Aluminum tantalum composite plate and its preparation method

Abstract

The present invention discloses an aluminum-tantalum composite plate and a preparation method thereof. According to the present invention, a vacuum diffusion welding connection method is used for connecting an aluminum plate and a tantalum plate. The connection strength of vacuum diffusion welding is much higher than that of bonding, and no welding deformation will occur, and the firmness of the welded connection is very good. Due to the surface contact connection form, the structural stability is relatively good.

Description

Technical Field

[0001] The present invention relates to an aluminum-tantalum composite plate, and the present invention also relates to a method for preparing the aluminum-tantalum composite plate. Background Art

[0002] Aluminum has a low density (the density of pure aluminum is 2.7 g / cm³, far less than the density of pure iron which is 7.68 g / cm³), and it is the most abundant metallic element in the earth's crust (second only to the non-metallic elements oxygen and silicon), so it has become the second most widely used metal after iron. For the aerospace industry, the self-weight is often an important consideration factor, especially in spaceflight where each launch requires precision down to grams. Therefore, due to its relatively low density, metallic aluminum is widely used in the aerospace industry.

[0003] In the aerospace field, for components such as those used to construct the shell, under the condition of meeting the design strength and stiffness requirements, there are specific requirements for shielding protection and anti-radiation protection. The defect of elemental aluminum in aerospace applications is its relatively low protection ability, which is manifested in its relatively weak shielding protection effect and anti-radiation ability. If a predetermined protection ability is to be achieved, it is necessary to solve the problem by, for example, increasing the thickness, which weakens the advantage of reducing the launch weight by virtue of its low density, or even fails to achieve the purpose of reducing the launch weight.

[0004] In view of this, using materials with better shielding efficiency to replace aluminum has become a research direction in the aerospace field. For example, metallic tantalum has good anti-radiation ability, but its density is relatively large (the density of pure tantalum is 16.6 g / cm³, which is 6.15 times that of pure aluminum). If elemental tantalum is used to construct the shell of a spaceship, for example, under the condition of meeting the design strength and stiffness requirements, it will cause the launch weight of the spaceship to be relatively large. And the reserves of tantalum are relatively low, resulting in its relatively high price, which is about 140 times that of electrolytic aluminum. Therefore, using it as a functional metal and aluminum as a structural metal is a good research direction.

[0005] As disclosed in Chinese patent document CN212324636U, it discloses an anti-radiation heat dissipation shell of a device. The shell includes an aluminum-tantalum composite shell body. The outer side of the aluminum-tantalum composite shell body is an aluminum shell part, and the inner side is a tantalum shell part. Its composite method is mainly through bonding with glue, and in some implementation modes, rivets are used for riveting. Since the linear expansion coefficients of aluminum and tantalum differ greatly, if glued, it is very easy to cause the bonding to fail. And when using rivets for riveting, it is easy to cause bulging of the tantalum layer and the aluminum layer at non-connected parts, that is, the phenomenon of local hollowing.

[0006] Furthermore, currently, aluminum-tantalum composite plates are mainly formed by cold rolling process. The cold rolling efficiency is relatively high, enabling rapid production. Cold rolling requires a strictly clean surface for the bonding surface. However, aluminum is an active alkaline metal. During the cold rolling process, it needs to be exposed to air for a long time, which easily generates an oxide film on its surface, affecting the bonding strength with the tantalum layer. Moreover, cold rolling will generate relatively severe processing stress. After the cold rolling is completed, the aluminum-tantalum composite plates produced by cold rolling need to be heat-treated 1-2 times, such as annealing treatment, and the overall working hours are not low.

[0007] In view of this, in some implementations, the aluminum-tantalum composite plate is prepared by hot rolling. Before hot rolling, the aluminum plate and the tantalum plate need to be stacked in a predetermined order to form a component first. Then, the component is heated to 450°C in a protective atmosphere. To ensure thorough heating, a relatively long holding time is often required, such as 30 minutes or longer, depending on the number of composite layers. The more composite layers, the longer the holding time. Then, the component needs to be quickly transferred to the rolling equipment for rolling. It should be noted that different from heating in a protective atmosphere, it is often difficult to protect the rolling equipment integrally. Under relatively high temperature conditions, the outer layers of the component are prone to oxidation by oxygen in the air. And it should be noted that the higher the temperature, the greater the thermal gradient with the ambient temperature. When the component is taken out from, for example, a heating furnace, its temperature will drop rapidly. Even if it is quickly placed in the rolling equipment for rolling, different from the continuous rolling in a steel mill, for this kind of component-based rolling, it is relatively difficult to unify or control the rolling temperature during the rolling process of the component, which affects the rolling quality.

[0008] In particular, it should be noted that the inventor believes that the necessity of producing aluminum-tantalum composite plates by rolling is not very great, because the application of aluminum-tantalum composite plates is often of high value, and a certain production efficiency can be sacrificed to obtain better product performance. Summary of the Invention

[0009] In view of this, the purpose of the present invention is to provide an aluminum-tantalum composite plate with relatively good bonding strength, and the present invention also provides a preparation method for the aluminum-tantalum composite plate.

[0010] In an embodiment of the present invention, an aluminum-tantalum composite plate is provided, which includes an aluminum plate and a tantalum plate stacked at intervals in sequence, and the adjacent aluminum plate and tantalum plate are connected by vacuum diffusion welding.

[0011] Optionally, the number of layers of the aluminum-tantalum composite plate is an odd number, and the outermost layer is an aluminum plate layer.

[0012] Optionally, the tantalum plate is a porous plate;

[0013] The holes on different tantalum plates are staggered from each other.

[0014] Optionally, the aperture of the hole is 1-5 mm.

[0015] Optionally, the holes on the tantalum plate are arranged in a row-column matrix with a row spacing of 8-10 mm and a column spacing of 8-10 mm.

[0016] Optionally, the thickness of the aluminum plate and the tantalum plate before lamination is 0.5 mm.

[0017] Optionally, the material purity of the aluminum plate is 99.9%; the material purity of the tantalum plate is 99.5%.

[0018] In an embodiment of the present invention, a method for preparing an aluminum-tantalum composite plate is further provided. The preparation method includes the following steps:

[0019] Cleaning: cleaning the surfaces of the aluminum plate and the tantalum plate to remove the oxide layers on the surfaces of the aluminum plate and the tantalum plate, and drying after cleaning;

[0020] Furnace feeding: stacking the aluminum plate and the tantalum plate in an alternating manner to form a stack, and then feeding the stack into a vacuum hot pressing and sintering furnace;

[0021] Vacuum diffusion welding: evacuating the vacuum hot pressing and sintering furnace to a predetermined vacuum degree, then raising the furnace temperature to 500-540 °C, and applying a normal pressure perpendicular to the plate surface of the stack to the stack. The normal pressure is 4-5.5 MPa, and heat preservation and pressure holding are carried out for 2.5-3 h to obtain the aluminum-tantalum composite plate.

[0022] Optionally, the furnace temperature for heat preservation and pressure holding is 510-520 °C, and the normal pressure is 4.5-5 MPa.

[0023] Optionally, the predetermined vacuum degree is 0.1 Pa.

[0024] In an embodiment of the present invention, the vacuum diffusion welding connection method is used for connecting the aluminum plate and the tantalum plate. The connection strength of the vacuum diffusion welding is much higher than that of bonding, and no welding deformation will occur. The firmness of the welded connection is very good. Since it belongs to the surface contact connection form, the structural stability is relatively good. Description of the Drawings

[0025] Figure 1 It is a schematic diagram of vacuum diffusion welding of an aluminum-tantalum composite plate in an embodiment.

[0026] Figure 2 It is an exploded view of an aluminum-tantalum composite plate in an embodiment.

[0027] Figure 3 It is the appearance of the tensile specimen of the aluminum-tantalum composite plate prepared in Example 1 after tensile fracture.

[0028] Figure 4 It is the tensile stress-strain curve of the tensile specimen of the aluminum-tantalum composite plate prepared in Example 1.

[0029] Figure 5 Appearance after tensile fracture of the tensile specimen of the aluminum-tantalum composite plate prepared in Example 2.

[0030] Figure 6 Tensile stress-strain curve of the tensile specimen of the aluminum-tantalum composite plate prepared in Example 2.

[0031] Figure 7 Appearance after tensile fracture of the tensile specimen of the aluminum-tantalum composite plate prepared in Example 3.

[0032] Figure 8 Tensile stress-strain curve of the tensile specimen of the aluminum-tantalum composite plate prepared in Example 3.

[0033] Figure 9 Appearance after tensile fracture of the tensile specimen of the aluminum-tantalum composite plate prepared in Example 4.

[0034] Figure 10 Tensile stress-strain curve of the tensile specimen of the aluminum-tantalum composite plate prepared in Example 4.

[0035] Figure 11 Appearance after tensile fracture of the tensile specimen of the aluminum-tantalum composite plate prepared in Example 5.

[0036] Figure 12 Tensile stress-strain curve of the tensile specimen of the aluminum-tantalum composite plate prepared in Example 5.

[0037] In the figure: 1. Lower die, 2. Sleeve die, 3. Aluminum-tantalum composite plate, 4. Upper die, 5. Aluminum plate, 6. Hole, 7. Tantalum plate. Embodiment

[0038] In the embodiments of the present invention, an important means to obtain the aluminum-tantalum composite plate 3 is vacuum diffusion welding. Therefore, a description of vacuum diffusion welding will be given first below.

[0039] Affected by its relatively low efficiency, the application of vacuum diffusion welding belongs to one of the relatively widely used welding techniques, rather than one of the most widely used welding techniques. Therefore, vacuum diffusion welding belongs to one of the most widely used welding techniques in applications with low efficiency requirements.

[0040] Vacuum diffusion welding belongs to a precision welding method, which will not cause welding deformation or distortion, and has high joint strength, almost negligible residual stress, no obvious interface and welding residues. In particular, it can weld dissimilar materials with very different properties together, which is difficult to achieve by traditional fusion welding methods. With the development of technology, the defect of low efficiency of vacuum diffusion welding is being gradually improved, and its application range is also getting larger and larger.

[0041] In an embodiment of the present invention, the basic steps for preparing the aluminum-tantalum composite plate 3 by vacuum diffusion bonding are as follows:

[0042] Step 1: According to the size of the target plate workpiece, select aluminum plates and tantalum plates and cut them into blanks of a preset size for standby.

[0043] Among them, the aluminum content of the aluminum plate is not less than 99.9%, that is, pure aluminum with a purity of not less than 99.9% is used; while the tantalum plate is made of pure tantalum with a purity of not less than 99.5%.

[0044] The thickness of the blank is preferably not thicker than 1 mm, and 0.5 mm is appropriate.

[0045] Step 2: Punch holes in the tantalum plate blank. In order to reduce cold working deformation, it is not advisable to use the punching method to form holes. The holes are preferably formed by a fiber laser, which will not produce corner collapse and burrs. After punching the tantalum plate blank, it is reserved for standby.

[0046] The holes can also be formed by using a gang drill. The main hole type formed by the gang drill is a round hole. This hole-forming method of drilling is not likely to produce corner collapse and burrs either. The hole-forming form of drilling is relatively single, and when using a fiber laser to form holes, the hole type is relatively flexible, for example, it can be a long-shaped hole.

[0047] The purpose of punching is to increase the actual contact area between the aluminum plate and the tantalum plate due to the unevenness of the plates.

[0048] The holes 6 between different layers of tantalum plates should be staggered.

[0049] The diameter of the holes formed by punching is 1 - 5 mm, and they are arranged in a matrix, which is convenient for punching. The row spacing in the row-column matrix of the holes 6 is 8 - 10 mm; the column spacing is 8 - 10 mm.

[0050] Step 3: Grind the surfaces to be pressed together of the aluminum plate blank and the tantalum plate blank processed in Step 1 and Step 2, remove the oxide layer on the surfaces to be pressed together of the blanks, and perform cleaning to remove the metal particles after grinding. After cleaning and drying, it is reserved for standby.

[0051] Among them, the method for removing the oxide layer on the surfaces to be pressed together of the blanks is mainly mechanical removal. In some implementations, the surfaces to be pressed together can be ground successively with sandpaper from coarse to fine.

[0052] For example, by successively grinding with 600#, 800#, 1000#, and 1200# sandpaper in sequence, a precision of level 1 or level 2, that is, mirror-level precision, can be basically achieved.

[0053] In some embodiments, after grinding with sandpaper, a polishing machine can also be used for surface polishing.

[0054] For cleaning, anhydrous ethanol can be used for cleaning in an ultrasonic cleaner, and the cleaning time is 0.5 - 1 h.

[0055] Cleaning can also be carried out with deionized water.

[0056] Relatively speaking, anhydrous ethanol has good volatility and can be directly dried by air drying after cleaning. For the blank parts after cleaning with deionized water, they can be dried in a drying room.

[0057] Step 4: Alternately stack the aluminum plate blanks and tantalum plate blanks processed in Step 3, that is, stack one layer of aluminum plate blanks and one layer of tantalum plate blanks in sequence. After combination, a stack is formed, and then place the stack on a pre-prepared mold, specifically on the lower mold 1 as shown in Figure 1 Then place the stack in a vacuum hot pressing and sintering furnace, and then perform a vacuum pumping operation on the vacuum hot pressing and sintering furnace to pump the vacuum of the vacuum hot pressing and sintering furnace to a vacuum degree of 0.1 - 0.5 Pa, with 0.1 Pa being appropriate.

[0058] In addition, during the heating and pressurizing process of the vacuum hot pressing and sintering furnace, vacuum pumping can be continuously or intermittently turned on to maintain a high vacuum degree in the vacuum hot pressing and sintering furnace.

[0059] Step 5: For the first heating step, first raise the temperature of the vacuum hot pressing and sintering furnace to 250 - 350 °C, first perform a homogenization treatment on the stack for 20 - 40 min, and then apply a pressure of 5 - 10 MPa to the stack.

[0060] Step 6: For the second heating step, continue to raise the temperature of the stack after pressing in Step 5 in the vacuum hot pressing and sintering furnace, raise the working temperature to 450 - 550 °C, and keep it warm for 1 - 3 h to complete diffusion welding of the stack in vacuum, and then an aluminum-tantalum composite plate can be obtained.

[0061] Step 7: After vacuum diffusion welding is completed, clean and polish the surface of the aluminum-tantalum composite plate, and perform machining according to requirements to obtain an aluminum-tantalum composite plate with the designed dimensions.

[0062] Taking the aluminum plate blanks and tantalum plate blanks with a blank thickness of 0.5 mm and clean surfaces to be pressed as an example for illustration, the embodiment is based on the above seven steps, adjusts the main process parameters, and the others are the same. Embodiment

[0063] The composite is carried out in a three-layer composite manner, with two layers of aluminum plates 5 and one layer of tantalum plate 7, and the tantalum plate 7 is clamped between the two aluminum plates 5.

[0064] The working temperature in Step 6 is 500 °C, and the corresponding working pressure, that is, the positive pressure applied to the stack from top to bottom is 4 MPa, and the positive pressure is shown inFigure 1 The positive pressure applied to the upper die 4 is shown in the figure.

[0065] Then, it is maintained for 2.5 h under the conditions of a working temperature of 500 °C and a working pressure of 4 MPa.

[0066] The aluminum-tantalum composite plate prepared in Example 1 is made into a tensile specimen and subjected to a tensile test in a tensile testing machine. Figure 3 The figure shows the result after the tensile test of the tensile specimen in Example 1. Figure 4 The figure is the tensile stress-strain curve of the tensile specimen in Example 1.

[0067] Through Figure 3 and Figure 4 It can be seen that the tensile strength of the aluminum-tantalum composite plate prepared in Example 1 is 19 MPa, the yield strength is 17 MPa, and the maximum bearing capacity is 1.16 KN. It can be observed that there is an obvious necking phenomenon at the fracture of the tensile specimen. The weak bonding interface cannot play a constraining role in the fracture of the plate during the tensile process, while the strong bonding surface can make the tantalum plate traction the aluminum plate, so that the aluminum and tantalum plates break synchronously, realizing a relatively consistent co-deformation. Example

[0068] The composite is carried out in a five-layer composite manner. As shown in the figure, it includes three aluminum plates 5 and two tantalum plates 7, which are arranged in an alternating manner in the order shown in the figure, and the two tantalum plates 7 are located between the two aluminum plates 5. Figure 2 shown, it includes three aluminum plates 5 and two tantalum plates 7, arranged in the order of alternating intervals as shown in the figure, and the two tantalum plates 7 are located between the two aluminum plates 5. Figure 2 The working temperature in Step 6 is 500 °C, and the corresponding working pressure, that is, the positive pressure applied to the stack from top to bottom, is 4 MPa. The positive pressure is shown as

[0069] the positive pressure applied to the upper die 4 in the figure. Figure 1 The positive pressure applied to the upper die 4 is shown in the figure.

[0070] Then, it is maintained for 2.5 h under the conditions of a working temperature of 500 °C and a working pressure of 4 MPa.

[0071] The aluminum-tantalum composite plate prepared in Example 2 is made into a tensile specimen and subjected to a tensile test in a tensile testing machine. Figure 5 The figure shows the result after the tensile test of the tensile specimen in Example 2. Figure 6 The figure is the tensile stress-strain curve of the tensile specimen in Example 2.

[0072] Through Figure 5 and Figure 6It can be seen that the tensile strength of the aluminum-tantalum composite plate prepared in Example 2 is 37 MPa, the yield strength is 30 MPa, and the maximum bearing capacity is 2.25 KN. By studying the stress-strain curve of the tensile specimen of the aluminum-tantalum composite plate prepared in Example 2, it can be observed that a stepped curve appears during the yield process, there is no consistent fracture and co-deformation phenomenon at the fracture surface, and the fracture times of each plate are also inconsistent. This indicates that a strong joint surface is not formed at the interface.

[0073] Compared with the three-layer composite in Example 1, when using a five-layer composite, the tensile strength and yield strength of the aluminum-tantalum composite plate are significantly improved. Example

[0074] For the composite in the five-layer composite method, as Figure 2 shown, it includes three aluminum plates 5 and two tantalum plates 7, arranged in the order of Figure 2 being arranged at intervals in sequence, and the two tantalum plates 7 are located between two aluminum plates 5.

[0075] The working temperature in Step 6 is 510 °C, and the corresponding working pressure, that is, the positive pressure applied to the stack from top to bottom, is 4.5 MPa. The positive pressure is shown as Figure 1 the positive pressure applied by the upper die 4 in

[0076] Then it is maintained for 2.75 h under the conditions of a working temperature of 510 °C and a working pressure of 4.5 MPa.

[0077] The aluminum-tantalum composite plate prepared in Example 3 is made into a tensile specimen and subjected to a tensile test in a tensile testing machine. Figure 7 is the result after the tensile test of the tensile specimen in Example 3. Figure 8 is the stress-strain curve of the tensile specimen in Example 3 during the tensile test.

[0078] Through Figure 7 and Figure 8 it can be known that the tensile strength of the aluminum-tantalum composite plate prepared in Example 3 is 38 MPa, the yield strength is 31 MPa, and the maximum bearing capacity is 2.26 KN. Comparing with Example 2, after changing the process parameters, Figure 8 the stress-strain curve in Example

[0079] For the composite in the five-layer composite method, as Figure 2 shown, it includes three aluminum plates 5 and two tantalum plates 7, arranged in the order of Figure 2 being arranged at intervals in sequence, and the two tantalum plates 7 are located between two aluminum plates 5.

[0080] The working temperature in Step 6 is 520 °C, and the corresponding working pressure, that is, the positive pressure applied to the stack from top to bottom, is 5 MPa. The positive pressure is shown as Figure 1 the positive pressure applied by the upper die 4 in

[0081] Then it is maintained for 3 h under the conditions of a working temperature of 520 °C and a working pressure of 5 MPa.

[0082] The aluminum-tantalum composite plate prepared in Example 4 is made into a tensile specimen and subjected to a tensile test in a tensile testing machine. Figure 9 is the result after the tensile test of the tensile specimen in Example 4, Figure 10 and is the tensile stress-strain curve of the tensile specimen in Example 4.

[0083] Through Figure 9 and Figure 10 it can be known that the tensile strength of the aluminum-tantalum composite plate prepared in Example 4 is 39 MPa, the yield strength is 31 MPa, and the maximum bearing capacity is 2.35 KN. Compared with the process parameters of Examples 1 to 3, in Example 4, with the yield strength unchanged, the tensile strength of the plate is improved, thereby increasing the reliability and life of the composite plate. In addition, a relatively obvious necking phenomenon appears at the fracture interface, indicating that the composite plate has good resistance to interface delamination and avoids the interface delamination problem of the composite plate. Example

[0084] The composite is carried out in a five-layer composite manner, as Figure 2 shown, which includes three aluminum plates 5 and two tantalum plates 7, and is arranged in the order of Figure 2 alternately arranged in sequence, and the two tantalum plates 7 are located between the two aluminum plates 5.

[0085] The working temperature in Step 6 is 540 °C, and the corresponding working pressure, that is, the positive pressure applied to the stack from top to bottom, is 5.5 MPa. The positive pressure is shown as Figure 1 the positive pressure applied by the upper die 4 in

[0086] Then it is maintained for 3 h under the conditions of a working temperature of 540 °C and a working pressure of 5.5 MPa.

[0087] The aluminum-tantalum composite plate prepared in Example 5 is made into a tensile specimen and subjected to a tensile test in a tensile testing machine. Figure 11 is the result after the tensile test of the tensile specimen in Example 5, Figure 12 and is the tensile stress-strain curve of the tensile specimen in Example 5.

[0088] Through Figure 11 and Figure 12It can be seen that the tensile strength of the aluminum-tantalum composite plate prepared in Example 5 is 34 MPa, the yield strength is 27 MPa, and the maximum bearing capacity is 2.05 KN. Compared with Example 4, in Example 5, the tensile strength and yield strength of the aluminum-tantalum composite plate are reduced. However, the stress-strain curve and the fracture surface show good performance, with a smooth curve and obvious necking phenomenon on the fracture surface. This indicates that the composite plate has a good bonding interface and the ability to resist shear forces generated during the tensile process.

Claims

1. An aluminum-tantalum composite plate, characterized in that, it comprises aluminum plates and tantalum plates stacked at intervals in sequence, and the adjacent aluminum plates and tantalum plates are connected by vacuum diffusion welding; the tantalum plate is a porous plate; the holes contained on different tantalum plates are staggered from each other; the aperture of the holes is 1-5 mm; the holes on the tantalum plate are arranged in a row-column matrix, the row spacing is 8-10 mm; the column spacing is 8-10 mm.

2. The aluminum-tantalum composite plate according to claim 1, characterized in that, the number of layers of the aluminum-tantalum composite plate is an odd number, and the outermost layer is an aluminum plate layer.

3. The aluminum-tantalum composite plate according to claim 2, characterized in that, the thicknesses of the aluminum plate and the tantalum plate before lamination are both 0.5 mm.

4. The aluminum-tantalum composite plate according to claim 1, characterized in that, the material purity of the aluminum plate is 99.9%; the material purity of the tantalum plate is 99.5%.

5. A preparation method of an aluminum-tantalum composite plate, characterized in that, the preparation method comprises the following steps: Punching holes, punching holes in the tantalum plate with a fiber laser; the aperture of the holes is 1-5 mm; the holes on the tantalum plate are arranged in a row-column matrix, the row spacing is 8-10 mm; the column spacing is 8-10 mm Cleaning, performing surface cleaning on the aluminum plate and the tantalum plate to remove the oxide layers on the surfaces of the aluminum plate and the tantalum plate, and drying after cleaning; Feeding into the furnace, stacking the aluminum plates and the tantalum plates in an alternating stacking manner to form a stack, and then feeding the stack into a vacuum hot-pressing sintering furnace; Vacuum diffusion welding, evacuating the vacuum hot-pressing sintering furnace to a predetermined vacuum degree, then raising the furnace temperature to 500-540 °C and applying a positive pressure normal to the plate surface of the stack to the stack, the positive pressure is 4-5.5 MPa, keeping the temperature and pressure for 2.5-3 h to obtain the aluminum-tantalum composite plate.

6. The preparation method according to claim 5, characterized in that, the furnace temperature for keeping the temperature and pressure is 510-520 °C, and the positive pressure is 4.5-5 MPa.

7. The preparation method according to claim 5, characterized in that, the predetermined vacuum degree is 0.1 Pa.

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