Method for heterogeneous brazing of Y2O3-MgO nano-composite ceramic and titanium alloy by using TiZrNi brazing filler metal

Abstract

The invention discloses a method for heterogeneous brazing of Y2O3-MgO nano-composite ceramic and titanium alloy by using TiZrNi brazing filler metal, and relates to a method for heterogeneous brazing of Y2O3-MgO nano-composite ceramic and titanium alloy. The invention aims to solve the technical problems of low strength, low air tightness and short service life of a joint of Y2O3-MgO nano-composite ceramic and metal obtained by a mechanical method and a bonding method at present. According to the method, the TiZrNi brazing filler metal and the Ti foil are used for successfully connecting the Y2O3-MgO nano-composite ceramic and the titanium alloy, after the Ti foil is introduced between the Y2O3-MgO nano-composite ceramic and the brazing filler metal piece, an obtained welding joint is compact in structure and free of obvious defects such as air holes and cracks, and the obdurability of the joint is improved. The invention provides a brazing method with high strength and high stability aiming at the current situation of connection application of an infrared window material Y2O3-MgO nano-composite ceramic and a titanium alloy.

Description

Technical Field

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

[0002] As the component at the front end of the aircraft imaging system, the infrared window not only needs to withstand the pressure from air and thermal erosion during high-speed flight, but also needs to withstand the impact of raindrops and gravel under high-speed flight conditions. At the same time, it also needs to overcome the optical degradation problems such as the decline in light transmittance caused by aerodynamic thermal effects and the enhancement of intrinsic radiation. Therefore, high Mach number flight places more stringent requirements on the performance of infrared windows. In order to achieve precise strikes in complex and changing battlefield environments, the infrared window materials selected for high-speed aircraft must meet the following performance requirements: (1) high optical transmittance; (2) low spontaneous radiation; (3) excellent thermal shock resistance; (4) high strength and hardness; (5) stable high-temperature mechanical and optical properties; (6) good corrosion resistance. To date, the main infrared window materials include ZnS, Al2O3, AlON, Y2O3, MgF2 and MgAl2O4. However, the optical and mechanical properties of traditional infrared transparent ceramics will degrade significantly at high temperatures. Therefore, in order to meet the needs of aircraft with higher flight speeds, the application of new high-performance infrared transparent materials is crucial.

[0003] Y2O3-MgO nanocomposite ceramics have high infrared transmittance. In the infrared band of 3~6μm, the transmittance can reach 80%~83%, which is close to the theoretical value. Y2O3-MgO ceramics have extremely low high-temperature emissivity, and their performance is significantly better than that of ceramic materials such as Al2O3. At the same time, Y2O3-MgO nanocomposite ceramics have excellent mechanical properties at high temperatures. In addition, they have excellent thermal shock resistance. Nano-scale grains (~200nm) and uniform phase distribution can effectively suppress thermal stress concentration. At 8MW / m 2 It can still work stably in ultra-high heat flux environments. Therefore, Y2O3-MgO nanocomposite ceramics are considered to be the most promising material for high-speed aircraft windows. As a window structure, the transparent ceramic window needs to be connected to the metal frame to realize the manufacturing of the structure. Ti6Al4V (TC4) alloy is a titanium alloy material widely used in commerce. It has excellent specific strength and good corrosion resistance. It also has excellent weldability, is easy to process, and can be made into forgings and complex components. If a reliable connection between Y2O3-MgO nanocomposite ceramics and TC4 alloy is achieved, it will have very important engineering significance for promoting the application of Y2O3-MgO nanocomposite ceramics in the field of infrared optoelectronics.

[0004] At present, when using traditional mechanical connection method and adhesive bonding method to connect Y2O3-MgO / TC4, problems such as low joint strength, poor air tightness and ageing resistance often occur. Brazing technology can weld heterogeneous materials with large performance differences, and the joint stability after welding is high, air tightness is good, and the impact on the parent material performance is also less. However, the report about Y2O3-MgO nanocomposite ceramic brazing technology is also less. Therefore, the present invention has developed a kind of brazing method that is applicable to Y2O3-MgO nanocomposite ceramic and TC4 alloy. Summary of the Invention

[0005] The present invention aims to solve the technical problems that the joints of Y2O3-MgO nanocomposite ceramics and metals obtained by the current mechanical and adhesive bonding methods have low strength and airtightness and short service life, and provides a method for heterogeneous brazing of Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal.

[0006] The method of brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal is carried out according to the following steps:

[0007] 1. Carry out preliminary cleaning of the parent material Y2O3-MgO nanocomposite ceramics and the parent material titanium alloy;

[0008] 2. Take a foil-shaped TiZrNi solder, polish both sides of the foil-shaped TiZrNi solder with sandpaper to remove the surface impurity layer, take a 10 μm thick Ti foil, ultrasonically clean the TiZrNi solder and the Ti foil in alcohol or acetone, blow dry and set aside; the composition of each element in the TiZrNi solder in atomic percentage is: 50% Ti, 25%-30% Zr and 20%-25% Ni;

[0009] 3. Place the TiZrNi solder and Ti foil processed in step 2 between the two base materials cleaned in step 1, and stack them in the order of titanium alloy / TiZrNi solder / Ti foil / Y2O3-MgO nanocomposite ceramic to obtain a sample to be welded;

[0010] 4. Place the sample to be welded in step 3 into a vacuum furnace. Apply pressure to the upper end of the sample to ensure close contact between the sample surface and the brazing material during brazing. The vacuum degree in the furnace is maintained at 6×10 -3 Pa; firstly, heat from room temperature to 300℃~320℃, then heat to 830℃~870℃, then heat to the connection temperature of 880℃~980℃ and keep it for 0~30min, then cool to 300℃~320℃. The vacuum degree of the whole process is ≤1×10 -2 Pa, and finally cooled to room temperature with the furnace, completing the brazing connection between Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal.

[0011] The beneficial effects of the present invention are as follows:

[0012] 1. The present invention uses a brazing method that is easy to operate and successfully achieves effective connection between Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal under vacuum conditions;

[0013] 2. The TiZrNi solder of the present invention has excellent wettability to the ceramic base material. During the brazing process, Ti and Zr elements diffuse toward the Y2O3-MgO nanocomposite ceramic side and react with the MgO in the Y2O3-MgO at the interface. The Y2O3 phase is retained, and a Y2O3+C-14Laves phase composite reaction layer is formed on the ceramic side, thereby forming a strong interface bond. The solder completely wets the titanium alloy, and a reaction occurs between the solder and the titanium alloy base material to form a continuous Ti-based solid solution interface reaction layer. The brazing seam structure is mainly composed of Ti-based solid solution + C14-Laves phase. The overall structure of the joint is Y2O3-MgO / Y2O3+C14-Laves layer / Ti(s,s)+C14-Laves / α-Ti+β-(Ti,Zr) / titanium alloy.

[0014] 3. This invention achieves a Y2O3-MgO nanocomposite ceramic / titanium alloy joint with excellent mechanical properties and the ability to withstand certain high temperatures. The invention innovatively introduces a 10μm-thick Ti foil between the Y2O3-MgO nanocomposite ceramic and the brazing filler metal. This foil dissolves after the brazing filler metal melts, increasing the proportion of Ti-based solid solution in the filler metal and reducing the proportion of intermetallic compound phases. This results in a brazed joint structure dominated by Ti-based solid solution, enhancing the joint's plasticity and toughness, and achieving a room-temperature shear strength of 36MPa. This invention addresses the current application of joining Y2O3-MgO nanocomposite ceramics, an infrared window material, to titanium alloys, and proposes a high-strength and highly stable brazing method. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a backscattered electron scanning image of the joint obtained in experiment three;

[0016] Figure 2 for Figure 1 A partial enlarged view of the middle area A;

[0017] Figure 3 for Figure 1 A partial enlarged view of the middle area B;

[0018] Figure 4 This is the high-angle annular dark field image (HAADF) of the Y2O3-MgO / TiZrNi interface in experiment three and the diffraction pattern in area i in the figure. DETAILED DESCRIPTION

[0019] Specific embodiment 1: This embodiment is a method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal, which is specifically carried out in the following steps:

[0020] 1. Carry out preliminary cleaning of the parent material Y2O3-MgO nanocomposite ceramics and the parent material titanium alloy;

[0021] 2. Take a foil-shaped TiZrNi solder, polish both sides of the foil-shaped TiZrNi solder with sandpaper to remove the surface impurity layer, take a 10 μm thick Ti foil, ultrasonically clean the TiZrNi solder and the Ti foil in alcohol or acetone, blow dry and set aside; the composition of each element in the TiZrNi solder in atomic percentage is: 50% Ti, 25%-30% Zr and 20%-25% Ni;

[0022] 3. Place the TiZrNi solder and Ti foil processed in step 2 between the two base materials cleaned in step 1, and stack them in the order of titanium alloy / TiZrNi solder / Ti foil / Y2O3-MgO nanocomposite ceramic to obtain a sample to be welded;

[0023] 4. Place the sample to be welded in step 3 into a vacuum furnace. Apply pressure to the upper end of the sample to ensure close contact between the sample surface and the brazing material during brazing. The vacuum degree in the furnace is maintained at 6×10 -3 Pa; firstly, heat from room temperature to 300℃~320℃, then heat to 830℃~870℃, then heat to the connection temperature of 880℃~980℃ and keep it for 0~30min, then cool to 300℃~320℃. The vacuum degree of the whole process is ≤1×10 -2 Pa, and finally cooled to room temperature with the furnace, completing the brazing connection between Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal.

[0024] Specific Embodiment 2: This embodiment differs from Specific Embodiment 1 in that the preliminary cleaning of the Y2O3-MgO nanocomposite ceramic and titanium alloy parent materials in step 1 is as follows: the Y2O3-MgO nanocomposite ceramic and titanium alloy parent materials are cut, and then the surfaces to be welded of the Y2O3-MgO nanocomposite ceramic and titanium alloy parent materials are polished using 600#, 1000#, 2000#, and 3000# metallographic sandpaper in sequence until the surfaces are glossy. The surfaces are then ultrasonically cleaned in alcohol for 10-15 minutes each, and dried with a hair dryer for later use. Other procedures are the same as Specific Embodiment 1.

[0025] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that the Y2O3-MgO nanocomposite ceramic described in step 1 is a dense ceramic material obtained by sintering nano-Y2O3 and nano-MgO in a volume ratio of 1:1. Other aspects are the same as specific embodiment 1 or 2.

[0026] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the titanium alloy described in step 1 is TC4. Other aspects are the same as specific embodiments 1 to 3.

[0027] Specific embodiment 5: This embodiment differs from specific embodiment 4 in that the TiZrNi solder in step 2 is made of Ti, Zr and Ni by vacuum arc melting or induction melting. Other aspects are the same as specific embodiment 4.

[0028] Specific embodiment 6: This embodiment differs from specific embodiment 5 in that the melting temperature in step 2 is 1100° C. and the melting is repeated 2 to 3 times. Other aspects are the same as specific embodiment 5.

[0029] Specific embodiment 7: This embodiment differs from specific embodiment 6 in that in step 2, the TiZrNi solder and the Ti foil are ultrasonically cleaned in alcohol or acetone for 10 to 15 minutes. Other aspects are the same as specific embodiment 6.

[0030] 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.

[0031] Specific embodiment 9: This embodiment differs from specific embodiment 8 in that in step 4, the temperature is subsequently raised to 830° C. to 870° C. at a heating rate of 10° C. / min. Other steps are the same as those of specific embodiment 8.

[0032] Specific embodiment 10: This embodiment differs from specific embodiment 9 in that in step 4, the temperature is further increased at a heating rate of 5°C / min to a connection temperature of 880°C to 980°C and held at that temperature for 0 to 30 minutes, and then the temperature is cooled at a cooling rate of 5°C / min to 300°C to 320°C. Other aspects are the same as specific embodiment 9.

[0033] The present invention is verified by the following test:

[0034] Experiment 1: This experiment is a method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal. The specific steps are as follows:

[0035] 1. Perform preliminary cleaning of the Y2O3-MgO nanocomposite ceramic and titanium alloy TC4: cut the Y2O3-MgO nanocomposite ceramic and titanium alloy, and then use 600#, 1000#, 2000# and 3000# metallographic sandpaper to polish the Y2O3-MgO nanocomposite ceramic and titanium alloy surfaces 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.

[0036] The Y2O3-MgO nanocomposite ceramic is a dense ceramic material obtained by sintering nano Y2O3 and nano MgO in a volume ratio of 1:1;

[0037] 2. Take a foil-shaped TiZrNi solder, polish both sides of the foil-shaped TiZrNi solder with sandpaper to remove the surface impurity layer, take a 10 μm thick Ti foil, ultrasonically clean the TiZrNi solder and the Ti foil in alcohol for 10 minutes, blow dry and set aside; the composition of each element in the TiZrNi solder in atomic percentage is: 50% Ti, 29% Zr and 21% Ni; the thickness of the TiZrNi solder is 100 μm;

[0038] The TiZrNi solder is made of Ti, Zr and Ni by vacuum arc melting at a temperature of 1100°C and repeated melting twice.

[0039] 3. Place the TiZrNi solder and Ti foil processed in step 2 between the two base materials cleaned in step 1, and stack them in the order of TC4 / TiZrNi solder / Ti foil / Y2O3-MgO nanocomposite ceramic to obtain a sample to be welded;

[0040] 4. Place the sample to be welded in step 3 into a vacuum furnace. Apply pressure to the upper end of the sample to ensure close contact between the sample surface and the brazing material during brazing. The vacuum degree in the furnace is maintained at 6×10 -3 Pa below; firstly, the temperature was raised from room temperature to 300°C at a heating rate of 5°C / min, then to 870°C at a heating rate of 10°C / min, then to the connection temperature of 940°C at a heating rate of 5°C / min and kept at that temperature for 10 minutes, and then cooled to 300°C at a cooling rate of 5°C / min. The vacuum degree of the whole process was ≤1×10 -2 Pa, and finally cooled to room temperature with the furnace, completing the brazing connection between Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal.

[0041] Experiment 2: This experiment differs from Experiment 1 in that the connection temperature in step 4 is 940°C and the holding time is 0 min. Other conditions are the same as Experiment 1.

[0042] Test 3: This test differs from Test 1 in that the connection temperature in step 4 is 940°C and kept at this temperature for 20 minutes. Other conditions are the same as in Test 1.

[0043] Test 4: This test differs from Test 1 in that the connection temperature in step 4 is 940°C and the temperature is maintained for 30 minutes. Other conditions are the same as in Test 1.

[0044] Comparative Experiment 1: This experiment differs from Experiment 1 in that no Ti foil is used. That is, in step 3, the TC4 / TiZrNi solder / Y2O3-MgO nanocomposite ceramics are stacked in this order to obtain the sample to be welded. Other procedures are the same as Experiment 1.

[0045] Table 1

[0046]

[0047] Table 1 shows the shear strength test data of Y2O3-MgO nanocomposite ceramic / titanium alloy dissimilar material joints completed in various experiments. It can be seen from the table that when the welding method of the present invention is used to connect Y2O3-MgO nanocomposite ceramic and titanium alloy, the room temperature shear strength of the obtained joint can reach a maximum of 36 MPa.

[0048] Figure 1 This is the backscattered electron scanning image of the joint obtained in experiment three. Region I is the reaction layer on the Y2O3-MgO nanocomposite ceramic parent material side, region II is the central structure of the brazing seam, and region III is the metallurgical reaction layer on the TC4 parent material side. It can be seen that the joint is dense as a whole, and the interfaces on both sides are well bonded without obvious defects.

[0049] Figure 2 for Figure 1 From the partial enlarged view of the middle area A, it can be seen that the solder TiZrNi reacts with one side of the Y2O3-MgO nanocomposite ceramic to form a reaction layer about 2μm thick.

[0050] Figure 3 for Figure 1 A partial enlarged view of area B in the middle.

[0051] Table 2 is Figure 2 and Figure 3 The elemental composition and possible phases of points 1-7. It is preliminarily speculated that the reaction layer on the ceramic side at point 1 is Y2O 3+ TiZrNi, the two light white areas are TiZrNi phases, the three dark gray areas are Ti-based solid solutions, and the four areas are TiZrNi phases; areas 5, 6, and 7 are all Ti-based solid solutions with different components.

[0052] Table 2

[0053]

[0054] Figure 4 The high angle annular dark field image (HAADF) of the Y2O3-MgO / TiZrNi interface in experiment 3 and the diffraction pattern of area i in the figure can determine that the TiZrNi phase in the brazing seam is C14-Laves phase (Ti 40 Zr 30 Ni 30 The interface reaction layer is composed of Y2O3 phase and C14-Laves phase distributed alternately, forming a composite structure.

Claims

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

1. Carry out preliminary cleaning of the parent material Y2O3-MgO nanocomposite ceramics and the parent material titanium alloy; 2. Take a foil-shaped TiZrNi solder, polish both sides of the foil-shaped TiZrNi solder with sandpaper to remove the surface impurity layer, take a 10 μm thick Ti foil, ultrasonically clean the TiZrNi solder and the Ti foil in alcohol or acetone, blow dry and set aside; the composition of each element in the TiZrNi solder in atomic percentage is: 50% Ti, 25%-30% Zr and 20%-25% Ni; 3. Place the TiZrNi solder and Ti foil processed in step 2 between the two base materials cleaned in step 1, and stack them in the order of titanium alloy / TiZrNi solder / Ti foil / Y2O3-MgO nanocomposite ceramic to obtain a sample to be welded; 4. Place the sample to be welded in step 3 into a vacuum furnace. Apply pressure to the upper end of the sample to ensure close contact between the sample surface and the brazing material during brazing. The vacuum degree in the furnace is maintained at 6×10 -3 Pa; firstly, heat from room temperature to 300℃~320℃, then heat to 830℃~870℃, then heat to the connection temperature of 880℃~980℃ and keep it for 0~30min, then cool to 300℃~320℃. The vacuum degree of the whole process is ≤1×10 -2 Pa, and finally cooled to room temperature with the furnace, completing the brazing connection between Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal.

2. The method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal according to claim 1, characterized in that: The steps for preliminary cleaning of the base material Y2O3-MgO nanocomposite ceramic and the base material titanium alloy in step 1 are as follows: cut the Y2O3-MgO nanocomposite ceramic base material and the titanium alloy base material, and then use 600#, 1000#, 2000# and 3000# metallographic sandpaper to polish the welded surface of the Y2O3-MgO nanocomposite ceramic and the welded surface of the titanium alloy base material until the surface is glossy, put them into alcohol for ultrasonic cleaning for 10min~15min, and blow dry them with a hair dryer for later use.

3. The method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal according to claim 1, characterized in that: The Y2O3-MgO nanocomposite ceramic described in step 1 is a dense ceramic material obtained by sintering nano Y2O3 and nano MgO in a volume ratio of 1:

1.

4. The method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal according to claim 1, characterized in that: The titanium alloy described in step 1 is TC4.

5. The method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal according to claim 1, characterized in that: The TiZrNi solder described in step 2 is prepared by vacuum arc melting or induction melting of Ti, Zr and Ni.

6. The method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal according to claim 5, characterized in that: The melting temperature in step 2 is 1100° C. and the melting is repeated 2 to 3 times.

7. The method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal according to claim 1, characterized in that: In step 2, the TiZrNi solder and the Ti foil are placed in alcohol or acetone and ultrasonically cleaned for 10 to 15 minutes.

8. The method for brazing Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal according to 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 TiZrNi brazing filler metal according to claim 8, characterized in that: In step 4, the temperature is then increased to 830°C~870°C at a heating rate of 10°C / min.

10. The method for heterogeneous brazing of Y2O3-MgO nanocomposite ceramics and titanium alloy using TiZrNi brazing filler metal according to claim 9, characterized in that: In step 4, the temperature is raised to the connection temperature of 880°C~980°C at a heating rate of 5°C / min and kept at this temperature for 0~30min, and then cooled to 300°C~320°C at a cooling rate of 5°C / min.

Images