Composite Brazing Research Articles

Microstructure and mechanical properties of high-quality AlN/Cu joints brazed by a novel AgCuTi + AlCoCrFeNi2.1 composite brazing alloy

AlN/Cu combinations offer high power electronic devices superior compatibility with large current transport and high voltage resistance, making them promising heat-dissipation candidates for electronic packaging. AlCoCrFeNi2.1 high-entropy alloy (HEA), known for its excellent mechanical properties, was incorporated into the traditional AgCuTi filler for brazing AlN and Cu in this work. The obtained AlN/Cu brazed joints exhibited homogeneous interfacial phases and high bonding strength. The maximum shear strength (277 MPa) was achieved when brazed at 850 °C for 5 min via composite filler containing 0.5 wt% AlCoCrFeNi2.1, which was 156 % higher than that brazed with single AgCuTi fillers. Enhanced mechanical properties were obtained by dispersion strengthening of intermetallic compounds (IMCs) resulting from the introduction of a medium AlCoCrFeNi2.1 concentration (less than 1 wt%) in filler alloys under tailored brazing parameters.

Microstructure and stress relief mechanism of C/C composite and GH3044 superalloy joints using (Cu)+Ti5Si3 foil filler

AbstractA Ti5Si3 reinforced (Cu) matrix foil composite filler was prepared and applied to join C/C composite and GH3044 superalloy, and a finite element model with random distribution particles was constructed to reveal the stress relief mechanism of composite brazing. Results showed the in‐situ synthesized Ti5Si3 reinforcements with a size of less than 5 µm were distributed uniformly in the (Cu) matrix, and their volume fraction reached 38%. The shear strength of the joint brazed with the composite filler reached 37.6 MPa, which is about 100% higher than that brazed with (Cu) filler. The Ti5Si3 reinforcements relieved the residual stress mainly by reducing residual stress values, introducing compressive stress into the joining layer, and transforming the continuous tensile stress into tensile stress/compressive stress.

Study on effects of ultrasound on microstructure refinement at semi-solid statement of ultrasonic-assisted brazing SiCp/Al composites

Ultrasonic composite brazing uses ultrasonic cavitation and acoustic flow effects to ameliorate the soakage property of SiC particles and brazing material, enabling flux-free brazing of SiCp/Al-MMCs under atmospheric conditions. However, its mechanical properties are limited by the performance of the brazing material, which is often difficult to apply in structures with high strength requirements. In order to break through the limitations of conventional ultrasonic composite brazing of SiCp/Al-MMCs, this paper uses 50 vol.% SiCp/Al MMCs as base material and Zn-16Al brazing material. It applies secondary ultrasound at different times during the solidification of the liquid brazing material to reduce the weld grain size and reinforce the weld intensity by using ultrasonic cavitation and acoustic flow effects. The results show that the addition of secondary ultrasound can reduce the α-Al size and make the SiC particles and α-Al evenly distributed in the joint, which can significantly reinforce the intensity of the weld. The shear performance enhanced with the increase of supersound application second, but too long secondary sonication caused atomization of the brazing material, resulting in unfilled brazing material in the weld, which seriously affected the properties of the weld.

Research on Ceramic/Steel Connection Using the Composite Brazing Method

Research on Ceramic/Steel Connection Using the Composite Brazing Method

Composite brazing of high thermal mismatched Cf/SiC and 304 stainless steel with foil (Cu) + Ti5Si3 alloy as filler

A novel foil (Cu) matrix filler reinforced by Ti5Si3 particles was designed to join Cf/SiC composite and 304 stainless steel. Results showed Ti and Si atoms in-situ reacted to form Ti5Si3 reinforcement during arc melting of mixed-powders of Cu, Ti and Si. The foil composite filler with Cu:Ti:Si = 86.5:5:9.5 (at.%) as raw material can not only reduce the thermal stress in the joint, but also react appropriately with Cf/SiC composite, and the corresponding joint shear strength was 126.5 MPa.

Microstructure and Shear Strength of SiC Joint Brazed with LiAlSiO4 Reinforced AgCuTi Composite Filler

In this work, SiC ceramics were successfully brazed at 900 °C using a composite brazing filler, and the effects of holding time and LiAlSiO4 addition on the interfacial microstructure and mechanical properties of the joints were systematically investigated. The results showed that the brazed joints were devoid of obvious defects, and the joint structure was mainly composed of SiC/Ti5Si3/TiC + TiCu2 + TiO2 + LAS + LiAlSi2O6 + Cu (s, s) + Ag (s, s)/Ti5Si3/TiC/SiC. When the brazing temperature was 900 °C for 10 min and the LiAlSiO4 addition was 1 wt%, the SiC brazed joints reached a maximum shear strength of 106.47 MPa, which was 4.7 times higher than that of the joints without LiAlSiO4 addition under the same conditions. According to theoretical calculations, the addition of LAS can successfully reduce residual stresses in SiC brazed joints and enhance the joint strength.

Releasing the residual stress of Cf/SiC-GH3536 joint by designing an Ag-Cu-Ti + Sc2(WO4)3 composite filler metal

• The work is the first one to introduce Sc 2 (WO 4 ) 3 into brazing process. • The Sc 2 (WO 4 ) 3 maintains its negative thermal expansion effect in Ag-Cu-Ti system. • The residual stress releasing mechanism is revealed by finite element analysis method. • The shear strength improves 2.6 times by introducing Sc 2 (WO 4 ) 3 reinforcing phase. Due to native character of thermal expansion coefficient (CTE) mismatch between C f /SiC and GH3536, achieving high strength joint was a huge challenge for C f /SiC-GH3536 joints. Herein, a composite filler metal of Ag-Cu-Ti + Sc 2 (WO 4 ) 3 was developed to join C f /SiC and GH3536. This work introduced Sc 2 (WO 4 ) 3 to Ag-Cu-Ti system as a negative thermal expansion (NTE) reinforcing phase to release joint residual stress. Sc 2 (WO 4 ) 3 was evenly distributed in the brazing seam and reacted with Ti to form Ti 3 O 5 reaction layer. The results of finite element analysis showed that the residual stress of the joints was effectively released by introducing Sc 2 (WO 4 ) 3 reinforcing phase, and the mises stress was decreased from 447 to 401 MPa. The maximum shear strength of the C f /SiC-GH3536 joint brazed with Ag-Cu-Ti + 6 vol% Sc 2 (WO 4 ) 3 filler alloys was 64 MPa, which was about 2.6 times higher than that of Ag-Cu-Ti alloys. The results of this study provide a promising strategy for the introduction of new Sc 2 (WO 4 ) 3 reinforcing phase in Ag-Cu-Ti system, and improve the reliability and feasibility of composite brazing alloy in brazing filed.

Negative thermal expansion Y2Mo3O12 particles reinforced AgCuTi composite filler for brazing Cf/SiC and GH3536

A novel composite brazing alloy by introducing negative thermal expansion Y 2 Mo 3 O 12 particles into AgCuTi alloy was developed to alleviate the residual stress of C f /SiC-GH3536 joint. The negative thermal expansion behavior of Y 2 Mo 3 O 12 material and its effects on the shear strength of brazed joints were investigated. The strong negative thermal expansion behavior of Y 2 Mo 3 O 12 material greatly reduce the coefficients of thermal expansion of composite filler, which can greatly alleviate the residual stress of C f /SiC-GH3536 joint. In addition, the interface structure has been greatly optimized, leading to enhanced bonding strength. The maximum shear strength of C f /SiC-GH3536 joints reached ~42 MPa after added 3 wt% Y 2 Mo 3 O 12 , which was 1.6 times higher than that of original joints. This study shows that Y 2 Mo 3 O 12 can maintain its strong negative expansion characteristics during the brazing process, which may provide a new idea to solve the hygroscopicity of Y 2 Mo 3 O 12 . • The Y 2 Mo 3 O 12 shows strong negative thermal expansion behavior in brazing process. • The CTE of composite filler greatly reduces by added Y 2 Mo 3 O 12 . • The joint strength improves 1.6 times by introducing Y 2 Mo 3 O 12 reinforcing phase.

Research Progress in Relation to Composite Brazing Materials with Flux

Brazing was one of the earliest material-joining methods to be invented and widely used by humans. In the past 30 years, the technology and materials employed for brazing have developed rapidly and continuously. With the rise of the international new industrial revolution, the manufacturing industry is moving towards diversification, and brazing filler metals are also evolving in the direction of eco-friendliness, compounding and diversification. In the “carbon neutral” environment of 2021, green composite brazing materials will become mainstream. In this paper, the classification and characteristics of flux-containing brazing materials are summarized, and the preparation technology, composition design and typical application of composite brazing materials such as flux-cored brazing filler metal, flux-coated brazing filler metal and powder metallurgy brazing filler metal are analyzed. The article highlights the problems encountered in the research and development of composite brazing materials and proposes future development directions, such as with low-silver and cadmium-free brazing filler metals, the creation of new powder brazing filler metal-forming technology and improvements to the quality of brazing filler metals by shape control and performance optimization, to accelerate the process of brazing automation.

A review on filler materials for brazing of carbon-carbon composites

Abstract It is needed to join C/C composite to other materials since its individual use is limited. Brazing is a method to join C/C composite that has been studied most, maturest and most widely used in recent decades. The quality of a brazed joint is largely determined by the intermediate layer material. It is significant to choose filler materials reasonably. C/C composite is difficult to be wetted by common brazing filler materials. Moreover, there is a large difference in the coefficient of thermal expansion between C/C composite and metals. At present, there is no brazing filler alloy exclusively recommended for commercial C/C composites and metal brazing. Usually, active elements are added into filler metals to improve the wettability of them on C/C composite surface. The existing research includes Al-based, Ag-based, Cu-based, Ti-based, Ni-based brazing filler metals, and so on. In addition, various particle reinforced composite filler materials and stress buffer metal interlayer added composite filler materials have been studied for brazing C/C composite. The summarization of the overview on the application of intermediate filler metals is made in this paper. The basic reference basis is provided for the subsequent brazing filler metals development and joint performance improvement for C/C composite brazing.

Composite brazing of C/C composite and Ni-based superalloy using (Ag-10Ti)+TiC filler material

With the aim of alleviating the residual thermal stress in the C/C-GH3044 joints, a novel composite brazing, which combines Ag-Ti reactive composite brazing and TiC particle-reinforced composite brazing, was adopted for joining C/C composite to Ni-based superalloy GH3044 using (Ag-10Ti)+TiC composite filler material. The results showed that the composite interlayer was strengthened by four kinds of reinforcements, containing the introduced TiC, the in situ synthesized AgTi and Ti 2 Ni phases, and the residual Ti particles. With increasing TiC content from 0 to 32 %, the thermal expansion coefficient of the composite interlayer declined by 18.2 %, which is helpful in alleviating the residual thermal stress in the joints. In addition, the introduced TiC particles decreased the fluidity of the filler material and inhibited the inter-diffusion of atoms between GH3044 and filler material. As a result, the continuous brittle compound Ti 2 Ni in the composite interlayer was effectively reduced, so the composite interlayer had good plasticity. Meanwhile, the thickness of the composite interlayer gradually increased from 260 μm to 520 μm, and the finite element analysis showed that the corresponding peak value of von Mises stress decreasedby 20.1 %. The highest shear strength of the joints was 67.2 MPa obtained with (Ag-10Ti)+24 %TiC at 1020°C for 30 min,which is almost the same strength as the C/C composite matrix used in this study.

AlN/Cu composite ceramic substrate fabricated using a novel TiN/AgCuTi composite brazing alloy

We developed a newly-designed TiN/AgCuTi composite brazing alloy to significantly improve the bonding strength of AlN/Cu composite ceramics, which can endow high power electronic devices with superior compatibility with large current transport and high voltage resistance. Via the systematic microstructure investigation of the brazed joint by scanning electron microscopy and X-ray diffractometer, we found that added TiN particles could decrease the thickness of brittle reaction layer and promote the formation of fine TiCu particles in brazed joint, leading to dispersion strengthened and decreased CTE mismatch of the ceramic/metal composite. Importantly, the maximum bonding strength of 131 MPa was obtained for AlN and copper foil brazed joining via composite filler with TiN(4 wt.%)/AgCuTi, which is approximately 150 % higher than the case without TiN addition.

The Microstructure and Shear Strength of SiC Joints Brazed with SiC Particle Reinforced Si-24Ti Alloy

To refine the microstructure and increase the joint strength of SiC ceramic brazed with Si-24Ti (wt.%), carbon nanotubes (CNT) were added into Si-24Ti brazing alloy to form SiC particles in the braze zone. The effect of the amount of CNT in the brazing alloy on the microstructure and shear strength of joints was investigated. The microstructure and element distribution of the joint was studied by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS). The results indicated that the addition of the proper amount (1-3 wt.%) of CNT could refine the microstructure of joints and achieve high-quality SiC joints. The shear strength of the joint brazed with 3 wt.% CNT addition reached the maximum value of 108 MPa, which was 21.3% higher than that of without CNT (89 MPa). However, when the amount of CNT increased to 5 wt.%, the shear strength of joint decreased to 55 MPa, due to the formation of cavity in the joint. The strengthening mechanism of in-situ formed SiC particle in the composite brazing alloy was evaluated.

A novel process with the characteristics of low-temperature bonding and high-temperature resisting for joining Cf/SiC composite to GH3044 alloy

Taking advantages of reaction composite brazing, transient liquid phase bonding (TLP) and partial transient liquid phase bonding (PTLP), a novel process with the characteristics of low-temperature bonding and high-temperature resisting was developed for joining Cf/SiC composite to GH3044 alloy by using (Cu-Ti) + C + Ni mixed powder filler. Under the bonding temperature (980 °C), the reaction between the liquid Cu-Ti alloy and C particles (reaction composite mechanism), composition homogenizations between the joining layer and Ni particles (PTLP mechanism) as well as Ni-based substrate (TLP mechanism) occurred to complete the transformation (Cu,Ti)l + Cs + Nis → TiCs + (Cu,Ni)s. Thereby, a joint with high-temperature resistance and excellent mechanical properties was obtained in relatively short holding time. The melting-point of the joint (1050 °C) was obviously higher than that of Cu-Ti alloy (898 °C) in the filler. The bonded joints exhibited shear strengths of 229, 225 and 104 MPa at room temperature, 600 °C and 1000 °C, respectively.

Microstructure and mechanical properties of the SiC/Nb joint brazed using AgCuTi+B4C composite filler metal

The residual stress is considered to be the driving force for the failure of ceramic/metal brazing joint. In this paper, the residual stress in a SiC/Nb joint is alleviated by using AgCuTi+B4C composite brazing filler. SEM, EDS and XRD are applied to characterised the microstructure of the joint, which is determined to be SiC/Ti3SiC2/Ag(s,s)+Cu(s,s)+TiB+TiC/TiCu+ Nb(s,s)/Nb. The effects of the B4C strengthening phase mass fraction and the brazing temperature on the microstructure and the mechanical properties of the joint are investigated. It is found that the reaction products between B4C and the brazing filler (TiB whisker and TiC particles) uniformly distribute inside the joint if the mass fraction of the B4C is not higher than 1.5 wt% and when the amount of B4C reaches 2 wt%, the reaction products begin to agglomerate. With the rising of the brazing temperature, the thickness of the Ti3SiC2 reaction layer next to the ceramic increases and when the brazing temperature reaches 910 °C, another reaction layer of Ti5Si3 can be found adjacent to the Ti3SiC2 reaction layer. The strength of the joint first increases and then decreases with the increase of both the strengthening phase and the brazing temperature. The highest shear strength of the joint reaches 98 MPa when the joint is achieved at 890 °C using AgCuTi+1.5 wt%B4C brazing filler.

Reactive composite brazing of C/C composite and GH3044 with Ag–Ti mixed powder filler material

In this study, a novel Ag–Ti reactive composite brazing technology was employed to join carbon fiber reinforced carbon matrix composite (C/C) to Nickel-based superalloy GH3044. The microstructural evolution mechanism and the effects of process parameters on the microstructures and shear strength of the brazed joints were investigated systematically. The results showed that, during the brazing holding stage, Ti (α-Ti) in the liquid phase would convert to β-Ti (above 1020°C) or react with Ag formed AgTi (below 1020°C). Solid phase β-Ti or AgTi inhibited the loss of the molten filler material, thus forming a thicker interlayer, which was beneficial to relieve the residual stress of the joints. After brazing, an Ag matrix composite interlayer reinforced by in situ synthesized phases and a few residual Ti particles could be obtained. Notably, the reinforcing phases were various with different brazing parameters. Under weaker parameters (lower Ti content, lower temperature and shorter holding time), the reinforcing phases were mainly in situ synthesized AgTi phase and residual Ti particles, with which the Ag matrix composite interlayer had good plasticity and low coefficient of thermal expansion. As a result, the residual stress of the joints was further effectively relieved. Under stronger parameters, the reinforcing phases were mainly brittle phases Ti2Ni and Cr1.93Ti1.07, which increased the brittleness of the composite interlayer. The maximum shear strength of the joints reached 45.8 MPa brazed at 1020°C for 30 min using Ag–20Ti (Wt.%).

Relieving residual stress in brazed joint between SiC and Nb using a 3D-SiO2-fiber ceramic interlayer

A robust joint between SiC and Nb was realized by using the combination of Ag-Cu-Ti + Ti composite brazing alloy and a 3D quartz-fiber braided interlayer (3D-SiO2-fiber). The 3D-SiO2-fiber, with ductile, loose and porous structure, can be filled up by the composite brazing alloy, which plays an important role in forming a sound joint. Furthermore, considerable and uniformly distributed α-Ti, Ti2Cu, Cu3Si and TiSi compounded particles in the joint effectively reduced the high coefficient of thermal expansion (CTE) mismatching between different materials. Thus the residual stress in the joint was greatly mitigated and the joint was strengthened.

Brazing of high-temperature heat exchangers with a composite brazing alloy of the Cr–Ni–Mn system

The results of investigations carried out to determine the optimum composition of the composite brazing alloy of a Cr–Ni–Mn system, the thickness of the layer, and sequence of deposition on the heat exchanger surface are presented. The recommended brazing parameters produce brazed joints satisfying the service requirements of the heat exchangers.

Microstructure and mechanical properties of C/C composite/Ti6Al4V joints with a Cu/TiCuZrNi composite brazing alloy

C/C composites and Ti6Al4V sheets were joined using a novel Cu/TiCuZrNi composite braze and the effect of Cu foil thickness on the microstructure and mechanical properties of the joints were investigated. A composite joining material, consisting of a TiC particle reinforced brazing alloy formed in situ during the brazing process was obtained. Before the joining process, the C/C composite surface was modified by solid state reaction with chromium to form a chromium carbide coating. This carbide reaction layer can react with the Ti-based brazing alloy and form evenly distributed TiC particles. The maximum apparent shear strength of as-received joint was 39±8.5 MPa obtained by using a 40μm thick Cu foil together with the TiCuZrNi alloy; this value was 70% higher than the mechanical strength obtained for joints brazed with the TiCuZrNi alloy only.

Interaction of Composite Brazing Alloy Sn-Cu-Co-W with Diamond at Brazing of Diamond Abrasive Tools

It was researched the interaction of composite brazing alloy Sn-Cu-Co-W with surface of diamond during formation of a diamond-bearing layer on abrasive tool. It was determined the influence of the composite brazing alloy components on wetting of diamond grains and their subsequent retention in metal matrix. The prototypes of stone-machining routers were manufactured with use of the designed composite brazing alloy. Thickness of obtained diamond containing coating is even over the entire surface is 2 mm. Due to the high viscosity of the composite brazing alloy it is well retained on the contoured surface of the substrate including the vertical sections.