A kind of multi-element aluminum-based brazing filler metal, preparation method and application thereof

Abstract

The present invention discloses a multi-component aluminum-based solder, a preparation method and application thereof. The multi-component aluminum-based solder comprises, by weight percentage, 60% to 75% aluminum, 20% to 32% copper, 1% to 3% gallium, 0.2% to 2.3% indium, 0.1% to 2.5% tin, and the remainder is strontium and nickel. The preparation method of the multi-component aluminum-based solder comprises: melting aluminum and an aluminum-copper intermediate alloy to obtain an aluminum-copper mixed liquid; adding gallium, indium, tin, strontium and nickel to the aluminum-copper mixed liquid and stirring and melting to obtain a multi-component aluminum-based solder casting liquid; casting the multi-component aluminum-based solder casting liquid into a multi-component aluminum-based solder mold to obtain a multi-component aluminum-based solder. The multi-component aluminum-based solder of the present invention has high strength and low melting point, and can prevent overburning and dissolution of the base material.

Description

Technical Field

[0001] The invention belongs to the technical field of new welding materials, and specifically relates to a multi-element aluminum-based solder, a preparation method and application thereof. Background Art

[0002] Aluminum alloy materials have the advantages of low density, high specific strength, good low-temperature toughness, and easy processing and forming. In the aviation, aerospace, automobile, machinery manufacturing and other industrial fields, they have become a type of non-ferrous light metal material with a large number of applications, second only to steel. Low-melting-point, high-strength aluminum-based brazing filler metals are widely used in high-speed rail, aviation, shipbuilding and other structural parts. Brazing is a precise and efficient welding method with a wide range of applications. The existing aluminum-based brazing filler metals have a high melting point, which can easily cause the base material to overburn during brazing. Therefore, it is of great significance to reduce the melting point of aluminum-based brazing filler metals.

[0003] In the process of developing new lead-free solders, in order to prevent the base material from overburning, reducing the melting point of aluminum-based solders has become a hot topic for many researchers. In recent years, more and more scholars have used Al-Si, Al-Cu, Al-Zn, Al-Mg binary alloys and Al-Si-Cu, Al-Si-Zn ternary alloys as theoretical support, and have developed and prepared a series of new lead-free, low-melting-point, high-strength aluminum-based solders using alloying and low-melting-point elements, and studied their welding performance. Zhang Qiyuan et al. and Zhou Fei et al. studied the effect of Si content in Al-Si solder on the melting point of the solder. When the solder is in a hypoeutectic state, the solder has good corrosion resistance, fluidity and wettability. However, the lamellar structure of Si in Al-Si brazing filler metal reduces the mechanical properties of the solder. At the same time, the melting point of Al-Si brazing filler metal is as high as 577°C, which will cause problems such as overburning and dissolution of the base material. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a multi-element aluminum-based brazing filler metal, a preparation method and application thereof, which has high strength and low melting point and can prevent overburning and dissolution of the base material.

[0005] In order to solve the above technical problems, the present invention is implemented by the following technical solutions:

[0006] A multi-element aluminum-based solder comprises, by weight percentage, 60% to 75% aluminum, 20% to 32% copper, 1% to 3% gallium, 0.2% to 2.3% indium, 0.1% to 2.5% tin, and the remainder being strontium and nickel.

[0007] A method for preparing a multi-element aluminum-based solder comprises:

[0008] Melting aluminum and aluminum-copper master alloy to obtain aluminum-copper mixed liquid;

[0009] Adding gallium, indium, tin, strontium and nickel into the aluminum-copper mixed solution and stirring and melting them to obtain a multi-component aluminum-based solder casting solution;

[0010] The multi-component aluminum-based solder casting liquid is poured into a multi-component aluminum-based solder mold to obtain the multi-component aluminum-based solder.

[0011] Furthermore, the copper content in the aluminum-copper master alloy is 50%.

[0012] Furthermore, adding gallium, indium, tin, strontium and nickel into the aluminum-copper mixed solution and stirring and melting the mixture also includes adding a refining agent for refining.

[0013] Furthermore, the refining agent is added to a depth of 1 cm to 4 cm.

[0014] Furthermore, the refining time is 1 min to 3 min.

[0015] Furthermore, the refining agent is argon.

[0016] An application of a multi-component aluminum-based brazing filler metal, using the multi-component aluminum-based brazing filler metal to weld a parent material.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects:

[0018] The present invention provides a multi-element aluminum-based solder, which includes, by weight percentage, 60% to 75% aluminum, 20% to 32% copper, 1% to 3% gallium, 0.2% to 2.3% indium, 0.1% to 2.5% tin, and the rest is strontium and nickel. The addition of low-melting-point elements Ga, In, and Sn can form GaIn3Sn phase and GaInSn4 phase. GaIn3Sn phase and GaInSn4 phase have liquid phase channel effect, which can improve the fluidity of Cu element, increase the wettability and spreadability of solder, and promote the metallurgical bonding effect of Cu element and parent material element Al. Cu element can form θ(Al2Cu) phase with Al element, which reduces the melting point of solder, and strontium and nickel can play the effect of grain refinement.

[0019] The melting range of the aluminum-based brazing filler metal of the present invention is 542°C to 554°C, and the minimum melting temperature range is △ t=18.77°C. It can braze aluminum alloys with a solidus line above 580°C, and has a wide range of applications. The aluminum-based brazing filler metal of the present invention does not require a vacuum environment during brazing, and the smelting equipment and brazing equipment have simple structures, convenient operation, low manufacturing costs, and can be mass-produced. The aluminum-based brazing filler metal of the present invention brazes pure aluminum at a brazing temperature of 570 to 580°C and a heat preservation time of 20 minutes. The hardness of the obtained brazed joint is as high as 120HV, and a jagged metallurgical bonding morphology can be formed, and the brazed joint is smooth and flat.

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the specific implementation modes of the present invention, the drawings required for use in the description of the specific implementation modes will be briefly introduced below. Obviously, the drawings described below are some implementation modes of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 In the figure, (a) is a melting characteristic analysis diagram of the aluminum-based solder of Examples 1 to 3, and (b) is a liquidus point change trend analysis diagram of the aluminum-based solder of Examples 1 to 3 (2% GaIn3Sn to 6% GaIn3Sn);

[0023] Figure 2 In the figure, (a) is a melting characteristic analysis diagram of the aluminum-based solder of Examples 3 to 6, and (b) is an analysis of the liquidus point variation trend of the aluminum-based solder of Examples 3 to 6 (2% GaInSn4 to 6% GaInSn4);

[0024] Figure 3 This is a melting characteristic analysis diagram of the aluminum-based solder of the comparative example;

[0025] Figure 4 This is a microstructure analysis diagram of the aluminum-based solder of Examples 1 to 3;

[0026] Figure 5 This is a microstructure analysis diagram of the aluminum-based solder of Examples 3 to 6;

[0027] Figure 6 This is a microstructure analysis diagram of the aluminum-based solder of the comparative example;

[0028] Figure 7 This is the metallographic microstructure of the joint of Al-30%Cu-GaIn3Sn ultrasonic brazing of pure aluminum;

[0029] Figure 8 This is the metallographic microstructure of the joint of Al-30%Cu-GaInSn4 ultrasonic brazing of pure aluminum;

[0030] Fig. 9 This is the metallographic microstructure diagram of the joint of Al-25%Cu ultrasonic brazing of pure aluminum;

[0031] Fig.10 is a microhardness distribution curve of the brazed joints of Examples 1 to 3;

[0032] Fig.11 is a microhardness distribution curve diagram of the brazed joints of Examples 3 to 6;

[0033] Fig.12 It is the microhardness distribution curve of the brazed joint of the comparative example. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Embodiment 1:

[0036] A multi-element aluminum-based solder comprises, by weight percentage, 67.9% aluminum, 30% copper, 1% gallium, 0.75% indium, 0.25% tin, 0.08% strontium and 0.02% nickel (2% GaInSn, In:Sn=3:1).

[0037] A method for preparing a multi-element aluminum-based solder is as follows:

[0038] 1) Weighing raw materials: Weighing each component according to the proportion of aluminum-based solder, wherein aluminum is added in the form of an aluminum ingot with a purity of 99.99%, the purity of Ga, In, Sn, Sr and Ni raw materials are all greater than 99.99%, and copper is added in the form of an aluminum-copper master alloy, in which the copper content is 50%;

[0039] Instead of pure copper, Al-50% Cu alloy raw material was selected. Firstly, it can lower the solidus and liquidus temperature of aluminum-based solder; secondly, it can reduce the burning loss of low-melting-point alloy elements, which is beneficial to the precise control of solder alloy composition and improve the accuracy of solder composition.

[0040] 2) Cleaning raw materials: Use alcohol to ultrasonically clean pure aluminum, aluminum-copper alloy, Ga, In, Sn, Sr and Ni raw materials to remove surface impurities and oil stains;

[0041] 3) Rough refining: put the aluminum ingot with a purity of 99.99% and the aluminum-copper master alloy into the graphite crucible of the high-frequency induction heating furnace, and melt them into an aluminum-copper mixed liquid at a melting temperature of 750°C;

[0042] Adding Ga, In, Sn, Sr and Ni elements according to the above weight percentages to the aluminum-copper mixed solution and stirring thoroughly, keeping the mixture at 750° C. for 5 minutes, removing the scum on the surface of the melt, and obtaining a multi-component aluminum-based brazing filler metal casting solution;

[0043] 4) Refining: Add a refining agent to the roughly refined multi-component aluminum-based solder casting liquid for refining. The refining agent is high-purity argon gas, which is introduced from the top of the solution using a graphite tube. The refining agent is introduced to a depth of 3 cm. The refining time is 2 minutes. At the same time, the refining agent is uniformly stirred to obtain the refined multi-component aluminum-based solder casting liquid;

[0044] 5) Casting: After the temperature of the refined multi-component aluminum-based brazing alloy casting liquid stabilizes to 750°C, remove the surface scum, stir evenly and cast it into the multi-component aluminum-based brazing alloy graphite casting mold. During casting, the graphite casting mold should be preheated to 100°C, and finally an aluminum-based brazing alloy with low melting point, high strength and excellent wetting and spreading properties is obtained.

[0045] The aluminum-based solder prepared in this embodiment is used to weld the base material, as follows:

[0046] a. Prepare the base material into a disc with a diameter of 30 mm and a thickness of 3 mm, polish it on a 500 to 3000 mesh water paper, put it in a sodium hydroxide solution, stay for 15 seconds, take it out and put it in nitric acid to neutralize the sodium hydroxide, then ultrasonically clean the base material for 2 to 3 minutes and blow it dry to remove surface grease and oxide film;

[0047] b. The aluminum-based solder is 10×10×3mm, then polished on 500 to 5000 mesh water paper, then put the aluminum-based solder into alcohol for ultrasonic cleaning for 2 to 3 minutes, and blow dry;

[0048] c. The aluminum-based brazing filler metal is sandwiched between two pieces of pure aluminum base metal, placed in a fixed fixture, and ultrasonic brazing is performed in a protective gas furnace under the protection of inert gas, heated to 570°C, and kept warm for 20 minutes;

[0049] d. After cooling to 400℃ in the furnace, air-cool it to obtain the brazed joint.

[0050] Embodiment 2:

[0051] A multi-component aluminum-based solder comprises, by weight percentage, 65.9% aluminum, 30% copper, 2% gallium, 1.5% indium, 0.5% tin, 0.06% strontium and 0.04% nickel (4% GaInSn, In:Sn=3:1).

[0052] The preparation method and brazing method are the same as those in Example 1.

[0053] Embodiment 3:

[0054] A multi-component aluminum-based solder comprises, by weight percentage, 63.9% aluminum, 30% copper, 3% gallium, 2.25% indium, 0.75% tin, 0.04% strontium and 0.06% nickel (6% GaInSn, In:Sn=3:1).

[0055] The preparation method and brazing method are the same as those in Example 1.

[0056] from Figure 1 As shown in (a) and (b), when the total amount of GaInSn element increases from 2% to 6%, the liquidus point drops from 550℃ to 546℃, indicating that the addition of GaInSn element can effectively modify the melting characteristics of the solder. The melting point of the prepared solder is lower than the temperature of pure aluminum base material, and the melting temperature is low, which can meet the requirements of ultrasonic assisted brazing of pure aluminum. Because the added content is small, the temperature drop is not obvious. There is only one peak in the three solders, indicating that the solder is almost entirely uniform and single eutectic structure, so the solder has good fluidity, which is conducive to filling the gap during brazing.

[0057] Figure 4 (a), (b), (c) are scanning electron microscope images of Al-30%Cu-2%GaIn3Sn, Al-30%Cu-4%GaIn3Sn, and Al-30%Cu-6%GaIn3Sn solders, respectively. The three groups of solder organization diagrams were observed and analyzed. The results showed that with the increase of GaIn3Sn content, the alloy weight remained unchanged, the Cu element content remained unchanged, the Al element content decreased, the eutectic θ(A12Cu) phase of Al-30%Cu-6%GaIn3Sn solder increased, and the α(Al) grain refinement became more obvious. Al-30%Cu-6%GaInSn solder is a eutectic solder.

[0058] Figure 7 (a), (b), and (c) are microstructure diagrams of Al / Al-30%Cu-2%GaIn3Sn / Al, Al / Al-30%Cu-4%GaIn3Sn / Al, and Al / Al-30%Cu-6%GaIn3Sn / Al joints, respectively. By observing and analyzing the fracture microstructure, with the increase of Ga, In, and Sn element content, the liquid phase channel effect in the semi-solid solder is obvious, and the Cu atoms in the aluminum-based solder can diffuse into the base material through the liquid phase channel. The interface between the solder and the base material begins to fluctuate, the fusion increases, and the interface diffusion is smooth.

[0059] Fig.10 The figure is a hardness curve of Al-Cu-Ga-In-Sn (In:Sn=3:1) brazed joint. The brazed joint is divided into three areas, including the base material, diffusion area and brazing center area. The base material hardness is 24HV, and the brazing material contains Al2Cu intermetallic compounds. Therefore, the hardness of the brazing center area in the brazed joint is the highest. Fig.10 It can be seen that the hardness of Al-30%-Cu-2%GaIn3Sn is about 80HV, the hardness of Al-30%Cu-4%GaIn3Sn is about 60HV, and the hardness of Al-30%Cu-6%GaIn3Sn is about 85HV. The Al-30%Cu-6%GaIn3Sn brazed joint has the highest hardness, so its tensile strength is also good, and the brazing effect is the best.

[0060] Embodiment 4:

[0061] A multi-element aluminum-based solder comprises, by weight percentage, 67.9% aluminum, 30% copper, 1% gallium, 0.2% indium, 0.8% tin, 0.08% strontium and 0.02% nickel (2% GaInSn, In:Sn=1:4).

[0062] The preparation method and brazing method are the same as those in Example 1.

[0063] Embodiment 5:

[0064] A multi-component aluminum-based solder comprises, by weight percentage, 65.9% aluminum, 30% copper, 2% gallium, 0.4% indium, 1.6% tin, 0.06% strontium and 0.04% nickel (4% GaInSn, In:Sn=1:4).

[0065] The preparation method and brazing method are the same as those in Example 1.

[0066] Embodiment 6:

[0067] A multi-component aluminum-based solder comprises, by weight percentage, 63.9% aluminum, 30% copper, 3% gallium, 0.6% indium, 2.4% tin, 0.04% strontium and 0.06% nickel (6% GaInSn, In:Sn=1:4).

[0068] The preparation method and brazing method are the same as those in Example 1.

[0069] from Figure 2 It can be seen that when the mass percentage of GaInSn element increases from 2% to 6%, the liquidus point drops from 550°C to 546°C, indicating that the addition of low-melting-point GaInSn elements can not only play the role of liquid phase channel, but also effectively improve the melting characteristics of the solder.

[0070] Figure 5(d), (e), and (f) are scanning electron microscope images of Al-30%Cu-2%GaInSn4, Al-30%Cu-4%GaInSn4, and Al-30%Cu-6%GaInSn4 solders, respectively. The three solder organization diagrams were observed and analyzed, and it was found that with the increase of GaInSn content, the alloy weight remained unchanged, the Cu element content remained unchanged, and the Al element content decreased. The eutectic θ(A12Cu) phase increased in the Al-30%Cu-6%GaInSn4 solder. The α(Al) grain refinement was more obvious. The Al-30%Cu-6%GaInSn4 solder is a eutectic solder. The InSn4 eutectic distribution in the Al-30%Cu-Ga-In-Sn (In:Sn=1:4) solder is uniform, and there is no aggregation phenomenon.

[0071] Figure 8 (d), (e), and (f) are the microstructures of Al / Al-30%Cu-2%GaInSn4 / Al, Al / Al-30%Cu-4%GaInSn4 / Al, and Al / Al-30%Cu-6%GaInSn4 / Al joints, respectively. By observing and analyzing the fracture microstructure, the results show that the brazed joint structure is mainly composed of α(Al) solid solution, θ(A12Cu) phase, and InSn4 phase. Ga is mainly dissolved in α(Al) solid solution. It can be clearly seen that the brazing filler metal diffuses into the base material, and the interface is in a wavy form. The diffusion depth at the interface of Al / Al-30%Cu-6%GaInSn4 / Al joint is as high as 50 microns. The undulations of the brazing seam interface are more obvious. Compared with the Al / Al-30%Cu-GaIn3Sn / Al brazing joint, the α(Al) equiaxed grains in the Al / Al-30%Cu-GaInSn4 / Al brazing joint are finer, with a diameter of about 20 microns, and the ultrasonic refinement effect is more obvious.

[0072] Fig.11 The figure is a hardness curve of Al-Cu-Ga-In-Sn (In:Sn=1:4) brazed joints, and the brazed joints are divided into three areas, including the base metal, the diffusion area and the brazing seam center area. The hardness of the brazing seam center of Al-30%Cu-2%GaInSn4 brazed joint is about 80HV, the hardness of the brazing seam center of Al-30%Cu-4%GaInSn4 brazed joint is about 60HV, and the hardness of the brazing seam center of Al-30%Cu-6%GaInSn4 brazed joint is about 85HV.

[0073] Embodiment 7:

[0074] A multi-component aluminum-based solder comprises, by weight percentage, 75% aluminum, 20% copper, 3% gallium, 1.8% indium, 0.1% tin, 0.04% strontium and 0.06% nickel.

[0075] The preparation method and brazing method are the same as those in Example 1.

[0076] Embodiment 8:

[0077] A multi-element aluminum-based solder comprises, by weight percentage, 60% aluminum, 32% copper, 3% gallium, 2.3% indium, 2.5% tin, 0.1% strontium and 0.1% nickel.

[0078] The preparation method and brazing method are the same as those in Example 1.

[0079] Comparative Example:

[0080] An aluminum-based brazing filler metal comprising 75% aluminum and 25% copper.

[0081] The preparation conditions and brazing method are the same as those in Example 1.

[0082] from Figure 3 It can be seen that the solidus point T of Al-30%Cu solder s is 531.4°C, the liquidus point temperature T L The end temperature is 554℃. f The temperature of the aluminum crystals is 567.5℃, the endothermic peak range is 531.4~567.4℃, the crystallization temperature interval is 22.6℃, and the aluminum grains are coarse and long strips with a length of about 80μm and a width of about 20μm.

[0083] Figure 6 The solidification structure of Al-25%Cu solder is composed of a small amount of α(Al) phase and dense lamellar eutectic structure, which is a typical hypoeutectic structure, and the morphology of the primary α(Al) phase is approximately circular, which is a typical non-small plane solidification mode. The microstructure of Al-25%Cu alloy, the aluminum grains are coarse and long strips, about 80μm in length and about 20μm in width.

[0084] Fig. 9 This is the microstructure diagram of the Al / Al-25%Cu / Al joint. The wetting and spreading effect of the solder is poor, and no good metallurgical bonding effect is formed. The solder diffuses into a single needle-like shape.

[0085] Fig.12 The Al-30%Cu brazing joint hardness curve has obvious peaks. The brazing joint is divided into three areas, including the base metal, diffusion area and brazing seam center area. From the brazing seam center area to the base metal, the hardness value decreases successively.

[0086] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A multi-element aluminum-based brazing filler metal, characterized in that: In terms of weight percentage, it includes: 67.9% aluminum, 30% copper, 1% gallium, 0.75% indium, 0.25% tin, 0.08% strontium and 0.02% nickel; or, 65.9% aluminum, 30% copper, 2% gallium, 1.5% indium, 0.5% tin, 0.06% strontium and 0.04% nickel; or, 63.9% aluminum, 30% copper, 3% gallium, 2.25% indium, 0.75% tin, 0.04% strontium and 0.06% nickel; or, 67.9% aluminum, 30% copper, 1% gallium, 0.2% indium, 0.8% tin, 0.08% strontium and 0.02% nickel; or, 65.9% aluminum, 30% copper, 2% gallium, 0.4% indium, 1.6% tin, 0.06% strontium and 0.04% nickel; or, 63.9% aluminum, 30% copper, 3% gallium, 0.6% indium, 2.4% tin, 0.04% strontium and 0.06% nickel; or, 75% aluminum, 20% copper, 3% gallium, 1.8% indium, 0.1% tin, 0.04% strontium and 0.06% nickel; or, 60% aluminum, 32% copper, 3% gallium, 2.3% indium, 2.5% tin, 0.1% strontium and 0.1% nickel; The method for preparing a multi-element aluminum-based solder comprises: Melting aluminum and an aluminum-copper master alloy to obtain an aluminum-copper mixed solution; the aluminum-copper master alloy has a copper content of 50%; Adding gallium, indium, tin, strontium and nickel into the aluminum-copper mixed solution and stirring and melting them to obtain a multi-component aluminum-based solder casting solution; The multi-component aluminum-based solder casting liquid is poured into a multi-component aluminum-based solder mold to obtain the multi-component aluminum-based solder.

2. A multi-element aluminum-based brazing filler metal according to claim 1, characterized in that: Adding gallium, indium, tin, strontium and nickel into the aluminum-copper mixed liquid for stirring and melting also includes adding a refining agent for refining.

3. A multi-element aluminum-based brazing filler metal according to claim 2, characterized in that: The adding depth of the refining agent is 1 cm to 4 cm.

4. A multi-element aluminum-based brazing filler metal according to claim 2, characterized in that: The refining time is 1 min to 3 min.

5. The multi-element aluminum-based brazing filler metal according to claim 2, characterized in that: The refining agent is argon.

6. The multi-component aluminum-based brazing filler metal according to claim 1, characterized in that: The multi-element aluminum-based brazing filler metal is used to weld the parent material.

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