Ultrasonic-assisted magnesium / aluminum low-temperature welding method with joint brittleness phase distribution regulation

Abstract

The present application relates to the technical field of dissimilar material brazing, in particular to a magnesium-aluminum low-temperature welding method capable of being applied to low-temperature brazing of two high-chemical-activity materials of magnesium and aluminum, and significantly improving the mechanical properties of the joint, adopting indium foil or indium alloy foil as the filler metal, realizing low-temperature preparation of the magnesium / aluminum joint under the action of the ultrasonic field, compared with the prior art, by adopting low-melting-point indium and indium alloy foil as the filler metal, under the thermal-ultrasonic coupling action, the microjet effect generated by the ultrasonic cavitation effect at the interface between the liquid filler metal and the solid base material can realize removal of the oxidation film on the surface of the base material, and promote wetting and dissolution between the filler metal and the base material; by means of the ultrasonic energy field, the magnesium / aluminum welding and joint regulation can be realized under the condition of macro low heat input.

Description

Technical Field

[0001] This invention relates to the field of brazing technology for dissimilar materials, specifically to a low-temperature brazing method for magnesium and aluminum that can be applied to the brazing of magnesium and aluminum, two highly chemically active materials, and significantly improves the mechanical properties of the joint by controlling the distribution of brittle phases in the joint using ultrasound assistance. Background Technology

[0002] Magnesium and aluminum alloys possess high specific strength, high specific stiffness, and good machinability, making them ideal lightweight materials for manufacturing various functional structures. Magnesium / aluminum bimetallic structures can integrate the performance advantages of both materials. In recent years, researchers have successfully applied magnesium / aluminum joints in aerospace, aviation, and rail transportation fields through welding, casting, and rolling. However, due to the high reactivity of both elements, they are easily oxidized in the atmosphere. The oxide film on the surface of the base material during welding and joining can hinder interfacial metallurgical reactions, leading to incomplete welding. Furthermore, magnesium and aluminum readily form brittle intermetallic compounds, typically Al12Mg17 and Al3Mg2 phases, and their content increases significantly with increasing processing temperature. Existing research indicates that when these brittle phases are abundant and continuously distributed in the joint, the shear strength of the joint does not exceed 30 MPa. Therefore, controlling the distribution of brittle phases in the joint is crucial for improving the service reliability of magnesium / aluminum bimetallic structures.

[0003] Currently, introducing a third element, such as Cu, Sn, Ni, Zn, or Ti, to participate in the interfacial metallurgical reaction to reduce the formation of brittle phases is the main measure to improve the strength of magnesium / aluminum joints. However, this method has a narrow process window, and in most cases, the welding temperature is higher than the recrystallization temperature of magnesium and aluminum, making it difficult to control the deformation and performance loss of the base material, which greatly limits its application in actual production. Summary of the Invention

[0004] This invention addresses the shortcomings and deficiencies of existing technologies by proposing an ultrasonic-assisted low-temperature magnesium-aluminum welding method with a welding temperature not exceeding 100℃ and high welding efficiency (≤10s), and controlling the distribution of brittle phases in the joint.

[0005] This invention achieves its purpose through the following measures: A method for low-temperature welding of magnesium / aluminum joints with ultrasonic-assisted control of brittle phase distribution is characterized by using indium foil or indium alloy foil as brazing filler metal, and achieving low-temperature fabrication of magnesium / aluminum joints under the action of an ultrasonic field. The method specifically includes the following steps: Step 1: Clean and dry the alloy plate and brazing foil to be soldered; Step 2: The alloy plate to be welded and the brazing foil are overlapped and fixed between the ultrasonic welding head and the heating table in the order of aluminum / brazing foil / magnesium; Step 3: Set the heating table temperature of the welding equipment to 60~100℃. After preheating, apply ultrasonic welding to the lap joint structure. Step 4: Remove the welded lap joint and allow it to cool to obtain the magnesium / aluminum alloy welded joint.

[0006] In this invention, the magnesium plate is made of AZ31B magnesium and the aluminum plate is made of 6061 aluminum.

[0007] In this invention, the solder foil material is pure indium or an indium-based alloy, with a thickness ranging from 30 to 60 μm. Furthermore, when the solder foil material is an indium-based alloy, the composition of the indium-based alloy is as follows: the mass percentage of indium is 87.6 to 93.3%, and the mass percentage of zinc is 6.7 to 12.4%.

[0008] In step 2 of this invention, the bottom dimension of the welding tooth on the ultrasonic welding head and heating platform of the ultrasonic welding equipment is 0.2±0.005mm, the top dimension is 0.05±0.005mm, the height of the welding tooth is 0.075±0.005mm, and the included angle between the left and right sides of the welding tooth is 90°. This welding tooth structure can be anchored to the surface of the base material to ensure the transmission efficiency of ultrasonic waves in the welded structure during the welding process.

[0009] In step 3 of this invention, the heating temperature range of the heating table is 60~100℃, the ultrasonic loading time range is 1~10s, and the welding head pressure is 0.4MPa.

[0010] In step 4 of this invention, the cooling environment is atmospheric, and the cooling rate is 3~5℃ / s.

[0011] Compared with existing technologies, this invention uses low-melting-point indium and indium-based alloy foil as the brazing filler metal. Under the action of thermo-ultrasonic coupling, the micro-jet effect generated by ultrasonic cavitation at the interface between the liquid brazing filler metal and the solid base material can remove the oxide film on the surface of the base material and promote wetting and dissolution between the brazing filler metal and the base material. The collapse of ultrasonic cavitation bubbles creates local high temperature and high pressure conditions, which can compensate for the energy of metallurgical bonding between atoms. In addition, the acoustic flow can promote the flow and diffusion of elements in the liquid environment, achieving the effects of mechanical dispersion and composition homogenization, thereby realizing the control of compound distribution in the joint. That is, this invention can realize the welding and joint control of magnesium / aluminum under macroscopic low heat input conditions by means of ultrasonic energy field. The data of the embodiments show that compared with the traditional welding process, the distribution of brittle aluminum-magnesium compounds in the magnesium / aluminum welded joint obtained by this invention is significantly improved, and the mechanical properties of the welded joint are significantly improved. Attached Figure Description

[0012] Appendix Figure 1 This is a schematic diagram of the magnesium / aluminum ultrasonic-assisted low-temperature welding assembly in this invention.

[0013] Appendix Figure 2 This is a schematic diagram of the ultrasonic welding head and the welding teeth on the upper part of the heating table in this invention.

[0014] Appendix Figure 3 This is a microstructure diagram of the magnesium / aluminum welded joint obtained in the embodiments of the present invention, wherein... Figure 3 (a) is a microstructure diagram of the magnesium / aluminum welded joint in Example 1. Figure 3 (b) is a microstructure diagram of the AZ31B magnesium / 6061 aluminum alloy welded joint in Example 2.

[0015] Appendix Figure 4 This refers to the magnesium / aluminum welded joint obtained by welding method in Embodiment 1 of the present invention (corresponding to...). Figure 3 a) Element distribution diagram, where Figure 4 (a) Microstructure of magnesium / aluminum welded joint in Example 1, 4(b) Aluminum distribution in joint, 4(c) Magnesium distribution in joint, 4(d) Indium distribution in joint, 4(e) Zinc distribution in joint, 4(f) Total element distribution in joint.

[0016] Figure reference numerals: 1. Ultrasonic welding head; 2. Aluminum plate of type 6061; 3. Brazing foil; 4. Magnesium plate of type AZ31B; 5. Heating table; 6. Heating tube. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments. Example

[0018] This example provides a low-temperature ultrasonic-assisted welding method for magnesium-aluminum alloys, including the following steps: S1: Place the AZ31B magnesium alloy and 6061 aluminum alloy plates and brazing foil to be soldered into alcohol, and after ultrasonic cleaning for 60 seconds, place them in a vacuum drying oven to dry at 80℃. S2: Fix the “6061 aluminum / pure indium foil / AZ31B magnesium” lap structure to be welded onto the ultrasonic welding equipment platform. The thickness of the brazing foil used is 30μm. S3: Set the heating table temperature of the welding equipment to 100℃. After preheating, apply ultrasonic welding to the lap structure. The ultrasonic loading time is 1 second. S4: Remove the welded lap joint from the equipment platform and allow it to cool to room temperature at a rate of 5℃ / s to obtain the AZ31B magnesium / 6061 aluminum alloy welded joint.

[0019] The microstructure of the AZ31B magnesium / 6061 aluminum alloy welded joint obtained using the method described in this implementation case is as follows: Figure 3As shown in (a), it can be seen that the joint has no obvious defects, and aluminum and magnesium elements have not formed layered Al12Mg17 and Al3Mg2 compound layers; the joint energy dispersive spectroscopy test results are as follows. Figure 4 As shown, it can be observed that under ultrasonic action, although a large amount of the base material elements dissolve into the weld, the presence of indium prevents the growth and continuous distribution of brittle aluminum-magnesium compounds.

[0020] Through shear testing, the average shear strength of the AZ31B magnesium / 6061 aluminum alloy lap joint obtained in this example reached 31.2 MPa. Example

[0021] This example provides a low-temperature ultrasonic-assisted welding method for magnesium-aluminum alloys, including the following steps: S1: Place the AZ31B magnesium alloy and 6061 aluminum alloy plates and brazing foil to be soldered into alcohol, and after ultrasonic cleaning for 60 seconds, place them in a vacuum drying oven to dry at 80℃. S2: Fix the “6061 aluminum / pure indium foil / AZ31B magnesium” lap structure to be welded onto the ultrasonic welding equipment platform. The thickness of the brazing foil used is 30μm. S3: Set the heating table temperature of the welding equipment to 100℃. After preheating, apply ultrasonic welding to the lap structure. The ultrasonic loading time is 4s. S4: Remove the welded lap joint from the equipment platform and allow it to cool to room temperature at a rate of 5℃ / s to obtain the AZ31B magnesium / 6061 aluminum alloy welded joint.

[0022] The microstructure of the AZ31B magnesium / 6061 aluminum alloy welded joint obtained using the method described in this implementation case is as follows: Figure 3 As shown in b, it can be seen that the joint is well formed; aluminum and magnesium elements do not form layered compounds, but are dispersed in the weld as small-volume Al12Mg17 compounds (black phase), which play a role in dispersion strengthening. Shear tests showed that the average shear strength of the AZ31B magnesium / 6061 aluminum alloy lap joint reached 38.2 MPa, which was 22.4% higher than that of Example 1. Example

[0023] This example provides a low-temperature ultrasonic-assisted welding method for magnesium-aluminum alloys, including the following steps: S1: Place the AZ31B magnesium alloy and 6061 aluminum alloy plates and brazing foil to be soldered into alcohol, and after ultrasonic cleaning for 60 seconds, place them in a vacuum drying oven to dry at 80℃. S2: Fix the “6061 aluminum / pure indium foil / AZ31B magnesium” lap structure to be welded onto the ultrasonic welding equipment platform. The thickness of the brazing foil used is 30μm. S3: Set the heating table temperature of the welding equipment to 60℃. After preheating, apply ultrasonic welding to the lap structure. The ultrasonic loading time is 2s. S4: Remove the welded lap joint from the equipment platform and allow it to cool to room temperature at a rate of 5℃ / s to obtain the AZ31B magnesium / 6061 aluminum alloy welded joint. The AZ31B magnesium / 6061 aluminum alloy welded joint obtained by the method of this embodiment has an average shear strength of 45.7 MPa after shear testing, which is 46.5% higher than that of Example 1. Example

[0024] This example provides a low-temperature ultrasonic-assisted welding method for magnesium-aluminum alloys, including the following steps: S1: Place the AZ31B magnesium alloy and 6061 aluminum alloy plates and brazing foil to be soldered into alcohol, and after ultrasonic cleaning for 60 seconds, place them in a vacuum drying oven to dry at 80℃. S2: Fix the “6061 aluminum / pure indium foil / AZ31B magnesium” lap structure to be welded onto the ultrasonic welding equipment platform. The thickness of the brazing foil used is 60μm. S3: Set the heating table temperature of the welding equipment to 100℃. After preheating, apply ultrasonic welding to the lap structure. The ultrasonic loading time is 4s. S4: Remove the welded lap joint from the equipment platform and allow it to cool to room temperature at a rate of 5℃ / s to obtain the AZ31B magnesium / 6061 aluminum alloy welded joint. The AZ31B magnesium / 6061 aluminum alloy welded joint obtained using the method of this embodiment has an average shear strength of 63.6 MPa after shear testing, which is 103.8% higher than that of Example 1. Example

[0025] This example provides a low-temperature ultrasonic-assisted welding method for magnesium-aluminum alloys, including the following steps: S1: Place the AZ31B magnesium alloy and 6061 aluminum alloy plates and brazing foil to be soldered into alcohol, ultrasonically clean for 60 seconds, and then dry them in a vacuum drying oven at 80℃.

[0026] S2: Fix the “6061 aluminum / indium-based alloy foil / AZ31B magnesium” lap structure to be welded on the ultrasonic welding equipment platform. The thickness of the brazing foil used is 30μm, and the foil composition is: 90% indium and 10% Zn (by mass). S3: Set the heating table temperature of the welding equipment to 80℃. After preheating, apply ultrasonic welding to the lap structure. The ultrasonic loading time is 6s. S4: Remove the welded lap joint from the equipment platform and allow it to cool to room temperature at a rate of 5℃ / s to obtain the AZ31B magnesium / 6061 aluminum alloy welded joint. The AZ31B magnesium / 6061 aluminum alloy welded joint obtained using the method of this embodiment has an average shear strength of 73.7 MPa after shear testing, which is 136.2% higher than that of Example 1.

[0027] Compared with existing technologies, this invention uses low-melting-point indium and indium-based alloy foil as the brazing filler metal. Under the action of thermo-ultrasonic coupling, the micro-jet effect generated by ultrasonic cavitation at the interface between the liquid brazing filler metal and the solid base material can remove the oxide film on the surface of the base material and promote wetting and dissolution between the brazing filler metal and the base material. The collapse of ultrasonic cavitation bubbles creates local high temperature and high pressure conditions, which can compensate for the energy of metallurgical bonding between atoms. In addition, the acoustic flow can promote the flow and diffusion of elements in the liquid environment, achieving the effects of mechanical dispersion and composition homogenization, thereby realizing the control of compound distribution in the joint. That is, this invention can realize the welding and joint control of magnesium / aluminum under macroscopic low heat input conditions by means of ultrasonic energy field. The data of the embodiments show that compared with the traditional welding process, the distribution of brittle aluminum-magnesium compounds in the magnesium / aluminum welded joint obtained by this invention is significantly improved, and the mechanical properties of the welded joint are significantly improved.

Claims

1. A method for low-temperature welding of magnesium and aluminum with ultrasonic-assisted control of brittle phase distribution in joints, characterized in that, Using indium foil or indium alloy foil as the solder, low-temperature fabrication of magnesium / aluminum joints is achieved under the action of an ultrasonic field. The specific steps include: Step 1: Clean and dry the alloy plate and brazing foil to be soldered; Step 2: The alloy plate to be welded and the brazing foil are overlapped and fixed between the ultrasonic welding head and the heating table in the order of aluminum / brazing foil / magnesium; Step 3: Set the heating table temperature of the welding equipment to 60~100℃. After preheating, apply ultrasonic welding to the lap joint structure. Step 4: Remove the welded lap joint and allow it to cool to obtain the magnesium / aluminum alloy welded joint.

2. The method for controlling the brittle phase distribution of a magnesium-aluminum joint using ultrasound assistance according to claim 1, characterized in that, The magnesium plate uses AZ31B magnesium, and the aluminum plate uses 6061 aluminum.

3. The method for controlling the brittle phase distribution of a magnesium-aluminum joint using ultrasound assistance according to claim 1, characterized in that, The solder foil material is pure indium or indium-based alloy, with a thickness ranging from 30 to 60 μm.

4. The method for controlling the brittle phase distribution of a magnesium-aluminum joint using ultrasound assistance according to claim 3, characterized in that, When the solder foil material is an indium-based alloy, the composition of the indium-based alloy is: indium by mass percentage of 87.6~93.3% and zinc by mass percentage of 6.7~12.4%.

5. The method for controlling the brittle phase distribution of a magnesium-aluminum joint using ultrasound assistance according to claim 1, characterized in that, In step 2, the bottom dimension of the welding tooth on the ultrasonic welding head and heating table of the ultrasonic welding equipment is 0.2±0.005mm, the top dimension is 0.05±0.005mm, the height of the welding tooth is 0.075±0.005mm, and the included angle between the left and right sides of the welding tooth is 90°. This welding tooth structure can be anchored to the surface of the base material to ensure the transmission efficiency of ultrasonic waves in the welded structure during the welding process.

6. The method for controlling the brittle phase distribution of a magnesium-aluminum joint using ultrasound assistance according to claim 1, characterized in that, In step 3, the heating temperature range of the heating table is 60~100℃, the ultrasonic loading time range is 1~10s, and the welding head pressure is 0.4MPa.

7. The method for controlling the brittle phase distribution of a magnesium-aluminum joint using ultrasound assistance according to claim 1, characterized in that, In step 4, the cooling environment is atmospheric, and the cooling rate is 3~5℃ / s.

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