Diffusion welding method for aluminum oxide ceramic and titanium alloy and prepared composite board

Abstract

The invention relates to an aluminum oxide ceramic and titanium alloy diffusion welding method and a prepared composite board. The diffusion welding method for the aluminum oxide ceramic and the titanium alloy comprises the steps that an aluminum oxide ceramic piece, a TC4 titanium alloy piece and a pure titanium piece are assembled into an Al2O3-Ti-TC4 diffusion couple, then the whole Al2O3-Ti-TC4 diffusion couple is fixed by applying 5-8 Mpa pressure through a graphite clamp, and the graphite clamp for fixing the Al2O3-Ti-TC4 diffusion couple is placed into a multifunctional front furnace to be subjected to vacuum radiation heating; and performing diffusion welding. According to the diffusion welding method, an electric field does not need to participate, expensive equipment does not need to be purchased, electric energy does not need to be continuously consumed in production, and production safety accidents can be reduced. Under the condition that no electric field participates in, reliable connection of the aluminum oxide ceramic and the titanium alloy is achieved by adjusting and changing the type of the metal of the middle layer and changing the applied pressure, and great progress is made technically.

Description

Technical Field

[0001] The present invention relates to the technical field of welding of dissimilar materials, and particularly relates to a diffusion welding method for alumina ceramics and titanium alloy and a composite plate prepared thereby. Background Art

[0002] In recent years, with the continuous development of IGBT (Insulated Gate Bipolar Transistor) components towards high power, high current density, high integration and miniaturization, the semiconductor industry has put forward more stringent performance requirements for the high-temperature stability and high reliability of IGBT modules. Especially in IGBT module components, realizing high-quality connection between metal and ceramic heat dissipation substrates is a technical difficulty in this field. Due to the huge differences in the internal structures and performance parameters between metals and ceramics, it is very difficult to achieve reliable connection by traditional fusion welding methods.

[0003] The applicant's existing diffusion bonding technology is a Chinese patent application with the publication number CN118893293A, which discloses a welding method for field-assisted rapid connection of alumina ceramics and titanium alloy: First, complete the pre-welding preparation work for the alumina ceramics and titanium alloy to be welded. Deposit a metal layer on the surface of the alumina ceramics to be welded through a specific plating technology. After assembly, fix the specimens to be welded in a specific hot pressing fixture in a vacuum heating furnace, apply a certain pressure, then heat at a heating rate of 5 - 15 °C / min to 700 - 900 °C, keep warm for 1 - 2 h, apply an electric field at the same time, then cool at a cooling rate of 5 - 10 °C / min to 400 °C, and then cool with the furnace to complete the diffusion bonding of alumina ceramics and titanium alloy. Through the method of field-assisted diffusion bonding, the present invention has successfully achieved high-quality connection of alumina ceramics and titanium alloy, greatly reducing the connection temperature and connection time required for welding, and effectively solving the problems of low efficiency and high production cost of traditional diffusion welding. In this technical solution, in order to connect alumina ceramics and titanium alloy, it is necessary to deposit a metal layer on the surface of alumina ceramics using a specific plating technology. Secondly, it is necessary to heat up and keep warm under pressure, and an electric field needs to be applied for cooling to achieve the diffusion bonding of alumina ceramics and titanium alloy. This process is relatively complex and has many operation requirements. The application of the electric field increases the production cost. Therefore, this technology needs to be improved. Summary of the Invention

[0004] In view of this, the object of the present invention is to propose a diffusion welding method for alumina ceramics and titanium alloy. By controlling the thickness of the intermediate titanium sheet, welding temperature, holding time and applied pressure, this method explores the bonding strength of Al2O3, Ti and TC4, optimizes the interface structure, and further improves the mechanical properties of the welding of dissimilar metal-ceramic materials, so as to prepare a product with excellent performance of Al2O3-Ti-TC4 composite structure.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A diffusion welding method for alumina ceramics and titanium alloy is to assemble alumina ceramics, TC4 titanium alloy and pure titanium sheet into an Al2O3-Ti-TC4 diffusion couple, and then fix the whole Al2O3-Ti-TC4 diffusion couple with a graphite fixture under pressure, and realize the diffusion welding of alumina ceramics and titanium alloy through a specific diffusion welding process.

[0007] Specifically, the contact surface sizes of TC4 titanium alloy, Al2O3 ceramic and pure titanium sheet (preferably a pure titanium sheet with a purity of 99.99%) are all the same. In the present invention, the contact surface sizes of the Al2O3 ceramic sheet, TC4 sheet and pure titanium sheet are all the same, and after being pressed and fitted tightly by a graphite fixture, diffusion welding is carried out under the condition of high temperature and pressure. On the one hand, it expands the effective contact area between the substrates and promotes the plastic deformation of the bonding surface; on the other hand, it avoids the occurrence of overall macroscopic deformation during the diffusion welding process. The thickness of the pure titanium sheet is 50 - 200 μm.

[0008] Preferably, before welding, the surfaces to be welded of the alumina ceramics, TC4 titanium alloy and pure titanium sheet are subjected to mechanical grinding and polishing treatment, and then ultrasonically cleaned with acetone and dried for use to remove the influence of impurities or oxide surfaces on the diffusion welding.

[0009] Preferably, the pressure applied by the graphite fixture is 5 - 8 MPa.

[0010] Preferably, the graphite fixture fixing the Al2O3-Ti-TC4 diffusion couple is placed in a vacuum radiation heating multi-functional pre-furnace for diffusion welding.

[0011] Preferably, after vacuum pumping, the temperature is raised to the welding temperature of 800 - 950 °C at a heating rate of 5 - 10 °C / min, held for 1 - 2.5 h, and then cooled to 400 °C at a cooling rate of 2 - 5 °C / min, and then cooled with the furnace. The selected temperature is below the melting points of the alumina ceramics and TC4 titanium alloy, and solid-state diffusion is carried out without reducing the properties of the base materials. The diffusion rate is relatively fast and the strength of the weld joint is relatively high.

[0012] In the present invention, since the melting point of alumina ceramics (2054 °C) is much higher than that of titanium alloy (1670 °C), the physical and chemical properties of alumina ceramics are much more stable than those of titanium alloy. During the diffusion welding process of alumina ceramics and titanium alloy, mainly relying on the local plastic deformation of titanium alloy to achieve close contact of the interface. Therefore, when selecting welding parameters, mainly based on the properties of titanium alloy.

[0013] According to the selection principle of diffusion welding temperature, the welding temperature range should be 0.6Tm - 0.8Tm. The melting point Tm of titanium alloy is about 1670 °C. According to the selection principle, that is 1000 °C - 1350 °C, the titanium alloy is an α + β dual-phase material. When the temperature reaches 882 °C, the α phase will transform into the β phase; when it exceeds 900 °C, the microstructure and mechanical properties of the titanium alloy will begin to decline. Therefore, in order not to affect the microstructure and mechanical properties of the base material and to ensure the activity of atoms, the diffusion welding temperature is selected as 800 - 950 °C. At the same time, in order to ensure the full diffusion of atoms and interface reaction during the welding process and to obtain an interface reaction layer with an appropriate thickness, a relatively long holding time of 1 - 2.5 h is also required.

[0014] In addition, due to the good plasticity and low high-temperature strength of titanium alloy, at 800 °C, the yield strength of titanium alloy is only about 50 MPa. Therefore, when performing diffusion welding of TC4, the applied pressure should not be too large, otherwise it will cause large deformation of the base material. Nor should the applied pressure be too small, which is not conducive to the smooth progress of diffusion welding. When the connection pressure is 5 - 8 MPa, the deformation of the titanium alloy is very small, and at the same time, it can ensure close contact with alumina ceramic at the interface and smooth welding. Therefore, the present invention selects the applied pressure as 5 - 8 MPa.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects:

[0016] The diffusion welding method of alumina ceramic and titanium alloy based on alumina - titanium - TC4 titanium alloy of the present invention can achieve reliable connection of ceramic and metal while overcoming the limitations of traditional fusion welding. Compared with the prior art, the diffusion welding method of the present invention does not require the participation of an electric field, so there is no need to purchase expensive equipment and continuously consume electric energy in production, and it can also reduce the occurrence of production safety accidents. In particular, compared with the prior art, without the participation of an electric field, by adjusting and changing the type of intermediate layer metal and at the same time adjusting the applied pressure, reliable connection of alumina ceramic and titanium alloy is achieved, and significant progress has been made technically.

[0017] The technical solution of the present invention will be further described below through the accompanying drawings and embodiments. Description of the Drawings

[0018] Figure 1 It is the EDS line scan diagram of the interface reaction layer of the Al2O3 - Ti - TC4 welded part in Embodiment 1 of the present invention.

[0019] Figure 2 It is the change of the microstructure and the thickness of the interface reaction layer with different welding temperatures set based on Embodiment 17, the connection pressure is 8 Mpa, the holding time is 2 h, and the thickness of the titanium sheet is 200 μm. In the figure, a)

[0020] 800 °C; b) 850 °C; c) 900 °C; d) 950 °C.

[0021] Figure 3 For the changes in the microstructure and the thickness of the interfacial reaction layer by setting different titanium intermediate layer thicknesses based on Example 17, the connection temperature is 950 °C, the connection pressure is 8 MPa, and the heat preservation time is 2 h. In the figure, a) 50 μm; b) 100 μm; c) 150 μm; d) 200 μm.

[0022] Figure 4 For the changes in the microstructure and the thickness of the interfacial reaction layer by setting different connection pressures based on Example 17, the connection temperature is 950 °C, the heat preservation time is 2 h, and the thickness of the titanium sheet is 200 μm. In the figure, a) 5 MPa; b) 6 MPa; c) 7 MPa; d) 8 MPa.

[0023] Figure 5 For the changes in the microstructure and the thickness of the interfacial reaction layer by setting different heat preservation times based on Example 17, the connection temperature is 950 °C, the connection pressure is 8 MPa, and the thickness of the titanium sheet is 200 μm. In the figure, a) 1 h; b) 1.5 h; c) 2 h; d) 2.5 h. Detailed implementation manners

[0024] To enable those skilled in the art to more clearly and intuitively understand the present invention, the present invention will be further described below in conjunction with the accompanying drawings. For the experimental methods without specific conditions indicated in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0025] Titanium is a metal with very active chemical properties and can react with many elements and compounds at high temperatures to promote diffusion. Through the Ti-Al binary phase diagram, it can be seen that Ti and Al are likely to form the Ti3Al phase at 800 - 1000 °C, which can be used as a strengthening phase to improve the performance of the welded joint.

[0026] A diffusion welding method for alumina ceramics and titanium alloys according to the present invention includes the following steps:

[0027] 1. After polishing the contact surfaces of the Al2O3 sheet, TC4 sheet and pure titanium sheet smooth and ultrasonically cleaning them with acetone, assemble them into an Al2O3-Ti-TC4 diffusion couple. The contact surface sizes of the TC4 titanium alloy, Al2O3 ceramic and pure titanium sheet are all the same, and the thickness of the pure titanium sheet is 50 - 200 μm.

[0028] 2. Fix the entire Al2O3-Ti-TC4 diffusion couple with a graphite fixture to apply pressure, and the applied pressure is 5 - 8 MPa.

[0029] 3. Place the graphite fixture with the fixed Al2O3-Ti-TC4 diffusion couple into the vacuum radiation heating multi-functional pre-furnace. After evacuating the air, heat it at a heating rate of 5-10 °C / min to the welding temperature of 800-950 °C, hold for 1-2.5 h, then cool it at a cooling rate of 2-5 °C / min to 400 °C, and then cool it in the furnace to achieve the diffusion welding of alumina ceramics and titanium alloy, obtaining a composite plate, i.e., the Al2O3-Ti-TC4 welded part.

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings and specific implementation cases. The specific embodiments are implemented according to the orthogonal experiment table of 4 factors and 4 levels (titanium sheet thickness: 50 μm, 100 μm, 150 μm, 200 μm; welding temperature: 800 °C, 850 °C, 900 °C, 950 °C; applied pressure: 5 MPa, 6 MPa, 7 MPa, 8 MPa; holding time: 1 h, 1.5 h, 2 h, 2.5 h). T represents the sum of the test data when a certain factor is at a certain level, and the range R represents the difference between the maximum value and the minimum value of T when a certain factor is considered. The larger the range R, the greater the influence of this factor on the test results, as shown in Table 1. max maximum value and T min minimum value, and the larger the range R, the greater the influence of this factor on the test results, as shown in Table 1.

[0031] Example 1:

[0032] Place a 50-μm-thick pure titanium sheet between the Al2O3 ceramic plate and the TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple, place it in a graphite fixture and press it firmly. The welding temperature is 800 °C, the applied pressure is 5 MPa, and the holding time is 1 h.

[0033] Example 2:

[0034] Place a 50-μm-thick pure titanium sheet between the Al2O3 ceramic plate and the TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple, place it in a graphite fixture and press it firmly. The welding temperature is 850 °C, the applied pressure is 6 MPa, and the holding time is 1.5 h.

[0035] Example 3:

[0036] Place a 50-μm-thick pure titanium sheet between the Al2O3 ceramic plate and the TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple, place it in a graphite fixture and press it firmly. The welding temperature is 900 °C, the applied pressure is 7 MPa, and the holding time is 2 h.

[0037] Example 4:

[0038] A 50-μm thick pure titanium sheet was placed between an Al2O3 ceramic plate and a TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple, which was then placed in a graphite fixture and clamped firmly. The welding temperature was 950 °C, the applied pressure was 8 MPa, and the holding time was 2.5 h.

[0039] Example 5:

[0040] A 100-μm thick pure titanium sheet was placed between an Al2O3 ceramic plate and a TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple, which was then placed in a graphite fixture and clamped firmly. The welding temperature was 800 °C, the applied pressure was 6 MPa, and the holding time was 2 h.

[0041] Example 6: A 100-μm thick pure titanium sheet was placed between an Al2O3 ceramic plate and a TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple, which was then placed in a graphite fixture and clamped firmly. The welding temperature was 850 °C, the applied pressure was 5 MPa, and the holding time was 2.5 h.

[0042] Example 7:

[0043] A 100-μm thick pure titanium sheet was placed between an Al2O3 ceramic plate and a TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple, which was then placed in a graphite fixture and clamped firmly. The welding temperature was 900 °C, the applied pressure was 8 MPa, and the holding time was 1 h.

[0044] Example 8:

[0045] A 100-μm thick pure titanium sheet was placed between an Al2O3 ceramic plate and a TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple, which was then placed in a graphite fixture and clamped firmly. The welding temperature was 950 °C, the applied pressure was 7 MPa, and the holding time was 1.5 h.

[0046] Example 9:

[0047] A 150-μm thick pure titanium sheet was placed between an Al2O3 ceramic plate and a TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple, which was then placed in a graphite fixture and clamped firmly. The welding temperature was 800 °C, the applied pressure was 7 MPa, and the holding time was 2.5 h.

[0048] Example 10:

[0049] A 150-μm thick pure titanium sheet was placed between an Al2O3 ceramic plate and a TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple, which was then placed in a graphite fixture and clamped firmly. The welding temperature was 850 °C, the applied pressure was 8 MPa, and the holding time was 2 h.

[0050] Example 11:

[0051] A 150-μm thick pure titanium sheet was placed between an Al2O3 ceramic plate and a TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple, which was placed in a graphite fixture and clamped firmly. The welding temperature was 900 °C, the applied pressure was 5 MPa, and the holding time was 1.5 h.

[0052] Example 12:

[0053] A 150-μm thick pure titanium sheet was placed between an Al2O3 ceramic plate and a TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple, which was placed in a graphite fixture and clamped firmly. The welding temperature was 950 °C, the applied pressure was 6 MPa, and the holding time was 1 h.

[0054] Example 13:

[0055] A 200-μm thick pure titanium sheet was placed between an Al2O3 ceramic plate and a TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple, which was placed in a graphite fixture and clamped firmly. The welding temperature was 800 °C, the applied pressure was 8 MPa, and the holding time was 1.5 h.

[0056] Example 14:

[0057] A 200-μm thick pure titanium sheet was placed between an Al2O3 ceramic plate and a TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple, which was placed in a graphite fixture and clamped firmly. The welding temperature was 850 °C, the applied pressure was 7 MPa, and the holding time was 1 h.

[0058] Example 15:

[0059] A 200-μm thick pure titanium sheet was placed between an Al2O3 ceramic plate and a TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple, which was placed in a graphite fixture and clamped firmly. The welding temperature was 900 °C, the applied pressure was 6 MPa, and the holding time was 2.5 h.

[0060] Example 16:

[0061] A 200-μm thick pure titanium sheet was placed between an Al2O3 ceramic plate and a TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple, which was placed in a graphite fixture and clamped firmly. The welding temperature was 950 °C, the applied pressure was 5 MPa, and the holding time was 2 h.

[0062] Performance test:

[0063] The shear strength test (GB / T43115-2023) was carried out on the Al2O3-Ti-TC4 welded joints prepared in each example to obtain the interfacial shear strength, and the results are shown in Table 1 below:

[0064] Summary of Related Experimental Parameters and Results in Table 1

[0065]

[0066]

[0067] Based on the analysis results in Table 1, set the optimal embodiment:

[0068] Example 17:

[0069] Place a 200-μm-thick pure titanium sheet between an Al2O3 ceramic plate and a TC4 titanium alloy plate to assemble an Al2O3-Ti-TC4 diffusion couple. Place it in a graphite fixture and press it tightly. The welding temperature is 950 °C, the applied pressure is 8 MPa, and the holding time is 2 h. After measurement, the shear strength of the Al2O3-Ti-TC4 welded joint reaches 80.2 MPa.

[0070] Data analysis:

[0071] Perform an EDS line scan on the interface reaction layer of the Al2O3-Ti-TC4 welded joint in Example 1. From Figure 1 it can be seen that Ti, Al, and O elements diffuse at the bonding interface of the Al2O3-Ti-TC4 welded joint, and chemical reactions occur between the Al2O3, Ti, and TC4 interfaces, forming Ti m Al n O x phase, realizing the effective bonding of the alumina ceramic and titanium alloy welding interface.

[0072] The welding process provided by the present invention prepares a welding joint of alumina-titanium-TC4 titanium alloy with good mechanical properties and large shear strength. The titanium intermediate layer is well connected to the TC4 titanium alloy and the alumina ceramic, the interface reaction is sufficient, and no pores and cracks are generated.

[0073] Based on Table 1, it can be seen that according to the factors and levels of the orthogonal experiment selected in the examples, the influencing factors are in the order of: applied pressure, welding temperature, titanium sheet thickness, holding time. The best diffusion welding process plan is: applied pressure 8 MPa, welding temperature 950 °C, titanium sheet thickness 200 μm, holding time 2 h.

[0074] From Figures 2 to 5It can be seen that, based on Embodiment 17, by comparing the effects of different welding temperatures, titanium interlayer thicknesses, applied pressures, and holding times on the thickness of the interfacial reaction layer under the same conditions, within a certain welding temperature range, the diffusion capabilities of Al atoms and O atoms in the ceramic and Ti atoms in the metal are improved, thereby promoting the interfacial reaction and causing the thickness of the reaction layer to gradually increase with the increase in welding temperature; the effects of the titanium interlayer thickness and the applied pressure on the thickness of the interfacial reaction layer are not obvious; with the increase in the holding time, the thickness of the interfacial reaction layer increases. However, the results of the orthogonal experiment show that the order of the influencing factors is: applied pressure, welding temperature, titanium sheet thickness, holding time. It can be seen that the shear strength is not only affected by the thickness of the interfacial reaction layer. Generally speaking, with the increase in welding temperature, applied pressure, and holding time, the residual stress of the joint increases; with the increase in the interlayer thickness, the residual stress of the joint decreases. Thus, it can be known that the shear strength of the diffusion welded joint is comprehensively affected by both the residual stress of the welded joint and the thickness of the interfacial reaction layer.

[0075] Those of ordinary skill in the art should understand that: the discussion of any above embodiment is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, and they are not provided in detail for the sake of brevity.

[0076] The present invention aims to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omission, modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A diffusion welding method for alumina ceramics and titanium alloys, characterized in that, An alumina ceramic sheet, a TC4 titanium alloy sheet and a pure titanium sheet are assembled into an Al2O3-Ti-TC4 diffusion couple. Then, the Al2O3-Ti-TC4 diffusion couple as a whole is fixed with a graphite fixture by applying a pressure of 5-8 Mpa, and the graphite fixture fixing the Al2O3-Ti-TC4 diffusion couple is placed in a multi-functional preheating furnace for vacuum radiation heating for diffusion welding; After the multi-functional preheating furnace is evacuated, it is heated at a heating rate of 5-10 °C / min to the welding temperature of 800-950 °C, held for 1-2.5 h, and then cooled to 400 °C at a cooling rate of 2-5 °C / min, and then cooled in the furnace.

2. The method according to claim 1, wherein The contact surface sizes of the alumina ceramic sheet, the TC4 titanium alloy sheet and the pure titanium sheet are all the same.

3. The method according to claim 1, characterized in that, The thickness of the pure titanium sheet is 50-200 μm.

4. The method according to claim 1, wherein Before diffusion welding, the welding surfaces of the alumina ceramic sheet, the TC4 titanium alloy sheet and the pure titanium sheet are subjected to mechanical grinding and polishing, and then ultrasonically cleaned with acetone and dried for use.

5. The method according to claim 1, wherein The welding temperature is 950 °C.

6. The method according to claim 1, wherein The thickness of the pure titanium sheet is 200 μm.

7. The method according to claim 1, wherein The applied pressure is 8 MPa.

8. The method according to claim 1, characterized in that, The holding time is 2 h.

9. A composite plate of alumina ceramic and titanium alloy prepared by the method according to any one of claims 1-8.

10. Use of the composite plate of alumina ceramic and titanium alloy prepared by the method according to any one of claims 1-8 in semiconductor production.

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