Method for assisting brazing of Y2O3-MgO nano-composite ceramic and titanium alloy by using plastic interlayer

Abstract

The invention relates to a method for brazing Y2O3-MgO nano-composite ceramic and titanium alloy, in particular to a method for assisting brazing of Y2O3-MgO nano-composite ceramic and titanium alloy through a plastic middle layer. The method aims at solving the technical problems that a large number of brittle compounds exist in an existing Y2O3-MgO nano-composite ceramic / Ag-based brazing filler metal / titanium alloy connector, and the residual stress is large. The process is simple, the surface of the sample to be welded does not need to be subjected to any modification treatment before welding, and the plastic middle layer plays two roles: on one hand, the thermal expansion coefficient of the brazing filler metal is large, a part of residual stress can be slowly released after the plastic middle layer is added, and the overall residual stress of a joint can be reduced; and on the other hand, diffusion of elements in the titanium alloy base metal from the liquid brazing filler metal to the interface on one side of the ceramic is blocked through the shaping middle layer, generation of excessive brittle compound phases on the interface of the ceramic is inhibited, and therefore the shear strength of the connector is improved by 100%-500%.

Description

Technical Field

[0001] The invention relates to a method for brazing Y2O3-MgO nano-composite ceramics and titanium alloy. Background Art

[0002] Infrared windows are key components in infrared imaging and precision guidance technology, protecting the delicate optoelectronic components within and transmitting target signals. Connecting the infrared window material to the external metal components is crucial in the assembly of aircraft infrared imaging systems. Current brazing techniques for Y2O3-MgO nanocomposite ceramics and titanium alloys often hinder the formation of brittle compound phases at the ceramic interface due to the continuous dissolution of the titanium alloy base material into the liquid brazing filler metal during the welding process. This excessive introduction of the active element Ti leads to the formation of brittle compound phases at the ceramic interface, hindering the mitigation of residual stress and reducing the service reliability of the brazed joint. Introducing a highly plastic metal foil into the braze joint can improve the joint properties and reduce residual stress. Furthermore, the addition of an intermediate layer can hinder the diffusion of elements from the base titanium alloy from the liquid brazing filler metal into the ceramic interface, suppressing the formation of excessive brittle compound phases at the interface and facilitating the creation of stable and reliable Y2O3-MgO nanocomposite ceramic / titanium alloy brazed joints. At present, there is no report on the technology of alleviating residual stress by inhibiting the formation of brittle compounds in the brazing joint of Y2O3-MgO nanocomposite ceramics and titanium alloys. Therefore, the present invention develops a method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloys with the aid of a plastic intermediate layer. Summary of the Invention

[0003] The present invention aims to solve the technical problems of the presence of a large amount of brittle compounds and large residual stress in the existing Y2O3-MgO nanocomposite ceramic / Ag-based solder / titanium alloy joints, and provides a method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloys using a plastic intermediate layer as an auxiliary.

[0004] The method of the present invention for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using a plastic intermediate layer is carried out according to the following steps:

[0005] 1. Use 600#, 1000#, 2000# and 3000# metallographic sandpaper to grind the Y2O3-MgO nanocomposite ceramic base material to be welded and the titanium alloy base material to be welded until the surface is glossy, then ultrasonically clean them in alcohol and blow dry them with a hair dryer for later use;

[0006] 2. Pre-welding treatment of the plastic intermediate layer: Grind both surfaces of the plastic intermediate layer to remove the surface impurities, ultrasonically clean it in alcohol or acetone for 10 to 15 minutes, and blow dry it for later use; the plastic intermediate layer can be Nb foil, Ni foil or Cu foil;

[0007] 3. Stack the plastic intermediate layer treated in step 2, Ag-Cu solder, Ag-Cu-Ti solder, and two cleaned base materials in the order of titanium alloy / Ag-Cu solder / plastic intermediate layer / Ag-Cu-Ti solder / Y2O3-MgO nanocomposite ceramic, and apply adhesive between the layers to obtain a sample to be welded;

[0008] 4. Welding process: Place the sample to be welded obtained in step 3 into a vacuum furnace, place a pressing block on the sample to be welded to ensure close contact between the sample and the brazing material during the brazing process; start vacuuming, then first raise the temperature from room temperature to 300℃~320℃, then raise the temperature to 790℃~830℃, then raise the temperature to 840℃~880℃ and keep it for 10min~15min, then cool it to 300℃~320℃, and finally cool it to room temperature with the furnace, thus completing the brazing of Y2O3-MgO nanocomposite ceramics and titanium alloy. The vacuum degree of the entire welding process is ≤1×10 -2 Pa.

[0009] The method of the present invention inhibits the formation of brittle compounds by virtue of the following principle: when the brazing temperature reaches the point where AgCuTi completely melts, the titanium alloy continuously dissolves into the liquid brazing filler metal, introducing a large amount of the active element Ti. Ti and Cu then continuously react with the Y2O3-MgO nanocomposite ceramic to form a large amount of the brittle phase Ti3Cu3O. The addition of the plastic intermediate layer of Nb foil hinders the diffusion of the active element Ti in the brazing filler metal toward the Y2O3-MgO nanocomposite ceramic, thereby suppressing the excessive formation of Ti3Cu3O. This regulates the weld microstructure, alleviates residual stress in the joint, and improves joint strength.

[0010] The beneficial effects of the present invention are as follows:

[0011] The process of the present invention is simple, and no modification treatment is required on the surface of the sample to be welded before welding. The plastic intermediate layer plays two roles: on the one hand, the thermal expansion coefficient of the solder is relatively large, and the addition of the plastic intermediate layer can relieve part of the residual stress, thereby reducing the overall residual stress of the joint; on the other hand, the plastic intermediate layer is used to block the diffusion of elements in the titanium alloy base material from the liquid solder to the interface on the ceramic side, thereby inhibiting the generation of excessive brittle compound phases at the ceramic interface, thereby increasing the shear strength of the joint by 100% to 500%. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of the assembly of the sample to be welded in step 3 of test 1;

[0013] Figure 2 Photographs of joint structures obtained for comparative tests;

[0014] Figure 3 for Figure 2 Energy spectrum analysis diagram of point A;

[0015] Figure 4 This is a photo of the joint structure obtained under the process parameters corresponding to No. 2 in Table 1;

[0016] Figure 5 for Figure 4 A local magnified image of the red box area in the middle;

[0017] Figure 6 for Figure 5 Energy spectrum analysis diagram of point B in the middle. DETAILED DESCRIPTION

[0018] Specific embodiment 1: This embodiment is a method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using a plastic intermediate layer as an auxiliary, which is specifically carried out in the following steps:

[0019] 1. Use 600#, 1000#, 2000# and 3000# metallographic sandpaper to grind the Y2O3-MgO nanocomposite ceramic base material to be welded and the titanium alloy base material to be welded until the surface is glossy, then ultrasonically clean them in alcohol and blow dry them with a hair dryer for later use;

[0020] 2. Pre-welding treatment of the plastic intermediate layer: Grind both surfaces of the plastic intermediate layer to remove the surface impurities, ultrasonically clean it in alcohol or acetone for 10 to 15 minutes, and blow dry it for later use; the plastic intermediate layer can be Nb foil, Ni foil or Cu foil;

[0021] 3. Stack the plastic intermediate layer treated in step 2, Ag-Cu solder, Ag-Cu-Ti solder, and two cleaned base materials in the order of titanium alloy / Ag-Cu solder / plastic intermediate layer / Ag-Cu-Ti solder / Y2O3-MgO nanocomposite ceramic, and apply adhesive between the layers to obtain a sample to be welded;

[0022] 4. Welding process: Place the sample to be welded obtained in step 3 into a vacuum furnace, place a pressing block on the sample to be welded to ensure close contact between the sample and the brazing material during the brazing process; start vacuuming, then first raise the temperature from room temperature to 300℃~320℃, then raise the temperature to 790℃~830℃, then raise the temperature to 840℃~880℃ and keep it for 10min~15min, then cool it to 300℃~320℃, and finally cool it to room temperature with the furnace, thus completing the brazing of Y2O3-MgO nanocomposite ceramics and titanium alloy. The vacuum degree of the entire welding process is ≤1×10 -2 Pa.

[0023] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that: in step 1, the mixture is ultrasonically cleaned in alcohol for 10 to 15 minutes. Other aspects are the same as those of specific embodiment 1.

[0024] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that the thickness of the plastic intermediate layer in step 2 is 100 μm. Other aspects are the same as specific embodiment 1 or 2.

[0025] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the Ag-Cu solder in step 3 is an AgCu eutectic solder. Other aspects are the same as specific embodiments 1 to 3.

[0026] Specific embodiment 5: This embodiment differs from specific embodiment 4 in that the Ag-Cu solder described in step 3 is made of solder sheet, solder paste, or solder powder; solder paste is applied directly to the surface to be soldered; solder powder is pressed into tablets using a tablet press and then cut to a predetermined size. Other aspects are the same as specific embodiment 4.

[0027] Specific embodiment 6: This embodiment differs from specific embodiment 5 in that the Ag-Cu-Ti solder described in step 3 is made of solder sheet, solder paste, or solder powder; solder paste is applied directly to the surface to be soldered; solder powder is pressed into tablets using a tablet press and then cut to a predetermined size. Otherwise, this is the same as specific embodiment 5.

[0028] Specific embodiment 7: This embodiment differs from specific embodiment 6 in that the adhesive in step 3 is 502 glue. Other aspects are the same as specific embodiment 6.

[0029] Specific embodiment eight: This embodiment differs from specific embodiment seven in that in step four, the temperature is first raised from room temperature to 300° C. to 320° C. at a heating rate of 5° C. / min. Other aspects are the same as specific embodiment seven.

[0030] Specific embodiment 9: This embodiment differs from specific embodiment 8 in that in step 4, the temperature is raised to 790°C-830°C at a heating rate of 10°C / min, then raised to 840°C-880°C at a heating rate of 5°C / min and held at that temperature for 10-15 minutes. Other aspects are the same as specific embodiment 8.

[0031] Specific embodiment 10: This embodiment differs from specific embodiment 9 in that in step 4, the temperature is lowered to 300°C-320°C at a cooling rate of 5°C / min, and finally cooled to room temperature in the furnace, completing the brazing of the Y2O3-MgO nanocomposite ceramic and the titanium alloy. Other aspects are the same as specific embodiment 9.

[0032] The present invention is verified by the following test:

[0033] Experiment 1: This experiment is a method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using a plastic intermediate layer as an auxiliary. The specific steps are as follows:

[0034] 1. Use 600#, 1000#, 2000# and 3000# metallographic sandpaper to grind the Y2O3-MgO nanocomposite ceramic base material to be welded and the titanium alloy TC4 base material to be welded until the surface is glossy, then ultrasonically clean them in alcohol for 10 minutes each, and blow dry them with a hair dryer for later use;

[0035] 2. Pre-welding treatment of the plastic intermediate layer: Grind both surfaces of the plastic intermediate layer to remove the surface impurities, ultrasonically clean it in acetone for 10 minutes, and blow dry it for later use; the plastic intermediate layer is Nb foil with a thickness of 100 μm;

[0036] 3. The plastic intermediate layer treated in step 2, the AgCu eutectic solder sheet, the Ag-Cu-Ti solder sheet (specific composition ratios are shown in Table 1) and the two cleaned base materials are stacked in the order of titanium alloy TC4 / Ag-Cu solder / plastic intermediate layer / Ag-Cu-Ti solder / Y2O3-MgO nanocomposite ceramics. 502 glue is applied between the layers to obtain a sample to be welded. Figure 1 The figure shows the assembly diagram of the sample to be welded, where 1 is titanium alloy TC4, 2 is AgCu eutectic solder, 3 is plastic intermediate layer Nb foil, 4 is AgCuTi solder, and 5 is Y2O3-MgO nanocomposite ceramic.

[0037] 4. Welding process: The sample to be welded obtained in step 3 is placed in a vacuum furnace with the titanium alloy at the bottom. A pressing block is placed on the sample to be welded to ensure close contact between the sample and the brazing material during the brazing process. Start vacuuming, first increase the temperature from room temperature to 300°C at a heating rate of 5°C / min, then increase the temperature to 800°C at a heating rate of 10°C / min, and then increase the temperature to the brazing temperature of 840°C~880°C at a heating rate of 5°C / min and keep it at that temperature for 10 minutes (see Table 1 for specific brazing temperatures), then cool it to 300°C at a cooling rate of 5°C / min, and finally cool it to room temperature with the furnace. The brazing of Y2O3-MgO nanocomposite ceramics and titanium alloy is completed. The vacuum degree of the whole process is ≤1×10 -2 Pa.

[0038] Comparative test: No intermediate layer was added in this test. The specific process is as follows:

[0039] 1. Use 600#, 1000#, 2000# and 3000# metallographic sandpaper to grind the Y2O3-MgO nanocomposite ceramic base material to be welded and the titanium alloy TC4 base material to be welded until the surface is glossy, then ultrasonically clean them in alcohol for 10 minutes each, and blow dry them with a hair dryer for later use;

[0040] 2. Place the AgCu eutectic solder sheet between the two cleaned base materials in step 1, and apply 502 glue between each layer to obtain a sample to be welded;

[0041] 3. Welding process: Place the sample to be welded obtained in step 2 into a vacuum furnace with the titanium alloy TC4 at the bottom. Place a pressing block on the sample to be welded to ensure close contact between the sample and the brazing material during the brazing process. Start vacuuming, first increase the temperature from room temperature to 300°C at a heating rate of 5°C / min, then increase the temperature to 800°C at a heating rate of 10°C / min, then increase the temperature to the brazing temperature of 860°C at a heating rate of 5°C / min and keep it at that temperature for 10 minutes, then cool it to 300°C at a cooling rate of 5°C / min, and finally cool it to room temperature with the furnace. The brazing of Y2O3-MgO nanocomposite ceramics and titanium alloy is completed. The vacuum degree of the whole process is ≤1×10 -2 Pa; the room temperature shear strength of the final joint is 15MPa.

[0042] Table 1

[0043]

[0044] Table 1 shows the shear strength test data for the Y2O3-MgO nanocomposite ceramic / titanium alloy joint obtained in Experiment 1. The maximum room-temperature shear strength of the resulting joint reaches 90 MPa. This is five times greater than the room-temperature shear strength of the joint obtained under the same conditions without the Nb foil interlayer (comparison test).

[0045] Figure 2 This is a photo of the joint structure obtained from the comparative test. Figure 3 for Figure 2 In the energy spectrum analysis diagram of point A, the Ti element from the titanium alloy continuously diffuses to the ceramic side and undergoes an interface reaction. Since it only reacts with MgO in the Y2O3-MgO nanocomposite ceramic, a mixed structure of Y2O3+Ti3Cu3O is formed at the ceramic interface, and the excess Ti element leads to the continuous formation of Ti3Cu3O granular phase.

[0046] Figure 4 This is a photo of the joint structure obtained under the process parameters corresponding to No. 2 in Table 1. Figure 5 for Figure 4 A partial enlarged view of the red box area. Figure 6 for Figure 5The energy spectrum analysis diagram of point B shows that after controlling the Ti content in the solder, the ceramic side interface reaction layer is only composed of Ti3Cu3O, with a thickness of about 2μm. No Ti3Cu3O is formed except at the ceramic interface. Figure 2 、 Figure 4 and Figure 5 From the comparison, it can be seen that the addition of the Nb intermediate layer blocks the diffusion of Ti element in the titanium alloy to one side of the ceramic, inhibits the excessive formation of Ti3Cu3O, and the reaction of the brazing material to the interior of the ceramic is suppressed. The formed interface reaction layer is composed only of Ti3Cu3O, rather than a mixed structure of Y2O3+Ti3Cu3O.

Claims

1. A method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using a plastic intermediate layer, characterized in that The method is carried out according to the following steps:

1. Use metallographic sandpaper to grind the Y2O3-MgO nanocomposite ceramic base material to be welded and the titanium alloy base material to be welded until the surface is glossy, then ultrasonically clean them in alcohol and blow dry them with a hair dryer for later use; 2. Pre-welding treatment of the plastic intermediate layer: Grind both surfaces of the plastic intermediate layer to remove the surface impurities, ultrasonically clean it in alcohol or acetone, and blow dry it for later use; the plastic intermediate layer can be Nb foil, Ni foil or Cu foil; 3. Stack the plastic intermediate layer treated in step 2, Ag-Cu solder, Ag-Cu-Ti solder, and two cleaned base materials in the order of titanium alloy / Ag-Cu solder / plastic intermediate layer / Ag-Cu-Ti solder / Y2O3-MgO nanocomposite ceramic, and apply adhesive between the layers to obtain a sample to be welded; 4. Welding process: Place the sample to be welded obtained in step 3 into a vacuum furnace, place a pressing block on the sample to be welded to ensure close contact between the sample and the brazing material during the brazing process; start vacuuming, then first raise the temperature from room temperature to 300℃~320℃, then raise the temperature to 790℃~830℃, then raise the temperature to 840℃~880℃ and keep it for 10min~15min, then cool it to 300℃~320℃, and finally cool it to room temperature with the furnace, thus completing the brazing of Y2O3-MgO nanocomposite ceramics and titanium alloy. The vacuum degree of the entire welding process is ≤1×10 -2 Pa.

2. The method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using a plastic intermediate layer as claimed in claim 1, characterized in that In step 1, place the sample in alcohol and ultrasonically clean it for 10 to 15 minutes.

3. The method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using a plastic intermediate layer as claimed in claim 1, characterized in that The thickness of the plastic intermediate layer in step 2 is 100 μm.

4. The method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using a plastic intermediate layer as claimed in claim 1, characterized in that The Ag-Cu solder described in step 3 is an AgCu eutectic solder.

5. The method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using a plastic intermediate layer as claimed in claim 1, characterized in that The Ag-Cu solder described in step 3 is made of solder sheet, solder paste or solder powder; the solder paste is directly applied to the surface to be soldered; the solder powder is pressed into tablets using a tablet press and then cut into a predetermined size.

6. The method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using a plastic intermediate layer as claimed in claim 1, characterized in that The Ag-Cu-Ti solder described in step 3 is made of solder sheet, solder paste or solder powder; the solder paste is directly applied to the surface to be soldered; the solder powder is pressed into tablets using a tablet press and then cut into a predetermined size.

7. The method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using a plastic intermediate layer as claimed in claim 1, characterized in that The adhesive described in step three is 502 glue.

8. The method of brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using a plastic intermediate layer as claimed in claim 1, characterized in that In step 4, the temperature is first raised from room temperature to 300°C~320°C at a heating rate of 5°C / min.

9. The method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using a plastic intermediate layer as claimed in claim 8, characterized in that In step 4, the temperature is increased to 790°C~830°C at a heating rate of 10°C / min, and then increased to 840°C~880°C at a heating rate of 5°C / min and kept at this temperature for 10min~15min.

10. The method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using a plastic intermediate layer as claimed in claim 9, characterized in that In step 4, the temperature is lowered to 300°C-320°C at a cooling rate of 5°C / min, and finally cooled to room temperature along with the furnace, thereby completing the brazing of the Y2O3-MgO nanocomposite ceramic and the titanium alloy.

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