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In this work, chromium coating conducted by magnetron sputtering was introduced to braze SiC ceramics using inactive AgCu filler metal. The results showed that reliable metallurgical bonding of SiC ceramics was obtained at 900°C for 10 minutes. SEM, XRD, and TEM were used to identify the reaction phase in the joint, and the typical interfacial microstructure was SiC/mixed CrSi2 + Cr23C6 layer/CrSi2/Ag(s,s)+Cu(s,s)/CrSi2/mixed CrSi2 + Cr23C6 layer/SiC. The shear strength of SiC joint using chromium coating brazed with inactive AgCu filler metal was 29.6 MPa and the joint fractured at the SiC substrate entirely after shear test. The proposed active element coating method provides a feasible way to achieve the brazing of ceramics. [ABSTRACT FROM AUTHOR]

By coating active titanium, Sn0.3Ag0.7Cu (SAC) filler wetted SiC effectively, as the contact angle decreased significantly from ~145° to ~10°. Ti3SiC2 and TiOx (x ≤ 1) reaction layers were formed at the droplet/SiC interface, leading to the reduction of contact angle. Reliable brazing of SiC was achieved using titanium deposition at 900°C for 10 minutes, and the typical interfacial microstructure of Ti‐coated SiC/SAC was SiC/TiOx + Ti3SiC2/Sn(s,s). Comparing to direct brazing, Ti–Sn compounds in the brazing seam were effectively reduced and the mechanical property of joints was dramatically improved by titanium coating. The optimal average shear strength of SiC joints reached 25.3 MPa using titanium coating‐ assisted brazing, which was ∼62% higher than that of SiC brazed joints using SAC‐Ti filler directly. [ABSTRACT FROM AUTHOR]

Laser brazing of Al to brass in lap configuration with Zn-based filler was performed in this work. The process parameters including laser power, defocused distance were found to have a significant influence on appearance, microstructure and mechanical properties. The process parameters were optimized to be laser power of 2700 W and defocusing distance of + 40 mm from brass surface. In addition, preheating exerted great influence on wetting and spreading ability of Zn filler on brass surface. The microstructure observation showed the thickness of reaction layer (CuZn phase) at the interface of the brass side would grow with the increase in laser power and the decrease in the laser defocusing distance. Moreover, preheating could increase the spreading area of the filler metal and induced the growth of the reaction layer. The highest tensile-shear load of the joint could reach 2100 N, which was 80% of that of Al alloy base metal. All the joints fractured along the CuZn reaction layer and brass interface. The fracture morphology displayed the characteristics of the cleavage fracture when without preheating before welding, while it displayed the characteristics of the quasi-cleavage fracture with preheating before welding. [ABSTRACT FROM AUTHOR]

Fiber laser welding-brazing of 1-mm-thick AZ31B Mg alloys to 1.5-mm-thick copper (T2) with Mg-based filler was performed in a lap configuration. The weld appearance, interfacial microstructure and mechanical properties were investigated with different heat inputs. The results indicated that processing windows for optimizing appropriate welding parameters were relatively narrow in this case. Visually acceptable joints with certain strength were achieved at appropriate welding parameters. The maximum tensile-shear fracture load of laser-welded-brazed Mg/Cu joint could reach 1730 N at the laser power of 1200 W, representing 64.1% joint efficiency relative to AZ31Mg base metal. The eutectic structure (α-Mg + Mg2Cu) and Mg-Cu intermetallic compound was observed at the Mg/Cu interface, and Mg-Al-Cu ternary intermetallic compound were identified between intermetallics and eutectic structure at high heat input. All the joints fractured at the Mg-Cu interface. However, the fracture mode was found to differ. For laser power of 1200 W, the surface was characterized by tearing edge, while that with poor joint strength was almost dominated by smooth surface or flat tear pattern. [ABSTRACT FROM AUTHOR]

Electron beam welding experiments of titanium alloy to stainless steel with V, Ni, Cu and Ag filler metals were carried out. The interfacial microstructures of the joints were examined by optical microscopy, scanning electron microscopy, and x-ray diffraction analysis. Mechanical properties of the joints were evaluated according to tensile strength and microhardness. The results showed that all the filler metals were helpful to restrain the Ti-Fe intermetallics formed in the Ti/Fe joint. The welds with different filler metals were all characterized by solid solution and interfacial intermetallics. And the type of solid solution and interfacial intermetallics were depended on the metallurgical reactions between the filler metals and base metals. The interfacial intermetallics were FeTi + NiTi + NiTi, TiFe, TiAg, and CuTi + CuTi + CuTi in the joints welded with Ni, V, Ag, and Cu filler metals, respectively. The tensile strengths of the joints were primarily determined by the hardness of the interfacial intermetallics. The highest tensile strength was obtained in the joint welded with silver filler metal, which is about 310 MPa. [ABSTRACT FROM AUTHOR]

Titanium and zirconia (ZrO2) ceramics are widely used in biomedical fields. This study aims to achieve reliable brazed joints of titanium/ZrO2 using biocompatible Au filler for implantable medical products. The effects of brazing temperature and holding time on the interfacial microstructures and mechanical properties of titanium/Au/ZrO2 joints were fully investigated by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS) and X-ray diffraction (XRD). The results indicated that the typical interfacial microstructure of the titanium/Au/ZrO2 joint was titanium/Ti3Au layer/TiAu layer/TiAu2 layer/TiAu4 layer/TiO layer/ZrO2 ceramic. With an increasing brazing temperature or holding time, the thickness of the Ti3Au + TiAu + TiAu2 layer increased gradually. The growth of the TiO layer was observed, which promoted metallurgical bonding between the filler metal and ZrO2 ceramic. The optimal shear strength of ~35.0 MPa was obtained at 1150 °C for 10 min. SEM characterization revealed that cracks initiated and propagated along the interface of TiAu2 and TiAu4 reaction layers. [ABSTRACT FROM AUTHOR]

Ti-Fe intermetallic compounds were effectively suppressed with Cu-based filler wire and weld formation was greatly improved with the preheating of substrates when joining TC4 titanium alloy and 304 stainless steel. A Ti/Cu transition zone consisting of complex TiCu, Ti2Cu3, TiFe, and TiFe2 phases was formed between Cu-weld/TC4 interface, while Cu-weld/304ss interface was mainly composed of α-Fe and ε-Cu solid solution. At lower heat input, the undercut defect in back surface had potential to cause crack initiation and joint fracture. Though increasing heat input would improve weld morphology, the formation of thick interfacial reaction layer and weld cracking led to low weld quality and joint strength. The preheating of substrates had an obvious effect on wetting ability of liquid filler metal and could achieve a better weld quality at lower heat input. The back formation of weld was improved to decrease the occurrence of weld defects. The highest tensile strength of 365 MPa occurred at welding heat input of 0.483 kJ/cm, increasing by 47% compared to the joint without preheating. The interfacial reaction mechanism was discussed to reveal the relationship between microstructural characteristics and fracture behavior of Ti/steel welded joints with Cu-based filler wire. [ABSTRACT FROM AUTHOR]

The present investigation was conducted to study vacuum brazing between carbon–carbon composites (CC) and TiAl alloys with Ag–Cu–Ti filler metal. The mutual exclusion between the Ag and Ti elements had a significant influence on the joint microstructure. The isothermal solidification of the Ag-based solid solution led to a layered microstructure, which was beneficial to the joining strength. A new method of making holes in the CC composite surface was introduced, and the joint was strengthened by the infiltration of filler metals into these holes. [ABSTRACT FROM AUTHOR]

The wetting and brazing of C f /C composites with a Si–10Zr eutectic alloy was investigated for the first time. Wetting of the Si–Zr alloy on the C f /C substrate was studied by applying in-situ variations in contact angle of the droplet placed on the C f /C substrate with temperature and time. The microstructure and the interfacial structure between the filler and the substrate, and the mechanical properties of the joints were determined using scanning electron microscopy, X-ray diffraction and transmission electron microscopy. The Si–Zr alloy has an equilibrium contact angle of approximately 22° on the C f /C substrate at 1460 °C, indicating excellent wettability. The liquid Si–Zr alloy can react with the C f /C substrate by forming nano-SiC and coarse-SiC layers, and promote the wetting behaviour and bonding performance. In addition, the liquid Si–Zr alloy can also infiltrate into the C f /C substrate along the carbon fibres, causing localised siliconisation and strengthening of the joint. An optimal shear strength of 32 MPa was achieved for the joint at a brazing temperature of 1460 °C for 10 min. Image 1 [ABSTRACT FROM AUTHOR]

A novel type of brazed joint with in situ TiSi 2 microarray strengthened Si–Ti eutectic colonies in a carbon fibre reinforced carbon (C f /C) composite was developed. The mechanical properties, microstructure evolution, fracture characteristics, and interfacial reaction mechanism of the joint were investigated. The shear strength of a pressure-less brazed joint can reach 41 MPa, which is comparable to other current joints developed under a certain pressure. Both the eutectic phases with uniform TiSi 2 sticks in the brazing seam and Si–Ti melt infiltration throughout the porous C f /C composite are conducive to relieving the thermal residual stress in the joining system. With more melt filling and a higher reaction with the porous C f /C substrate, an in situ TiSi 2 microarray reinforced SiC/carbon assembly is formed and the mechanical properties of the joint are significantly improved. In addition, an excellent high-temperature shear strength of 46 MPa is achieved at a test temperature of 1000 °C in air. Moreover, a thermal shock test leads to the generation of cracks in the brazing seam and the interface regions, which is a hindrance the joint strength. [ABSTRACT FROM AUTHOR]

• Join Mg and Cu-coated Ti using laser welding-brazing process. • Influence of Cu coating thickness on welding quality and interfacial reaction was studied. • A elements diffusion mechanism on Mg/Cu-coated Ti interface was clarified. • Joint strength and fracture path and were associated with interfacial bonding and thickness. Butt laser welding-brazing of Mg to Ti with Mg based filler was performed with the assistance of Cu coating. The thickness of Cu coating was varied in the study, to investigate its influence on microstructure and mechanical properties of the joint. Two main regions were distinguished along the Mg/Cu coated Ti interface. At the upper interface, the bonding mechanism evolved from mechanical bonding into a "Ti 3 Al and AlCu 2 Ti" metallurgical bonding, and into a "Ti 3 Al + Ti 2 Cu + AlCu 2 Ti" metallurgical bonding as Cu coating thickness varied from 0 μm to 19.7 μm to 24.9 μm. At the lower interface, mechanical bonding changed into the IMC layer consisted of Ti 3 Al, Ti 2 Cu and AlCu 2 Ti when Cu coating thickness reached 28.2 μm. The chemical potential calculated by the developed Toop model suggested that Cu played a role in promoting the mutual diffusion between Al and Ti. Ti tended to react with Al first compared with Cu suggesting Ti-Al compounds were produced easily at Mg/Ti interface. In the case of Cu coating thickness of 19.7 μm, the joint load reached a peak value of 3457 N, as high as 85.35% of that of Mg base metal. The fracture mode changed from interfacial failure to fusion zone failure when the coating thickness reached 19.7 μm. [ABSTRACT FROM AUTHOR]

Highlights • A high-quality Ti/Cu joint was obtained using 0.7 mm thick Cu66V34 filler metal by uncentered EBW. • The microstructures of the joints by different thick Cu66V34 filler metals were investigated. • (Ti,V) solid solution phase was formed to replace the Ti-Cu IMCs at the interface of titanium side. • The joint with 0.7 mm thick Cu66V34 alloy fractured in the HAZ of copper with a tensile strength of 384 MPa. Abstract The joint with 1.0mm Cu66V34 filler metal produced a large amount of unmelted V alloy, weakening the joining quality of Ti/Cu joint. Due to the decreased thickness of filler metal, the melting quantity of Ti increased notably in the joint with 0.5mm Cu66V34 alloy, resulting in the formation of Ti-Cu compounds. The 0.7mm Cu66V34 filler metal could restrain the Ti-Cu compounds formed in the joint. The microstructure in zone A3 and FZ was mainly characterized by solid solution phases including (Ti,V) solid solution and Cu solid solution, improving the bonding strength at the interface of titanium side. The joint with 0.7mm Cu66V34 alloy presented the highest tensile strength of 384 MPa, approaching ∼80% of that of the copper base metal, and fractured in the HAZ of copper side, due to local softening by grains coarsening. [ABSTRACT FROM AUTHOR]

To development large-size and complex high-entropy ceramic (HEC) components, the joining of (Ti 0.2 Zr 0.2 Nb 0.2 Ta 0.2 Cr 0.2)C and Nb metal with nickel-based filler alloy was performed. The microstructure was characterized by SEM and the phase composition was analyzed by EDS and XRD. The brazing mechanism of the joint was mainly derived from the diffusion of Nb, which formed the NbC reaction layer in the HEC part and the diffusion zone in Nb metal part. The highest shear strength of the brazed joints at 1170 °C/10min was 139 MPa at room temperature and 117 MPa at 800 °C. In addition, the effect of brazing temperature on the microstructure and shear strength was discussed. This work provided a key method to prepare high-temperature resistant complex and large-size HEC components. • This work provides a feasible method to fabricate large-size and complex HEC component. • The brazing mechanism is ascribed to the diffusion of Nb to form Nb(s,s) diffusion zone and NbC reaction layer. • A maximum shear strength of the joint is 139 MPa at room temperature and 119 MPa at 800 °C. [ABSTRACT FROM AUTHOR]

The development of new composite fillers is crucial for joining ceramics or ceramics to metals because the composite fillers exhibit more advantages than traditional brazing filler metal. In this research, novel B 4 C reinforced Ag–Cu–Ti composite filler was developed to braze SiC ceramics. The interfacial microstructure of the joints was characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effect of B 4 C addition and brazing temperature on the microstructure evolution and mechanical properties of the joints was analyzed. The results revealed that TiB whisker and TiC particles were simultaneously synthesized in the Ag-based solid solution and Cu-based solid solution due to the addition of B 4 C particles. As the brazing temperature increased, the thickness of Ti 3 SiC 2 +Ti 5 Si 3 layers adjacent to SiC ceramic increased. Desirable microstructure similar to the metal matrix reinforced by TiB whisker and TiC particles could be obtained at brazing temperature of 950 °C. The maximum bending strength of 140 MPa was reached when the joints brazed at 950 °C for 10 min, which was 48 MPa (~52%) higher than that of the joints brazed using Ag–Cu–Ti filler. [ABSTRACT FROM AUTHOR]

Abstract: Composite V/Cu based filler metals for electron beam welding of titanium–stainless steel joint were designed, based on the element metallurgical compatibility. Powder metallurgy method was used to manufacture the filler metal. To determine the feasibility of these filler metals, microstructures were analyzed by optical microscopy, scanning electron microscopy and X-ray diffraction. Mechanical properties of the joints were evaluated by tensile strength tests. The feasibility of the Cu/V filler metal was poor for the differences in physical properties between copper and vanadium, vanadium and titanium. A non-fusion defect was produced in the joint under low heat input, and cracking occurred in the joint under higher heat input due to the continuously distributed brittle TiCu, TiFe and τ2 compounds. However, such defects were eliminated using a powder metallurgical V/Cu–V filler metal. A joint with a tensile strength of 395 MPa, 72% of that of the stainless steel was obtained. And almost no intermetallics were detected in Ti/V/Cu–V/Fe joint. [Copyright &y& Elsevier]

Abstract: Microstructural evolution and shear strength of vacuum brazed TiAl alloys to C/SiC composites using Ag–Cu filler metal were investigated. The dissolution of active elements Ti and Al from TiAl substrate has a strong influence on the microstructure and shear strength of the joint. Ag is the less active element of the filler and Cu has strong tendency to the formation of AlCu2Ti phase with the dissolved Ti and Al. Ag–Cu eutectic is gradually taken place by AlCu2Ti blocks and Ag-based solid solution with the increase of brazing temperature or time. The TiC reaction layer including a small amount of Ti5Si3 phase is formed adjacent to C/SiC composites when active element Ti diffused into C/SiC composite and chemical reaction occurred in the composite interface. The shear strength of the joint depends heavily on the thickness of the TiC reaction layer. The maximum shear strength achieved 85MPa for the joint vacuum brazed at 900°C for 10min. Cracks primarily propagate along Ag-rich phase and TiC layer. The TiC layer with the thickness of 4–5μm is formed at the boundary of SiC matrix. [Copyright &y& Elsevier]

The composite structures of TZM alloy and 30CrMnSiA steel have broad application prospects in nuclear power and aerospace industries, while the problem of the joint embrittlement has not been solved. Therefore, pure vanadium, which has excellent metallurgical compatibility with base materials is selected as the filler metal to produce high strength joints. Microstructures, mechanical properties, and TZM/FZ interfacial characteristics of the joints without V foil and with V foil were analyzed. The results indicate that: (i) there is a Fe 2 Mo intermetallic compound layer along with the TZM/FZ interface without V foil, which will deteriorate the mechanical properties of the joint. After adding pure V foil, there is no reactive layer appearing at the TZM/FZ interface; (ii) the joint without V foil fractured along the interface between TZM and Fe 2 Mo, the strength of which is only 165.2 MPa, while the tensile strength of the joint with V foil reaches 312.7 MPa; (iii) through calculating the interfacial ideal adhesion energy, it can be found that the interfacial bonding strength of the Mo (111)/V(Fe) ss (111) interface is higher than that of the Mo (111)/Fe 2 Mo(100) interface. [ABSTRACT FROM AUTHOR]

Joining the transparent ceramic with metal could help to realise their applications. In this paper, the AlON ceramic was successfully bonded to the Ti6Al4V using the active element brazing approach. The microstructure of the achieved joints is characterised via scanning electron microscope (SEM), electron probe microanalyser (EPMA) and transmission electron microscope (TEM), which turned out to be AlON/Ti 3 (Cu,Al) 3 O/Ag(s,s) and Cu(s,s)/Ti 4 Cu/TiCu/Ti 2 Cu/Ti6Al4V. The effects of the brazing temperature and the holding time on the microstructure and the shear strength of the joint are investigated. It is found that with the increase of the brazing temperature and the holding time, the thickness of the Ti 3 (Cu, Al) 3 O, TiCu and Ti 2 Cu reaction layers increases while the thickness of the Ti 4 Cu reaction layer declines. The shear strength of the joint first increases with the brazing temperature/holding time and then decreases. The highest shear strength of 78.3 MPa is achieved when the joint is achieved at 840 °C for 10 min. The relationship between the joint microstructure and its mechanical properties is also revealed. [ABSTRACT FROM AUTHOR]

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+B 4 C composite brazing filler. SEM, EDS and XRD are applied to characterised the microstructure of the joint, which is determined to be SiC/Ti 3 SiC 2 /Ag(s,s)+Cu(s,s)+TiB+TiC/TiCu+ Nb(s,s)/Nb. The effects of the B 4 C 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 B 4 C and the brazing filler (TiB whisker and TiC particles) uniformly distribute inside the joint if the mass fraction of the B 4 C is not higher than 1.5 wt% and when the amount of B 4 C reaches 2 wt%, the reaction products begin to agglomerate. With the rising of the brazing temperature, the thickness of the Ti 3 SiC 2 reaction layer next to the ceramic increases and when the brazing temperature reaches 910 °C, another reaction layer of Ti 5 Si 3 can be found adjacent to the Ti 3 SiC 2 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%B 4 C brazing filler. • Joining of SiC and Nb has been achieved using AgCuTi+B 4 C composite brazing filler. • The joint consists of Ti 3 SiC 2 phase, in-situ grown TiB whiskers and TiC particles. • The effects of the temperature and the B 4 C content on the joint are investigated. [ABSTRACT FROM AUTHOR]

Reliable brazing of ZrC-SiC ceramic and TiAl alloy was achieved using active Ag Zr filler metal. During the brazing process, Ti and Al were dissolved into the filler metal, and TiC+(Ti,Zr) 3 SiC 2 layer formed due to the reaction between the ZrC-SiC and Ti. Meanwhile, strong affinity of Ti, Al and Zr produced dispersive (Ti,Zr)(Al,Ag) in the brazing seam. The effect of Zr content and holding time on the microstructure and mechanical property of the joints was investigated. With the increase of Zr content, the formation of (Ti,Zr)(Al,Ag) phase was promoted and its volume became large. The consumption of Ti in (Ti,Zr)(Al,Ag) phase restrained the formation of TiC, decreasing the thickness of TiC layer. Excess Zr addition could induce large bulks of (Ti,Zr)(Al,Ag) and cracks in the brazing seam. The holding time mainly affected the distribution of Ti-Zr-Al-Ag phases in the brazing seam. The joint strength reached a maximum value of 65 MPa when the Zr content of the filler was 5 wt% and holding time was 5 min. The crack propagated in the ZrC-SiC ceramic substrate. • The ZrC-SiC and TiAl were successfully brazed using Ag Zr filler. • The typical microstructure of the ZrC-SiC/TiAl joint was investigated by SEM, XRD and TEM. • The Zr content and holding time affected the joint strength through controlling the microstructure of the brazing seam. • The maximum strength was 65MPa when the joint brazed using Ag 5Zr at 980°C for 5min. [ABSTRACT FROM AUTHOR]