will inevitably be produced during the welding process. The thickness, phase and morphology of IMC will directly affect the mechanical properties of the welded joint.

[0003] In order to avoid the formation of IMC layer, many researchers have adjusted process parameters, changed the composition of welding / brazing filler materials and added intermediate layer materials. Among them, the purpose of adding intermediate layer materials is to prevent the mutual diffusion of Fe and Al elements. The intermediate layer materials currently used are mainly pure metals, such as copper, nickel and zinc, and their addition methods include mechanical coating, plating and thin sheets. However, research to date has shown that although adding intermediate layer materials can achieve direct isolation between steel plates and aluminum plates, it cannot avoid the formation of brittle compounds between added metal elements and Fe or Al elements, such as CuAl 2 、Al 3 Ni and FeZn 10 Etc. Therefore, it is urgent to find a simple and effective welding method to improve the interface structure of steel / aluminum dissimilar metal welding. High entropy alloy is a multi-component alloy of five or more components with equiatomic ratio or nearly equiatomic ratio. The alloy has high entropy effect in thermodynamics, hysteresis diffusion effect in kinetics, lattice distortion effect in structure and cocktail effect in performance. Among them, the high entropy effect will make it easy to obtain a simple disordered solid solution in its solidification structure; the hysteresis diffusion effect will make the diffusion of atoms in the alloy more difficult by utilizing the complexity of its alloy chemical composition and the severity of lattice distortion. Therefore, these two effects of high entropy alloys will be beneficial to prevent the formation of brittle intermetallic compounds at the interface during steel / aluminum dissimilar metal welding.

[0004] At present, only a small amount of high entropy alloys are prepared as intermediate layers. For example, the invention with patent publication number CN117324758A discloses a method for optimizing the parameters of laser welding of dissimilar metals based on alloy powder filling. This method is aimed at the laser welding of DP780 dual-phase steel and 5052 aluminum alloy. The added high entropy alloy powder composition is FeCoNiCrTi. Although it can reduce Fe-Al intermetallic compounds, it still increases Al 3 Ni and other intermetallic compounds, thereby generating a brittle phase. There is also an invention with patent publication number CN114951997A that discloses a method based on in-situ synthesis of Al X Aluminum / steel laser welding method for CoCrFeNi high entropy alloy intermediate layer, the method adds three kinds of foils of Co, Cr and Ni as intermediate layer materials, and uses laser welding to generate Al X The CoCrFeNi intermediate layer method is used for steel-aluminum welding. This method reduces the welding brittleness to a certain extent. However, this method requires high-frequency ultrasonic vibration to act on the molten pool, but due to the short welding time, it is still difficult to completely form a high-entropy alloy layer. Summary of the invention

[0005] In view of the above problems, the present invention provides a steel / aluminum dissimilar metal laser welding method based on a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer to solve the problem of poor welding performance and mechanical properties caused by the generation of brittle intermetallic compounds during steel / aluminum dissimilar metal welding.

[0006] The present invention is achieved through the following technical solutions:

[0007] A FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer, wherein the atomic ratio of the FeCoCuSiNi high entropy alloy in the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer is 4-7:1:1:1:1, and the atomic ratio of the FeCoCuSiNiAl high entropy alloy is 1:1:1:1:1:1:4-7.

[0008] Furthermore, the atomic ratio of the FeCoCuSiNi high entropy alloy is 6:1:1:1:1, and the atomic ratio of the FeCoCuSiNiAl high entropy alloy is 1:1:1:1:1:6.

[0009] A method for preparing the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer as described above comprises the following steps:

[0010] (1) Ball milling: According to the alloy component ratio, the raw material powders of FeCoCuSiNi high entropy alloy and FeCoCuSiNiAl high entropy alloy are placed in a vacuum ball milling tank, and ball milling media are added, and ball milling is performed under an argon atmosphere. After the ball milling, the raw material powders are placed in a vacuum drying oven for drying. After the drying, the raw material powders are taken out after cooling;

[0011] (2) Sintering: The ball-milled raw material powder is sieved, and the FeCoCuSiNi high entropy alloy raw material powder is loaded into a graphite mold and sintered once in a vacuum environment. Thereafter, the FeCoCuSiNiAl high entropy alloy raw material powder is placed thereon and sintered twice. After sintering, the raw material powder is demolded and processed to obtain a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer.

[0012] Furthermore, in step (2), the primary sintering temperature is 900-1100° C., the pressure is 20-35 MPa, the heating rate is maintained at 50-100° C. / min, and the heat preservation time is 4-6 min.

[0013] Furthermore, in step (2), the secondary sintering temperature is 500-600° C., the pressure is 20-35 MPa, the heating rate is maintained at 25-50° C. / min, and the heat preservation time is 4-6 min.

[0014] Furthermore, in step (1), the weight ratio of the ball milling medium to the FeCoCuSiNi high entropy alloy raw material powder is 1:2-4, and the weight ratio of the ball milling medium to the FeCoCuSiNiAl high entropy alloy raw material powder is 1:2-4;

[0015] The ball milling time of the FeCoCuSiNi high entropy alloy raw material powder and the FeCoCuSiNiAl high entropy alloy raw material powder are both 22 to 24 hours, and the rotation speed is 400 to 600 r / min; the vacuum drying temperature is 110 to 130° C., and the drying time is 1.5 to 2 hours.

[0016] A steel / aluminum dissimilar metal laser welding method based on the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer described above comprises the following steps:

[0017] a. Pretreatment: Before laser welding, the surfaces of the stainless steel and aluminum alloy workpieces and the transition layer of the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy are polished with sandpaper, and then the polished stainless steel and aluminum alloy are immersed in acetone solution and ethanol solution in turn, ultrasonically cleaned, and then placed in a vacuum drying oven for drying;

[0018] b. Welding: Argon gas is introduced into the surfaces of the dried stainless steel and aluminum alloy, and then a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer is added between the two welded workpieces. The FeCoCuSiNi high entropy alloy is butt-jointed with the stainless steel, and the FeCoCuSiNiAl high entropy alloy is butt-jointed with the aluminum alloy, and the two butt-jointed surfaces are laser welded respectively.

[0019] Furthermore, in step b, the welding process of the FeCoCuSiNi high entropy alloy and the stainless steel butt surface is: welding power 900-1200W, welding speed 200-500mm / min, and spot diameter 2-3mm.

[0020] Furthermore, in step b, the welding process of the FeCoCuSiNiAl high entropy alloy and the aluminum alloy butt surface is: welding power 1000-1500W, welding speed 400-800mm / min, spot diameter 2-3mm.

[0021] Furthermore, in step b, the purity of the argon gas is 99.99%, and the gas flow rate is 12-15 L / min.

[0022] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0023] 1. The present invention prepares an intermediate layer material for laser welding of steel / aluminum dissimilar metals through a spark plasma sintering (SPS) process. By calculating and satisfying the three conditions of mixing entropy, mixing enthalpy and atomic size difference of the high entropy alloy, the prepared FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer has the highest Fe content and the lowest Al content in the FeCoCuSiNi high entropy alloy, and the highest Al content and the lowest Fe content in the FeCoCuSiNiAl high entropy alloy. During welding, the FeCoCuSiNi high entropy alloy is butt-jointed with stainless steel, and the FeCoCuSiNiAl high entropy alloy is butt-jointed with aluminum alloy, and the two butt-jointed surfaces are laser welded to solve the problem of poor welding performance and mechanical properties caused by the generation of brittle Al / Fe intermetallic compounds during steel / aluminum dissimilar metal welding.

[0024] 2. The present invention uses laser as a welding heat source, and adds a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer as an intermediate layer material for steel / aluminum dissimilar metal welding, and adopts different welding processes to respectively weld the FeCoCuSiNi high entropy alloy and stainless steel butt surfaces, and the FeCoCuSiNiAl high entropy alloy and aluminum alloy butt surfaces. The high entropy effect and hysteresis diffusion effect of the high entropy alloy are used to curb the formation of brittle Al / Fe metal compounds in the steel / aluminum dissimilar metal welding joint, improve the welding interface organization, and enhance the bonding strength of the welding interface, thereby improving the mechanical properties of the welded joint. The yield strength of the welded joint can reach 57% of that of the aluminum alloy parent material, and the tensile strength can reach 70% of that of the aluminum alloy parent material. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of metal placement during welding of the high entropy alloy transition layer with 304 stainless steel and 5083 aluminum alloy in the present invention.

[0026] Figure 2 Schematic diagram of welding the high entropy alloy transition layer with 304 stainless steel and 5083 aluminum alloy in the present invention; Figure 2 In the figure, 1-stainless steel, 2-5083 aluminum alloy, 3-high iron high entropy alloy composition, 4-high aluminum high entropy alloy composition, 5-weld, 6-melting zone.

[0027] Figure 3 This is the tensile stress-strain diagram of the steel / aluminum dissimilar metal laser welding sample in Example 1. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below by way of examples. These examples are only used to illustrate the present invention and do not limit the protection scope of the present invention.

[0029] Example 1

[0030] A method for preparing a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer comprises the following steps:

[0031] (1) According to the atomic ratio of FeCoCuSiNi high entropy alloy of 6:1:1:1:1, and the atomic ratio of FeCoCuSiNiAl high entropy alloy of 1:1:1:1:1:6, the raw material powders of FeCoCuSiNi high entropy alloy and FeCoCuSiNiAl high entropy alloy are placed in a vacuum ball mill respectively, and stainless steel balls are added as ball milling media. The weight ratio of ball milling media to raw material powder is 1:3. The rotation speed is 500r / min, and the ball milling is carried out in an argon atmosphere for 24 hours. During the ball milling process, a PCA control agent accounting for 5% of the weight of the powder is added to each ball mill to avoid sticking to the ball, sticking to the jar, cold welding, etc. After the ball milling is completed, the raw material powder is placed in a vacuum drying oven and dried at 120°C for 2 hours. After the drying is completed, it is taken out after cooling.

[0032] (2) Sintering: After the ball milled raw material powder is passed through a 100-mesh sieve, it is placed in a customized high-strength graphite mold cavity, and the upper and lower ends are compacted and flattened with a high-strength graphite press. To facilitate demolding after molding, graphite paper is placed between the graphite mold and the sample to isolate them. The raw material powder of FeCoCuSiNi high entropy alloy is loaded into a graphite mold and sintered once in a vacuum environment. The specific sintering process is as follows: sintering temperature 1000℃, sintering pressure 30MPa, heating to 800℃ in the furnace, rising to 1000℃ at 50℃ / min, and keeping at this temperature for 5min. After the first sintering is completed, the obtained sample is polished smooth with sandpaper, and then placed in a graphite mold, and FeCoCuSiNiAl high entropy alloy raw material powder is placed on it, and the secondary sintering is continued. The specific sintering process is as follows: sintering temperature 500℃, sintering pressure 30MPa, heating to 400℃ in the furnace, rising to 500℃ at 50℃ / min, and keeping at this temperature for 5min. After sintering, demoulding and processing are performed to obtain FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer. Before welding, the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer is wire cut, and the cutting size is 100mm×5mm×2mm.

[0033] A steel / aluminum dissimilar metal laser welding method based on the above-mentioned FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer comprises the following steps:

[0034] a. Pretreatment: The welding workpieces are 304 stainless steel and 5083 aluminum alloy with sizes of 100mm×30mm×2mm and 100mm×30mm×2mm respectively. Before laser welding, the end faces and inner and outer walls of the workpieces to be welded and the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer are polished with 1000-grit sandpaper to remove the oxide film on the metal surface. The polished stainless steel and aluminum alloy are then immersed in acetone solution and ethanol solution in turn, and cleaned in an ultrasonic bath to remove grease and dirt on the surface of the stainless steel and aluminum alloy, and then placed in a vacuum drying oven for drying.

[0035] b. Welding: After drying, argon gas with a purity of 99.99% is introduced into the surface of the stainless steel and aluminum alloy at a gas flow rate of 15L / min to prevent oxidation of the upper and lower surfaces of the welded workpieces after welding. A FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer is added between the two welded workpieces to butt the FeCoCuSiNi high entropy alloy with the stainless steel and the FeCoCuSiNiAl high entropy alloy with the aluminum alloy (the metal placement diagram is shown in the figure). Figure 1 Then, the two butt joints are welded (the welding diagram is shown in Figure 2 As shown in the figure, the welding process of the FeCoCuSiNi high entropy alloy and the stainless steel butt surface is: welding power 1000W, welding speed 400mm / min, and spot diameter 3mm; the welding process of the FeCoCuSiNiAl high entropy alloy and the aluminum alloy butt surface is: welding power 1200W, welding speed 600mm / min, and spot diameter 3mm.

[0036] Example 2

[0037] A method for preparing a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer comprises the following steps:

[0038] (1) According to the atomic ratio of FeCoCuSiNi high entropy alloy of 4:1:1:1:1, and the atomic ratio of FeCoCuSiNiAl high entropy alloy of 1:1:1:1:1:4, the raw material powders of FeCoCuSiNi high entropy alloy and FeCoCuSiNiAl high entropy alloy are placed in a vacuum ball mill respectively, and stainless steel balls are added as ball milling media. The weight ratio of ball milling media to raw material powder is 1:2. The rotation speed is 400r / min, and the ball milling is carried out in an argon atmosphere for 22 hours. During the ball milling process, a PCA control agent accounting for 5% of the weight of the powder is added to each ball mill to avoid sticking to the ball, sticking to the jar, cold welding, etc. After the ball milling is completed, the raw material powder is placed in a vacuum drying oven and dried at 110°C for 2 hours. After the drying is completed, it is taken out after cooling.

[0039] (2) Sintering: After the ball milled raw material powder is passed through a 100-mesh sieve, it is placed in a customized high-strength graphite mold cavity, and the upper and lower ends are compacted and flattened with a high-strength graphite press. To facilitate demolding after molding, graphite paper is placed between the graphite mold and the sample to isolate them. The raw material powder of FeCoCuSiNi high entropy alloy is loaded into a graphite mold and sintered once in a vacuum environment. The specific sintering process is as follows: sintering temperature 900℃, sintering pressure 20MPa, heating to 800℃ in the furnace, rising to 900℃ at 50℃ / min, and keeping at this temperature for 4min. After the first sintering, the obtained sample is polished smooth with sandpaper, and then placed in a graphite mold, and FeCoCuSiNiAl high entropy alloy raw material powder is placed on it, and the secondary sintering is continued. The specific sintering process is as follows: sintering temperature 500℃, sintering pressure 20MPa, heating to 400℃ in the furnace, rising to 500℃ at 25℃ / min, and keeping at this temperature for 4min. After sintering, demoulding and processing are performed to obtain FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer. Before welding, the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer is wire cut, and the cutting size is 100mm×5mm×2mm.

[0040] A steel / aluminum dissimilar metal laser welding method based on the above-mentioned FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer comprises the following steps:

[0041] a. Pretreatment: The welding workpieces are 304 stainless steel and 5083 aluminum alloy with sizes of 100mm×30mm×2mm and 100mm×30mm×2mm respectively. Before laser welding, the surfaces of the workpieces to be welded and the transition layer of the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy are polished with sandpaper to remove the oxide film on the metal surface. The polished stainless steel and aluminum alloy are then immersed in acetone solution and ethanol solution in turn, and cleaned in an ultrasonic bath to remove grease and dirt on the surface of the stainless steel and aluminum alloy, and then placed in a vacuum drying oven for drying.

[0042] b. Welding: argon gas with a purity of 99.99% is introduced into the surfaces of the dried stainless steel and aluminum alloy at a gas flow rate of 12 L / min to avoid oxidation of the upper and lower surfaces of the welded workpieces after welding, and a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer is added between the two welded workpieces, the FeCoCuSiNi high entropy alloy is butt-jointed with the stainless steel, the FeCoCuSiNiAl high entropy alloy is butt-jointed with the aluminum alloy, and then the two butt-jointed surfaces are welded respectively. The welding process of the FeCoCuSiNi high entropy alloy butt-jointed with the stainless steel is: welding power 900 W, welding speed 500 mm / min, and spot diameter 2 mm; the welding process of the FeCoCuSiNiAl high entropy alloy butt-jointed with the aluminum alloy is: welding power 1000 W, welding speed 400 mm / min, and spot diameter 2 mm.

[0043] Example 3

[0044] A method for preparing a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer comprises the following steps:

[0045] (1) According to the atomic ratio of FeCoCuSiNi high entropy alloy of 6:1:1:1:1, and the atomic ratio of FeCoCuSiNiAl high entropy alloy of 1:1:1:1:1:6, the raw material powders of FeCoCuSiNi high entropy alloy and FeCoCuSiNiAl high entropy alloy are placed in a vacuum ball mill respectively, and stainless steel balls are added as ball milling media. The weight ratio of ball milling media to raw material powder is 1:4. The rotation speed is 600r / min, and the ball milling is carried out in an argon atmosphere for 24 hours. During the ball milling process, a PCA control agent accounting for 5% of the weight of the powder is added to each ball mill to avoid sticking to the ball, sticking to the jar, cold welding, etc. After the ball milling is completed, the raw material powder is placed in a vacuum drying oven and dried at 130°C for 1.5 hours. After the drying is completed, it is taken out after cooling.

[0046] (2) Sintering: After the ball milled raw material powder is passed through a 100-mesh sieve, it is placed in a customized high-strength graphite mold cavity, and the upper and lower ends are compacted and flattened with a high-strength graphite press. To facilitate demolding after molding, graphite paper is placed between the graphite mold and the sample to isolate them. The raw material powder of FeCoCuSiNi high entropy alloy is loaded into a graphite mold and sintered once in a vacuum environment. The specific sintering process is as follows: sintering temperature 1100℃, sintering pressure 35MPa, heating to 800℃ in the furnace, rising to 1100℃ at 100℃ / min, and keeping at this temperature for 6min. After the first sintering, the obtained sample is polished smooth with sandpaper, and then placed in a graphite mold, and FeCoCuSiNiAl high entropy alloy raw material powder is placed on it, and the secondary sintering is continued. The specific sintering process is as follows: sintering temperature 600℃, sintering pressure 35MPa, heating to 400℃ in the furnace, rising to 600℃ at 50℃ / min, and keeping at this temperature for 6min. After sintering, demoulding and processing are performed to obtain FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer. Before welding, the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer is wire cut, and the cutting size is 100mm×5mm×2mm.

[0047] A steel / aluminum dissimilar metal laser welding method based on the above-mentioned FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer comprises the following steps:

[0048] a. Pretreatment: The welding workpieces are 304 stainless steel and 5083 aluminum alloy with sizes of 100mm×30mm×2mm and 100mm×30mm×2mm respectively. Before laser welding, the surfaces of the workpieces to be welded and the transition layer of the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy are polished with sandpaper to remove the oxide film on the metal surface. The polished stainless steel and aluminum alloy are then immersed in acetone solution and ethanol solution in turn, and cleaned in an ultrasonic bath to remove grease and dirt on the surface of the stainless steel and aluminum alloy, and then placed in a vacuum drying oven for drying.

[0049] b. Welding: argon gas with a purity of 99.99% is introduced into the surfaces of the dried stainless steel and aluminum alloy at a gas flow rate of 15 L / min to avoid oxidation of the upper and lower surfaces of the welded workpieces after welding, and a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer is added between the two welded workpieces, the FeCoCuSiNi high entropy alloy is butt-jointed with the stainless steel, the FeCoCuSiNiAl high entropy alloy is butt-jointed with the aluminum alloy, and then the two butt-jointed surfaces are welded respectively. The welding process of the FeCoCuSiNi high entropy alloy butt-jointed with the stainless steel is as follows: welding power 1200 W, welding speed 500 mm / min, and spot diameter 3 mm; the welding process of the FeCoCuSiNiAl high entropy alloy butt-jointed with the aluminum alloy is as follows: welding power 1500 W, welding speed 800 mm / min, and spot diameter 3 mm.

[0050] Example 4

[0051] A method for preparing a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer comprises the following steps:

[0052] (1) According to the atomic ratio of FeCoCuSiNi high entropy alloy of 7:1:1:1:1, and the atomic ratio of FeCoCuSiNiAl high entropy alloy of 1:1:1:1:1:7, the raw material powders of FeCoCuSiNi high entropy alloy and FeCoCuSiNiAl high entropy alloy are placed in a vacuum ball mill respectively, and stainless steel balls are added as ball milling media. The weight ratio of ball milling media to raw material powder is 1:4. The rotation speed is 500r / min, and the ball milling is carried out in an argon atmosphere for 24 hours. During the ball milling process, a PCA control agent accounting for 5% of the weight of the powder is added to each ball mill to avoid sticking to the ball, sticking to the jar, cold welding, etc. After the ball milling is completed, the raw material powder is placed in a vacuum drying oven and dried at 130°C for 2 hours. After the drying is completed, it is taken out after cooling.

[0053] (2) Sintering: After the ball milled raw material powder is passed through a 100-mesh sieve, it is placed in a customized high-strength graphite mold cavity, and the upper and lower ends are compacted and flattened with a high-strength graphite press. To facilitate demolding after molding, graphite paper is placed between the graphite mold and the sample to isolate them. The raw material powder of FeCoCuSiNi high entropy alloy is loaded into a graphite mold and sintered once in a vacuum environment. The specific sintering process is as follows: sintering temperature 900℃, sintering pressure 35MPa, heating to 800℃ in the furnace, rising to 900℃ at 50℃ / min, and keeping at this temperature for 6min. After the first sintering is completed, the obtained sample is polished smooth with sandpaper, and then placed in a graphite mold, and FeCoCuSiNiAl high entropy alloy raw material powder is placed on it, and the secondary sintering is continued. The specific sintering process is as follows: sintering temperature 600℃, sintering pressure 30MPa, heating to 400℃ in the furnace, rising to 600℃ at 50℃ / min, and keeping at this temperature for 6min. After sintering, demoulding and processing are performed to obtain FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer. Before welding, the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer is wire cut, and the cutting size is 100mm×5mm×2mm.

[0054] A steel / aluminum dissimilar metal laser welding method based on the above-mentioned FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer comprises the following steps:

[0055] a. Pretreatment: The welding workpieces are 304 stainless steel and 5083 aluminum alloy with sizes of 100mm×30mm×2mm and 100mm×30mm×2mm respectively. Before laser welding, the surfaces of the workpieces to be welded and the transition layer of the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy are polished with sandpaper to remove the oxide film on the metal surface. The polished stainless steel and aluminum alloy are then immersed in acetone solution and ethanol solution in turn, and cleaned in an ultrasonic bath to remove grease and dirt on the surface of the stainless steel and aluminum alloy, and then placed in a vacuum drying oven for drying.

[0056] b. Welding: argon gas with a purity of 99.99% is introduced into the surfaces of the dried stainless steel and aluminum alloy at a gas flow rate of 12 L / min to avoid oxidation of the upper and lower surfaces of the welded workpieces after welding, and a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer is added between the two welded workpieces, the FeCoCuSiNi high entropy alloy is butt-jointed with the stainless steel, the FeCoCuSiNiAl high entropy alloy is butt-jointed with the aluminum alloy, and then the two butt-jointed surfaces are welded respectively. The welding process of the FeCoCuSiNi high entropy alloy butt-jointed with the stainless steel is: welding power 1000 W, welding speed 400 mm / min, and spot diameter 3 mm; the welding process of the FeCoCuSiNiAl high entropy alloy butt-jointed with the aluminum alloy is: welding power 1300 W, welding speed 600 mm / min, and spot diameter 3 mm.

[0057] Example 5

[0058] A method for preparing a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer comprises the following steps:

[0059] (1) According to the atomic ratio of FeCoCuSiNi high entropy alloy of 6:1:1:1:1, and the atomic ratio of FeCoCuSiNiAl high entropy alloy of 1:1:1:1:1:6, the raw material powders of FeCoCuSiNi high entropy alloy and FeCoCuSiNiAl high entropy alloy are placed in a vacuum ball mill respectively, and stainless steel balls are added as ball milling media. The weight ratio of ball milling media to raw material powder is 1:2. The rotation speed is 400r / min, and the ball milling is carried out in an argon atmosphere for 22 hours. During the ball milling process, a PCA control agent accounting for 5% of the weight of the powder is added to each ball mill to avoid sticking to the ball, sticking to the jar, cold welding, etc. After the ball milling is completed, the raw material powder is placed in a vacuum drying oven and dried at 120°C for 2 hours. After the drying is completed, it is taken out after cooling.

[0060] (2) Sintering: After the ball milled raw material powder is passed through a 100-mesh sieve, it is placed in a customized high-strength graphite mold cavity, and the upper and lower ends are compacted and flattened with a high-strength graphite press. To facilitate demolding after molding, graphite paper is placed between the graphite mold and the sample to isolate them. The raw material powder of FeCoCuSiNi high entropy alloy is loaded into a graphite mold and sintered once in a vacuum environment. The specific sintering process is as follows: sintering temperature 1000℃, sintering pressure 30MPa, heating to 800℃ in the furnace, rising to 1000℃ at 100℃ / min, and keeping at this temperature for 5min. After the first sintering is completed, the obtained sample is polished smooth with sandpaper, and then placed in a graphite mold, and FeCoCuSiNiAl high entropy alloy raw material powder is placed on it, and the secondary sintering is continued. The specific sintering process is as follows: sintering temperature 500℃, sintering pressure 25MPa, heating to 400℃ in the furnace, rising to 500℃ at 50℃ / min, and keeping at this temperature for 5min. After sintering, demoulding and processing are performed to obtain FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer. Before welding, the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer is wire cut, and the cutting size is 100mm×5mm×2mm.

[0061] A steel / aluminum dissimilar metal laser welding method based on the above-mentioned FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer comprises the following steps:

[0062] a. Pretreatment: The welding workpieces are 304 stainless steel and 5083 aluminum alloy with sizes of 100mm×30mm×2mm and 100mm×30mm×2mm respectively. Before laser welding, the surfaces of the workpieces to be welded and the transition layer of the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy are polished with sandpaper to remove the oxide film on the metal surface. The polished stainless steel and aluminum alloy are then immersed in acetone solution and ethanol solution in turn, and cleaned in an ultrasonic bath to remove grease and dirt on the surface of the stainless steel and aluminum alloy, and then placed in a vacuum drying oven for drying.

[0063] b. Welding: argon gas with a purity of 99.99% is introduced into the surfaces of the dried stainless steel and aluminum alloy at a gas flow rate of 13 L / min to avoid oxidation of the upper and lower surfaces of the welded workpieces after welding, and a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer is added between the two welded workpieces, the FeCoCuSiNi high entropy alloy is butt-jointed with the stainless steel, the FeCoCuSiNiAl high entropy alloy is butt-jointed with the aluminum alloy, and then the two butt-jointed surfaces are welded respectively. The welding process of the FeCoCuSiNi high entropy alloy butt-jointed with the stainless steel is as follows: welding power 1000 W, welding speed 400 mm / min, and spot diameter 2 mm; the welding process of the FeCoCuSiNiAl high entropy alloy butt-jointed with the aluminum alloy is as follows: welding power 1200 W, welding speed 600 mm / min, and spot diameter 2 mm.

[0064] Comparative Example 1

[0065] The article "Effect of filler wire composition on performance of Al / Galvanized steel joints by twin spot laser welding-brazing method" was used as a comparative example. This article used the filler wire method to perform butt laser brazing of 6022 aluminum alloy and galvanized steel, focusing on the study of four different filler wire materials (AlSi 12 , AlSi 5 , AlSi 3 Mn, ZnAl 15 ) on the macroscopic morphology, intermetallic compound layer thickness and mechanical properties of the welded joint. The results show that all four welding wires have good welded joint macroscopic morphology, no obvious cracks or pores are generated, and AlSi 12 The intermetallic compound produced by the filler wire is the thinnest, less than 2μm, ZnAl 15 The intermetallic compound thickness produced by the filler wire is 7μm, AlSi 3 Mn has the lowest surface roughness (Ra = 0.917 μm), ZnAl 15 The surface roughness obtained is the highest (Ra = 2.83μm), while the ZnAl 15 The maximum tensile strength of the welded joint with filler wire is 180N / mm, AlSi 12 The maximum tensile strength of the filler wire is 120N / mm. 15 The mechanical properties of the filler wire joint are good, reaching up to 180N / mm.

[0066] Material mechanical properties test

[0067] According to the provisions of GB / T 2651-2008 "Welding Joint Tensile Test Method", tensile test specimens were prepared. The tensile shear properties of the steel / aluminum dissimilar metal laser welded joints in Examples 1-5 were tested using a tensile testing machine, and the tensile speed was 0.5 mm / min. The tensile stress-strain diagram of the steel / aluminum dissimilar metal laser welded sample in Example 1 is shown in Figure 2. Figure 3 The tensile properties data of the welded samples obtained in Examples 1-5 are shown in Table 1.

[0068] Table 1 Tensile performance data of welded samples in Examples 1-5

[0069]

[0070] Depend on Figure 3 It can be seen that after the tensile force is applied to the weld joint, it is mainly elastic deformation before fracture. When the deformation reaches point a, the elastic deformation ends, and the weld joint undergoes obvious and uniform plastic deformation. As the stress increases and reaches point b, the sample begins to undergo uneven plastic deformation and necking. Therefore, the cross-sectional area of ​​the weld joint decreases sharply, resulting in a decrease in load, and the stress begins to decrease, resulting in instantaneous fracture, which means that the crack propagates very quickly during the joint fracture process.

[0071] As shown in Table 1, the yield strength of the welded joints obtained in Examples 1-5 is 129.8-132.8MPa (average value is 131.06MPa), and the tensile strength is 189.9-193.5MPa (average value is 191.54MPa). By querying the national standard GB / T3880.1-2012, it can be seen that the yield strength of the 5083 aluminum alloy grade is ≥230MPa, and the tensile strength is ≥275-350MPa. It can be seen that the average yield strength of the welded joint samples in Examples 1-5 can reach 57% of the parent material, and the average tensile strength can reach 70% of the parent material, and the mechanical properties of the welded joints are good.

[0072] The tensile strength of the welding samples in Examples 1-5 of the present invention was compared with that in Comparative Example 1. In Comparative Example 1, 6022 aluminum alloy and galvanized steel were butt-welded by laser brazing using a filling wire method, wherein ZnAl 15 The tensile strength of the filler wire joint is up to 180 N / mm (i.e., 180 MPa), while the tensile strength of the welded joints in Examples 1-5 of the present invention can reach up to 193.5 MPa. Compared with Comparative Example 1, the tensile strength of the welded joints of the present invention is increased by 7.5%. 15The FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer is used as a filler welding wire to carry out butt laser brazing of 6022 aluminum alloy and galvanized steel. The present invention adopts the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer as an intermediate layer material to carry out steel / aluminum dissimilar metal laser welding, and the welded joint has higher tensile strength and better mechanical properties.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer, characterized in that: The atomic ratio of the FeCoCuSiNi high entropy alloy in the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer is 4-7:1:1:1:1, and the atomic ratio of the FeCoCuSiNiAl high entropy alloy is 1:1:1:1:1:4-7.

2. The FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer according to claim 1, characterized in that: The atomic ratio of the FeCoCuSiNi high entropy alloy is 6:1:1:1:1, and the atomic ratio of the FeCoCuSiNiAl high entropy alloy is 1:1:1:1:1:

6.

3. A method for preparing a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer as claimed in claim 1 or 2, characterized in that: The following steps are involved: (1) Ball milling: According to the alloy component ratio, the raw material powders of FeCoCuSiNi high entropy alloy and FeCoCuSiNiAl high entropy alloy are placed in a vacuum ball milling tank, and ball milling media are added, and ball milling is performed under an argon atmosphere. After the ball milling, the raw material powders are placed in a vacuum drying oven for drying. After the drying, the raw material powders are taken out after cooling; (2) Sintering: The ball-milled raw material powder is sieved, and the FeCoCuSiNi high entropy alloy raw material powder is loaded into a graphite mold and sintered once in a vacuum environment. Thereafter, the FeCoCuSiNiAl high entropy alloy raw material powder is placed thereon and sintered twice. After sintering, the raw material powder is demolded and processed to obtain a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer.

4. The method for preparing the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer according to claim 3, characterized in that: In step (2), the primary sintering temperature is 900-1100° C., the pressure is 20-35 MPa, the heating rate is maintained at 50-100° C. / min, and the heat preservation time is 4-6 min.

5. The method for preparing the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer according to claim 3, characterized in that: In step (2), the secondary sintering temperature is 500-600° C., the pressure is 20-35 MPa, the heating rate is maintained at 25-50° C. / min, and the heat preservation is 4-6 min.

6. The method for preparing the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer according to claim 3, characterized in that: In step (1), the weight ratio of the ball milling medium to the FeCoCuSiNi high entropy alloy raw material powder is 1:2-4, and the weight ratio of the ball milling medium to the FeCoCuSiNiAl high entropy alloy raw material powder is 1:2-4; The ball milling time of the FeCoCuSiNi high entropy alloy raw material powder and the FeCoCuSiNiAl high entropy alloy raw material powder are both 22 to 24 hours, and the rotation speed is 400 to 600 r / min; the vacuum drying temperature is 110 to 130° C., and the drying time is 1.5 to 2 hours.

7. A steel / aluminum dissimilar metal laser welding method based on the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer according to claim 1 or 2, characterized in that: The following steps are involved: a. Pretreatment: Before laser welding, the surfaces of the stainless steel and aluminum alloy workpieces and the transition layer of the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy are polished with sandpaper, and then the polished stainless steel and aluminum alloy are immersed in acetone solution and ethanol solution in turn, ultrasonically cleaned, and then placed in a vacuum drying oven for drying; b. Welding: Argon gas is introduced into the surfaces of the dried stainless steel and aluminum alloy, and then a FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer is added between the two welded workpieces. The FeCoCuSiNi high entropy alloy is butt-jointed with the stainless steel, and the FeCoCuSiNiAl high entropy alloy is butt-jointed with the aluminum alloy, and the two butt-jointed surfaces are laser welded respectively.

8. The steel / aluminum dissimilar metal laser welding method based on the FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer according to claim 7, characterized in that: In step b, the welding process of the FeCoCuSiNi high entropy alloy and the stainless steel butt surface is: welding power 900-1200W, welding speed 200-500mm / min, and spot diameter 2-3mm.

9. The steel / aluminum dissimilar metal laser welding method based on FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer according to claim 7, characterized in that: In step b, the welding process of the FeCoCuSiNiAl high entropy alloy and the aluminum alloy butt surface is: welding power 1000-1500W, welding speed 400-800mm / min, spot diameter 2-3mm.

10. The steel / aluminum dissimilar metal laser welding method based on FeCoCuSiNi / FeCoCuSiNiAl high entropy alloy transition layer according to claim 7, characterized in that: In step b, the purity of the argon gas is 99.99% and the gas flow rate is 12-15 L / min.

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