CN103722261A - Low frequency and amplitude reciprocating friction assisted low-temperature active soft soldering method - Google Patents

Abstract

The invention discloses a low frequency and amplitude reciprocating friction assisted low-temperature active soft soldering method. The method serves as another assisted manner on low-temperature conditions, when low frequency and amplitude friction is applied, liquid phase fluidity, membrane removing effect and wettability are improved more significantly. The method includes compressing and heating solder after presetting, releasing the pressure till 330 DEG C, heating continuously till 400 to 550 DEG C, and introducing low frequency and amplitude friction. According to the method, soldering flux is omitted, the solder can be prevented from premature losing, obvious corrosion and ceramic particle segregation are avoided, the solder permeates evenly, required time for spreading is shortened, and protective gas can be provided selectively.

Description

Low-frequency low-amplitude reciprocating friction-assisted low-temperature active soldering method

Technical field:

The invention relates to the improvement of Zn-based low-melting-point brazing filler metal formula of aluminum-based composite materials and aluminum alloys and the improvement of the brazing process, and develops a flux-free low-melting-point Zn-Al-Mg series ternary active brazing filler metal formula, and for it Used in conjunction with low frequency low amplitude friction assisted active brazing methods.

Background technique:

As we all know, the primary problem to be solved in the brazing of aluminum matrix composite materials and aluminum alloys is how to effectively remove the oxide film on the surface of the aluminum substrate. At present, there are three methods to break the oxide film on the surface of aluminum alloy or aluminum matrix composite materials: (1) chemical methods, such as flux [1], cleaning with chemical reagents before welding [2], adding active elements to the solder [ 3] and other methods; (2) physical methods, such as vacuum environment [4], using the principle of liquefaction under the film [5], electroplating surface modification [2,6], etc.; (3) mechanical methods, such as using mechanical scraping method [7], wire brush [2], and ultrasonic cavitation effect (Ultrasonic cavitation effect) [8], etc. These methods have their own advantages and disadvantages. Among them, flux removal brazing, vacuum brazing, and liquid phase diffusion welding (with or without ultrasonic vibration) are commonly used, depending on the activity of the base material of the composite material, the activity of the solder alloy system, the difficulty of dissolving the base metal, and After alloying, the liquid phase viscosity and fluidity are good or bad, brazing temperature and other factors are selected comprehensively.

Among the solders that have been reported so far, the medium and low temperature solders used for welding aluminum alloys and aluminum matrix composites can be divided into three categories:

(1) Al-Si-Cu based solders[4,9,10], such as Al-28Cu-5Si[9], Al-20Cu-5Si-2Ni[10], Al-20Cu-3.3Ni-10Si[10] ], Al-28Cu-5Si-2Mg[4], Al-7Si-20Cu-2Sn-1Mg[4], Al-6Si-30Cu-20Zn[9] and other solders, the melting points of these solders are all between 450 and 550 ℃, and the welding temperature is above 550 ℃, which requires a higher melting point of the aluminum alloy matrix, and high welding temperature will also damage the interface between the ceramic phase and the aluminum alloy matrix in the aluminum matrix composite material; and it is necessary to use brazing Flux or welded in a vacuum environment. If flux is used, the corrosion resistance of the welded joint will be poor. If a vacuum environment is required, the welding cost will be high;

(2) Zn-Al series[1], Zn-Al-Cu series[7] and Al-Ge series[11], such as Zn-5Al[1], Zn-20Al[12], Zn-28Al[13] , Al-4.5Si-40Zn[14], Zn-20Al-15Cu, Zn-4Al-3Cu-1Mg[7], Al-45Ge[11], Al-45Ge-2Si[11] and other solders, these solders The melting point of the solder is between 370 and 450°C, and the welding temperature can be controlled below 550°C, but these solders need to be welded with flux or high pressure or ultrasonic assistance, which requires high equipment and increases the welding process. Or welding costs; and the cost of Cu, Ag or Ge solders is higher;

(3) Sn-Zn series[15], Sn-Pb series[6], Sn-Ag-Ti series[16] and Zn-Cd series[17], such as Sn-9Zn[15], Sn-37Pb[6] ], Sn-10Ag-4Ti[16], Zn-39Cd[17] and other solders have melting points between 150°C and 370°C, and the welding temperature generally does not exceed 450°C, but flux or ultrasonic waves must be used for welding Auxiliary to break the oxide film on the surface of the aluminum substrate; the corrosion resistance of the Sn-based solder joints is poor; the Zn-Cd-based solder containing the toxic element Cd will threaten personal safety and the environment.

Considering that the influence of the base metal structure should be reduced as much as possible during the welding process (for example, for 2024 and 475°C 7075 aluminum alloys with solidus lines of 500°C and 475°C respectively, it is necessary to prevent the aluminum alloy matrix from melting and overaging; Aluminum matrix grains need to prevent coarsening), which requires the development of low-melting point solders and soldering at as low a temperature as possible. In the field of low-temperature brazing, Zn-based low-melting-point solders are mostly used at present. For example, the reported melting points of Zn-5Al[1] and Zn-5Al-3Cu[7] are 360°C-430°C and 385°C-400°C, respectively. At the same time, in low-temperature brazing, in order to remove the film and improve wettability, the use of flux [1], especially the use of ultrasonic vibration [7] has been reported more. Relatively speaking, although the active element (Ti) has the effect of accelerating the breaking of the oxide film on the surface of the aluminum matrix in the high-temperature active liquid phase diffusion welding (610°C) of aluminum matrix composites, it has been confirmed by the applicant's research group[18,19] , but whether active elements can successfully realize the film removal reaction in low-temperature brazing is still a research blank, and its potential needs to be further studied. Especially for the commonly used Zn-Al binary solder, the applicant has confirmed in the previous research that when no flux is used and ultrasonic vibration is not introduced, it is difficult for the Zn-5Al binary eutectic solder to dissolve the base metal uniformly. , leading to insufficient and uneven liquefaction under the film (dissolution only occurs in very few positions); when the amount of solder is sufficient, Zn can penetrate into the matrix of the composite material, but the interface gap has not been eliminated, and the interface wettability is very poor[20] . Based on the above analysis, the applicant tried to obtain the dual mechanism by adding active elements (Mg) to the low-melting point Zn-Al series solder to add reactive film removal (chemical mechanism) and strengthen the liquefaction film removal under the film (physical mechanism). Aluminum substrates have ideal wettability.

On the other hand, there is another problem in the welding of aluminum matrix composites - how to avoid the segregation and depletion of the ceramic reinforced phase in the welded joint [21] and ensure the ceramic phase/surrounding matrix interface, ceramic phase/brazing seam in the welding zone Density between metal interfaces [3]. The former is related to the degree of dissolution of the base metal, that is, it depends on the interaction between the solder and the aluminum matrix; the latter depends on the improvement of the wettability between the solder and the ceramic phase. The methods for improving the wettability of the brazing joint and the ceramic phase include: optimizing the reinforcement phase, pretreatment of the ceramic reinforcement phase, adding active elements, and applying ultrasonic vibrations. However, for a given composite material base material, only the latter two methods can be selected. Among them, the method of using ultrasonic cavitation has been successfully used by Yan Jiuchun, Xu Zhiwu [8] and others in the welding of aluminum matrix composites, but the equipment cost is relatively high.

It should also be pointed out that although the low welding temperature can dissolve the aluminum matrix, it does not mean that the fluidity of the liquid phase after alloying is good. Considering that the low welding temperature is unfavorable to the fluidity of the underflow under the membrane, other improvement measures need to be considered.

The present invention aims at the above-mentioned low-melting-point Zn-Al binary brazing filler metals with uneven base metal dissolution reaction (local corrosion), poor fluidity of the liquid phase, difficulty in breaking and removing the oxide film, difficulty in removing interface gaps, etc., and properly taking into account ceramics The wettability of the phase/brazing joint metal is improved, and it is planned to develop a new ternary active solder and an auxiliary process under low temperature welding by adding active elements (Mg). According to the design principle of the active liquid phase diffusion welding (A-TLP) intermediate layer [3], the applicant successfully developed an aluminum alloy and aluminum matrix composite material by using the idea of combining active element reaction film removal and underflow film removal under the film Use low-melting point Zn-Al-Mg series ternary active solder, and develop a low-cost, low-frequency, low-amplitude friction-assisted active brazing method that can be used for this solder, which can further improve the joint strength (the effective coefficient of the joint can reach 90% ).

references:

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[2] Huang Y., Ridley N., Humphreys F.J., Cui J.Z.. Diffusion bonding of superplastic7075aluminum alloy. Materials Science and EngineeringA,1999,266:295–302.

[3] Zhang Guifeng, Zhang Jianxun, Pei Yi, Li Siyu, Chai Donglang. Joining of Al ₂ O ₃ p/Al composites by transient liquid phase (TLP) bonding and a novel process of active-transient liquid phase (A-TLP) Bonding. Materials Science Engineering A, 2008, 488:146-156.

[4] Chuang T.H., Yeh M.S., Tsao L.C., Tsai T.C., and Wu C.S.. Development of a low-melting-point filler metal for brazing aluminum alloys, Metallurgical and Materials Transactions A, 2000, 31A: 2239-2245.

[5]Gale W.F., Butts D.A..Transient liquid phase bonding,Science and Technology of Welding and Joining,2004,9(4):283-300.

[6]Zhao Zhenqing, Wang Chunqing, Du Miao, Huang Yi. Soldering of LD31 Aluminum Alloy Brush-plated SnPb Solder Alloy, Journal of Welding, 2005,26(7):67-74.

[7] Lu Shixiong, Yu Zhishui, Xu Zhiwu, Yan Jiuchun, Yang Shiqin, Wu Lin. SiCw/6061Al composite materials brazing without flux under pressure, Journal of Welding, 2001,22(4):73-75.

[8]Xu Zhiwu, Yan Jiuchun, Zhang Baoyou, Kong Xiangli, YangShiqin.Behaviors of oxide film at the ultrasonic aided interactioninterface of Zn–Al alloy and Al2O3p/6061Al composites in air[J].Materials Science and Engineering, 2 415:80–86.

[9]Tsao L.C.,Chiang M.J.,Lin W.H.,Cheng M.D.,Chuang.T H..Effects of zinc additions on the microstructure and melting temperatures of Al-Si-Cu filler metals,Materials Characterization,2002,48:341-346.

[10] Yu Wenhua, Zhu Ying, Kang Hui, Qu Ping, Hu Gang. Influence of Alloying Elements in Al-Si-Cu-Ni Low Melting Point Solder on Its Properties, Welding, 2002, 11: 21-23.

[11]Schubert T.H., Loser W., Teresiak A., Mattern N., Bauer H.D.. Preparation and phase transformations of melt-spun Al–Ge–Si brazingfoils, Journal of Materials Science, 1997,32:2181-2189.

[12]Yu Z.S., Li R.F., Qi K..Joining of SiC particle reinforcement aluminum metal matrix composites by electromagnetic field aided brazing method,Materials Science and Technology,2010,26(6):695-698

[13]Shi Lei, Yan Jiuchun, Peng Bo, Han Yanfei. Deformation behavior of semi-solid Zn–Al alloy filler metal during compression, Materials Science and Engineering: A, 528(22), :7084-7092

[14]Suzuki K, Kagayama M, Takeuchi Y. Eutectic phase equilibrium of Al-Si-Zn system and its applicability for lower temperature brazing. J Jpn Inst Light Met,1993;43(10):533-538.

[15] Toru Nagaoka, Yoshiaki Morisada, Masao Fukusumi, Tadashi Takemoto. Ultrasonic-Assisted Soldering of 5056 Aluminum Alloy Using Quasi-Melting Zn-Sn Alloy, Metallurgical and Materials Transactions B, 2010, 41:864-871.

[16] Weng WP, Chuan TH. Brazing of Aluminum Matrix Composite with Sn ₁₀ Ag ₄ Ti Active Filler Metal, Materials and Manufacturing Processes, 1997, 12(6): 1107-1132.

[17] Cao Qi, Gao Peng, Zhong Yi, Cui Xiaodong, Yao Xuefeng, Fang Daining. Forming and Microstructure Properties of 5052 Aluminum Alloy Pyramid Lattice Sandwich Panel, Materials Herald, 2011,25(2):104-106.

[18] Su Wei. Active liquid phase diffusion welding of aluminum matrix composites using Al-Si-Ti ternary active intermediate layer, Xi'an: Xi'an Jiaotong University, 2010.

[19] Zhang Gui-feng, Su Wei, Zhang Jian-xun, Suzumura Akio. Development of Al-12Si-xTi system active ternary filler metals for Almetal matrix composites. Transaction of Nonferrous Metals Society of China. Online

[20] Zhang Guifeng, Su Wei, Guo yang, Liao xianjin, Zhang jianxun and Suzumura Akio. Development of three kinds of active ternary fillermetals of Al-Si-Ti, Zn-Al-Ti and Cu-Al-Ti systems for Al metal matrixcomposites, China Welding, 2011,20(2):73-80.

[21]Zhai Y.,North T.H..Counteracting particulate segregationduring transient liquid-phase bonding of MMC-MMC and Al2O3-MMC joints,Journal of Materials Science,1997,32:5571-5575

Invention content:

The purpose of the present invention is to improve the low-melting point Zn-Al solder and the Al matrix interface without reaction, there is an interfacial gap, or the reaction is not uniform (reacts with the Al matrix only at the dissolution and part of the grain boundary), resulting in the surface of the grain itself. The effect of breaking the oxide film is not good, the wettability is still obviously poor in a large range, and the interface has the disadvantages of voids. The technical scheme of the present invention is: in terms of solder composition design (main aspect), adding active element Mg can increase the activity of solder, improve the uniformity of interface reaction and further reduce the melting point of solder; in terms of welding process (secondary aspect) ), considering the low welding temperature, high viscosity and poor fluidity of the Zn alloy liquid, when the solder is about to melt, low-cost low-frequency and low-amplitude friction is applied along the direction of the welding interface, so as to mechanically break the solder, Al and the surface of the body. The oxide film promotes the contact of the fresh liquid solder with a larger area of the solid Al matrix (especially the surface of the grain itself, not just the surface of the grain boundary), thereby further creating favorable conditions for the removal of the film through the above metallurgical approach, so that, It can further improve the wettability of the interface and increase the strength of the joint.

It is worth pointing out that, in the improvement of the above two aspects, the improvement of the solder composition design is a more important basic premise, because in fact, even if the applicant applies the same Zn-Al binary solder in the previous research The joint strength (70MPa) obtained by low-amplitude friction is also significantly lower than that of Zn-5Al-4Mg without auxiliary friction (78MPa, see Figure 6). Compared with Zn-Al solder and traditional brazing methods, the dual action of the active element Mg and interfacial friction can simultaneously break the oxide film on the surface of the liquid solder and the aluminum substrate at low temperature, and furthermore, it is also for the improvement of fresh solder. The wettability between the aluminum/matrix (M/M) interface and the ceramic reinforcement phase in the composite and the fresh filler metal (P/M) interface creates the conditions.

The object of the present invention is under the guidance of above-mentioned train of thought, realizes by following detailed, serial technical scheme:

1. Solder alloy system: first, the alloy system of the Zn-based low melting point ternary active solder determined in the present invention is Zn-Al-Mg system. The design idea is to add the active element Mg on the basis of the Zn-Al binary eutectic to increase the activity of the solder, improve the uniformity of the interface reaction and further reduce the melting point of the solder, thereby forming a low-melting point Zn-Al-Mg system three Element active solder.

Although Ti, Li, and Mg are optional active elements for the oxide film on the surface of the Al matrix and most of the ceramic reinforcement phases, the applicant has confirmed through previous research that Zn-Al-Ti and Zn-Al-Li three Element active solders were unsuccessful. The main problem of Zn-Al-Ti ternary active solder is that it is very difficult to prepare, which is manifested in three aspects: one is the volatilization of Zn liquid. It has been proved by experiments that it becomes very difficult at 600°C, especially above 650°C. Obviously; the second is that below 600-650 ° C, Ti with a high melting point is difficult to melt, even if an intermediate alloy is used; the third is that the segregation of Ti to the upper smelted block in the Zn liquid is very obvious, and the occurrence of this problem is related to the difficulty of Ti. It is related to smooth melting and the density is much lower than Zn. At this time, even if the quenching belt is used, it will not help. For related research, see the applicant's thesis: Zhang Guifeng, Su Wei, Guo Yang, Liao Xianjin, et al. Development of three kinds of active ternary filler metals of Al-Si-Ti, Zn-Al-Ti and Cu-Al-Ti systems for Al metal matrix composites. ChinaWelding,2011,20(2):73-80.

Although the Zn-Al-Li ternary active solder is denser at the solder/base metal interface (better than Li-free Zn-5Al solder), it can be observed that although the solder has infiltrated, the magnification is about 200 times. The oxide film at the substrate/solder interface can only be effectively broken in a local area, but most of the oxide film at the substrate/solder interface still exists continuously. This is due to the high activity of Li, which is easily oxidized (for example, the Zn-Al-Li solder will be oxidized and blackened after being placed in the air for about 1 hour), which makes the oxide film thicken rapidly, thereby limiting the activity of Li. It is related to the play of Li atoms and the fact that the Li atoms that have entered the matrix will diffuse in the depth direction due to the small radius of Li atoms. For related research, see the applicant's paper: Zhang Guifeng, Guo Yang, Zhang Jianxun, Zhang Linjie: Wettability of Zn-Al-Li and Zn-Al solders on SiCp/ZL101 aluminum matrix composites. Chinese Journal of Nonferrous Metals, 2012, has Accepted, pending publication.

Both positive and negative experimental results show (see the introduction about the implementation results in the following examples), the alloy system of the Zn-Al-Mg system ternary active solder proposed by the present invention has the advantages of preparation, wettability improvement, It is feasible to improve joint organization and performance.

2. In terms of the composition range of the solder: for the established Zn-Al-Mg ternary active solder, from the perspective of lowering the melting point of the solder, the mass fraction of each alloy element is determined to be: 3-10% Al, 2-7% % Mg, and the rest is Zn; the corresponding melting range is 337-475°C.

3. Aspects of solder preparation method: its main problem is to prevent the oxidation of Mg and the volatilization of Zn liquid. The preparation method of the low-melting point Zn-Al-Mg series ternary active solder is as follows: 1) material selection: select raw materials as pure Al, pure Zn, pure Mg block (or grain, sheet); 2) ingredients: pure Al, pure Zn, and pure Mg are 3-10% Al, 2-7% Mg, and the rest is Zn according to the mass percentage; wherein pure Zn is placed on the top of the mixture and placed in a closeable crucible; 3) Melting: first Pass pure Ar into the closed crucible to remove the air; then, under the protection of Ar, under high-frequency heating, when the pure Zn first melts rapidly, part of the liquid protects the pure Mg and quickly dissolves Mg in the Zn liquid, and then Pure Al is also quickly dissolved in the Zn-Mg alloy liquid; then, the alloy liquid is smelted at 500°C to 600°C when heating is continued (when it exceeds 600°C, especially 650°C, a large amount of Zn will volatilize), and the temperature is kept for 30 minutes Continuously dissolve the unmelted metal into the previously melted liquid alloy, and homogenize the composition of the alloy liquid; then stop heating, continue to cool and solidify into a solder alloy block under the protection of Ar. 4) It is prepared into a foil strip by adopting a quenching and stripping process or a brazing sheet or a brazing rod by a hot rolling process.

4. Active brazing assisted by low-frequency and low-amplitude friction using the above-mentioned low-melting point Zn-Al-Mg series ternary active solder, the specific process is as follows: 1) Use 100#, 400# sandpaper to grind the surface of the workpiece to be welded 2) Use alcohol or acetone to degrease and decontaminate; 3) Preset the solder sheet or foil between the workpieces to be welded, and apply a pressure of 1MPa; 4) Pass 1 to 5L/min Ar protection Under the environment or in the air, after heating to 330°C, reduce the pressure to 0.01-0.5MPa and continue to heat the workpiece to be welded to 400-550°C; 5) After holding the heat for 0-1min, apply Friction assistance lasts for 5-200s, with an amplitude of 0.1-1 mm and a frequency of 10-50 Hz; 6) After vibration, apply a pressure of 0.05-2 MPa and keep warm for 0-10 minutes to obtain a good welded joint.

5. The composition and working principle of the low-cost, low-frequency and low-amplitude auxiliary friction mechanical transmission system are (see Figure 2): powered by a single-phase DC speed-regulating motor or a single-phase asynchronous motor; the motor shaft (14) is driven by a keyway Eccentric wheel (10); the eccentric distance between the axis of the eccentric wheel and the axis of the motor shaft is set to 0.05~1mm, the amplitude of the eccentric wheel mechanism determined by this is 0.1~2mm, and the frequency is determined by the motor speed, which is 10~50Hz Mechanical vibration; in order to avoid vibration amplitude errors due to wear between parts, the eccentric wheel drives the connecting rod (11) through a replaceable brass bearing; the connecting rod drives the slider (12) through another bearing. With this transmission system, the reciprocating linear motion of the slider is realized, and finally the friction-assisted film removal along the welding interface is realized, which can replace manual scraping. The physical photo of the transmission system is shown in Figure 3.

6. Slider guide rail (13, see Fig. 2) is a kind of in inverted T shape, dovetail groove or directional guide rod.

The low-melting point Zn-Al-Mg system ternary active solder developed by the present invention is simple to prepare, low in cost, does not require flux, and has far better film removal ability and wettability than pure Zn and Zn-Al system binary solder, The strength of the welded joint is high; the application range is wide, especially suitable for low-melting-point aluminum alloys and aluminum-based composite materials based on low-melting-point aluminum alloys.

Description of drawings

Figure 1 Zn-5Al-4Mg solder melting point test (DSC: differential calorimeter) results and quenching strip forming effect;

Figure 2 is a schematic diagram of an active brazing device assisted by low-frequency and low-amplitude friction and a schematic diagram of a low-frequency micro-amplitude friction system;

Note: 1—furnace body heating element; 2—thermocouple; 3—loading tool; 4—fixed frame; 5—brazing sheet or brazing foil strip;

6—workpiece to be welded; 7—induction coil; 8—shielding gas inlet; 9—mechanical vibration platform;

10—eccentric wheel (see Figure 2b and 2c) or cam (see Figure 2d and 2e); 11—connecting rod; 12—stage;

13—base (rail with dovetail groove (see Figure 2b and d) or inverted T-slot (see Figure 2c and e)); 14—power shaft

Figure 3 is a schematic diagram of active brazing process parameters assisted by low-frequency and low-amplitude reciprocating friction;

Fig.4 The wettability test interface photo of Mg-free binary eutectic solder Zn-5Al on SiCp/ZL101 under the protection of flowing argon at 520℃×20min (a, b) and 520℃×30min (c,d) (Explanation: Mg-free solder has poor film removal effect, non-dense interface and poor wettability);

Fig. 5 Zn-5Al-4Mg low-melting point ternary active solder foil strip developed by the present invention is under the protection of Ar atmosphere, at 520 ℃ to SiCp/ZL101 wettability test interface photos: (a) and (b) 1min ; (c) and (d) 3min; (e) and (f) 5min; (g) and (h) 20min (Note: the new solder reacts with the base metal early and fully);

Fig. 6 The joint strength comparison results of Zn-5Al-4Mg ternary active solder of the present invention and Zn-5Al binary eutectic solder with/without low-frequency and low-amplitude reciprocating friction auxiliary working conditions (Zn-5Al-4Mg three of the present invention Even without applying friction, the joint strength of Zn-5Al solder is better than that of Zn-5Al solder after friction is applied; when friction assistance is applied, the joint strength obtained by Zn-5Al-4Mg ternary active solder is higher, reaching composite materials 91% of the base metal);

Fig. 7 Comparative test Zn-5Al brazing filler metal at 520℃ welding temperature and 0.06MPa pressure mechanically vibrating for 20s time, low-frequency and low-amplitude friction-assisted active brazed joint structure photos (indicating that although the auxiliary friction is effective, the effect is far less than that of Zn-5Al -4Mg);

Fig. 8 A-TLP joint structure photo of Zn-5Al-4Mg solder at a welding temperature of 520°C and a pressure of 1 MPa for 20 min Oxide film exists on part of the interface);

Fig. 9 Microstructure photo of Zn-5Al-4Mg solder under low-frequency and low-amplitude friction-assisted active brazed joint after mechanical vibration at 520°C and 0.06MPa pressure for 20s (indicating that the oxide film on the entire interface is better broken after applying auxiliary friction) ;

Fig. 10 Ceramic particle/brazing filler metal (P/M) interface structure of Zn-5Al-4Mg ternary active solder held at 520°C for 1 min on wettability test of 10vol.%SiC _p /ZL101 aluminum matrix composite (It shows that Mg can also promote the P/M interface reaction and eliminate the P/M interface gap).

Detailed ways

The following examples describe the present invention in more detail. The main content includes three aspects: (1) preparation of low melting point Zn-5Al-4Mg ternary active solder; (3) Comparative test of brazing process of two kinds of solder (with/without Mg) under two working conditions (with/without low-frequency and low-amplitude reciprocating friction assistance). The aluminum matrix composite base metal used in wettability evaluation and brazing process test is 10Vol.%SiCp/ZL101.

●Preparation test of Zn-5Al-4Mg ternary active solder of the present invention:

Taking the preparation of 30g of low melting point Zn-5Al-4Mg ternary active solder as an example, the specific steps of the preparation method: 1) Material selection: select raw materials: pure Al block, pure Zn block, pure Mg block; 2) Ingredients: according to A block of Al with a mass of 1.5g, Mg of 1.2g, and the rest is Zn; where pure Zn is placed on the top of the mixture and the mixture is placed in a closeable crucible; 3) Melting: First, 3.5L is passed into the closed crucible /mind pure Ar, exclude air; then, under the protection of Ar, under high-frequency heating, when pure Zn melts rapidly first, part of the liquid protects pure Mg and quickly dissolves Mg in Zn liquid, and then pure Al also dissolves rapidly In the Zn-Mg alloy liquid; then, the alloy liquid is smelted at 500 ° C when the heating is continued, and the heating is stopped after the heat preservation for 30 minutes; then, it is continued to be cooled and solidified under the protection of Ar to form a solder alloy block. 4) Foil strips were prepared by the quenching and stripping process (the diameter of the copper roll is 105mm, the thickness of the copper roll is 10mm, and the line speed is 12.65m/min).

Wettability comparative test: As a comparative test, for the Mg-free Zn-5Al solder foil strip, the wettability evaluation condition is 520℃×20min (long time); for the Zn-5Al-4Mg solder developed by the present invention For foil tape, the wettability evaluation conditions are 520°C×1min, 520°C×3min, 520°C×5min (short time). The base material of aluminum matrix composite material used is 10Vol.%SiC _p /ZL101 aluminum matrix composite material; the atmosphere condition is flowing Ar to protect the environment.

Brazing process comparison test: In order to verify the innovation and good effect of the present invention in terms of solder composition design (adding active element Mg) and brazing process (applying low-frequency and low-amplitude interface friction), a 10Vol.% SiC _p /ZL101 aluminum-based composite material as the base material, and the Mg-free Zn-5Al binary solder as the comparison solder, under the condition of with and without low-frequency and low-amplitude reciprocating friction assistance, the Zn-5Al containing Mg The comparative test of the low-temperature brazing process of -4Mg ternary active solder and Mg-free Zn-5Al binary solder.

The test method and conditions of the active brazing welding process assisted by low-frequency and low-amplitude reciprocating friction: 1) Use 100#, 400# sandpaper to polish the surface of the workpiece to be welded; 2) Use alcohol or acetone to remove oil and dirt; 3 ) Preset the two kinds of solder foil strips between 10Vol.%SiC _p /ZL101 aluminum matrix composite materials, and apply a pressure of 1MPa; 4) Pass 5L/min under the protection of Ar or in the air, through high After frequency induction heating to 330°C, reduce the pressure to 0.05MPa and continue to heat the welded workpiece to 520°C; 5) After keeping warm for 1min, apply friction assistance to the lower welded workpiece for 20s, with an amplitude of 0.25 mm, the frequency is 24Hz; 6) Continue to apply 0.05MPa pressure after friction, keep warm for 0min, and then cool down.

Test method and conditions of active brazing welding process without low-frequency low-amplitude friction assistance: 1) Use 100#, 400# sandpaper to polish the surface of the workpiece to be welded; 2) Use alcohol or acetone to remove oil and dirt; 3) Preset the two kinds of solder foil strips between the base metals of the aluminum matrix composite material to be welded, and apply a pressure of 1 MPa; 4) Under the protection of 5L/min Ar or in the air, heat through high-frequency induction to After 330°C, reduce the pressure to 0.05MPa, and continue to heat the workpiece to be welded to 520°C; 5) After holding the heat for 1 minute, apply a pressure of 1MPa to the lower part to be welded; 6) Cool after holding for 20 minutes.

Implementation result of the present invention is as follows:

Fig. 1 is a low-melting-point ternary active solder Zn-5Al-4Mg solder melting point test (using differential calorimeter—DSC) results and the forming effect of the quenching strip in the present invention. However, when using a differential calorimeter for thermal analysis, that is, when measuring the melting curve, the temperature rise rate is 10°C/min under the protection of an argon atmosphere, which is different from the equilibrium reaction of the phase diagram and belongs to non-equilibrium melting. It is found that there are two endothermic peaks in the curve, the first endothermic peak is due to the melting endothermic of the Zn-Al-Mg ternary four-phase eutectic composition in the solder foil strip structure; the second endothermic peak is It is caused by the dissolution of the intermetallic compound MgZn ₂ in the solder. According to the DSC melting curve shown in Figure 1, the melting point of the Zn-5Al-4Mg solder foil is 344.9°C to 356.9°C.

The obtained Zn-5Al-4Mg solder foil has a smoother appearance through a self-made strip spinning device at a linear speed of 12.65m/min, and the solder foil has a neat periphery and good ribbon formation. But the solder foil is relatively brittle and easy to break.

Fig. 2 is the schematic diagram of the device of the active brazing method assisted by low frequency and low amplitude reciprocating friction; wherein Fig. 2a is one of the schematic diagrams of the device of the assisted active brazing method of low frequency and low amplitude reciprocating friction, and Fig. 2b, 2c, 2d and 2e All are schematic diagrams of the mechanical transmission structure in the brazing. Its basic principle is: a. Heating system: the alternating magnetic field generated by the induction coil (7) through the high-frequency alternating current passes through the heating element (1) of the furnace body, and the welded workpiece (6) and the solder ( 5) Heating, while measuring the temperature of the welded workpiece (6) through the thermocouple (2); b. Welding environment system: if welding is performed under protective gas, the protective gas enters the furnace cavity through the gas inlet (8); c. Micro-amplitude reciprocating friction system: during the welding process, the mechanical vibration generating mechanism (10, 11, 12, 13, 14) introduces mechanical vibration through the vibration platform (9); d. Pressurization system: the loading pressure during the welding process The pressure is applied to the welded workpiece (6) and solder (5) through the loading tool (3).

Fig. 3 is a schematic diagram of active brazing process parameters assisted by low-frequency and low-amplitude friction. It can be seen from the figure that before the temperature of the sample rises to near the solidus temperature of the solder, a large pressure is applied without applying low-frequency and low-amplitude friction assistance; when the temperature rises to the solidus temperature, the pressure is reduced to A certain value; continue to heat the sample to the welding temperature and keep it warm for a period of time; apply low-frequency and low-amplitude friction-assisted brazing with a certain frequency and amplitude, and then maintain or increase the pressure, cool down or cool down after a certain period of time.

Figure 4 is a photo of the wettability test of binary eutectic solder Zn-5Al on SiCp/ZL101 under the protection of flowing argon at 520°C for 20 minutes and 30 minutes of holding time as a comparative test. It can be seen from Figure 4a and b that the Zn-5Al solder does not have any interaction with SiCp/ZL101, that is, it cannot wet the base metal at 520°C for 20 minutes without the help of flux. In Figure 4c and d, it can be found that although Zn precipitates along the grain boundaries in the SiCp/ZL101 base material, the interface gap and oxide film between the residual solder and the SiCp/ZL101 base material still exist, which indicates that Zn makes SiCp The degree of liquefaction and subsurface flow under the surface film of the /ZL101 substrate is not enough to break the continuity of the oxide film. Therefore, Zn cannot break the oxide film on the surface of the substrate without any other auxiliary conditions.

Figure 5 shows the wettability test of Zn-5Al-4Mg solder foil strip on 10Vol.%SiC _p /ZL101 base metal under the protection of Ar atmosphere and holding time of 1min, 3min, 5min and 20min at 520℃ Organize photos. It can be seen from Figure 5a and b that within 1 minute of heat preservation, the solder and the base metal have been effectively connected in some areas, and the surface area of the base metal has liquefied, that is, the dissolution under the film begins to break the surface of the base metal. The oxide film has begun to wet the base metal locally; and in Figure 5c and d, there are more effective connection areas between the solder and the base metal, and the solder can already wet the 10Vol.%SiC _p / ZL101 base metal; in Figure 5e and f, it can be seen that the residual solder has grown columnar grains with the base metal across the original interface; in Figure 5g and h, the solder has been completely welded to the base metal ; SiC particles are segregated on the surface, and the residual amount of Zn is very small, which shows that the dissolution and diffusion are sufficient, and the isothermal solidification is basically realized.

Figure 6 is the joint shear of brazing 10Vol.%SiC _p /ZL101 base metal using Zn-5Al solder and Zn-5Al-4Mg solder at 520°C under 0.06MPa pressure with low-frequency and low-amplitude auxiliary friction for 5s and 20s The shear strength is compared with the shear strength of friction brazed joints without low-frequency and low-amplitude assistance at 520 °C and held at 1 MPa for 20 minutes. It can be seen from Figure 6 that the shear strength of the base metal is 130 MPa, while the shear strength of the brazed joint under low-frequency and low-amplitude auxiliary friction for 5 seconds is 97 MPa (74.6% of the base metal shear strength). The shear strength of the brazed joint with friction lasting 20s is 119MPa (91.5% of the base metal shear strength); while the shear strength of the brazed joint without low-frequency and low-amplitude friction assistance using this solder also reaches 78MPa (reaches 91.5% of the base metal shear strength). 60% of the shear strength); but using the traditional Zn-5Al solder, the strength of the brazed joint without low-frequency low-amplitude friction is only 13MPa; while the friction time of Zn-5Al solder lasts for 20s at low frequency The low-amplitude friction-assisted brazed joint has a shear strength of 70 MPa (53.8% of the base metal shear strength).

Fig. 7 is a photo of the brazed joint structure of the Zn-5Al brazing foil strip after low-frequency and low-amplitude auxiliary friction for 20 seconds at a welding temperature of 520°C and a pressure of 0.06 MPa. It can be seen from Figure 7 that there is no interfacial gap in the welded joint structure, and there are no defects such as segregation of ceramic phase particles or voids around the ceramic phase due to poor wettability; but most areas still have 10Vol.% The original interface of SiC _p /ZL101 base metal. This shows that friction-assisted brazing can break the oxide film on the surface of the substrate. Since the Zn-5Al solder cannot effectively remove the oxide film, there is a discontinuous oxide film.

Figure 8 is a photo of the microstructure of the Zn-5Al-4Mg solder foil strip without low-frequency and low-amplitude auxiliary friction welding 10Vol.%SiC _p /ZL101 base metal joint after holding at a welding temperature of 520 °C and a pressure of 1 MPa for 20 minutes. It can be seen from Figure 8 that there is no oxide film in most areas of the welded joint structure, and the joint structure is dense and uniform, and there are no defects such as segregation of ceramic phase particles or voids; only intermittent oxide films exist in local areas, which It shows that the solder can remove the oxide film on the surface of the substrate, but because the fluidity of the liquefied metal liquid on the surface of the base metal is not good, the oxide film on the surface of the substrate cannot be fully removed.

Figure 9 is a photo of the microstructure of the brazed joint brazed with Zn- _5Al -4Mg filler metal at a welding temperature of 520°C and under a pressure of 0.06 MPa at a low-frequency and low-amplitude auxiliary friction for 20 seconds. It can be seen from Figure 9a and b that there are no voids and no oxide film in the brazing seam; at the same time, there are a small amount of SiC ceramic phase particles in the brazing seam, and the interface between these particles and the brazing seam metal is dense; The continuous growth of columnar grains across the original interface has occurred between the materials, which can be considered that the solder has been completely welded with the base material.

Figure 10 is the P/M interface structure of the Zn-5Al-4Mg ternary active solder held at 520 ° C for 1 min on the wettability test of the 10vol.% SiC _p /ZL101 aluminum matrix composite material. It can be seen from Figure 10a and b that there is no interfacial gap between the SiC particles and the metal interface (P/M interface) distributed in the Zn-5Al-4Mg ternary active solder diffusion zone, but a layer of 1 μm is formed near the SiC particles Thick thin layer, the energy spectrum point analysis of this thin layer is Zn-Mg-Si-C alloy or intermetallic compound. Whether this thin layer is a new phase formed by the reaction remains to be determined; but it can be confirmed that the P/M interface is dense .

In summary, the wettability evaluation test and the welding test all show that the reaction between the low melting point Zn-Al-Mg series ternary active solder of the present invention and the Al matrix can be carried out early, the reaction distribution is uniform, the reaction degree is sufficient, and it can be quickly and effectively The continuity of the oxide film on the surface of the aluminum substrate is broken to a minimum, so it has good wettability to aluminum alloy and aluminum matrix composite materials; considering the particularity of Zn-based solder (brazing temperature is low; the eutectic reaction is located on the Zn-rich side so that the solution The degree of dissolution of Al is limited, etc.), when supplemented by low-frequency and low-amplitude reciprocating interface friction mechanical film removal, it can more effectively break the oxide film on the surface of the Al substrate and improve the strength of the joint. In addition, Mg also helps to improve the wettability of the interface between ceramic particles and molten metal (P/M) (see Figure 10).

The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this field Those skilled in the art, without departing from the scope of the technical solution of the present invention, may use the method and technical content disclosed above to make some changes or modify equivalent embodiments with equivalent changes, but if they do not depart from the content of the technical solution of the present invention, Any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims (2)

1. A low-frequency and low-amplitude reciprocating friction-assisted active brazing method is characterized in that: the "saddle-shaped" pressurization program control is adopted; the "saddle-shaped" pressurization program is: 1) Preset the solder sheet or foil strip between the workpieces to be welded, and apply a pressure of 1 MPa to make the interface close, introduce micro deformation and prevent oxidation; 2) After heating to 330°C close to the solidus line of the solder, reduce the pressure to 0.01-0.5MPa to avoid solder extrusion, and continue to heat the workpiece to be welded to 400-550°C; 3) After 0-1min of heat preservation, apply 5-200s of interface auxiliary friction to one of the workpieces to be welded, with an amplitude of 0.1-2mm and a frequency of 10-50Hz; 4) After the vibration stops, apply a pressure of 0.05~2MPa, keep warm for 0~10min, and cool down. 2. The active brazing method assisted by low-frequency and low-amplitude reciprocating friction according to claim 1, characterized in that its low-cost interface-assisted friction system consists of a single-phase DC speed-regulating motor or a single-phase asynchronous motor, and the eccentricity is 0.05～ Composed of 1mm eccentric wheel transmission mechanism and slider guide rail, the interface friction amplitude generated by it is 0.1-2mm, and the frequency is 10-50Hz; the slider guide rail is one of inverted T-shaped, dovetail groove or directional guide rod.

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