Preparation method and application of aluminum-steel composite plate

Abstract

The present invention discloses a preparation method and application of an aluminum-steel composite plate, comprising the following steps: S1. removing impurities from the surface of a steel plate and an aluminum alloy plate; S2. overlapping the steel plate and the aluminum alloy plate after the impurities have been removed and connecting them by stirring and friction adding to obtain a plate; S3. subjecting the plate to aging treatment; in terms of weight percentage, the components of the aluminum alloy plate include: Zn: 6.67%, Mg: 2.71%, Cu: 1.55%, Cr: 0.21%, Mn: 0.07%, Fe: 0.19%, Si: 0.58%, and the remainder is Al. The method proposed by the present invention significantly improves the interface performance of the aluminum-steel composite material, and can meet the service and use of the composite material in the fields of automobiles, ships, high-pressure vessels, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and in particular to a preparation method and application of an aluminum-steel composite plate. Background Art

[0002] Aluminum and steel alloys are considered to be the most important engineering materials because aluminum alloys have many advantages such as low density, good corrosion resistance, excellent thermal and electrical conductivity, and high strength-to-weight ratio. In addition, steel alloys have the advantages of high strength, good toughness, good creep resistance, and low cost. However, in some cases, it is difficult for one of these alloys to meet the practical requirements of industrial applications. The use of combined structures composed of aluminum and steel alloys as bimetallic composites may be the most effective way to meet the needs of engineering applications, especially in the automotive industry, because they combine several promising properties that monolithic materials cannot provide. However, due to the large difference in thermophysical properties between aluminum and steel (such as melting point, thermal conductivity, and thermal expansion coefficient), defects such as pore cracks will occur at the aluminum and steel joint interface. Due to the difference in thermal conductivity, a thick brittle compound layer will also be generated at the joint interface, which greatly reduces the shear strength of the joint interface.

[0003] Existing research still has the problem that the thickness of the interface compound is too thick and the connection strength is low. In view of the above problems, it is necessary to find a new preparation method for aluminum-steel composite materials to improve the shear strength of the connection interface and meet the service requirements in practical applications. Summary of the invention

[0004] The present invention aims to solve the above technical problems existing in the prior art. To this end, the present invention proposes a preparation method and application of an aluminum-steel composite plate, which improves the interface performance of the aluminum-steel composite material and can meet the service and use of the composite material in the fields of automobiles, ships, high-pressure vessels, etc.

[0005] The invention also proposes a method for preparing the aluminum-steel composite plate and its application in aerospace, automobile, chemical and transportation industries.

[0006] According to one aspect of the present invention, a method for preparing an aluminum-steel composite plate is provided, comprising the following steps:

[0007] S1. Remove impurities from the surface of steel plates and aluminum alloy plates;

[0008] S2. overlapping the removed steel plate and the aluminum alloy plate and connecting them by friction stir additive to obtain a plate;

[0009] S3. aging the sheet;

[0010] In terms of weight percentage, the components of the aluminum alloy plate include: Zn: 6.5-7.5%, Mg: 2.6-3.2%, Cu: 1-2%, Cr: 0.2-0.4%, Mn: 0.05-0.1%, Fe: 0.1-0.25%, Si: 0.2-0.6%, and the balance is Al.

[0011] The embodiments according to the first aspect of the present invention have at least the following beneficial effects:

[0012] The present invention utilizes the stirring friction preparation process to make the aluminum alloy part undergo dynamic recrystallization, forming fine equiaxed crystals, and reducing the diffusion activation energy of aluminum atoms. At the same time, the stirring needle does not contact the surface of the steel plate, which can reduce the heat input between the aluminum plate and the steel plate. The two work together to induce the connection interface to fully undergo mechanical alloying, thereby producing a large area of ​​amorphous and then completing the connection, and realizing the preparation of high-strength aluminum-steel composite materials. At the interface where aluminum and iron contact, due to temperature and pressure conditions, aluminum and iron atoms will diffuse with each other, which may lead to the formation of compounds at the interface, such as FeAl and Fe3Al. The Cr and Zn contents under the above component contents can hinder the diffusion of Fe atoms when Al and Fe diffuse with each other, thereby playing a role in reducing the generation of impurity compounds.

[0013] The aluminum-steel composite material prepared by the present invention has a thinned interface compound thickness to 0.07 μm, an increased interface shear strength to 126 MPa, and an amorphous layer with a thickness of about 120 nm obtained at the interface. It can be seen that the method proposed by the present invention significantly improves the interface performance of the aluminum-steel composite material, and can meet the requirements for the service and use of the composite material in the fields of automobiles, ships, and high-pressure vessels.

[0014] In some embodiments of the present invention, the material of the steel plate includes 316L.

[0015] In some embodiments of the present invention, Pandat software is used to calculate the Al-Fe binary alloy phase diagram in the temperature range of 500°C-1500°C. In order to avoid the generation of a large amount of iron-aluminum compounds, the aluminum-steel material used is designed according to the calculation results. Among them, the aluminum alloy plate is composed of the following components by weight fraction: Zn: 6.67%, Mg: 2.71%, Cu: 1.55%, Cr: 0.21%, Mn: 0.07%, Fe: 0.19%, Si: 0.58%, and the balance is Al; the steel plate is composed of the following components by weight fraction: C: 0.02%, Si: 0.57%, Mn: 0.87%, Cr: 18.01%, Ni: 10.29%, Cu: 0.11%, Mo: 2.05%, and the balance is Fe.

[0016] The present invention selects two alloys with similar strengths, and each utilizes the advantages of its material properties to prepare a lightweight and high-strength aluminum-steel composite material. This method not only has high production efficiency, but is also pollution-free and environmentally friendly. At the same time, it can obtain an aluminum-steel composite material with significantly refined grains, uniform distribution of reinforcement items and no defects.

[0017] In some embodiments of the present invention, the impurity removal step includes grinding the oxide layer and impurities on the surface of the steel plate and the aluminum alloy plate with sandpaper and cleaning them with acetone.

[0018] The oxides on the surface of steel plates and aluminum alloy plates have extremely high melting points, which can easily cause defects at the connection interface during the connection process, greatly reducing the shear strength of the connection interface. Therefore, they need to be thoroughly polished and cleaned with acetone to ensure the generation of a high-quality connection interface.

[0019] In some embodiments of the present invention, the aluminum alloy plate and the steel plate have the same plate size.

[0020] In some embodiments of the present invention, the plate sizes of the aluminum alloy plate and the steel plate are both 200×80 mm.

[0021] In some embodiments of the present invention, the friction stir additive includes a first pass of friction stir additive and a second pass of friction stir additive;

[0022] The process parameters of the first friction stir additive process and the second friction stir additive process are the same.

[0023] The process parameters of the friction stir additive include: the rotation speed of the stirring tool is 1200-1500 rpm, and the welding speed of the stirring tool is 50-150 mm / min.

[0024] In some embodiments of the present invention, the stirring tool comprises a nickel-based high-temperature alloy split stirring tool.

[0025] In some embodiments of the present invention, during the friction stir additive process, the distance between the stirring tool and the surface of the steel plate is 0.15 to 0.3 mm.

[0026] In the above distance range, it is avoided that the bottom of the stirring tool contacts the steel and generates too high a temperature, thereby causing the aluminum alloy to melt and then forming an excessively thick compound layer at the connection interface. In the above distance range, it is avoided that the aluminum and steel cannot be connected due to too large a distance, and it is avoided that the stirring needle easily contacts the surface of the steel plate due to too low a distance, resulting in excessive heat input and forming a large compound layer.

[0027] At the same time, the factor affecting the thickness of the compound mainly depends on the temperature during the additive process, so the stirring needle is set not to contact the steel plate to avoid overheating.

[0028] Since the stirring tool will have a certain degree of high temperature wear during the friction stir additive process, a nickel-based high temperature alloy split stirring tool is used. In the actual friction stir additive process, only the needle cloth of the stirring tool is rotated and pressed down, so the actual connection area between aluminum and steel is small. Therefore, multiple passes of friction stir are used to increase the contact area between the aluminum plate and the steel plate.

[0029] In some embodiments of the present invention, the aluminum alloy plate is placed above the steel plate.

[0030] In some embodiments of the present invention, the thickness of the aluminum alloy plate is d, and the distance between the starting point of the first friction stir additive processing and the leftmost side of the plate is 1.5 to 2.5 d;

[0031] The width of the friction stir additive process is 3d;

[0032] The processing direction of the friction stir additive is parallel to the leftmost side of the aluminum alloy plate.

[0033] In the present invention, the aluminum alloy plate needs to be placed on the upper side of the steel plate. Since the melting point of aluminum is lower than that of steel, in order to avoid excessive temperature at the connection interface, the aluminum plate is placed on the upper side of the steel plate.

[0034] The above method of the present invention is suitable for medium-thick aluminum plates (2-6mm). If the plate is too thin, the heat input is too large to ensure the forming of the plate. If the plate is too thick, the fluidity is poor and the connection between the aluminum plate and the steel plate cannot be guaranteed. Under the above conditions, the stirring friction track is prevented from overlapping over a large area, which leads to a large number of defects in the connection interface and the processed aluminum alloy layer. During the process of stirring friction additive, there is a large axial force between the stirring tool and the processed plate, so the placed steel plate and aluminum alloy plate need to be clamped to ensure normal processing.

[0035] In some embodiments of the present invention, the thickness of the aluminum alloy plate and the steel plate is d, and the first pass of friction stir additive processing and the second pass of friction stir additive processing are both processed parallel to one side of the steel plate and the aluminum alloy plate. The distance between the starting point of the first pass processing and the leftmost side of the plate is d, the processing width is 3d, and the position distance between the starting points of the first pass and the second pass processing is 3d. This method is suitable for medium and thick aluminum plates (2-6mm). If the plate is too thin, the heat input is too large to ensure the forming of the plate. If the plate is too thick, the fluidity is poor and the connection between the aluminum plate and the steel plate cannot be guaranteed.

[0036] In some embodiments of the present invention, the temperature of the aging treatment is 160-180° C., and the time of the aging treatment is 24-48 hours.

[0037] After friction stir additive manufacturing, the aluminum alloy plate will experience solid solution softening in some areas due to the high temperature generated by the stirring tool. In order to ensure the uniformity of the mechanical properties of the composite plate, the aluminum-steel composite plate after friction stir additive manufacturing is subjected to aging treatment at 170°C to improve the mechanical properties of the aluminum alloy after solid solution softening and restore its performance to a level close to that of the parent material.

[0038] In some embodiments of the present invention, the aging treatment further includes removing the flash of the aluminum alloy plate.

[0039] According to one aspect of the present invention, a method for preparing an aluminum-steel composite plate is provided for use in the aerospace, automobile, chemical and transportation industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0041] Figure 1 This is a flow chart of a method for preparing a high-strength aluminum-steel composite plate by friction stir additive manufacturing according to an embodiment of the present invention.

[0042] Figure 2 (a) is a SEM image of the composite interface morphology of the aluminum-steel composite plate prepared in Example 1, Figure 2 (b) is the interface scanning electron microscope microstructure image of the aluminum-steel composite plate prepared in Example 1.

[0043] Figure 3 This is a grain size diagram of the aluminum-steel composite plate prepared in Example 1 of the present invention; wherein, Figure 3 (a) is an aluminum alloy plate, Figure 3 (b) is a steel plate, Figure 3 (c) is the composite interface of aluminum-steel composite plate.

[0044] Figure 4 The mechanical properties test results of the aluminum-steel composite plate prepared by the present invention; wherein, Figure 4 (a) is the hardness distribution, Figure 4 (b) is the interface shear strength test result.

[0045] Figure 5 Schematic diagram of the processing process of aluminum-steel composite plates.

[0046] Figure 6 This is the HRTEM characterization result of the aluminum-steel composite interface in Example 1.

[0047] Figure 7 This is the enlarged result of HRTEM characterization of the aluminum-steel composite interface in Example 1. DETAILED DESCRIPTION

[0048] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0049] Example 1

[0050] This embodiment provides a method for preparing an aluminum-steel composite plate, wherein the size of the aluminum plate and the steel plate is 200×80mm×6.5mm, and the method comprises the following steps:

[0051] S1. Pandat software was used to calculate the Al-Fe binary alloy phase diagram in the temperature range of 500℃-1500℃. In order to avoid the generation of a large amount of iron-aluminum compounds, the aluminum-steel material used was designed based on the calculation results. The aluminum alloy is composed of the following components by weight: Zn: 6.67%, Mg: 2.71%, Cu: 1.55%, Cr: 0.21%, Mn: 0.07%, Fe: 0.19%, Si: 0.58%, and the balance is Al; 316L steel material was selected, and SiC sandpaper was used to polish the oxide film on the surface of the aluminum alloy and stainless steel. After wiping with acetone, the aluminum plate and the steel plate were stacked up and down and clamped with a clamp;

[0052] S2. Use a nickel-based high-temperature alloy adjustable friction stir welding stirring head, the bottom of the stirring needle does not contact the steel plate, and is offset upward by 0.15mm. Use a rotation speed of 1500rpm and a welding speed of 50mm / min to complete two passes along the rolling direction of the plate, where the first track is 10mm away from the leftmost side of the plate, and the second track is 20mm away from the rightmost side of the first track. Then use a milling cutter to process the surface of the aluminum plate to remove the trace flash defects on the surface to obtain the plate;

[0053] S3. The processed samples are treated at 170°C for 24 hours using a tubular carbon rod furnace to complete artificial aging.

[0054] Figure 1 This is a flow chart of the method for preparing a high-strength aluminum-steel composite plate by friction stir additive manufacturing in this embodiment;

[0055] Figure 2 (a) is a SEM image of the composite interface morphology of the aluminum-steel composite plate prepared in Example 1;

[0056] Figure 2 (b) is a scanning electron microscope microstructure diagram of the interface of the aluminum-steel composite plate prepared in Example 1; the connection interface of the aluminum-steel composite plate prepared in Example 1 has no defects such as crack inclusions, and the formed compound layer is relatively thin.

[0057] Figure 3 This is a grain size diagram of the aluminum-steel composite plate prepared in Example 1 of the present invention;

[0058] in, Figure 3 (a) is an aluminum alloy plate, Figure 3 (b) is a steel plate, Figure 3 (c) is the composite interface of aluminum-steel composite plate. Figure 3 This indicates that grain refinement occurred on the aluminum side, that is, an aluminum-steel composite fine-grained plate was prepared.

[0059] Figure 4 The mechanical properties test results of the aluminum-steel composite plate prepared by the present invention; Figure 4 (a) is the shear strength test of the material prepared from sample 1, where the shear strength of sample 1 is 118 MPa. Figure 4 (b) is the shear strength test result of the material prepared from sample 2. The shear strength of sample 2 was measured to be 126 MPa, and the average shear strength was 122 MPa.

[0060] Figure 5 This is the processing process of aluminum-steel composite plates, where the distance of the leftmost side of the first pass depends on the thickness d of the plate, the processing width is about three times the thickness of the plate, and the distance between the starting points of the first and second passes is also three times the thickness of the plate. This method is suitable for medium-thick aluminum plates (2-6mm). If the plate is too thin, the heat input is too large to ensure the forming of the plate. If the plate is too thick, the fluidity is poor and the connection between the aluminum plate and the steel plate cannot be guaranteed. The first pass of friction stir additive and the second pass of friction stir additive are both processed along the side of the steel plate and the aluminum alloy plate with a length of 200mm, where the first track is 10mm away from the leftmost side of the plate, the second track is 20mm away from the right side of the first track, and the third track is 20mm away from the right side of the second track. The subsequent tracks are analogous until the tracks cover the entire plate.

[0061] Figure 6 The amorphous layer structure prepared in Example 1, Figure 6 is the HRTEM characterization result of the aluminum-steel composite interface, where Figure 6 It can be observed that there is a compound layer with a thickness of about 120nm at the aluminum-steel interface. In order to further determine the composition of the compound layer, Figure 6 The dotted box in the middle is enlarged for characterization, and the result is as follows Figure 7 As shown, the region is subjected to FFT processing, and its diffraction spots are typical amorphous diffraction spots, thus proving that the region is an amorphous layer.

[0062] Example 2

[0063] This embodiment provides a method for preparing an aluminum-steel composite plate, comprising the following steps:

[0064] S1. Pandat software was used to calculate the Al-Fe binary alloy phase diagram in the temperature range of 500℃-1500℃. In order to avoid the generation of a large amount of iron-aluminum compounds, the aluminum-steel material used was designed based on the calculation results. The aluminum alloy is composed of the following components by weight fraction: Zn: 6.67%, Mg: 2.71%, Cu: 1.55%, Cr: 0.21%, Mn: 0.07%, Fe: 0.19%, Si: 0.58%, and the balance is Al; the steel plate is composed of the following components by weight fraction: C: 0.02%, Si: 0.57%, Mn: 0.87%, Cr: 18.01%, Ni: 10.29%, Cu: 0.11%, Mo: 2.05%, and the balance is Fe. SiC sandpaper was used to polish the oxide film on the surface of the aluminum alloy and stainless steel, and the aluminum plate and steel plate were stacked up and down and clamped with a clamp;

[0065] S2. Use a nickel-based high-temperature alloy adjustable friction stir welding stirring head, the bottom of the stirring needle does not contact the steel plate, and is offset upward by 0.15mm. Use a rotation speed of 1500rpm and a welding speed of 300mm / min along the rolling direction of the plate to complete two passes of processing, where the first track is 10mm away from the leftmost side of the plate, and the second track is 20mm away from the rightmost side of the first track. Then use a milling cutter to process the surface of the aluminum plate to remove the trace flash defects on the surface to obtain the plate;

[0066] S3. The processed samples were treated at 170°C for 24 hours using a tubular carbon rod furnace to complete artificial aging;

[0067] Example 3

[0068] This embodiment provides a method for preparing an aluminum-steel composite plate, comprising the following steps:

[0069] S1. Pandat software was used to calculate the Al-Fe binary alloy phase diagram in the temperature range of 500℃-1500℃. In order to avoid the generation of a large amount of iron-aluminum compounds, the aluminum-steel material used was designed based on the calculation results. The aluminum alloy is composed of the following components by weight fraction: Zn: 6.67%, Mg: 2.71%, Cu: 1.55%, Cr: 0.21%, Mn: 0.07%, Fe: 0.19%, Si: 0.58%, and the balance is Al; the steel plate is composed of the following components by weight fraction: C: 0.02%, Si: 0.57%, Mn: 0.87%, Cr: 18.01%, Ni: 10.29%, Cu: 0.11%, Mo: 2.05%, and the balance is Fe. SiC sandpaper was used to polish the oxide film on the surface of the aluminum alloy and stainless steel, and the aluminum plate and steel plate were stacked up and down and clamped with a clamp;

[0070] S2. Use a nickel-based high-temperature alloy adjustable friction stir welding stirring head, the bottom of the stirring needle does not contact the steel plate, and is offset upward by 0.15mm. Use a rotation speed of 1200rpm and a welding speed of 300mm / min along the rolling direction of the plate to complete two passes of processing, where the first track is 10mm away from the leftmost side of the plate, and the second track is 20mm away from the rightmost side of the first track. Then use a milling cutter to process the surface of the aluminum plate to remove the trace flash defects on the surface to obtain the plate;

[0071] S3. The processed samples were treated at 170°C for 24 hours using a tubular carbon rod furnace to complete artificial aging;

[0072] Example 4

[0073] This embodiment provides a method for preparing an aluminum-steel composite plate, comprising the following steps:

[0074] S1. Pandat software was used to calculate the Al-Fe binary alloy phase diagram in the temperature range of 500℃-1500℃. In order to avoid the generation of a large amount of iron-aluminum compounds, the aluminum-steel material used was designed based on the calculation results. The aluminum alloy is composed of the following components by weight fraction: Zn: 6.67%, Mg: 2.71%, Cu: 1.55%, Cr: 0.21%, Mn: 0.07%, Fe: 0.19%, Si: 0.58%, and the balance is Al; the steel plate is composed of the following components by weight fraction: C: 0.02%, Si: 0.57%, Mn: 0.87%, Cr: 18.01%, Ni: 10.29%, Cu: 0.11%, Mo: 2.05%, and the balance is Fe. SiC sandpaper was used to polish the oxide film on the surface of the aluminum alloy and stainless steel, and the aluminum plate and steel plate were stacked up and down and clamped with a clamp;

[0075] S2. Use a nickel-based high-temperature alloy adjustable friction stir welding stirring head, the bottom of the stirring needle does not contact the steel plate, and is offset upward by 0.15mm. Use a rotation speed of 1500rpm and a welding speed of 50mm / min to complete two passes along the rolling direction of the plate, where the first track is 10mm away from the leftmost side of the plate, and the second track is 20mm away from the rightmost side of the first track. Then use a milling cutter to process the surface of the aluminum plate to remove the trace flash defects on the surface to obtain the plate;

[0076] S3. The processed samples were treated at 160°C for 24 hours using a tubular carbon rod furnace to complete artificial aging;

[0077] Example 5

[0078] This embodiment provides a method for preparing an aluminum-steel composite plate, comprising the following steps:

[0079] S1. Pandat software was used to calculate the Al-Fe binary alloy phase diagram in the temperature range of 500℃-1500℃. In order to avoid the generation of a large amount of iron-aluminum compounds, the aluminum-steel material used was designed based on the calculation results. The aluminum alloy is composed of the following components by weight fraction: Zn: 6.67%, Mg: 2.71%, Cu: 1.55%, Cr: 0.21%, Mn: 0.07%, Fe: 0.19%, Si: 0.58%, and the balance is Al; the steel plate is composed of the following components by weight fraction: C: 0.02%, Si: 0.57%, Mn: 0.87%, Cr: 18.01%, Ni: 10.29%, Cu: 0.11%, Mo: 2.05%, and the balance is Fe. SiC sandpaper was used to polish the oxide film on the surface of the aluminum alloy and stainless steel, and the aluminum plate and steel plate were stacked up and down and clamped with a clamp;

[0080] S2. Use a nickel-based high-temperature alloy adjustable friction stir welding stirring head, the bottom of the stirring needle does not contact the steel plate, and is offset upward by 0.15mm. Use a rotation speed of 1500rpm and a welding speed of 50mm / min to complete two passes along the rolling direction of the plate, where the first track is 10mm away from the leftmost side of the plate, and the second track is 20mm away from the rightmost side of the first track. Then use a milling cutter to process the surface of the aluminum plate to remove the trace flash defects on the surface to obtain the plate;

[0081] S3. The processed samples were treated at 170°C for 48 hours using a tubular carbon rod furnace to complete artificial aging;

[0082] Comparative Example 1

[0083] This comparative example provides a method for preparing an aluminum-steel composite plate. The difference between this comparative example and the embodiment is that the specific steps are as follows:

[0084] S1. Use the following aluminum-steel materials to complete the stirring and adding of materials, wherein the composition of the aluminum plate and the steel plate is the same as that of Example 1; the steel plate is composed of the following components by weight: C: 0.14%, Mn: 0.30%, Si: 0.30%, S: 0.050%, P: 0.045%, and the balance is Fe. Use SiC sandpaper to complete the grinding of the oxide film on the surface of the aluminum alloy and stainless steel, stack the aluminum plate and the steel plate up and down and clamp them with a clamp;

[0085] S2. Use a nickel-based high-temperature alloy adjustable friction stir welding stirring head, the bottom of the stirring needle does not contact the steel plate, and is offset upward by 0.15mm. Use a rotation speed of 1500rpm and a welding speed of 50mm / min to complete two passes along the rolling direction of the plate, where the first track is 10mm away from the leftmost side of the plate, and the second track is 20mm away from the rightmost side of the first track. Then use a milling cutter to process the surface of the aluminum plate to remove the trace flash defects on the surface to obtain the plate;

[0086] S3. The processed samples were treated at 170°C for 24 hours using a tubular carbon rod furnace to complete artificial aging;

[0087] Comparative Example 2

[0088] This comparative example provides a method for preparing an aluminum-steel composite plate, which specifically comprises the following steps:

[0089] S1. Use the following aluminum steel materials to complete stirring additive, where the aluminum alloy is composed of the following weight fractions: Zn: 0.05%, Mg: 2.71%, Cu: 0.24%, Cr: 1.82%, Mn: 0.07%, Fe: 0.19%, Si: 0.58%, and the balance is Al; the steel plate is composed of the following weight fractions: C: 0.22%, Mn: 0.30%, Si: ≤0.30%, S: ≤0.050%, P: ≤0.045%, and the balance is Fe. Use SiC sandpaper to complete the oxide film grinding on the surface of the aluminum alloy and stainless steel, stack the aluminum plate and the steel plate up and down and clamp them with a clamp;

[0090] S2. Use a nickel-based high-temperature alloy adjustable friction stir welding stirring head, the bottom of the stirring needle does not contact the steel plate, and is offset upward by 0.15mm. Use a rotation speed of 1500rpm and a welding speed of 50mm / min to complete two passes along the rolling direction of the plate, where the first track is 10mm away from the leftmost side of the plate, and the second track is 20mm away from the rightmost side of the first track. Then use a milling cutter to process the surface of the aluminum plate to remove the trace flash defects on the surface to obtain the plate;

[0091] S3. The processed samples were treated at 170°C for 24 hours using a tubular carbon rod furnace to complete artificial aging;

[0092] Comparative Example 3

[0093] This comparative example provides a method for preparing an aluminum-steel composite plate. The difference between this comparative example and the embodiment is that the stirring needle is in contact with the steel plate, and the other conditions are the same.

[0094] Comparative Example 4

[0095] This comparative example provides a method for preparing an aluminum-steel composite plate. The difference between this comparative example and the embodiment is that the aluminum-steel composite plate is prepared by a hot extrusion method, and other conditions are the same.

[0096] Test example

[0097] The test results of the embodiments and comparative examples are shown in Table 1. Among them, Examples 2 and 3 respectively increase the feed speed and rotation speed, resulting in less sufficient mechanical alloying at the connection interface, and the thickness of the generated amorphous layer becomes lower, so the interface shear performance decreases. Examples 4 and 5 respectively change the temperature and time of the aging process, which slightly decreases the thickness of the interface amorphous layer, but the overall effect is not significant. Comparative Examples 1 and 2 respectively reduce the content of Cu, Zn, Ni, and Cr elements in aluminum alloy and steel, resulting in sufficient diffusion of Al and Fe elements at the connection interface, forming a large amount of brittle compounds, resulting in decreased performance of the connection interface; Comparative Example 3, due to the contact between the stirring needle and the steel plate, causes the heat input of the connection interface to be too high, thereby generating a large amount of compounds, resulting in reduced performance. Comparative Example 4, since the steel plate and the aluminum plate are connected through a hot extrusion process, the heat input of the connection interface is too large, resulting in the formation of thicker compounds at the interface, so the performance decreases.

[0098] Mechanical properties testing standard: GB / T228 Metal material room temperature tensile test method;

[0099] Table 1 Performance results

[0100]

[0101] In the embodiment, the friction stir preparation process is used to make the aluminum alloy part undergo dynamic recrystallization, forming fine equiaxed crystals, which reduces the diffusion activation energy of aluminum atoms. At the same time, the stirring needle does not contact the surface of the steel plate, which can reduce the heat input between the aluminum plate and the steel plate. The two work together to induce the mechanical alloying phenomenon to fully occur at the connection interface, thereby producing a large area of ​​amorphous and completing the connection, and realizing the preparation of high-strength aluminum-steel composite materials.

[0102] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for preparing an aluminum-steel composite plate, characterized in that: The following steps are involved: S1. Remove impurities from the surface of steel plates and aluminum alloy plates; S2. placing the aluminum alloy plate on top of the steel plate and then completing the connection by friction stir additive to obtain a plate; S3. aging the sheet; The components of the aluminum alloy plate include, by weight percentage: Zn: 6.5-7.5%, Mg: 2.6-3.2%, Cu: 1-2%, Cr: 0.2-0.4%, Mn: 0.05-0.1%, Fe: 0.1-0.25%, Si: 0.2-0.6%, and the balance is Al; The steel plate comprises 316L stainless steel; The friction stir material addition includes multiple passes of friction stir material addition; The multi-pass friction stirring material addition includes a first pass of friction stirring material addition and a second pass of friction stirring material addition; The multi-pass friction stir additive process parameters are the same. The process parameters of the friction stir additive include: the rotation speed of the stirring tool is 1200-1500 rpm, and the welding speed of the stirring tool is 50-150 mm / min.

2. The method for preparing the aluminum-steel composite plate according to claim 1, characterized in that: The components of the steel plate include: C: 0.02%, Si: 0.55-0.60%, Mn: 0.87-0.89%, Cr: 18.01-18.51%, Ni: 10.02-10.29%, Cu: 0.11%, Mo: 2.01-2.05%, and the balance is Fe.

3. The method for preparing the aluminum-steel composite plate according to claim 1, characterized in that: The aluminum alloy plate and the steel plate have the same plate size.

4. The method for preparing the aluminum-steel composite plate according to claim 1, characterized in that: During the friction stir additive process, the distance between the stirring tool and the surface of the steel plate is 0.15 to 0.3 mm.

5. The method for preparing the aluminum-steel composite plate according to claim 1, characterized in that: The thickness of the aluminum alloy plate is d, and the distance between the starting point of the first friction stir additive processing and the leftmost side of the plate is 1.5 to 2.5 d; The width of the friction stir additive processing is 3d; The processing direction of the friction stir additive is parallel to the leftmost side of the aluminum alloy plate.

6. The method for preparing the aluminum-steel composite plate according to claim 1, characterized in that: The temperature of the aging treatment is 160-180° C., and the time of the aging treatment is 24-48 hours.

7. The method for preparing the aluminum-steel composite plate according to claim 1, characterized in that: The aging treatment also includes removing the flash of the aluminum alloy plate.

8. Application of the method for preparing the aluminum-steel composite plate according to any one of claims 1 to 7 in the aerospace, automobile, chemical and transportation industries.

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