Method for connecting skutterudite thermoelectric material and electrode by using Al-containing high-entropy alloy barrier layer

Abstract

The invention discloses a method for connecting a skutterudite thermoelectric material and an electrode by using a novel Al-containing high-entropy alloy diffusion barrier layer, and relates to the design and preparation of the diffusion barrier layer and the method for connecting the skutterudite thermoelectric material and the electrode. The method aims at solving the problems that diffusion cavities are huge due to unbalanced diffusion in a connector interface obtained through an existing skutterudite thermoelectric material welding method, and consequently a connecting connector is difficult to consider heat stability, interface resistance and mechanical performance at the same time. The method comprises the following steps: 1, cleaning a skutterudite thermoelectric material and an electrode; 2, preparing a diffusion barrier layer by using an electric arc melting or high-energy ball milling or rapid solidification method, and carrying out diffusion welding or brazing; and the diffusion barrier layer is made of an Al-Co-Cr-Fe-Ni system. The joint obtained by utilizing the novel Al-containing high-entropy alloy diffusion barrier layer can simultaneously have extremely low contact resistance, extremely high thermal stability and excellent mechanical properties. The method is suitable for connecting the skutterudite thermoelectric material and the electrode.

Description

Technical Field

[0001] The invention relates to a method for preparing a novel Al-containing high-entropy alloy barrier layer and connecting a skutterudite thermoelectric material and an electrode. Background Art

[0002] Thermoelectric materials can use the thermoelectric effect to achieve direct solid-state conversion between thermal energy and electrical energy. Among them, skutterudite thermoelectric materials have both good thermoelectric properties and mechanical stability, and are one of the most promising thermoelectric materials in the medium temperature range. In practical applications, skutterudite thermoelectric materials need to be connected to electrodes to form thermoelectric devices to achieve heat and electricity conversion, and are widely used in automotive, aviation, aerospace and other fields. In the process of connecting thermoelectric materials to electrodes, there are problems such as contact effect, element diffusion and thermal expansion coefficient matching. It is necessary to select a suitable diffusion barrier layer to obtain lower contact resistance, more stable connection interface and higher mechanical properties, so as to achieve long-term service of thermoelectric devices at high temperatures.

[0003] In terms of the types of diffusion barriers, there are currently mainly: the first is a pure metal barrier, such as Ti, Co, Nb, etc.; the second is an alloy barrier, such as CoMo alloy, Ni-Cr-Cu alloy, etc. Although pure metals, alloys, and multilayer barriers of the combination of the two can slow down the diffusion of atoms in the interface to a certain extent, they cannot solve the problem of diffusion voids introduced by non-equilibrium diffusion in the interface, and the microstructure of the joint is complex. At present, research mainly uses pure metals and alloys as barrier layers. The degree of freedom in the design of barrier properties is very low, and it is difficult to simultaneously regulate the diffusion and reaction in the interface, the microstructure and stress distribution, and it cannot meet the high requirements of the interface thermal stability, electrical properties and mechanical properties of thermoelectric devices for long-term service at high temperatures.

[0004] High entropy alloy is a multi-principal (five or more) solid solution alloy, in which the alloy elements are not simply mixed. The low system free energy, lattice distortion effect and diffusion hysteresis effect brought by its high entropy effect can effectively inhibit the diffusion of joint elements, prevent the formation of brittle intermetallic compounds, and improve the joint performance. The "cocktail" effect can achieve the synergy of multiple performances by changing the element ratio, while improving the matching of the thermal expansion coefficient between the skutterudite thermoelectric material and the electrode, and improving the mechanical properties of the joint. Different from traditional pure metals and alloys, high entropy alloys as diffusion barriers can achieve the coordinated regulation of joint interface diffusion and reaction, microstructure and mechanical properties. Although some studies have used CoCrFeNi quaternary alloys and FeCoNiCrMo high entropy alloys as intermediate layers to connect skutterudites and electrodes, the diffusion barrier effect of the two is still limited, the interface resistivity is still high, and there is a lack of experimental data on the mechanical properties of the joint. Among them, FeCoNiCrMo high entropy alloys have poor deformation ability and it is difficult to relieve the residual stress of the joint, which will lead to poor mechanical properties of the joint. Therefore, there is no report on the successful welding of skutterudite thermoelectric materials and metal or alloy electrodes by introducing a single-layer high-entropy alloy diffusion barrier layer to obtain an electrical connection joint with high thermal stability, extremely low interface resistance and high mechanical properties under long-term service at working temperature. Summary of the invention

[0005] The present invention aims to solve the problem that existing pure metal, alloy and high entropy alloy barrier layers are difficult to simultaneously achieve high thermal stability, extremely low interface resistance and high mechanical properties of the connection joints between skutterudite thermoelectric materials and electrodes, and proposes a method for connecting skutterudite thermoelectric materials and electrodes using a new type of Al-containing high entropy alloy diffusion barrier layer.

[0006] The method of connecting the skutterudite thermoelectric material and the electrode by using a novel high entropy alloy diffusion barrier layer containing Al is carried out in the following steps:

[0007] 1. Clean the cobalt ore thermoelectric material and the welding surface of the electrode;

[0008] 2. preparing a high entropy alloy diffusion barrier layer by arc melting, high energy ball milling or rapid solidification, preparing a diffusion barrier layer on the surface of an electrode, or preparing a diffusion barrier layer on the surface of a skutterudite thermoelectric material; then stacking the obtained electrode and the skutterudite thermoelectric material with the diffusion barrier layer facing inward to obtain a workpiece to be welded; and performing diffusion welding on the workpiece to be welded;

[0009] Alternatively, a diffusion barrier layer is prepared by arc melting, high-energy ball milling or rapid solidification, and a diffusion barrier layer is prepared on the surface of the skutterudite thermoelectric material; an electrode and the skutterudite thermoelectric material are stacked with the diffusion barrier layer facing inward, and a brazing material is placed between the skutterudite thermoelectric material and the electrode to obtain a workpiece to be welded; and the workpiece to be welded is brazed;

[0010] The material of the high entropy alloy diffusion barrier layer is Al x Co y Cr z Fe r Ni m , x, y, z, r, and m in the diffusion barrier intermediate layer are 0~2.

[0011] The principles and beneficial effects of the present invention are:

[0012] The present invention utilizes a single-layer high-entropy alloy containing Al as a diffusion barrier layer to achieve matching of the thermal expansion coefficients between the skutterudite thermoelectric material and the electrode, while effectively blocking the mutual diffusion of elements between the skutterudite thermoelectric material and the electrode, and effectively suppressing diffusion voids caused by non-equilibrium diffusion in the interface. The resulting joint has extremely low interface resistivity, high thermal stability and high mechanical properties.

[0013] The reason for achieving thermal expansion coefficient matching and high mechanical properties is that the "cocktail" effect of Al-containing high entropy alloys can achieve synergy of multiple performances by changing the element ratio, while improving the matching of thermal expansion coefficients between skutterudite thermoelectric materials and electrodes. x The distribution range of thermal expansion coefficient of CoCrFeNi high entropy alloy with Al content is 8.84~11.25×10 -6 K -1 , can cover the P type 10~12×10 -6 K -1 and N type 8~10×10 -6 K -1 The range of thermal expansion coefficient variation. Al-containing high entropy alloys have very low yield strength and excellent deformability, for example, Al 0.1 The yield strength of CoCrFeNi high entropy alloy at room temperature and 600℃ is only 300MPa and 120MPa respectively, and the elongation at 500℃ can reach 40%. Therefore, Al-containing high entropy alloy as the connecting intermediate layer between skutterudite and electrode can effectively release the thermal stress in the joint through plastic deformation. Combined with excellent thermal expansion coefficient matching, the stress size and distribution of the joint can be regulated, effectively improving the mechanical strength of the joint.

[0014] The reason for blocking the mutual diffusion of elements between the skutterudite thermoelectric material and the electrode is that the diffusion barrier intermediate layer material used in the present invention is an Al-containing high entropy alloy, which has low system free energy, lattice distortion effect and diffusion hysteresis effect, which can effectively inhibit the diffusion of joint elements, reduce the degree of non-equilibrium diffusion in the interface, prevent the generation and growth of diffusion voids in the joint, and improve the electrical and mechanical properties of the joint.

[0015] The reasons for low interfacial resistivity and high thermal stability are: the reaction product between the Al-containing high entropy alloy barrier layer and the skutterudite thermoelectric material is single, and the reaction product is a metal-like compound with high electrical conductivity, and the interface barrier between the Al-containing high entropy alloy barrier layer, the interface product and the skutterudite is low, so the interface resistance of the joint is extremely low. Combined with the high entropy retardation mechanism of the above-mentioned element interdiffusion, the growth of the interface reaction product can be effectively inhibited, thereby obtaining high thermal stability in microstructure and electrical properties.

[0016] The present invention adopts arc melting or high-energy ball milling or rapid solidification method suitable for large-scale production method to prepare Al-containing high entropy alloy diffusion barrier layer, realizes direct welding of skutterudite thermoelectric material and metal or alloy electrode, and the process control is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a photograph of the joint structure obtained in Example 1;

[0018] Figure 2 This is the EDS line scan of the joint obtained in Example 1;

[0019] Figure 3 is the interfacial resistance of the joint obtained in Example 1. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any reasonable combination of the specific implementation modes.

[0021] Specific implementation method 1: In this implementation method, the method of connecting the skutterudite thermoelectric material and the electrode using a new type of high entropy alloy diffusion barrier layer containing Al is carried out in the following steps:

[0022] 1. Clean the cobalt ore thermoelectric material and the welding surface of the electrode;

[0023] 2. Prepare a diffusion barrier layer of a high entropy alloy containing Al by arc melting, high-energy ball milling or rapid solidification, prepare a diffusion barrier layer on the surface of an electrode, or prepare a diffusion barrier layer on the surface of a skutterudite thermoelectric material; then stack the obtained electrode and the skutterudite thermoelectric material with the diffusion barrier layer facing inward to obtain a workpiece to be welded; and perform diffusion welding on the workpiece to be welded;

[0024] Alternatively, a diffusion barrier layer is prepared by arc melting, high-energy ball milling or rapid solidification, and a diffusion barrier layer is prepared on the surface of the skutterudite thermoelectric material; an electrode and the skutterudite thermoelectric material are stacked with the diffusion barrier layer facing inward, and a brazing material is placed between the skutterudite thermoelectric material and the electrode to obtain a workpiece to be welded; and the workpiece to be welded is brazed;

[0025] The material of the high entropy alloy diffusion barrier layer is Al x Coy Cr z Fe r Ni m , x, y, z, r, and m in the diffusion barrier intermediate layer are 0~2.

[0026] This embodiment uses a single layer of Al-containing high entropy alloy as a diffusion barrier layer to achieve matching of thermal expansion coefficients between the skutterudite thermoelectric material and the electrode, while effectively blocking the mutual diffusion of elements between the skutterudite thermoelectric material and the electrode, effectively suppressing diffusion voids caused by non-equilibrium diffusion within the interface, and the resulting joint has extremely low interface resistivity, high thermal stability and high mechanical properties.

[0027] The reason for achieving thermal expansion coefficient matching and high mechanical properties is that the "cocktail" effect of Al-containing high entropy alloys can achieve synergy of multiple performances by changing the element ratio, while improving the matching of thermal expansion coefficients between skutterudite thermoelectric materials and electrodes. x The distribution range of thermal expansion coefficient of CoCrFeNi high entropy alloy with Al content is 8.84~11.25×10 -6 K -1 , can cover the P type 10~12×10 -6 K -1 and N type 8~10×10 -6 K -1 The range of thermal expansion coefficient variation. Al-containing high entropy alloys have very low yield strength and excellent deformability, for example, Al 0.1 The yield strength of CoCrFeNi high entropy alloy at room temperature and 600℃ is only 300MPa and 120MPa respectively, and the elongation at 500℃ can reach 40%. Therefore, Al-containing high entropy alloy as the connecting intermediate layer between skutterudite and electrode can effectively release the thermal stress in the joint through plastic deformation. Combined with excellent thermal expansion coefficient matching, the stress size and distribution of the joint can be regulated, effectively improving the mechanical strength of the joint.

[0028] The reason for blocking the mutual diffusion of elements between the skutterudite thermoelectric material and the electrode is that the diffusion barrier intermediate layer material used in the present invention is an Al-containing high entropy alloy, which has low system free energy, lattice distortion effect and diffusion hysteresis effect, which can effectively inhibit the diffusion of joint elements, reduce the degree of non-equilibrium diffusion in the interface, prevent the generation and growth of diffusion voids in the joint, and improve the electrical and mechanical properties of the joint.

[0029] The reasons for low interfacial resistivity and high thermal stability are: the reaction product between the Al-containing high entropy alloy barrier layer and the skutterudite thermoelectric material is single, and the reaction product is a metal-like compound with high electrical conductivity, and the interface barrier between the Al-containing high entropy alloy barrier layer, the interface product and the skutterudite is low, so the interface resistance of the joint is extremely low. Combined with the high entropy retardation mechanism of the above-mentioned element interdiffusion, the growth of the interface reaction product can be effectively inhibited, thereby obtaining high thermal stability in microstructure and electrical properties.

[0030] This embodiment adopts arc melting or high-energy ball milling or rapid solidification method suitable for large-scale production method to prepare Al-containing high entropy alloy diffusion barrier layer, realizes direct welding of skutterudite thermoelectric material and metal or alloy electrode, and the process control is simple.

[0031] Specific implementation method 2: This implementation method is different from specific implementation method 1 in that: the cleaning process in step 1 is: first rinse with anhydrous ethanol, then ultrasonically clean in acetone for 5 to 30 minutes, and finally air-dry.

[0032] Specific implementation method three: This implementation method is different from specific implementation methods one or two in that: the electrode in step one is a metal electrode or an alloy electrode;

[0033] The metal electrode is made of Co, Cr, Fe, Ni or Cu;

[0034] The alloy electrode is made of Co-based alloy, Cr-based alloy, Fe-based alloy, Ni-based alloy, or Cu-based alloy;

[0035] The Co-based alloy is CoMo, CoW, CoCr, CoFe or CoNi; the Cr-based alloy is CrMo, CrW, CrFeNi or CrCoNi; the Fe-based alloy is FeMo, FeW, FeCr or FeCoNi; the Ni-based alloy is NiMo, NiW or NiCr; and the Cu-based alloy is CuMo or CuW.

[0036] Specific embodiment 4: This embodiment is different from one of the specific embodiments 1 to 3 in that: the diffusion barrier intermediate layer in step 2 is made of Al x Co y Cr z Fe r Ni m , x, y, z, r, and m in the diffusion barrier intermediate layer are 0~2.

[0037] Specific implementation mode 5: This implementation mode is different from any one of specific implementation modes 1 to 4 in that: the thickness of the diffusion barrier intermediate layer in step 2 is 1-500 μm.

[0038] Specific embodiment 6: This embodiment is different from the specific embodiments 1 to 5 in that: the molecular formula of the skutterudite thermoelectric material in step 1 is R r T t X x , wherein: R is one or more elements of alkali metal, alkaline earth metal, rare earth metal or third main group element; T is one or more elements of Cr, Mn, Fe, Co, Ni, Ru, Os, Rh, Ir, Pt or Au; X is one or more elements of P, As, Sb, Bi, Se, Te, Si, Ge, Sn, Ga or In; 0 <r≤1,t=4,11.8≤x≤12.4。

[0039] Specific embodiment 7: This embodiment is different from any one of the specific embodiments 1 to 6 in that: the brazing process in step 2 is: the vacuum pressure in the vacuum heating furnace is less than 2×10 -3 Pa, the pressure applied to the workpiece during welding is 0.003~0.1MPa, first heated to 550~650℃ at a rate of 5~30℃ / min and kept warm for 1~40min, then cooled to 50~100℃ at a rate of 2~5℃ / min, and then cooled to room temperature with the furnace.

[0040] Specific embodiment 8: This embodiment differs from any one of specific embodiments 1 to 7 in that: the diffusion welding process described in step 2 is: the diffusion welding is carried out in a heating furnace, the atmosphere of the heating furnace is a vacuum or Ar gas protective atmosphere, and the vacuum pressure of the furnace chamber is less than 2×10 -3 Pa, when the heating furnace is Ar gas protective atmosphere, the Ar gas pressure is -0.5Mpa; during welding, the pressure applied to the workpiece to be welded is 5~20Mpa, first heated to 550~650℃ at a rate of 5~30℃ / min and kept warm for 1~40min, then cooled to 50~100℃ at a rate of 2~5℃ / min, and then cooled to room temperature with the furnace.

[0041] Specific embodiment 9: This embodiment is different from any one of specific embodiments 1 to 8 in that: the solder described in step 2 is an Ag-based solder or an Al-based solder having a liquidus at 550° C. to 650° C.

[0042] Embodiment 1:

[0043] The method of connecting the skutterudite thermoelectric material and the electrode using the Al-containing novel high entropy alloy diffusion barrier layer in this embodiment is carried out in the following steps:

[0044] 1. Clean the skutterudite thermoelectric material and the surface to be welded of the electrode; the skutterudite thermoelectric material is Yb 0.35 Co 4 Sb 12 , the electrode is a CuW electrode;

[0045] The cleaning process in step 1 is: first rinse with anhydrous ethanol, then ultrasonically clean in acetone for 15 minutes, and finally air dry;

[0046] 2. High-entropy alloy powder is prepared by high-energy ball milling, and a diffusion barrier layer is prepared on the surface of the electrode; the obtained electrode and the skutterudite thermoelectric material are then stacked with the diffusion barrier layer facing inward to obtain a workpiece to be welded; and diffusion welding is performed on the workpiece to be welded;

[0047] The diffusion barrier intermediate layer in step 2 is made of Al x CoCrFeNi; x is 0.1 in the diffusion barrier interlayer;

[0048] The thickness of the diffusion barrier intermediate layer in step 2 is 300 μm.

[0049] The diffusion welding process described in step 2 is as follows: the diffusion welding is carried out in a heating furnace, the atmosphere of the heating furnace is an Ar gas protective atmosphere, and the Ar gas pressure is -0.5Mpa; the pressure applied to the workpiece to be welded during welding is 60Mpa, first heated to 700°C at a rate of 110°C / min, 50°C / min, and 25°C / min and kept warm for 10min, then cooled to 50°C at a rate of 30°C / min, and then cooled to room temperature with the furnace.

[0050] Figure 1 is a photo of the joint structure obtained in Example 1; Figure 1 As shown, Yb 0.35 Co 4 Sb 12 The skutterudite thermoelectric material and the CuW alloy electrode joint are well combined without any interface defects. The diffusion barrier layer Al 0.1 CoCrFeNi effectively blocks the diffusion of Cu in the electrode into skutterudite, and the Yb and Sb atoms in the skutterudite matrix are effectively blocked from the Yb 0.35 Co 4 Sb 12 Skutterudite thermoelectric material side.

[0051] Figure 2 This is the EDS line scan image of the joint obtained in Example 1. Figure 2 It can be seen that the joint is well bonded without any interface defects, and the Yb and Sb elements filled in the skutterudite parent material are effectively blocked by the Yb 0.35 Co 4 Sb 12 Skutterudite thermoelectric material side.

[0052] Figure 3 is the interface resistance of the joint obtained in Example 1. 0.35 Co4 Sb 12 The skutterudite thermoelectric material and the CuW alloy electrode joint are well bonded, and the interface resistivity of the joint is 0.98μΩcm 2 The shear strength of the joint is 38MPa. After annealing at 550℃ for 384h, the joint is well bonded, and the interface resistivity of the joint is only 2.36μΩcm 2 , the shear strength of the joint is 30MPa.

[0053] Embodiment 2:

[0054] The method of connecting the skutterudite thermoelectric material and the electrode using the Al-containing novel high entropy alloy diffusion barrier layer in this embodiment is carried out in the following steps:

[0055] 1. Clean the skutterudite thermoelectric material and the surface to be welded of the electrode; the skutterudite thermoelectric material is La 0.8 Ti 0.1 Ga 0.1 Fe 3 oeLh 12 , the electrode is a CuW electrode;

[0056] The cleaning process in step 1 is: first rinse with anhydrous ethanol, then ultrasonically clean in acetone for 15 minutes, and finally air dry;

[0057] 2. High-entropy alloy powder is prepared by high-energy ball milling, and a diffusion barrier layer is prepared on the surface of the electrode; the obtained electrode and the skutterudite thermoelectric material are then stacked with the diffusion barrier layer facing inward to obtain a workpiece to be welded; and diffusion welding is performed on the workpiece to be welded;

[0058] The diffusion barrier intermediate layer in step 2 is made of Al x CoCrFeNi; x is 0.3 in the diffusion barrier interlayer;

[0059] The thickness of the diffusion barrier intermediate layer in step 2 is 250 μm.

[0060] The diffusion welding process described in step 2 is as follows: the diffusion welding is carried out in a heating furnace, the atmosphere of the heating furnace is an Ar gas protective atmosphere, and the Ar gas pressure is -0.5 MPa; the pressure applied to the workpiece to be welded during welding is 55 MPa, first heated to 690°C at a rate of 110°C / min, 50°C / min, and 25°C / min and kept warm for 10 minutes, then cooled to 50°C at a rate of 30°C / min, and then cooled to room temperature with the furnace.

[0061] After testing, La 0.8 Ti 0.1 Ga 0.1 Fe 3 oeLh 12The skutterudite thermoelectric material and the CuW alloy electrode joint are well bonded, and the interface resistivity of the joint is 0.95μΩcm 2 The shear strength of the joint is 37MPa. After annealing at 550℃ for 384h, the joint is well bonded, and the interface resistivity of the joint is only 2.74μΩcm 2 , the shear strength of the joint is 28MPa.

[0062] Embodiment 3:

[0063] The method of connecting the skutterudite thermoelectric material and the electrode using the Al-containing novel high entropy alloy diffusion barrier layer in this embodiment is carried out in the following steps:

[0064] 1. Clean the skutterudite thermoelectric material and the surface to be welded of the electrode; the skutterudite thermoelectric material is Yb 0.35 Co 4 Sb 12 , the electrode is a CuMo electrode;

[0065] The cleaning process in step 1 is: first rinse with anhydrous ethanol, then ultrasonically clean in acetone for 25 minutes, and finally air dry;

[0066] 2. High-entropy alloy powder is prepared by high-energy ball milling, and a diffusion barrier layer is prepared on the surface of the electrode; the obtained electrode and the skutterudite thermoelectric material are then stacked with the diffusion barrier layer facing inward to obtain a workpiece to be welded; and diffusion welding is performed on the workpiece to be welded;

[0067] The diffusion barrier intermediate layer in step 2 is made of AlCo y CrFeNi; y is 0.5 in the diffusion barrier intermediate layer;

[0068] The thickness of the diffusion barrier intermediate layer in step 2 is 300 μm.

[0069] The diffusion welding process described in step 2 is: diffusion welding is carried out in a heating furnace, the atmosphere of the heating furnace is an Ar gas protective atmosphere, and the Ar gas pressure is -0.5Mpa; the pressure applied to the workpiece to be welded during welding is 60Mpa, first heated to 710℃ at a rate of 110℃ / min, 50℃ / min, and 25℃ / min and kept warm for 10min, then cooled to 50℃ at a rate of 30℃ / min, and then cooled to room temperature with the furnace.

[0070] After testing, the skutterudite thermoelectric material and the alloy electrode joint in this embodiment are well combined without any interface defects. The diffusion barrier layer AlCo 0.5 CrFeNi effectively blocks the diffusion of Cu in the electrode into skutterudite, and the Yb and Sb atoms in the skutterudite matrix are effectively blocked from the Yb 0.35 Co 4 Sb12 On the skutterudite thermoelectric material side, the interface resistivity of the joint is 1.08μΩcm 2 The shear strength of the joint is 35MPa. After annealing at 550℃ for 384h, the joint is well bonded, and the interface resistivity of the joint is only 2.94μΩcm 2 , the shear strength of the joint is 27MPa.

[0071] Embodiment 4:

[0072] The method of connecting the skutterudite thermoelectric material and the electrode using the Al-containing novel high entropy alloy diffusion barrier layer in this embodiment is carried out in the following steps:

[0073] 1. Clean the skutterudite thermoelectric material and the surface to be welded of the electrode; the skutterudite thermoelectric material is La 0.8 Ti 0.1 Ga 0.1 Fe 3 oeLh 12 , the electrode is a CuMo electrode;

[0074] The cleaning process in step 1 is: first rinse with anhydrous ethanol, then ultrasonically clean in acetone for 25 minutes, and finally air dry;

[0075] 2. High-entropy alloy powder is prepared by high-energy ball milling, and a diffusion barrier layer is prepared on the surface of the electrode; the obtained electrode and the skutterudite thermoelectric material are then stacked with the diffusion barrier layer facing inward to obtain a workpiece to be welded; and diffusion welding is performed on the workpiece to be welded;

[0076] The diffusion barrier intermediate layer in step 2 is made of AlCoCr z FeNi; z is 0.75 in the diffusion barrier interlayer;

[0077] The thickness of the diffusion barrier intermediate layer in step 2 is 300 μm.

[0078] The diffusion welding process described in step 2 is as follows: the diffusion welding is carried out in a heating furnace, the atmosphere of the heating furnace is an Ar gas protective atmosphere, and the Ar gas pressure is -0.5Mpa; the pressure applied to the workpiece to be welded during welding is 60Mpa, first heated to 700°C at a rate of 110°C / min, 50°C / min, and 25°C / min and kept warm for 15 minutes, then cooled to 50°C at a rate of 30°C / min, and then cooled to room temperature with the furnace.

[0079] After testing, La 0.8 Ti 0.1 Ga 0.1 Fe 3 oeLh 12 The skutterudite thermoelectric material and the CuMo alloy electrode joint are well bonded, and the interface resistivity of the joint is 0.94μΩcm2 The shear strength of the joint is 39MPa. After annealing at 550℃ for 384h, the joint is well bonded, and the interface resistivity of the joint is only 2.35μΩcm 2 , the shear strength of the joint is 32MPa.

[0080] Embodiment 5:

[0081] The method of connecting the skutterudite thermoelectric material and the electrode using the Al-containing novel high entropy alloy diffusion barrier layer in this embodiment is carried out in the following steps:

[0082] 1. Clean the skutterudite thermoelectric material and the surface to be welded of the electrode; the skutterudite thermoelectric material is Yb 0.35 Co 4 Sb 12 , the electrode is a CuW electrode;

[0083] The cleaning process in step 1 is: first rinse with anhydrous ethanol, then ultrasonically clean in acetone for 15 minutes, and finally air dry;

[0084] 2. High-entropy alloy powder was prepared by high-energy ball milling, and a diffusion barrier layer was prepared on the surface of the skutterudite thermoelectric material; the electrode and the skutterudite thermoelectric material were stacked with the diffusion barrier layer facing inward, and Ag-Cu-In-Sn brazing material was placed between the skutterudite thermoelectric material and the electrode to obtain a workpiece to be welded; the workpiece to be welded was brazed; the mass fractions of Ag, Cu, In, and Sn in the Ag-Cu-In-Sn brazing material were 57.6%, 22.4%, 8%, and 12%, respectively;

[0085] The diffusion barrier intermediate layer in step 2 is made of Al x CoCrFeNi; x is 0.1 in the diffusion barrier interlayer;

[0086] The thickness of the diffusion barrier intermediate layer in step 2 is 200 μm.

[0087] The brazing process in step 2 is as follows: the vacuum pressure in the vacuum heating furnace is less than 2×10 -3 Pa, the pressure applied to the workpiece during welding is 0.05MPa, first heated to 695℃ at a rate of 30℃ / min and kept warm for 10min, then cooled to 100℃ at a rate of 5℃ / min, and then cooled to room temperature with the furnace.

[0088] After testing, Yb 0.35 Co 4 Sb 12 The skutterudite thermoelectric material and the CuW alloy electrode joint are well combined without any interface defects. The diffusion barrier layer Al 0.1CoCrFeNi effectively blocks the diffusion of Cu in the electrode into skutterudite, and the Yb and Sb atoms in the skutterudite matrix are effectively blocked from the Yb 0.35 Co 4 Sb 12 On the skutterudite thermoelectric material side, the interface resistivity of the joint is 0.97μΩcm 2 The shear strength of the joint is 36MPa. After annealing at 550℃ for 384h, the joint is well bonded, and the interface resistivity of the joint is only 2.41μΩcm 2 , the shear strength of the joint is 30MPa.

[0089] Embodiment 6:

[0090] The method of connecting the skutterudite thermoelectric material and the electrode using the Al-containing novel high entropy alloy diffusion barrier layer in this embodiment is carried out in the following steps:

[0091] 1. Clean the skutterudite thermoelectric material and the surface to be welded of the electrode; the skutterudite thermoelectric material is La 0.8 Ti 0.1 Ga 0.1 Fe 3 oeLh 12 , the electrode is a CuMo electrode;

[0092] The cleaning process in step 1 is: first rinse with anhydrous ethanol, then ultrasonically clean in acetone for 20 minutes, and finally air dry;

[0093] 2. High-entropy alloy powder was prepared by high-energy ball milling, and a diffusion barrier layer was prepared on the surface of the skutterudite thermoelectric material; the electrode and the skutterudite thermoelectric material were stacked with the diffusion barrier layer facing inward, and Ag-Cu-In-Sn brazing material was placed between the skutterudite thermoelectric material and the electrode to obtain a workpiece to be welded; the workpiece to be welded was brazed; the mass fractions of Ag, Cu, In, and Sn in the Ag-Cu-In-Sn brazing material were 57.6%, 22.4%, 8%, and 12%, respectively;

[0094] Step 2: The diffusion barrier intermediate layer is made of AlCoCrFe r Ni; r is 0.5 in the diffusion barrier intermediate layer;

[0095] The thickness of the diffusion barrier intermediate layer in step 2 is 200 μm.

[0096] The brazing process in step 2 is as follows: the vacuum pressure in the vacuum heating furnace is less than 2×10 -3 Pa, the pressure applied to the workpiece during welding is 0.1MPa, first heated to 700℃ at a rate of 30℃ / min and kept warm for 5min, then cooled to 100℃ at a rate of 5℃ / min, and then cooled to room temperature with the furnace.

[0097] After testing, La 0.8 Ti 0.1 Ga 0.1 Fe 3 oeLh 12 The skutterudite thermoelectric material and the CuMo alloy electrode joint are well bonded, and the interface resistivity of the joint is 1.02μΩcm 2 The shear strength of the joint is 35MPa. After annealing at 550℃ for 384h, the joint is well bonded, and the interface resistivity of the joint is only 2.48μΩcm 2 , the shear strength of the joint is 29MPa.

[0098] Embodiment 7:

[0099] The method of connecting the skutterudite thermoelectric material and the electrode using the Al-containing novel high entropy alloy diffusion barrier layer in this embodiment is carried out in the following steps:

[0100] 1. Clean the skutterudite thermoelectric material and the surface to be welded of the electrode; the skutterudite thermoelectric material is La 0.8 Ti 0.1 Ga 0.1 Fe 3 oeLh 12 , the electrode is a Cu electrode;

[0101] The cleaning process in step 1 is: first rinse with anhydrous ethanol, then ultrasonically clean in acetone for 20 minutes, and finally air dry;

[0102] 2. High-entropy alloy powder was prepared by high-energy ball milling, and a diffusion barrier layer was prepared on the surface of the skutterudite thermoelectric material; the electrode and the skutterudite thermoelectric material were stacked with the diffusion barrier layer facing inward, and Ag-Cu-In-Sn brazing filler metal was placed between the skutterudite thermoelectric material and the electrode to obtain a workpiece to be welded; the workpiece to be welded was brazed; the mass fractions of Ag, Cu, In, and Sn in the Ag-Cu-In-Sn brazing filler metal were 57.6%, 22.4%, 5%, and 15%, respectively;

[0103] The diffusion barrier intermediate layer in step 2 is made of AlCoCrFeNi m ; m is 0.75 in the diffusion barrier interlayer;

[0104] The thickness of the diffusion barrier intermediate layer in step 2 is 200 μm.

[0105] The brazing process in step 2 is as follows: the vacuum pressure in the vacuum heating furnace is less than 2×10 -3Pa, the pressure applied to the workpiece during welding is 0.05MPa, first heated to 690℃ at a rate of 30℃ / min and kept warm for 10min, then cooled to 100℃ at a rate of 3℃ / min, and then cooled to room temperature with the furnace.

[0106] After testing, La 0.8 Ti 0.1 Ga 0.1 Fe 3 oeLh 12 The skutterudite thermoelectric material and the Cu electrode joint are well bonded, and the interface resistivity of the joint is 1.15μΩcm 2 The shear strength of the joint is 37MPa. After annealing at 550℃ for 384h, the joint is well bonded, and the interface resistivity of the joint is only 2.99μΩcm 2 , the shear strength of the joint is 27MPa.

[0107] Embodiment 8:

[0108] The method of connecting the skutterudite thermoelectric material and the electrode using the Al-containing novel high entropy alloy diffusion barrier layer in this embodiment is carried out in the following steps:

[0109] 1. Clean the skutterudite thermoelectric material and the surface to be welded of the electrode; the skutterudite thermoelectric material is Co 4 Sb 12 , the electrode is a Cu electrode;

[0110] The cleaning process in step 1 is: first rinse with anhydrous ethanol, then ultrasonically clean in acetone for 25 minutes, and finally air dry;

[0111] 2. High-entropy alloy powder was prepared by high-energy ball milling, and a diffusion barrier layer was prepared on the surface of the skutterudite thermoelectric material; the electrode and the skutterudite thermoelectric material were stacked with the diffusion barrier layer facing inward, and Ag-Cu-Sn brazing material was placed between the skutterudite thermoelectric material and the electrode to obtain a workpiece to be welded; the workpiece to be welded was brazed; the mass fractions of Ag, Cu, and Sn in the Ag-Cu-Sn brazing material were 57.6%, 22.4%, and 20%, respectively;

[0112] The diffusion barrier intermediate layer in step 2 is made of Al x CoCrFeNi; x is 1 in the diffusion barrier interlayer;

[0113] The thickness of the diffusion barrier intermediate layer in step 2 is 300 μm.

[0114] The brazing process in step 2 is as follows: the vacuum pressure in the vacuum heating furnace is less than 2×10 -3Pa, the pressure applied to the workpiece during welding is 0.1MPa, first heated to 690℃ at a rate of 15℃ / min and kept warm for 15min, then cooled to 100℃ at a rate of 5℃ / min, and then cooled to room temperature with the furnace.

[0115] After testing, Co 4 Sb 12 The skutterudite thermoelectric material and the Cu electrode joint are well combined without any interface defects. The high entropy alloy diffusion barrier layer AlCoCrFeNi effectively blocks the diffusion of Cu elements in the electrode into skutterudite, while the Sb element in the skutterudite parent material is effectively blocked by Co 4 Sb 12 On the skutterudite thermoelectric material side, the interface resistivity of the joint is 1.02μΩcm 2 The shear strength of the joint is 35MPa. After annealing at 550℃ for 384h, the joint is well bonded, and the interface resistivity of the joint is only 2.84μΩcm 2 , the shear strength of the joint is 26MPa.

Claims

1. A method for connecting a skutterudite thermoelectric material and an electrode using a novel high entropy alloy diffusion barrier layer containing Al, characterized in that: The method proceeds as follows:

1. Clean the cobalt ore thermoelectric material and the welding surface of the electrode; 2. preparing a high entropy alloy diffusion barrier layer by arc melting, high energy ball milling or rapid solidification, preparing a diffusion barrier layer on the surface of an electrode, or preparing a diffusion barrier layer on the surface of a skutterudite thermoelectric material; then stacking the obtained electrode and the skutterudite thermoelectric material with the diffusion barrier layer facing inward to obtain a workpiece to be welded; and performing diffusion welding on the workpiece to be welded; Alternatively, a diffusion barrier layer is prepared by arc melting, high-energy ball milling or rapid solidification, and a diffusion barrier layer is prepared on the surface of the skutterudite thermoelectric material; an electrode and the skutterudite thermoelectric material are stacked with the diffusion barrier layer facing inward, and a brazing material is placed between the skutterudite thermoelectric material and the electrode to obtain a workpiece to be welded; and the workpiece to be welded is brazed; The material of the high entropy alloy diffusion barrier layer is Al x Co y Cr z Fe r Ni m , x, y, z, r, and m in the diffusion barrier intermediate layer are 0~2.

2. The method for connecting skutterudite thermoelectric material and electrode by using a novel high entropy alloy diffusion barrier layer containing Al according to claim 1, characterized in that: The cleaning process in step 1 is: first rinse with anhydrous ethanol, then ultrasonically clean in acetone for 5 to 30 minutes, and finally air dry.

3. The method for connecting skutterudite thermoelectric material and electrode by using a novel high entropy alloy diffusion barrier layer containing Al according to claim 1, characterized in that: In step 1, the electrode is a metal electrode or an alloy electrode.

4. The method for connecting skutterudite thermoelectric material and electrode by using a novel high entropy alloy diffusion barrier layer containing Al according to claim 3, characterized in that: The metal electrode is made of Co, Cr, Fe, Ni or Cu; the alloy electrode is made of Co-based alloy, Cr-based alloy, Fe-based alloy, Ni-based alloy or Cu-based alloy.

5. The method for connecting a skutterudite thermoelectric material and an electrode using a novel high entropy alloy diffusion barrier layer containing Al according to claim 4, characterized in that: The Co-based alloy is CoMo, CoW, CoCr, CoFe or CoNi; the Cr-based alloy is CrMo, CrW, CrFeNi or CrCoNi; the Fe-based alloy is FeMo, FeW, FeCr or FeCoNi; the Ni-based alloy is NiMo, NiW or NiCr; and the Cu-based alloy is CuMo or CuW.

6. The method for connecting skutterudite thermoelectric material and electrode by using a novel high entropy alloy diffusion barrier layer containing Al according to claim 1, characterized in that: The thickness of the diffusion barrier layer in step 2 is 1-500 μm.

7. The method for connecting skutterudite thermoelectric material and electrode by using a novel high entropy alloy diffusion barrier layer containing Al according to claim 1, characterized in that: The skutterudite thermoelectric material described in step 1 has a molecular formula of R r T t X x , wherein: R is one or more elements of alkali metal, alkaline earth metal, rare earth metal or third main group element; T is one or more elements of Cr, Mn, Fe, Co, Ni, Ru, Os, Rh, Ir, Pt or Au; X is one or more elements of P, As, Sb, Bi, Se, Te, Si, Ge, Sn, Ga or In; 0 <r≤1,t=4,11.8≤x≤12.4。 8. The method for connecting skutterudite thermoelectric material and electrode by using a novel high entropy alloy diffusion barrier layer containing Al according to claim 1, characterized in that: The brazing process in step 2 is as follows: the vacuum pressure in the vacuum heating furnace is less than 2×10 -3 Pa, the pressure applied to the workpiece during welding is 0.003~0.1MPa, first heated to 550~650℃ at a rate of 5~30℃ / min and kept warm for 1~40min, then cooled to 50~100℃ at a rate of 2~5℃ / min, and then cooled to room temperature with the furnace.

9. The method for connecting skutterudite thermoelectric material and electrode by using a novel high entropy alloy diffusion barrier layer containing Al according to claim 1, characterized in that: The diffusion welding process in step 2 is as follows: the diffusion welding is carried out in a heating furnace, the atmosphere of the heating furnace is a vacuum or Ar gas protective atmosphere, and the vacuum pressure of the furnace chamber is less than 2×10 -3 Pa, when the heating furnace is Ar gas protective atmosphere, the Ar gas pressure is -0.5Mpa; during welding, the pressure applied to the workpiece to be welded is 5~20Mpa, first heated to 550~650℃ at a rate of 5~30℃ / min and kept warm for 1~40min, then cooled to 50~100℃ at a rate of 2~5℃ / min, and then cooled to room temperature with the furnace.

10. The method for connecting skutterudite thermoelectric material and electrode by using a novel high entropy alloy diffusion barrier layer containing Al according to claim 1, characterized in that: The solder described in step 2 is an Ag-based solder or an Al-based solder having a liquidus temperature of 550° C. to 650° C.

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