首次采用Al-5.6Si-25.2Ge钎料对Cu/Al异种金属进行了炉中钎焊,分别从钎料的熔化特性、铺展润湿性、Cu侧界面组织以及钎焊接头强度等方面进行了系统研究,并与Zn-22Al钎料钎焊结果进行对比。结果表明,Al-5.6Si-25.2Ge钎料具有较低的熔化温度(约541 ℃),同时在Cu、Al母材上均具有良好的铺展润湿性。Al-5.6Si-25.2Ge/Cu界面由CuAl2/CuAl/Cu3Al2三层化合物组成,其中CuAl和Cu3Al2呈层状,厚度较薄,仅为1~2 μm;CuAl2呈胞状,平均厚度约为3 μm。Zn-22Al/Cu界面结构为CuAl2/CuAl/Cu9Al4,其中CuAl2层平均厚度高达15 μm。接头抗剪切强度测试结果表明,Zn-22Al钎料钎焊Cu/Al接头抗剪切强度仅为42.7 MPa,而Al-5.6Si-25.2Ge钎料钎焊Cu/Al接头具有更高的抗剪切强度,为53.4 MPa。
Cu/Al brazing has good prospect for applications in the air conditioning and refrigeration industry. A suitable filler metal is the key of Cu/Al brazing. The chemical and physical properties of the filler metal have great influence on the brazing process and parameters. And the strength of the brazing joint is closely related to the properties of the filler metal and the brazing process. While the previous studies have not developed a kind of Cu/Al brazing filler metal which can achieve a tough joint at a low brazing temperature. In this work, the Al-5.6Si-25.2Ge filler metal was first used to braze Cu/Al dissimilar metals, and the melting characteristics of the filler metal, spreading wettability, Cu interfacial structure and strength of brazed joint were investigated systematically. Additionally, the common Zn-22Al filler metal was also used for comparison. The results show that the Al-5.6Si-25.2Ge filler metal possesses low melting temperature (about 541 ℃) and excellent spreading wettability on Cu and Al base metals. The interfacial structure of Al-5.6Si-25.2Ge/Cu was CuAl2/CuAl/Cu3Al2. The thickness of planar CuAl and Cu3Al2 phases was only 1~2 μm, and the thickness of cellular CuAl2 phase was about 3 μm. The interfacial structure of Zn-22Al/Cu was CuAl2/CuAl/Cu9Al4, but the average thickness of the CuAl2 layer was up to 15 μm. The test results of the shearing strength show that the shearing strength of the Cu/Al joint brazed with Zn-22Al filler metal was only 42.7 MPa, but the shearing strength brazed with Al-5.6Si-25.2Ge filler metal was higher (53.4 MPa).
实验所用钎料成分为Al-5.6Si-25.2Ge、Zn-22Al和Al-12Si (质量分数,%)。其中Zn-22Al为常用的商业钎料,作为钎焊接头组织和性能研究的对比钎料;Al-12Si为共晶钎料,因其钎焊Cu/Al接头强度极低[10,17],仅作为钎料熔点研究的对比钎料。所有钎料均采用纯度99.999%的Ge、99.999%的Zn、99.99%的Si和99.6%的Al为原材料,在井式坩埚炉中进行熔炼,为了防止钎料合金在熔炼过程中被氧化,采用NaCl∶KCl=1∶1 (质量比)熔盐进行覆盖保护。熔化后进行充分搅拌,以尽量减少元素在金属液中的比重偏析。
2种钎料在Cu、Al母材上的铺展润湿性测试在Ar气保护钎焊炉中进行,钎料的质量为0.15 g,所用钎剂为自行研制的AlF3-KF-KCl-CsF无腐蚀钎剂,熔化区间为415~488 ℃。钎焊接头采用搭接的形式,母材采用尺寸为60 mm×20 mm×3 mm的1060纯Al板和60 mm×20 mm×2 mm的TP2脱氧纯Cu板,搭接长度为2 mm,搭接间隙控制在(0.3±0.05) mm,钎料的质量为0.2 g,钎焊接头装配示意图如
采用CR-G型高温差热分析仪(DTA)测定钎料合金的熔化温度,加热速率为15 ℃/min。采用XTZ-AT体视显微镜对铺展实验试样进行拍照,并利用ImageTool3.0软件对铺展面积进行测量。采用Quanta 250型扫描电子显微镜(SEM)和其附带的能谱仪(EDS)对 Cu/Al 接头界面结构和断口形貌以及Cu/Al 接头界面化合物成分进行分析。采用MiniFlex 600 X射线衍射仪(XRD,Cu
在钎焊过程中,钎料在Cu、Al母材上的铺展面积反应了钎料润湿填缝的能力。经测量,Al-5.6Si-25.2Ge和Zn-22Al钎料在Al母材上的平均铺展面积分别为566.2和478.5 mm2,由于Zn在Al中具有极大的固溶度,导致Zn向Al母材中产生严重的晶间渗透,减弱了Zn-Al钎料在Al母材上的铺展。相对于在Al母材上的铺展,Al-5.6Si-25.2Ge和Zn-22Al钎料在Cu上的铺展面积均较小,分别为119.6和69.8 mm2,但Al-5.6Si-25.2Ge钎料的铺展面积更大,约为Zn-22Al钎料的2倍。因此,相对于Zn-22Al钎料而言,Al-5.6Si-25.2Ge钎料在Cu、Al母材上均具有较好的铺展润湿性,更有利于实现Cu/Al异种金属的钎焊连接。
采用Al-5.6Si-25.2Ge和Zn-22Al钎料钎焊Cu/Al接头,Cu侧界面结构在化合物种类和形态上存在较大的差异,这种差异势必对Cu/Al接头的力学性能产生显著的影响。2种钎料钎焊Cu/Al接头所获得的抗剪切强度差别较大,Zn-22Al钎料钎焊Cu/Al接头抗剪切强度为42.7 MPa,与文献研究结果基本一致;Al-5.6Si-25.2Ge钎料钎焊Cu/Al接头抗剪切强度较大,达到53.4 MPa。
(2) Al-5.6Si-25.2Ge/Cu界面处由CuAl2/CuAl/Cu3Al2三层化合物组成,其中CuAl和Cu3Al2呈层状,厚度较薄,为1~2 μm;CuAl2呈胞状,平均厚度约为3 μm,钎焊接头抗剪切强度较高,为53.4 MPa。Zn-22Al/Cu界面结构为CuAl2/CuAl/Cu9Al4,其中CuAl2层平均厚度高达15 μm,钎焊接头抗剪切强度仅为42.7 MPa。
The authors have declared that no competing interests exist.
Current proposals for the divertor component of a thermonuclear fusion reactor include tungsten and copper as potentially suitable materials. This paper presents the procedures developed for the successful brazing of tungsten to oxygen free high conductivity (OFHC) copper using a fusion appropriate gold based brazing alloy, Orobraze 890 (Au80Cu20). The objectives were to develop preparation techniques and brazing procedures in order to produce a repeatable, defect free butt joint for tungsten to copper. Multiple brazing methods were utilised and brazing parameters altered to achieve the best joint possible. Successful and unsuccessful brazed specimens were sectioned and analysed using optical and scanning electron microscopy, EDX analysis and ultrasonic evaluation. It has been determined that brazing with Au80Cu20 has the potential to be a suitable joining method for a tungsten to copper joint.
A Sn-based metallization layer was successfully prepared on the surface of alumina at 90002°C by using Ti-containing Sn0.3Ag0.7Cu (SAC, wt.%) metal powder. Reliable alumina/copper joints were obtained by brazing pre-metallized alumina and copper using SAC filler at 580–66002°C for 502min. The typical interfacial microstructure of brazed joint was copper/Cu 3 Sn layer/Cu 6 Sn 5 layer/β-Sn layer containing Ti 6 Sn 5 phase and Al 2 O 3 particles/alumina. As brazing temperature increased, the Cu–Sn intermetallic layers thickened rapidly and the amount of β-Sn phase reduced. When brazing temperature exceeded 64002°C, Kirkendall voids and microcracks formed at copper/Cu 3 Sn interface. The joints brazed at 580–62002°C possessed high shear strength and the highest average shear strength of 3202MPa was achieved when brazed at 62002°C. Fracture analyses indicated that the joints mainly fractured inside of the Cu 6 Sn 5 layer and β-Sn layer. The joints brazed above 62002°C demonstrated low shear strength due to the formation of Kirkendall voids which caused the joints fractured along the Cu/Cu 3 Sn interface.
The formation of intermetallic reaction layers and their influence on shear strength and fractography was investigated between the Zn–Sn–Cu–Bi (ZSCB) and Cu substrate during the liquid state reaction at 450°C after 10–90s. Results showed that reliable solder joints could be obtained at 450°C after 15–30s of wetting, accompanied by the creation of scallop ε-CuZn 5 , flat γ-Cu 5 Zn 8 and β-CuZn intermetallic layers in ZSCB/Cu interface. However, with excess increase of soldering time, a transient intermetallic ε-CuZn 4 phase was nuclear and grew at ε-CuZn 5 /γ-Cu 5 Zn 8 interface, which apparently deteriorated the shear strength of solder joints from 76.5MPa to 51.6MPa. The sensitivity of the fracture proportion was gradually transformed from monotonic ε-CuZn 5 to the mixture of ε-CuZn 4 and ε-CuZn 5 intermetallic cleavage. Furthermore, the growth mechanism of ε-CuZn 4 intermetallic phase at the ZSCB/Cu interface was discussed.
The effects of Ni content on the microstructure and the wetting behavior of Sn-9Zn-xNi solders on Al and Cu substrates, as well as the mechanical properties and electrochemical corrosion behavior of Al/Sn-9Zn-xNi/Cu solder joints, were investigated. The microstructure of Sn-9Zn-xNi revealed that tiny Zn and coarsened Ni 5 Zn 21 phases dispersed in the -Sn matrix. The wettability of Sn-9Zn-xNi solders on Al substrate was much better than that on Cu substrate. With increasing Ni content, the wettability on Cu substrate was slightly improved but became worse on Al substrate. In the Al/Sn-9Zn-xNi/Cu joints, an Al4.2Cu3.2Zn0.7 intermetallic compound (IMC) layer formed at the Sn-9Zn-xNi/Cu interfaces, while an Al-Zn-Sn solid solution layer formed at the Sn-9Zn-xNi/Al interface. The mixed compounds of Ni3Sn4 and Al3Ni dispersed in the solder matrix and coarsened with increasing Ni content, thus leading to a reduction in shear strength of the Al/Sn-9Zn-xNi/Cu joints. Al particles were segregated at both interfaces in the solder joints. The corrosion potentials of Sn-9Zn-xNi solders continuously increased with increasing Ni content. The Al/Sn-9Zn-0.25Ni/Cu joint was found to have the best electrochemical corrosion resistance in 5% NaCl solution.
Ultrasound-assisted brazing of Cu/Al dissimilar metals was performed using a Zn–3Al filler metal. The effects of brazing temperature on the microstructure and mechanical properties of Cu/Al joints were investigated. Results showed that excellent metallurgic bonding could be obtained in the fluxless brazed Cu/Al joints with the assistance of ultrasonic vibration. In the joint brazed at 400°C, the filler metal layer showed a non-uniform microstructure and a thick CuZn 5 IMC layer was found on the Cu interface. Increasing the brazing temperature to 440°C, however, leaded to a refined and dispersed microstructure of the filler metal layer and to a thin Al 4.2 Cu 3.2 Zn 0.7 serrate structure in the Cu interfacial IMC layer. Further increasing the brazing temperature to 480°C resulted in the coarsening of the filler metal and the significantly growth of the Al 4.2 Cu 3.2 Zn 0.7 IMC layer into a dendrite structure. Nanoindentation tests showed that the hardness of the Al 4.2 Cu 3.2 Zn 0.7 and CuZn 5 phase was 11.4 and 4.65GPa, respectively. Tensile strength tests showed that all the Cu/Al joints were failed in the Cu interfacial regions. The joint brazed at 440°C exhibited the highest tensile strength of 78.93MPa.
The mechanical properties and microstructural distribution of the Cu/Al brazing joints formed by torch-brazing with different Zn-Al filler metals were investigated.The microstructure of the Zn-Al alloys was studied by optical microscopy and scanning electron microscopy,and the phase constitution of the Cu/Al joints was analyzed by energy dispersion spectrometry.The results show that the spreading area of the Zn-Al filler metals on the Cu and Al substrates increases as the Al content increases.The mechanical results indicate that the shear strength reaches a peak value of 88 MPa when Al and Cu are brazed with Zn-15Al filler metal.Microhardness levels from HV122 to HV515 were produced in the three brazing seam regions corresponding to various microstructure features.The Zn-and Al-rich phases exist in the middle brazing seam regions.However,two interface layers,CuZn3 and Al2Cu are formed on the Cu side when the Al content in the filler metals is 2% and more than 15%,respectively.The relationship between intermetallic compounds on Cu side and Zn-xAl filler metals was investigated.
The structure development and growth rate of intermetallic compounds in Cu/Al brazed joint formed under aging treatment were investigated in this paper. Trace amount of rare earth Ce (0.0502wt.%) was added into Zn–22Al filler metal in order to reform the properties of the Cu/Al joint. The interfacial morphology and constituent phases at the interface were examined by the scanning electron microscopes (SEM) and X-ray energy dispersion spectrometry (EDS), respectively. The growth kinetics of intermetallic compounds formed in both systems (Zn–22Al and Zn–22Al–0.05Ce) was also investigated under different aging conditions. The results indicated that interface structure of Cu/Al brazed joints changed from CuAl 2 /CuZn 3 to CuAl 2 /CuAl/CuZn 3 and finally to ε/CuAl 2 /CuAl/CuZn 3 during aging. The growth rate of intermetallic compounds observed in the Zn–22Al system was higher than that in Zn–22Al–0.05Ce. Meanwhile, the activation energy of CuAl 2 phase increased from 76.902kJ/mol to 87.602kJ/mol with the 0.0502wt.% Ce addition. The results also revealed that the joint brazed with Zn–22Al–0.05Ce constantly possessed higher shear strength than that of Zn–22Al throughout the aging treatment. The addition of Ce into the Zn–22Al filler metal decreased the thickness of the intermetallic compound layer produced in the aging, resulting in higher fracture toughness.
Abstract IMC. Further experimental results also show that the rare earth element La in filler metal can not only refine the grain, but also promote the dispersion of intermetallic compounds into the brazing seam, which significantly improves the brazing seam microstructure and mechanical properties of the joints.
Brazing of Cu to Al using Al-Si filler metal has been carried out by vacuum brazing technology. The microstructure and the phase constitution in Cu/Al joint were studied by means of metallography, electron probe microanalyser (EPMA) and X-ray diffraction (XRD). Experimental results obtained showed that two kinds ofintermetallic compounds (IMCs) are formed near the interface of copper and brazing seam region and those are Cu
The combined and separate effects of microstructural scale and silicon phase morphology on the mechanical properties of Al–Si eutectic alloys are investigated here. The Bridgman-type gradient-zone directional solidification method is employed to produce as-cast structures characteristic of the full range of practical (i.e. casting) growth velocities, and the corresponding mechanical properties are characterized by uniaxial tension testing. The results are analyzed in light of previously reported microstructural changes associated with the flake to fiber or “quench modification” transition  . Both tensile strength and elongation were found to increase with solidification rate. Application of the Nan–Clarke  micromechanical analysis to the Al–Si composite structure, incorporating the strengthening effects of reinforcement-induced dislocations, suggests that the decreasing microstructural scale alone is sufficient to account for the increase in tensile strength with solidification rate. However, the flake to fiber transition was found to have a particular relevance with regard to the fracture behavior of the alloy, increasing tensile elongation and decreasing the overall variability of tensile properties. A maximum in elongation was observed at approximately 600μm/s, corresponding to the upper threshold of the flake to fiber transition associated with complete disappearance of the flake morphology and dominance of the fibrous structure. These results emphasize the importance of understanding and controlling the flake to fiber transition that occurs with increasing solidification rate in Al–Si eutectic alloys.
The effect of Cu with low contents of 10, 12, 1502wt.% on the microstructure and melting point of Al–Si–Cu–Ni alloy has been investigated. Results showed that low-melting-point properties of Al–Si–Cu–Ni alloys with low contents of Cu were attributed to disappearance of Al–Si binary eutectic reaction and introduction of Al–Si–Cu–Ni quaternary reaction. With raising Cu content from 10 to 1502wt.%, the amount of complex eutectic phases formed during low temperature reactions (Al–Cu, Al–Si–Cu and Al–Si–Cu–Ni alloy reactions) increased and the melting temperature of Al–Si–Cu–Ni filler metals declined. Brazing of 6061 aluminum alloy with Al–10Si–15Cu–4Ni (all in wt.%) filler metal of a melting temperature range from 519.3 to 540.202°C has been carried out successfully at 57002°C. Sound joints can be obtained with Al–10Si–15Cu–4Ni filler metal when brazed at 57002°C for holding time of 6002min or more, and achieved high shear strength up to 144.402MPa.
A series of Al-Si-Ge filler metals were studied for brazing aluminum. The microstructures and properties of the filler metals were investigated systematically. The results show that the liquidus temperature of Al-Si-Ge filler metals drops from 592 to 519 C as the content of Ge increases from 0 to 30% (mass fraction). As the content of Ge increases, bright eutectic Ge forms. However, as the Ge content exceeds 20%, the aggregation growth of the eutectic structure tends to happen and coarsened primary Si-Ge particle forms, which is detrimental to the properties of alloys. The Al-10.8Si-10Ge filler metal has good processability and wettability with the base metal Al. When this filler metal is used to braze 1060 aluminum, the complete joint can be achieved. Furthermore, the shear strength test results show that the fracture of brazed joint with Al-10.8Si-10Ge filler metal occurs in the base metal.
A series of Al-Ge-Si alloys was melt spun into ribbons of about 40 μm thickness. The alloy compositions were selected so as to be suitable as filler metals with brazing temperatures <500°C. In the as-quenched state the foils were relatively brittle due to the occurrence of metastable phases. After appropriate annealing treatments between 300–400°C the metastable phases were transformed into a fine-grained microstructure of β-Ge(Si) particles within the α-Al matrix. This led to considerably improved mechanical properties, which are manifested in decreased microhardness levels near 100 HV 0.02 and bend radii <1 mm. The transformation process of foils on annealing was investigated by differential scanning calorimetry, transmission electron microscopy and X-ray diffraction methods. The intensity of X-ray reflections of the metastable and equilibrium phases as well as the lattice parameters of α-Al and β-Ge(Si) were evaluated as functions of the annealing temperature. Differences in the transformation behaviour of binary Al-Ge and ternary Al-Ge-Si alloys, in particular, the decreased transformation temperature for the decay of metastable phases in ternary alloys, were revealed.
The study is concerned with developing a filler metal with low melting temperature and good processability for brazing aluminum and its alloys. For this purpose, a novel Al-Si-Ge-Zn alloy was prepared according to Al-Si-Ge and Al-Si-Zn ternary phase diagrams. The melting characteristics, microstructures, wettability, and processing property of the alloy were investigated. The results showed that the melting temperature range of the novel filler metal was 505.2-545.1°C, and the temperature interval between the solidus and the liquidus was 39.9°C. Compared with a common Al-Si-Ge alloy, it had smaller and better dispersed β-GeSi solid solution precipitates, and the Zn-rich phases distributed on the boundary of the β-GeSi precipitates. The novel filler metal has good processability and good wettability with Al. There was one obvious transition layer with a thin α-Al solid solution between the filler metal and base metal, which is favorable to improve the strength of brazing joint.
研究了Ag元素的添加量对Zn-Al钎料的熔化温度、铺展性能、 接头力学性能以及显微组织的影响.结果表明,随着Al元素含量的增加,钎料的熔化温度略有提高,在铝板及铜板上的铺展性能明显改善,钎焊接头力学性能显著 提高.当Ag元素的添加量达到3.3%(质量分数)时,钎焊接头力学性能最佳.继续增加Al元素含量,钎焊接头强度变化不大.在Zn-Al钎料中添加Ag 元素能够显著改善钎缝的显微组织,随着Al元素含量的增加,钎缝内部块状铜铝脆性相尺寸变小,产生应力集中的倾向减小,对应的接头强度提高.当Al元素含 量达到3.3%(质量分数)时,钎料的综合性能最佳.