CN115415656B - Connection method of skutterudite thermoelectric material and copper electrode by using Fe-Cr-Mo/W as barrier layer - Google Patents

Connection method of skutterudite thermoelectric material and copper electrode by using Fe-Cr-Mo/W as barrier layer Download PDF

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CN115415656B
CN115415656B CN202211138051.1A CN202211138051A CN115415656B CN 115415656 B CN115415656 B CN 115415656B CN 202211138051 A CN202211138051 A CN 202211138051A CN 115415656 B CN115415656 B CN 115415656B
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barrier layer
thermoelectric material
copper electrode
welded
skutterudite
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CN115415656A (en
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张丽霞
潘辉
耿慧远
张博
常青
孙湛
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Harbin Institute of Technology
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Harbin Institute of Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
    • B23K20/001—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating by extrusion or drawing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K1/00—Soldering, e.g. brazing, or unsoldering
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K1/00—Soldering, e.g. brazing, or unsoldering
    • B23K1/20—Preliminary treatment of work or areas to be soldered, e.g. in respect of a galvanic coating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
    • B23K20/14—Preventing or minimising gas access, or using protective gases or vacuum during welding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
    • B23K20/16—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating with interposition of special material to facilitate connection of the parts, e.g. material for absorbing or producing gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
    • B23K20/24—Preliminary treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/18—Dissimilar materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

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Abstract

A connection method of skutterudite thermoelectric material and copper electrode with Fe-Cr-Mo/W as barrier layer relates to a connection method of thermoelectric material and electrode. In order to solve the problem of low strength of the welded joint due to element diffusion in the process of connecting skutterudite with a copper electrode. According to the invention, after smelting, the barrier layer raw material is sucked and cast into a water-cooled copper mold die for rapid solidification, and the non-equilibrium solidification principle is innovatively adopted to greatly improve the solid solubility of large-size Mo/W elements in Fe-Cr alloy, reduce element diffusion, reduce joint residual stress and improve joint strength. The skutterudite and the copper electrode are connected by adopting methods such as diffusion welding, brazing, nano silver sintering and the like, so that the operation is convenient, the process is flexible, a proper method can be selected according to actual use requirements, and the cost is low.

Description

Connection method of skutterudite thermoelectric material and copper electrode by using Fe-Cr-Mo/W as barrier layer
Technical Field
The invention relates to a method for connecting skutterudite thermoelectric material and a copper electrode by taking Fe-Cr-Mo/W as a barrier layer.
Background
Skutterudite (CoSb) 3 ) Is one of thermoelectric materials with highest conversion efficiency in a medium temperature section (room temperature 600 ℃), and has excellent mechanical property and thermal stability. However, the preparation of a reliable welded joint between skutterudite and electrodes is an indispensable step in the fabrication of thermoelectric devices.
At present, because skutterudite and copper electrode joint have serious element diffusion problem, the conversion efficiency of the device can be drastically reduced in the service process, and the use effect is affected. Meanwhile, the difference of thermal expansion coefficients of the welding joints causes too low joint connection strength, which severely restricts the use of devices. The diffusion-preventing barrier layer materials which can be used for skutterudite thermoelectric materials at present are pure metals and alloys thereof, but because the melting point of Sb element in the skutterudite thermoelectric materials is only 630 ℃, the Sb element can react with most metal elements to form intermetallic compounds, so that the interface resistance is increased, and the joint strength is reduced.
At present, no barrier layer metal material capable of meeting long-term service requirements of skutterudite thermoelectric materials exists. It is therefore very important to devise a method of achieving a long-term reliable connection between skutterudite thermoelectric material and copper electrode.
Disclosure of Invention
The invention provides a method for connecting skutterudite thermoelectric material and a copper electrode by taking Fe-Cr-Mo/W as a barrier layer, aiming at solving the problems that element diffusion is easy to occur between skutterudite and the copper electrode and the strength of a welded joint is low in the existing skutterudite and copper electrode connecting process.
The connection method of skutterudite thermoelectric material and copper electrode with Fe-Cr-Mo/W as barrier layer includes the following steps:
1. firstly cutting a skutterudite thermoelectric material, sequentially polishing, ultrasonically cleaning with alcohol and ultrasonically cleaning with acetone on a surface to be welded of the skutterudite thermoelectric material step by step, and then storing in an inert gas atmosphere; polishing and ultrasonically cleaning a surface to be welded of the copper electrode, drying to obtain the copper electrode to be welded, and storing in an inert atmosphere;
2. weighing raw materials according to the atomic percentage of the barrier layer, placing the raw materials into a vacuum arc melting furnace for arc melting, and then carrying out suction casting into a water-cooling copper mold die for rapid solidification to obtain a supersaturated solid solution barrier layer cast ingot with uniform components; cutting the supersaturated solid solution barrier layer cast ingot into slices, polishing, cleaning and blow-drying in sequence to obtain a barrier layer slice for later use;
the barrier layer consists of 10-19.9% of Cr, 0.1-10% of Mo or W and the balance of Fe according to the atomic percentage, and the sum of the atomic percentages of Cr, mo and Cr and W is 20%; the sum of the atomic percentages of Cr, mo and Cr and W is 20 percent, so that weld cracking can be avoided;
the speed of rapid solidification is at least 1000 ℃/min;
3. placing the barrier layer sheet between the skutterudite thermoelectric material processed in the first step and the surface to be welded of the copper electrode to be welded for assembly, so as to obtain a connecting piece to be welded; the to-be-welded connecting piece is welded at the position of 1 multiplied by 10 -4 -5×10 -3 And simultaneously applying welding pressure of 10-30MPa under the vacuum environment of Pa, heating to 550-650 ℃, preserving heat and pressure for 3-30min, and then slowly cooling to room temperature to complete the connection of the skutterudite thermoelectric material and the copper electrode.
The other connection method of skutterudite thermoelectric material and copper electrode with Fe-Cr-Mo/W as barrier layer is carried out according to the following steps:
1. weighing raw materials according to the atomic percentage of the barrier layer, placing the raw materials into a vacuum arc melting furnace for arc melting or vacuum induction melting, and then carrying out suction casting into a water-cooling copper mold die for rapid solidification to obtain a supersaturated solid solution barrier layer cast ingot with uniform components; cutting the supersaturated solid solution barrier layer cast ingot into slices, polishing, cleaning and blow-drying in sequence to obtain a barrier layer slice for later use; polishing and ultrasonically cleaning a surface to be welded of the copper electrode, drying to obtain the copper electrode to be welded, and storing in an inert atmosphere;
the barrier layer consists of 10-19.9% of Cr, 0.1-10% of Mo or W and the balance of Fe according to the atomic percentage, and the sum of the atomic percentages of Cr, mo and Cr and W is 20%; the sum of the atomic percentages of Cr, mo and Cr and W is 20 percent, so that weld cracking can be avoided;
the speed of the rapid solidification is at least 1000 ℃/min;
2. placing a barrier layer sheet in a graphite mold filled with skutterudite thermoelectric material powder to be welded, covering the skutterudite thermoelectric material powder with the barrier layer sheet, performing hot-pressing sintering on the barrier layer and the thermoelectric material powder, and cooling along with a furnace to obtain a thermoelectric material with the barrier layer; cutting, polishing step by step, cleaning to obtain a thermoelectric material to be welded, and storing in an inert gas environment for later use; the hot-press sintering process parameters are determined according to factors such as the type of thermoelectric materials;
the particle size of the thermoelectric material powder is not more than 10 μm;
3. placing a layer of brazing filler metal between the barrier layer of the to-be-welded thermoelectric material obtained in the second step and the copper electrode, wherein the barrier layer of the to-be-welded thermoelectric material faces the to-be-welded surface of the copper electrode, so as to obtain a to-be-welded piece, and brazing; or arranging nano silver soldering paste between the barrier layer of the to-be-soldered thermoelectric material obtained in the second step and the copper electrode, wherein the barrier layer of the to-be-soldered thermoelectric material faces the to-be-soldered surface of the copper electrode, so as to obtain a to-be-soldered piece, and performing solid-phase sintering.
The invention has the beneficial effects that:
1. the existing barrier layer is not quickly solidified, only the element content is changed to be a research point, so that the alloy added with Mo/W elements with large volume fraction cannot be obtained, a large amount of compounds are generated in the alloy, the brittleness of the metal of the barrier layer is caused, and the joint strength is reduced. The invention innovatively adopts the unbalanced solidification principle to greatly improve the solid solubility of large-size Mo/W elements in Fe-Cr alloy, so that the lattice constant of the Fe-Cr alloy is obviously increased, the original Cr atom position is occupied, the lattice distortion is increased, the adjacent atoms are difficult to move, in addition, the Mo/W elements are not reacted with the elements in skutterudite thermoelectric material, other atomic diffusion can only bypass MoW, the element diffusion distance is increased, the element diffusion degree is reduced, and the element diffusion rate is obviously reduced. And because the Cr-Mo/W elements can be infinitely and mutually dissolved, the thermal expansion coefficient of the Fe-Cr alloy can be linearly adjusted, so that the residual stress of the joint is reduced, and the joint strength is improved.
Therefore, the method for connecting the skutterudite thermoelectric material with the copper electrode by taking Fe-Cr-Mo/W as the barrier layer can obtain the novel supersaturated diffusion-resistant barrier layer by non-equilibrium solidification and rapid cooling, effectively reduces the element diffusion easily occurring between skutterudite and the copper electrode in the brazing connection process of the prior skutterudite and the copper electrode, and solves the problem of low strength of a welding joint. The skutterudite and the barrier layer are well connected at the interface, no crack is generated, the shearing strength of the joint can reach 20MPa at room temperature, the diffusion of interface elements is extremely small, the thickness of the interface reaction layer is less than 5 mu m, and the contact resistance and the contact thermal resistance of the welding joint are small.
2. The invention can connect skutterudite with copper electrode by diffusion welding, brazing, nano silver sintering, etc., has convenient operation and flexible process, can select proper method according to actual use requirement, and has lower cost.
3. According to the invention, the barrier layer is prepared into a sheet, and then the skutterudite thermoelectric material is connected with the copper electrode, so that one-step diffusion connection is realized, the operation is simple and convenient, the welded joint can be obtained by only one furnace, the low-temperature connection and high-temperature service can be realized, and the interface reaction layer is thinner.
4. According to the invention, the barrier layer and the thermoelectric material powder are sintered together and then are connected with the copper electrode, the barrier layer and the thermoelectric material are connected firstly, and then the electrodes are connected by adopting brazing/nano silver solid-phase sintering and the like, so that the thermoelectric devices with various structures can be prepared and assembled more conveniently and flexibly, and the thermoelectric devices are not limited by a diffusion welding clamp.
Drawings
FIG. 1 is an SEM image of the FeCrMo alloy barrier layer/skutterudite thermoelectric material interface in example 1.
Detailed Description
The technical scheme of the invention is not limited to the specific embodiments listed below, and also comprises any reasonable combination of the specific embodiments.
The first embodiment is as follows: the method for connecting skutterudite thermoelectric material and copper electrode by using Fe-Cr-Mo/W as barrier layer in the embodiment comprises the following steps:
1. firstly cutting a skutterudite thermoelectric material, sequentially polishing, ultrasonically cleaning with alcohol and ultrasonically cleaning with acetone on a surface to be welded of the skutterudite thermoelectric material step by step, and then storing in an inert gas atmosphere; polishing and ultrasonically cleaning a surface to be welded of the copper electrode, drying to obtain the copper electrode to be welded, and storing in an inert atmosphere;
2. weighing raw materials according to the atomic percentage of the barrier layer, placing the raw materials into a vacuum arc melting furnace for arc melting, and then carrying out suction casting into a water-cooling copper mold die for rapid solidification to obtain a supersaturated solid solution barrier layer cast ingot with uniform components; cutting the supersaturated solid solution barrier layer cast ingot into slices, polishing, cleaning and blow-drying in sequence to obtain a barrier layer slice for later use;
the barrier layer consists of 10-19.9% of Cr, 0.1-10% of Mo or W and the balance of Fe according to the atomic percentage, and the sum of the atomic percentages of Cr, mo and Cr and W is 20%;
the speed of rapid solidification is at least 1000 ℃/min;
3. placing the barrier layer sheet between the skutterudite thermoelectric material processed in the first step and the surface to be welded of the copper electrode to be welded for assembly, so as to obtain a connecting piece to be welded; the to-be-welded connecting piece is welded at the position of 1 multiplied by 10 -4 -5×10 -3 And simultaneously applying welding pressure of 10-30MPa under the vacuum environment of Pa, heating to 550-650 ℃, preserving heat and pressure for 3-30min, and then slowly cooling to room temperature to complete the connection of the skutterudite thermoelectric material and the copper electrode.
The present embodiment has the following advantageous effects:
1. the existing barrier layer is not quickly solidified, only the element content is changed to be a research point, so that the alloy added with Mo/W elements with large volume fraction cannot be obtained, a large amount of compounds are generated in the alloy, the brittleness of the metal of the barrier layer is caused, and the joint strength is reduced. The non-equilibrium solidification principle is innovatively adopted in the embodiment to greatly improve the solid solubility of large-size Mo/W elements in the Fe-Cr alloy, so that the lattice constant of the Fe-Cr alloy is obviously increased, the original Cr atom position is occupied, the lattice distortion is increased, the adjacent atoms are difficult to move, in addition, the Mo/W elements do not react with the elements in the skutterudite thermoelectric material, other atomic diffusion can only bypass MoW, the element diffusion distance is increased, the element diffusion degree is reduced, and the element diffusion rate is obviously reduced. And because the Cr-Mo/W elements can be infinitely and mutually dissolved, the thermal expansion coefficient of the Fe-Cr alloy can be linearly adjusted, so that the residual stress of the joint is reduced, and the joint strength is improved.
Therefore, according to the method for connecting the skutterudite thermoelectric material and the copper electrode, which take Fe-Cr-Mo/W as the barrier layer, the novel supersaturated diffusion-resistant barrier layer is obtained by non-equilibrium solidification and rapid cooling, so that element diffusion easily occurs between skutterudite and the copper electrode in the existing brazing connection process of skutterudite and the copper electrode is effectively reduced, and the problem of low strength of a welded joint is solved. The skutterudite and the barrier layer are well connected at the interface, no crack is generated, the shearing strength of the joint can reach 20MPa at room temperature, the diffusion of interface elements is extremely small, the thickness of the interface reaction layer is less than 5 mu m, and the contact resistance and the contact thermal resistance of the welding joint are small.
2. The method can be used for connecting skutterudite with a copper electrode by adopting methods such as diffusion welding, brazing, nano silver sintering and the like, is convenient to operate and flexible in process, can select a proper method according to actual use requirements, and is low in cost.
3. According to the embodiment, the barrier layer is prepared into a sheet, and then the skutterudite thermoelectric material is connected with the copper electrode, so that one-step diffusion connection is realized, the operation is simple and convenient, a welding joint can be obtained by only one furnace, the high-temperature service of low-temperature connection can be realized, and the interface reaction layer is thinner.
The second embodiment is as follows: the first difference between this embodiment and the specific embodiment is that: step one, the ultrasonic cleaning time of the alcohol is 10min; the ultrasonic cleaning time of the acetone is 10min.
And a third specific embodiment: the first difference between this embodiment and the specific embodiment is that: and step two, the raw materials are pure Fe, pure Cr, pure Mo, pure W, crMo or CrW.
The specific embodiment IV is as follows: the first difference between this embodiment and the specific embodiment is that: the arc melting process comprises the following steps: the electric arc melting current is 130A, each time of melting is conducted for 20s, the material is turned over once by a ladle after each time of melting is finished, and the melting is repeated for at least 5 times.
Fifth embodiment: the first difference between this embodiment and the specific embodiment is that: and step two, the thickness of the barrier layer sheet is 100-300 mu m.
Specific embodiment six: the method for connecting skutterudite thermoelectric material and copper electrode by using Fe-Cr-Mo/W as barrier layer in the embodiment comprises the following steps:
1. weighing raw materials according to the atomic percentage of the barrier layer, placing the raw materials into a vacuum arc melting furnace for arc melting or vacuum induction melting, and then carrying out suction casting into a water-cooling copper mold die for rapid solidification to obtain a supersaturated solid solution barrier layer cast ingot with uniform components; cutting the supersaturated solid solution barrier layer cast ingot into slices, polishing, cleaning and blow-drying in sequence to obtain a barrier layer slice for later use; polishing and ultrasonically cleaning a surface to be welded of the copper electrode, drying to obtain the copper electrode to be welded, and storing in an inert atmosphere;
the barrier layer consists of 10-19.9% of Cr, 0.1-10% of Mo or W and the balance of Fe according to the atomic percentage, and the sum of the atomic percentages of Cr, mo and Cr and W is 20%;
the speed of the rapid solidification is at least 1000 ℃/min;
2. placing a barrier layer sheet in a graphite mold filled with skutterudite thermoelectric material powder to be welded, covering the skutterudite thermoelectric material powder with the barrier layer sheet, performing hot-pressing sintering on the barrier layer and the thermoelectric material powder, and cooling along with a furnace to obtain a thermoelectric material with the barrier layer; cutting, polishing step by step, cleaning to obtain a thermoelectric material to be welded, and storing in an inert gas environment for later use; the hot-press sintering process parameters are determined according to factors such as the type of thermoelectric materials;
the particle size of the thermoelectric material powder is not more than 10 μm;
3. placing a layer of brazing filler metal between the barrier layer of the to-be-welded thermoelectric material obtained in the second step and the copper electrode, wherein the barrier layer of the to-be-welded thermoelectric material faces the to-be-welded surface of the copper electrode, so as to obtain a to-be-welded piece, and brazing; or arranging nano silver soldering paste between the barrier layer of the to-be-soldered thermoelectric material obtained in the second step and the copper electrode, wherein the barrier layer of the to-be-soldered thermoelectric material faces the to-be-soldered surface of the copper electrode, so as to obtain a to-be-soldered piece, and performing solid-phase sintering.
1. The existing barrier layer is not quickly solidified, only the element content is changed to be a research point, so that the alloy added with Mo/W elements with large volume fraction cannot be obtained, a large amount of compounds are generated in the alloy, the brittleness of the metal of the barrier layer is caused, and the joint strength is reduced. The non-equilibrium solidification principle is innovatively adopted in the embodiment to greatly improve the solid solubility of large-size Mo/W elements in the Fe-Cr alloy, so that the lattice constant of the Fe-Cr alloy is obviously increased, the original Cr atom position is occupied, the lattice distortion is increased, the adjacent atoms are difficult to move, in addition, the Mo/W elements do not react with the elements in the skutterudite thermoelectric material, other atomic diffusion can only bypass MoW, the element diffusion distance is increased, the element diffusion degree is reduced, and the element diffusion rate is obviously reduced. And because the Cr-Mo/W elements can be infinitely and mutually dissolved, the thermal expansion coefficient of the Fe-Cr alloy can be linearly adjusted, so that the residual stress of the joint is reduced, and the joint strength is improved.
Therefore, according to the method for connecting the skutterudite thermoelectric material and the copper electrode, which take Fe-Cr-Mo/W as the barrier layer, the novel supersaturated diffusion-resistant barrier layer is obtained by non-equilibrium solidification and rapid cooling, so that element diffusion easily occurs between skutterudite and the copper electrode in the existing brazing connection process of skutterudite and the copper electrode is effectively reduced, and the problem of low strength of a welded joint is solved. The skutterudite and the barrier layer are well connected at the interface, no crack is generated, the shearing strength of the joint can reach 20MPa at room temperature, the diffusion of interface elements is extremely small, the thickness of the interface reaction layer is less than 5 mu m, and the contact resistance and the contact thermal resistance of the welding joint are small.
2. The method can be used for connecting skutterudite with a copper electrode by adopting methods such as diffusion welding, brazing, nano silver sintering and the like, is convenient to operate and flexible in process, can select a proper method according to actual use requirements, and is low in cost.
3. According to the embodiment, the blocking layer is sintered with the thermoelectric material powder and then connected with the copper electrode, the blocking layer is connected with the thermoelectric material, and then the electrodes are connected by adopting brazing/nano silver solid-phase sintering and the like, so that thermoelectric devices with various structures can be prepared and assembled more conveniently and flexibly, and the thermoelectric devices are not limited by a diffusion welding clamp.
Seventh embodiment: the sixth embodiment differs from the first embodiment in that: the arc melting process comprises the following steps: the electric arc melting current is 130A, each time of melting is conducted for 20s, the material is turned over once by a ladle after each time of melting is finished, and the melting is repeated for at least 5 times.
Eighth embodiment: the sixth embodiment differs from the first embodiment in that: the raw materials in the first step are pure Fe, pure Cr, pure Mo, pure W, crMo or CrW.
Detailed description nine: the sixth embodiment differs from the first embodiment in that: the solid phase sintering process comprises the following steps: at a vacuum degree of 1X 10 -4 -5×10 -3 And under Pa, applying 0.5-10MPa pressure to the to-be-welded piece, heating to 200-500 ℃, preserving heat for 5-30min, and cooling along with the furnace.
Detailed description ten: the sixth embodiment differs from the first embodiment in that: the brazing process comprises the following steps: at a vacuum degree of 1X 10 -4 -5×10 -3 Heating to 650-700 deg.C at 5-15 deg.C/min under Pa, maintaining for 3-10min, cooling with furnace, and cooling at 2-10 deg.C/min.
Eleventh embodiment: the sixth embodiment differs from the first embodiment in that: and step three, the brazing filler metal is Ag-Cu-In-Sn or Ag-Cu-In-Ti or CuSn10.5PNi2.
Twelve specific embodiments: the sixth embodiment differs from the first embodiment in that: step one, the thickness of the sheet is 100-300 mu m.
Example 1
The method for connecting skutterudite thermoelectric material with copper electrode by using Fe-Cr-Mo/W as barrier layer comprises the following steps:
1. firstly cutting a skutterudite thermoelectric material, sequentially polishing and polishing a surface to be welded of the skutterudite thermoelectric material step by sand paper, ultrasonically cleaning with alcohol for 10min, ultrasonically cleaning with acetone for 10min, and then preserving in a nitrogen atmosphere; polishing and ultrasonically cleaning a surface to be welded of the copper electrode, drying to obtain the copper electrode to be welded, and storing in an inert atmosphere;
2. weighing raw materials according to the atomic percentage of the barrier layer, placing the raw materials into a vacuum arc melting furnace for arc melting, and then carrying out suction casting into a water-cooling copper mold die for rapid solidification to obtain a supersaturated solid solution barrier layer cast ingot with uniform components; cutting the supersaturated solid solution barrier layer cast ingot into slices, polishing, cleaning and blow-drying in sequence to obtain a barrier layer slice for later use;
the barrier layer consists of 15% of Cr, 5% of Mo and the balance of Fe according to atomic percentage;
the raw materials are pure Fe, pure Cr and pure Mo;
the arc melting process comprises the following steps: the electric arc melting current is 130A, the arc is started for 20s each time, the material is turned once by a ladle after each time, and the melting is repeated for 5 times;
the speed of the rapid solidification is 1000 ℃/min;
the thickness of the barrier layer sheet is 300 mu m;
3. placing the barrier layer sheet between the skutterudite thermoelectric material processed in the first step and the surface to be welded of the copper electrode to be welded for assembly, so as to obtain a connecting piece to be welded; the to-be-welded connecting piece is welded at the position of 1 multiplied by 10 -4 -5×10 -3 And (3) under the vacuum environment of Pa, simultaneously applying welding pressure of 10MPa, heating to 600 ℃, preserving heat and pressure for 10min, and then slowly cooling to room temperature at the speed of 5 ℃/min to finish the connection of the skutterudite thermoelectric material and the copper electrode.
Fig. 1 is an SEM image of the FeCrMo alloy barrier layer/skutterudite thermoelectric material interface in example 1, in which the FeCrMo barrier layer and skutterudite thermoelectric material are sequentially arranged from left to right. Fig. 1 can illustrate that the interface bonding of the joints is good, and the thickness of the reaction layer is small and uniform. The supersaturated solid solution barrier layer added with the Mo/W element with large volume fraction is prepared by using the non-equilibrium solidification principle rapid solidification method, the expansion coefficient is linearly adjustable, and the element barrier effect is good. After aging at 550 ℃ for 600 hours, the joint reaction layer is not more than 25 mu m, and the interface resistivity is less than 4 mu omega cm 2 The shear strength of the joint can reach 18MPa.
Example 2
The method for connecting skutterudite thermoelectric material with copper electrode by using Fe-Cr-Mo/W as barrier layer comprises the following steps:
1. weighing raw materials according to the atomic percentage of the barrier layer, placing the raw materials into a vacuum arc melting furnace for arc melting or vacuum induction melting, and then carrying out suction casting into a water-cooling copper mold die for rapid solidification to obtain a supersaturated solid solution barrier layer cast ingot with uniform components; cutting the supersaturated solid solution barrier layer cast ingot into slices, polishing, cleaning and blow-drying in sequence to obtain a barrier layer slice for later use; polishing and ultrasonically cleaning a surface to be welded of the copper electrode, drying to obtain the copper electrode to be welded, and storing in an inert atmosphere;
the barrier layer consists of 15% of Cr, 5% of W and the balance of Fe according to atomic percentage; the raw materials are pure Fe, pure Cr and pure W;
the arc melting process comprises the following steps: the electric arc melting current is 130A, the arc is started for 20s each time, the material is turned once by a ladle after each time, and the melting is repeated for 5 times;
the speed of the rapid solidification is 1000 ℃/min;
the thickness of the sheet is 300 μm;
2. placing a barrier layer sheet in a graphite mold filled with skutterudite thermoelectric material powder to be welded, covering the skutterudite thermoelectric material powder with the barrier layer sheet, performing hot-pressing sintering on the barrier layer and the thermoelectric material powder, and cooling along with a furnace to obtain a thermoelectric material with the barrier layer; cutting, polishing step by step, cleaning to obtain a thermoelectric material to be welded, and storing in an inert gas environment for later use; the hot-press sintering process parameters are determined according to factors such as the type of thermoelectric materials;
the particle size of the thermoelectric material powder is 8-10 mu m;
the skutterudite thermoelectric material powder comprises La 0.8 Ti 0.1 Ga 0.1 Fe 3.3 Co 0.7 Sb 12 The sintering process is as follows: under Ar gas atmosphere, rapidly heating to 650 ℃ at a speed of 100 ℃/min, preserving heat for 10min, keeping the pressure at 60MPa, and then slowly cooling to room temperature at a speed of 5 ℃/min;
3. setting nano silver soldering paste between the barrier layer of the to-be-soldered thermoelectric material obtained in the second step and the copper electrode, wherein the barrier layer of the to-be-soldered thermoelectric material faces the to-be-soldered surface of the copper electrode, so as to obtain a to-be-soldered piece, and performing solid-phase sintering;
the solid phase sintering process comprises the following steps: at a vacuum degree of 5X 10 -3 Under Pa, 5MPa pressure is applied to a piece to be welded, the temperature is raised to 500 ℃ and kept for 10min, and the piece to be welded is cooled along with a furnace;
the embodiment realizes the connection of the thermoelectric material and the supersaturated solid solution blocking layer by one-time hot-pressing sintering, and then adopts the nano silver soldering paste to carry out solid-phase sintering connection on the thermoelectric material and the Cu electrode, thereby realizing the reliable connection of the thermoelectric material and the Cu electrode and effectively blocking the element diffusion between the thermoelectric material and the Cu; the shear strength of the obtained joint can reach 17MPa, and the contact resistance is less than 5 mu omega cm after aging for 600 hours at 550 DEG C 2 。

Claims (10)

1. A connection method of skutterudite thermoelectric material and copper electrode with Fe-Cr-Mo/W as barrier layer is characterized in that: the connection method of skutterudite thermoelectric material and copper electrode with Fe-Cr-Mo/W as barrier layer is carried out according to the following steps:
1. firstly cutting a skutterudite thermoelectric material, sequentially polishing, ultrasonically cleaning with alcohol and ultrasonically cleaning with acetone on a surface to be welded of the skutterudite thermoelectric material step by step, and then storing in an inert gas atmosphere; polishing and ultrasonically cleaning a surface to be welded of the copper electrode, drying to obtain the copper electrode to be welded, and storing in an inert atmosphere;
2. weighing raw materials according to the atomic percentage of the barrier layer, placing the raw materials into a vacuum arc melting furnace for arc melting, and then carrying out suction casting into a water-cooling copper mold die for rapid solidification to obtain a supersaturated solid solution barrier layer cast ingot with uniform components; cutting the supersaturated solid solution barrier layer cast ingot into slices, polishing, cleaning and blow-drying in sequence to obtain a barrier layer slice for later use;
the barrier layer consists of 10-19.9% of Cr, 0.1-10% of Mo or W and the balance of Fe according to the atomic percentage, and the sum of the atomic percentages of Cr, mo and Cr and W is 20%;
the speed of rapid solidification is at least 1000 ℃/min;
3. placing the barrier layer sheet between the skutterudite thermoelectric material processed in the first step and the surface to be welded of the copper electrode to be welded for assembly, so as to obtain a connecting piece to be welded; the to-be-welded connecting piece is welded at the position of 1 multiplied by 10 -4 -5×10 -3 And simultaneously applying welding pressure of 10-30MPa under the vacuum environment of Pa, heating to 550-650 ℃, preserving heat and pressure for 3-30min, and then slowly cooling to room temperature to complete the connection of the skutterudite thermoelectric material and the copper electrode.
2. The method for connecting a skutterudite thermoelectric material with a copper electrode using Fe-Cr-Mo/W as a barrier layer according to claim 1, characterized in that: step one, the ultrasonic cleaning time of the alcohol is 10min; the ultrasonic cleaning time of the acetone is 10min.
3. The method for connecting a skutterudite thermoelectric material with a copper electrode using Fe-Cr-Mo/W as a barrier layer according to claim 1, characterized in that: and step two, the raw materials are pure Fe, pure Cr, pure Mo, pure W, crMo or CrW.
4. The method for connecting a skutterudite thermoelectric material with a copper electrode using Fe-Cr-Mo/W as a barrier layer according to claim 1, characterized in that: the arc melting process comprises the following steps: the electric arc melting current is 130A, each time of melting is conducted for 20s, the material is turned over once by a ladle after each time of melting is finished, and the melting is repeated for at least 5 times.
5. The method for connecting a skutterudite thermoelectric material with a copper electrode using Fe-Cr-Mo/W as a barrier layer according to claim 1, characterized in that: and step two, the thickness of the barrier layer sheet is 100-300 mu m.
6. A connection method of skutterudite thermoelectric material and copper electrode with Fe-Cr-Mo/W as barrier layer is characterized in that: the connection method of skutterudite thermoelectric material and copper electrode with Fe-Cr-Mo/W as barrier layer is carried out according to the following steps:
1. weighing raw materials according to the atomic percentage of the barrier layer, placing the raw materials into a vacuum arc melting furnace for arc melting or vacuum induction melting, and then carrying out suction casting into a water-cooling copper mold die for rapid solidification to obtain a supersaturated solid solution barrier layer cast ingot with uniform components; cutting the supersaturated solid solution barrier layer cast ingot into slices, polishing, cleaning and blow-drying in sequence to obtain a barrier layer slice for later use; polishing and ultrasonically cleaning a surface to be welded of the copper electrode, drying to obtain the copper electrode to be welded, and storing in an inert atmosphere;
the barrier layer consists of 10-19.9% of Cr, 0.1-10% of Mo or W and the balance of Fe according to the atomic percentage, and the sum of the atomic percentages of Cr, mo and Cr and W is 20%;
the speed of the rapid solidification is at least 1000 ℃/min;
2. placing a barrier layer sheet in a graphite mold filled with skutterudite thermoelectric material powder to be welded, covering the skutterudite thermoelectric material powder with the barrier layer sheet, performing hot-pressing sintering on the barrier layer and the thermoelectric material powder, and cooling along with a furnace to obtain a thermoelectric material with the barrier layer; cutting, polishing step by step, cleaning to obtain a thermoelectric material to be welded, and storing in an inert gas environment for later use; the hot-press sintering process parameters are determined according to the type factors of the thermoelectric materials;
the particle size of the thermoelectric material powder is not more than 10 μm;
3. placing a layer of brazing filler metal between the barrier layer of the to-be-welded thermoelectric material obtained in the second step and the copper electrode, wherein the barrier layer of the to-be-welded thermoelectric material faces the to-be-welded surface of the copper electrode, so as to obtain a to-be-welded piece, and brazing; or arranging nano silver soldering paste between the barrier layer of the to-be-soldered thermoelectric material obtained in the second step and the copper electrode, wherein the barrier layer of the to-be-soldered thermoelectric material faces the to-be-soldered surface of the copper electrode, so as to obtain a to-be-soldered piece, and performing solid-phase sintering.
7. The method for connecting a skutterudite thermoelectric material with a copper electrode using Fe-Cr-Mo/W as a barrier layer according to claim 6, wherein: the arc melting process comprises the following steps: the electric arc melting current is 130A, each time of melting is conducted for 20s, the material is turned over once by a ladle after each time of melting is finished, and the melting is repeated for at least 5 times.
8. The method for connecting a skutterudite thermoelectric material with a copper electrode using Fe-Cr-Mo/W as a barrier layer according to claim 6, wherein: the raw materials in the first step are pure Fe, pure Cr, pure Mo, pure W, crMo or CrW.
9. The method for connecting a skutterudite thermoelectric material with a copper electrode using Fe-Cr-Mo/W as a barrier layer according to claim 6, wherein: the solid phase sintering process comprises the following steps: at a vacuum degree of 1X 10 -4 -5×10 -3 And under Pa, applying 0.5-10MPa pressure to the to-be-welded piece, heating to 200-500 ℃, preserving heat for 5-30min, and cooling along with the furnace.
10. The method for connecting a skutterudite thermoelectric material with a copper electrode using Fe-Cr-Mo/W as a barrier layer according to claim 6, wherein: the brazing process comprises the following steps: at a vacuum degree of 1X 10 -4 -5×10 -3 Heating to 650-700 deg.C at 5-15 deg.C/min under Pa, maintaining for 3-10min, cooling with furnace, and cooling at 2-10 deg.C/min.
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