A ceramic / metal low-stress brazing method based on negative thermal expansion phase modification and ultrasonic energy field cooperation

Abstract

A low-stress brazing method for ceramics / metals based on the synergistic effect of negative thermal expansion phase modification and ultrasonic energy field is proposed. This invention aims to solve the problems of excessive residual thermal stress in existing ceramic / metal brazed joints, which leads to decreased joint strength, ceramic cracking, and even failure. The low-stress brazing method includes: 1. Ball milling and uniformly mixing negative thermal expansion phase particles with brazing filler metal powder; 2. Pressing the composite brazing filler metal powder into brazing filler metal foil; 3. Grinding the surfaces of the ceramic and metal to be brazed; 4. Placing the composite brazing filler metal between the pre-treated surfaces of the ceramic and metal to be brazed; 5. Brazing at a temperature of 300-500℃ while applying ultrasonic vibration; 6. Cooling to room temperature. This invention utilizes the cavitation and acoustic flow effects of ultrasound to achieve low-temperature bonding between ceramics and metals, and uses the negative thermal expansion phase to modify the thermal expansion coefficient of the brazed joint, reducing thermal mismatch in the brazed joint, thereby obtaining a ceramic / metal brazed joint with low residual stress and high bonding strength.

Description

Technical Field

[0001] This invention belongs to the field of dissimilar material joining technology, specifically relating to a method for achieving low-stress brazing of ceramics and metals by utilizing the negative thermal expansion phase to modify the thermal expansion behavior of the brazing filler metal and combining it with the synergistic effect of the ultrasonic energy field. Background Technology

[0002] Composite components made of ceramics and metals combine the advantages of ceramics, such as high hardness, high insulation, and low dielectric loss, with the good plasticity, high thermal conductivity, and machinability of metals. These components are increasingly widely used in power electronics, medical devices, aerospace, and other fields. These components are typically subjected to complex service environments with high external loads and drastic temperature fluctuations, which places high demands on the interfacial bonding quality and long-term service reliability of brazed joints.

[0003] Brazing is the most suitable method for joining ceramics and metals. However, there is a significant difference in the coefficients of thermal expansion between ceramics and metals: ceramics generally have a lower coefficient of thermal expansion (typically 1~10×10). -6 / K), while the coefficient of thermal expansion of metals is relatively high (e.g., Cu is about 17 × 10⁻⁶ K ...). -6 / K, Al is approximately 23 × 10 -6 Conventional brazing temperatures are generally above 500℃. Brazed joints need to undergo a cooling process from the brazing temperature to room temperature. The mismatch in thermal expansion between the two components generates significant residual thermal stress at the joint interface and within the brazed seam. This significantly reduces the mechanical properties of the joint and can even directly lead to interface cracking, resulting in product scrap. This has become a key bottleneck restricting the yield and long-term reliability of ceramic-metal components. Therefore, a method needs to be developed to effectively alleviate the thermal stress problem of ceramic-metal brazed joints.

[0004] Negative thermal expansion materials exhibit anomalous thermodynamic behavior, contracting with increasing temperature and expanding with decreasing temperature. Introducing them into welded joints can create a counter-synergistic effect with the shrinkage deformation of the base brazing filler metal, offsetting some of the stress in the joint. However, directly adding negative thermal expansion phase particles to the brazing filler metal easily leads to precipitation and agglomeration, resulting in uneven particle distribution. Furthermore, the poor wettability of negative thermal expansion phase particles with the brazing filler metal matrix makes it difficult to form an effective interfacial bond. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of excessive residual thermal stress caused by the difference in thermal expansion coefficients between ceramic / metal brazed joints, which leads to decreased joint strength, ceramic cracking, or even failure. The invention provides a low-stress brazing method for ceramic / metal based on the synergy of negative thermal expansion phase modification and ultrasonic energy field.

[0006] This invention utilizes a low-stress brazing method for ceramics / metals based on the synergistic effect of negative thermal expansion phase modification and ultrasonic energy field, implemented according to the following steps:

[0007] 1. The negative thermal expansion phase powder and the brazing filler metal powder are mixed evenly by mechanical ball milling to obtain composite brazing filler metal powder containing the negative thermal expansion phase;

[0008] 2. Press the composite solder powder containing the negative thermal expansion phase obtained in step 1 into foil, or mix the composite solder powder containing the negative thermal expansion phase obtained in step 1 with an organic binder to form solder paste, thereby obtaining composite solder.

[0009] 3. Grind the surface of the ceramic to be welded with a diamond grinding disc, then polish it with diamond polishing paste, and then ultrasonically clean it to obtain the pretreated ceramic to be welded.

[0010] The surface of the metal to be welded is polished with diamond sandpaper and ultrasonically cleaned to obtain pretreated metal to be welded.

[0011] 4. Place the composite brazing filler metal obtained in step 2 between the pretreated ceramic and metal surfaces to be welded to form a "ceramic / composite brazing filler metal / alloy" sandwich structure to obtain the workpiece to be welded.

[0012] 5. Place the assembled workpiece obtained in step 4 on a heating platform and heat it to a temperature of 300~500℃. Hold it at this temperature to melt the composite brazing filler metal for brazing. Then place the ultrasonic probe on the upper surface of the ceramic or metal to be brazed and apply ultrasonic vibration.

[0013] 6. After the ultrasonic vibration stops, cool to room temperature to complete the low-stress brazing method for ceramics / metals.

[0014] The negative thermal expansion phase is ZrW₂O₈, LiAlSiO₄, ZrV₂O₇, PbTiO₃, or Mg₂Al₄Si₅O₂. 12 .

[0015] This invention introduces a negative thermal expansion phase into the matrix brazing filler metal to prepare a composite brazing filler metal, while simultaneously introducing an ultrasonic energy field during the brazing process. The cavitation and acoustic flow effects of ultrasound are utilized to achieve low-temperature bonding between ceramic and metal, promoting the uniform dispersion of the negative thermal expansion phase in the liquid brazing filler metal and its interfacial bonding with the filler metal matrix. By modifying the thermal expansion coefficient of the brazed joint with the negative thermal expansion phase, the thermal mismatch of the brazed joint is reduced, thereby obtaining a ceramic / metal brazed joint with low residual stress and high bonding strength.

[0016] The ceramic / metal low-stress brazing method based on the synergy of negative thermal expansion phase modification and ultrasonic energy field of this invention has the following beneficial effects:

[0017] 1. This invention uses an ultrasonic energy field to promote the uniform dispersion of negative thermal expansion phase particles in liquid brazing filler metal and their bonding with the matrix interface, effectively solving the problems of particle agglomeration and uneven distribution in traditional external particle-reinforced brazing filler metals.

[0018] 2. This invention utilizes the synergistic effect of negative thermal expansion phase modification of brazed joint thermal expansion behavior and ultrasonic energy field low-temperature connection to reduce ceramic brazing temperature, reduce the generation of residual thermal stress in the joint during cooling process, and significantly improve the yield and reliability of the joint.

[0019] 3. The brazing method of the present invention is not limited by the types of ceramic and metal materials, and is applicable to the connection of various ceramics such as alumina, zirconium oxide, silicon nitride, and aluminum nitride with various metals such as aluminum alloys, copper alloys, titanium alloys, and stainless steel, and has wide material applicability and process flexibility.

[0020] 4. This invention does not require complex ceramic surface metallization pretreatment, does not require the use of corrosive flux, and the ultrasonic-assisted process does not produce harmful emissions. It has low production costs, simple process, and convenient operation, and has good application and promotion value and green environmental protection advantages. Attached Figure Description

[0021] Figure 1 This is a backscattered image of the microstructure of the 6061Al alloy / ZrO2 ceramic joint based on the synergistic effect of negative thermal expansion phase LiAlSiO4 modification and ultrasonic energy field in Example 1.

[0022] Figure 2 This is a backscattered image of the ZrO2 ceramic interface microstructure in the 6061Al alloy / ZrO2 ceramic joint based on the synergistic effect of negative thermal expansion phase LiAlSiO4 modification and ultrasonic energy field in Example 1.

[0023] Figure 3 This is a backscattered image of the 6061Al alloy interface microstructure in the 6061Al alloy / ZrO2 ceramic joint based on the synergistic effect of the negative thermal expansion phase LiAlSiO4 modification and the ultrasonic energy field in Example 1. Detailed Implementation

[0024] Specific Implementation Method 1: This implementation method, based on the synergistic effect of negative thermal expansion phase modification and ultrasonic energy field, is carried out according to the following steps:

[0025] 1. The negative thermal expansion phase powder and the brazing filler metal powder are mixed evenly by mechanical ball milling to obtain composite brazing filler metal powder containing the negative thermal expansion phase;

[0026] 2. Press the composite solder powder containing the negative thermal expansion phase obtained in step 1 into foil, or mix the composite solder powder containing the negative thermal expansion phase obtained in step 1 with an organic binder to form solder paste, thereby obtaining composite solder.

[0027] 3. Grind the surface of the ceramic to be welded with a diamond grinding disc, then polish it with diamond polishing paste, and then ultrasonically clean it to obtain the pretreated ceramic to be welded.

[0028] The surface of the metal to be welded is polished with diamond sandpaper and ultrasonically cleaned to obtain pretreated metal to be welded.

[0029] 4. Place the composite brazing filler metal obtained in step 2 between the pretreated ceramic and metal surfaces to be welded to form a "ceramic / composite brazing filler metal / alloy" sandwich structure to obtain the workpiece to be welded.

[0030] 5. Place the assembled workpiece obtained in step 4 on a heating platform and heat it to a temperature of 300~500℃ for brazing. Hold the temperature to allow the composite brazing filler metal containing the negative thermal expansion phase to completely melt. Then place the ultrasonic probe on the upper surface of the ceramic or metal to be welded and apply ultrasonic vibration.

[0031] 6. After the ultrasonic vibration stops, cool to room temperature to complete the low-stress brazing method for ceramics / metals.

[0032] The negative thermal expansion phase is ZrW₂O₈, LiAlSiO₄, ZrV₂O₇, PbTiO₃, or Mg₂Al₄Si₅O₂. 12 .

[0033] This embodiment utilizes the acoustic flow effect of the ultrasonic energy field to drive the redistribution of negative thermal expansion phase particles in the liquid brazing filler metal, breaking particle agglomeration. Simultaneously, the localized high temperature and pressure generated by cavitation bubble collapse promotes interfacial bonding between the negative thermal expansion phase and the brazing filler metal matrix. Furthermore, the cavitation and acoustic flow effects of the ultrasonic energy field can also achieve low-temperature wetting of the brazing filler metal on the ceramic surface, reducing the brazing temperature between ceramic and metal, thereby decreasing thermal stress. Through the synergistic effect of negative thermal expansion phase modification and ultrasonic energy field action, low-stress brazing of ceramic and metal is achieved.

[0034] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the mass ratio of the negative thermal expansion phase and the solder powder in step one is (1~10):(90~99).

[0035] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the solder powder mentioned in step 1 is Sn-based solder, Zn-based solder, or Al-based solder.

[0036] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method Three in that the solder powder is Zn5Al solder, Zn2Al solder, Sn powder, or Sn-5Al solder.

[0037] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the preparation process of the composite solder is replaced by:

[0038] A composite solder is prepared by mixing a negative thermal expansion phase powder with an organic binder to form a solder paste, which is then coated onto the surface of a solder foil with a thickness of 0.1~0.5mm.

[0039] In this embodiment, the organic binder is selected from terpineol or ethyl cellulose.

[0040] In this embodiment, the mass ratio of the negative thermal expansion phase powder to the solder foil is 1~10:90~99. The solder foil is Zn5Al solder, Zn2Al solder, Sn powder, or Sn-5Al solder.

[0041] In this embodiment, the negative thermal expansion phase powder can also be directly and uniformly laid on the brazing foil, or multiple layers of negative thermal expansion phase powder and brazing foil can be laid alternately.

[0042] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the ceramic to be welded in step three is ZrO2 ceramic, Al2O3 ceramic, ZTA ceramic, SiO2 ceramic, SiC ceramic, Si3N4 ceramic, or AlN ceramic.

[0043] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the metal to be welded in step three is an Al alloy, Ti alloy, Mg alloy, or stainless steel.

[0044] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the heat preservation time in step five is 3 to 10 minutes.

[0045] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the frequency of ultrasonic vibration in step five is 30~60kHz, and the ultrasonic action time is 5~50s.

[0046] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 1 to 9 in that the cooling rate is controlled to be 2 to 10°C / min in step 6.

[0047] Example 1: This example describes a low-stress brazing method for ZrO2 ceramic / 6061Al alloy based on the synergistic effect of negative thermal expansion phase modification and ultrasonic energy field, implemented according to the following steps:

[0048] 1. LiAlSiO4 powder with a particle size of about 5μm is mixed with an organic binder to form a solder paste. The solder paste is then coated between two Sn foils. The mass ratio of LiAlSiO4 powder to Sn foil is 1:99 to prepare a composite solder.

[0049] 2. Grind the ZrO2 ceramic to be welded step by step with a diamond abrasive disc (400#, 800#, 1200#), then polish with diamond polishing paste, and ultrasonically clean in anhydrous ethanol for 5 minutes. Repeat the cleaning 3 times to obtain the pretreated ceramic to be welded.

[0050] The surface of the 6061 aluminum alloy to be welded was polished step by step with diamond sandpaper (400#, 800#, 1200#), and ultrasonically cleaned in anhydrous ethanol for 5 minutes. The cleaning was repeated 3 times to obtain the pretreated metal to be welded.

[0051] 3. Place the composite brazing filler metal between the pretreated ceramic and metal surfaces to be soldered to form a "ZrO2 ceramic / composite brazing filler metal / 6061 aluminum alloy" sandwich structure. After the solder paste dries, the workpiece to be soldered is obtained.

[0052] 4. Place the assembled workpiece on the heating platform and heat it to a brazing temperature of 400℃. Hold it at this temperature for 3 minutes to allow the composite brazing filler metal to melt completely. Apply a pressure of 500 kPa to the workpiece. Then place the ultrasonic probe on the upper surface of the ZrO2 ceramic and apply ultrasonic vibration. Control the frequency of the ultrasonic vibration to be 35 kHz and the ultrasonic time to be 10 seconds.

[0053] 5. After the ultrasonic vibration stops, cool to room temperature at 5℃ / min to complete the low-stress brazing of ZrO2 ceramic / 6061Al alloy based on the synergistic effect of negative thermal expansion phase LiAlSiO4 modification and ultrasonic energy field.

[0054] from Figure 1 It can be seen that under the action of an ultrasonic energy field, the Sn-based solder modified with the negative thermal expansion phase LiAlSiO4 achieved an effective connection between 6061Al alloy and ZrO2 ceramic, and no defects such as cracks or pores appeared at the joint. Figure 2 As can be seen, the interface between the ZrO2 ceramic and the solder is tightly bonded, and no obvious brittle compound layer is formed. From... Figure 3 As can be seen, the 6061Al alloy and the brazing filler metal are also metallurgically bonded, with no obvious cracks or other defects. Shear test results show that the joint shear strength can reach up to 35 MPa. These results indicate that low-stress brazing of ZrO2 ceramics and 6061Al alloy can be achieved through the synergistic effect of negative thermal expansion phase LiAlSiO4 modification and ultrasonic energy field.

[0055] Example 2: This example describes a low-stress brazing method for Al2O3 ceramic / Mg alloy based on the synergistic effect of negative thermal expansion phase modification and ultrasonic energy field, implemented according to the following steps:

[0056] 1. Using mechanical ball milling, ZrW2O8 negative thermal expansion phase powder and Zn5Al powder with a mass ratio of 2:98 were mixed evenly. The ball milling speed was controlled at 350 r / min and the ball milling time was 3 hours to obtain composite brazing filler metal powder containing negative thermal expansion phase.

[0057] 2. Press the composite solder powder containing the negative thermal expansion phase obtained in step 1 into a foil with a thickness of 0.3 mm to obtain the composite solder;

[0058] 3. Grind the surface of the Al2O3 ceramic to be welded step by step with a diamond abrasive disc (400#, 800#, 1200#), then polish with diamond polishing paste, and ultrasonically clean in anhydrous ethanol for 5 minutes. Repeat the cleaning 3 times to obtain the pretreated ceramic to be welded.

[0059] The surface of the Mg alloy to be welded was polished step by step with diamond sandpaper (400#, 800#, 1200#), and ultrasonically cleaned in anhydrous ethanol for 5 minutes. The cleaning was repeated 3 times to obtain the pretreated metal to be welded.

[0060] 4. Place the composite brazing filler metal between the pretreated ceramic and metal surfaces to be welded to form an "Al2O3 ceramic / composite brazing filler metal / Mg alloy" sandwich structure to obtain the workpiece to be welded.

[0061] 5. Place the workpiece to be welded on the heating platform and heat it to a brazing temperature of 450℃. Hold it at this temperature for 5 minutes to allow the composite brazing filler metal to melt completely. Apply a pressure of 500 kPa to the workpiece to be welded. Then place the ultrasonic probe on the upper surface of the Al2O3 ceramic and apply ultrasonic vibration. Control the frequency of the ultrasonic vibration to be 35 kHz and the ultrasonic time to be 20 seconds.

[0062] VI. After the ultrasonic vibration stops, cool to room temperature at 2℃ / min to complete the low-stress brazing of Al2O3 ceramic and Mg alloy based on the synergistic effect of negative thermal expansion phase ZrW2O8 modification and ultrasonic energy field.

[0063] This invention prepares composite brazing filler metal by adding a negative thermal expansion phase to the filler metal matrix. Utilizing the cavitation and acoustic flow effects of the ultrasonic energy field, it achieves low-temperature bonding between ceramics and metals without the need for flux. Simultaneously, it promotes the uniform dispersion of the negative thermal expansion phase particles in the liquid filler metal and their interfacial bonding with the matrix. The ceramic / metal brazed joint prepared by this invention exhibits low residual stress and high interfacial bonding strength. It eliminates the need for complex ceramic surface metallization pretreatment, resulting in low production costs, a simple process, and ease of operation, making it highly valuable for application and promotion.

Claims

1. A low-stress brazing method for ceramics / metals based on the synergistic effect of negative thermal expansion phase modification and ultrasonic energy field, characterized in that... The ceramic / metal low-stress brazing method is implemented according to the following steps:

1. The negative thermal expansion phase powder and the brazing filler metal powder are mixed evenly by mechanical ball milling to obtain composite brazing filler metal powder containing the negative thermal expansion phase; 2. Press the composite solder powder containing the negative thermal expansion phase obtained in step 1 into foil, or mix the composite solder powder containing the negative thermal expansion phase obtained in step 1 with an organic binder to form solder paste, thereby obtaining composite solder.

3. Grind the surface of the ceramic to be welded with a diamond grinding disc, then polish it with diamond polishing paste, and then ultrasonically clean it to obtain the pretreated ceramic to be welded. The surface of the metal to be welded is polished with diamond sandpaper and ultrasonically cleaned to obtain pretreated metal to be welded.

4. Place the composite brazing filler metal obtained in step 2 between the pretreated ceramic and metal surfaces to be welded to form a "ceramic / composite brazing filler metal / alloy" sandwich structure to obtain the workpiece to be welded; 5. Place the assembled workpiece obtained in step 4 on a heating platform and heat it to a temperature of 300~500℃. Hold it at this temperature to melt the composite brazing filler metal for brazing. Then place the ultrasonic probe on the upper surface of the ceramic or metal to be brazed and apply ultrasonic vibration.

6. After the ultrasonic vibration stops, cool to room temperature to complete the low-stress brazing method for ceramics / metals. The negative thermal expansion phase is ZrW₂O₈, LiAlSiO₄, ZrV₂O₇, PbTiO₃, or Mg₂Al₄Si₅O₂. 12 .

2. The ceramic / metal low-stress brazing method based on the synergistic effect of negative thermal expansion phase modification and ultrasonic energy field as described in claim 1, characterized in that... The mass ratio of the negative thermal expansion phase to the solder powder in step one is (1~10):(90~99).

3. The ceramic / metal low-stress brazing method based on the synergistic effect of negative thermal expansion phase modification and ultrasonic energy field as described in claim 1, characterized in that... The solder powder mentioned in step one is Sn-based solder, Zn-based solder, or Al-based solder.

4. The ceramic / metal low-stress brazing method based on the synergistic effect of negative thermal expansion phase modification and ultrasonic energy field as described in claim 3, characterized in that... The solder powder is Zn5Al solder, Zn2Al solder, Sn powder, or Sn-5Al solder.

5. The ceramic / metal low-stress brazing method based on the synergistic effect of negative thermal expansion phase modification and ultrasonic energy field as described in claim 1, characterized in that... The preparation process of composite solder is replaced by: A composite solder is prepared by mixing a negative thermal expansion phase powder with an organic binder to form a solder paste, which is then coated onto the surface of a solder foil with a thickness of 0.1~0.5 mm.

6. The ceramic / metal low-stress brazing method based on the synergistic effect of negative thermal expansion phase modification and ultrasonic energy field as described in claim 1, characterized in that... The ceramic to be welded in step three is ZrO2 ceramic, Al2O3 ceramic, ZTA ceramic, SiO2 ceramic, SiC ceramic, Si3N4 ceramic, or AlN ceramic.

7. The ceramic / metal low-stress brazing method based on the synergistic effect of negative thermal expansion phase modification and ultrasonic energy field as described in claim 1, characterized in that... The metal to be welded in step three is an Al alloy, Ti alloy, Mg alloy, or stainless steel.

8. The ceramic / metal low-stress brazing method based on the synergistic effect of negative thermal expansion phase modification and ultrasonic energy field as described in claim 1, characterized in that... The heat preservation time in step five is 3 to 10 minutes.

9. The ceramic / metal low-stress brazing method based on the synergistic effect of negative thermal expansion phase modification and ultrasonic energy field as described in claim 1, characterized in that... In step five, the frequency of ultrasonic vibration is 30~60kHz, and the ultrasonic treatment time is 5~50s.

10. The ceramic / metal low-stress brazing method based on the synergistic effect of negative thermal expansion phase modification and ultrasonic energy field as described in claim 1, characterized in that... In step six, the cooling rate is controlled to be 2–10 °C / min.

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