Ti Active Filler Research Articles

Brazing mechanism and shear strength of SiAlON/WC‐Co joint using Ag–Cu–Ti active filler

AbstractThis work investigated the formation mechanism and the effects of temperature on the microstructure and shear strength of vacuum‐brazed SiAlON ceramic/WC‐Co cemented carbide joints using an Ag–Cu–Ti active filler as the interlayer. The diffusion of Ti elements toward substrates and their subsequent reaction during the brazing process led to the formation of TiN, TiC, and Ti5Si3 phases, where the featured reaction layers were established. A continuous reaction layer of TiN in the SiAlON substrate side and TiC in the WC substrate side were formed. The ceramic phases (Ti5Si3 TiN, and TiC) were distributed in a brazed intermediate layer. The highest shear strength of the brazed joints obtained at 850°C was 325.28 ± 20.27 MPa, demonstrating the feasibility of the Ag–Cu–Ti active filler in producing robust joints.

Ultrasonic-assisted soldering of Si and Cu joint with SnAgTi solder in air

The reliable connection of single crystal Si and Cu at low temperature is widely utilized and plays a crucial role in the field of electronic packaging. In this study, Sn–Ag–Ti active filler is ultrasonically coated onto the Si surface to facilitate the subsequent ultrasonic soldering process to realize the bonding of Cu to pre-metallized Si. Furthermore, a detailed analysis was conducted on the influence of ultrasonic time on both the bonding mechanism and mechanical properties of the joint. The results revealed that Ti–Sn compound within the solder decomposed with ultrasonic action duration time of 20 s, resulting that Ti elements enriched at the Si/solder interface and reacted with SiO2 to form a mixture comprising TiO2 and SiTi phase. It contributed to higher strength (43.9 MPa) at the Si/solder interface. Additionally, it has been found that microstructure and property at the Cu/solder interface were directly affected by ultrasonic time. Specifically, when subjected to 3 s of ultrasonic action, poor load-bearing capacity exhibited by thin infiltration layers caused fracture at the Cu/solder interface; When the ultrasonic action time is 6 s, the joint strength reaches its maximum value of 41.3 MPa, leading to fracture occurring within the Si material. However, when the ultrasonic holding time is extended to 20 s, the joint strength decreases to 20.3 MPa. This phenomenon arises from impaired plasticity of Cu6Sn5 near the Cu–Sn layer, which is attributed to the presence of attached dendritic Cu6Sn5 phases and shed bulk Cu6Sn5 that are prone to crack initiation. This research presents a promising approach for ceramic/metal heterogeneous joining.

Joining Si3N4 ceramic to Invar using Mo mesh and Cu foil interlayer

Si3N4/Invar joints with Mo mesh and Cu foil as interlayers, individually and together, were vacuum brazed using Ag27.5Cu4.5Ti active filler at 1153 K for 10 min with following configurations: Si3N4/Ag26.7Cu4.5Ti + Mo/Invar, and Si3N4/Ag26.7Cu4.5Ti + Mo/Cu/Ag–Cu/Invar. The correlation between the microstructure of the brazing seam and shear strength of the joints are investigated. Ti segregated at Si3N4/filler interface and metallurgical bonding is established by formation of TiN and Ti5Si3 reaction products. Vickers microharndess profiles unveiled varying degrees of hardness across the brazing seam, resembling the layered structure. Individually introducing Mo mesh as interlayer suppressed the Fe2Ti and Ni3Ti intermetallic compounds (IMC) within the brazing seam, resulting in shear strength of 191.7 MPa. Hybrid combination of Mo mesh with Cu foil as interlayers, yielded 235.5 MPa shear strength in brazed Si3N4/Invar joints. This improvement is attributed to simultaneous favorable effects of Mo such as reduced residual stress near the Si3N4/filler interface and Cu, which prevents Fe2Ti and Ni3Ti IMC in the brazing seam, thereby enhancing the plastic flow.

Microstructure and Mechanical Properties of the Joint between Si3N4 and Mo Brazed by Near‐Eutectic Ag–Cu–In–Ti Filler Alloy

The joining of Si3N4 and Mo using Ag–Cu–In–Ti active filler alloy with the brazing temperature ranging from 720 to 860 °C for 10 min is investigated in this article. The correlation between the joint strength and the microstructures of the brazed joints is discussed. In the results, it is shown that the activity of Ti is different at different temperatures, and thus the degree of diffusion of Ti to the interface is different. The activity of Ti gradually increases as the brazing temperature increases, and more Ti atoms diffuse into both sides of the base materials, resulting in a progressively thicker TiN + Ti5Si3 reaction layer on the Si3N4 ceramic side. Between 720 and 860 °C, the shear strength of the joint first increases and then decreases with brazing temperature. The maximum shear strength (223 MPa) is obtained at 830 °C.

Microstructures and bonding strength of synthetic diamond brazed by near-eutectic Ag–Cu–in–Ti filler alloy

Synthetic diamond is often bonded to metals or itself to fulfil the functional requirements for the applications in machine tools or the fabrication of thermal management materials. The knowledge on the relationship between interfacial microstructure and bonding strength of the synthetic diamond is therefore of significant scientific and technological implications. In this work, the epitaxial growth of titanium carbides formed on synthetic diamond grits brazed using a near-eutectic Ag–Cu–In–Ti active filler alloy was systematically investigated. An ultra-thin TiC layer was identified on the synthetic girts brazed at 680 °C and the epitaxial growth of Ti3InC carbides together with Ag3In and Cu2InTi intermetallics (IMCs) were subsequently examined at the brazing temperatures of up to 880 °C. The solidification microstructures of the Ag–Cu–In–Ti filler alloy in the brazed diamond joints were discussed based on composition analysis and phase diagram information. The growth morphologies of the interfacial products were exemplified by taking the bonding strength, fracture behaviours, and integrity of the brazed synthetic diamond into account. The results obtained would be of great value for developing diamond related devices and materials.

Designing of a thin Mo diffusion barrier towards strong and reliable Ti/Cu dissimilar brazing

The dissimilar brazing of Ti and Cu has been recognized to be challenging owing to the affinity of forming brittle intermetallic compounds at joint interface. In the current investigation, it was demonstrated that such detrimental interfacial reaction products can be readily circumvented by employing a Mo diffusion barrier deposited on Ti substrate. Combining Mo interlayer and a Ag–Cu–Ti active filler alloy, intermetallic compounds free Ti/Cu brazed joints consisting of Ti–Mo solid solution, Mo interlayer and remnant braze can be obtained. As a result of the eradication of brittle phases, the resultant joints exhibit excellent structural integrity with bonding strength comparable to the parent material properties. Additionally, as a consequence of sluggish solid state diffusion at the Ti/Mo interface and limited dissolution of the Mo interlayer by filler alloy during brazing, the desirable joint microstructure can be reproduced within a wide range of bonding duration. Such results indicate that strong and reliable Ti/Cu dissimilar brazing can be achieved by the combination of a Mo diffusion barrier and Ag–Cu–Ti active filler alloy.

Reactive wetting behavior and mechanism of AlN ceramic by CuNi-Xwt%Ti active filler metal

In order to propel the application of the developed CuNi-Xwt%Ti active filler metal in AlN brazing and get the universal reactive wetting mechanism between liquid metal and solid ceramic, the reactive wetting behavior and mechanism of AlN ceramic by CuNi-Xwt%Ti active filler metal were investigated. The results indicate that, with the increasing Ti content, surface tension for liquid CuNi-Xwt%Ti filler metal increases at low-temperature interval, but very similar at high-temperature interval, which influence the wetting behavior on AlN ceramic obviously. CuNi/AlN is the typical non-reactive wetting system, the wetting process including rapid wetting stage and stable stage. The wettability is depended on surface tension of the liquid CuNi filler metal completely. However, the wetting process of CuNi-8wt.%Ti/AlN and CuNi-16 wt%Ti/AlN reactive wetting system is composed by three stages, which are rapid wetting stage decided by surface tension, slow wetting stage caused by interfacial reaction and stable stage. For CuNi-8wt.%Ti/AlN and CuNi-16 wt%Ti/AlN reactive wetting system, although the surface tension of liquid filler metal is the only factor to influence the instant wetting angle θ0 at rapid wetting stage, the reduced free energy caused by interfacial reaction at slow wetting stage plays the decisive role in influencing the final wettability.

Investigation on viscosity, surface tension and non-reactive wettability of melting Ag-Cu-Xwt%Ti active filler metals

The microstructure, viscosity and surface tension of melting Ag-Cu-Xwt%Ti active filler metals were researched, the influence mechanism of microstructure on the viscosity and surface tension was discussed, the non-reactive wetting behavior of melting Ag-Cu-Xwt%Ti filler metals on W substrate was investigated. The research results indicate that, the microstructure of Ag-Cu filler metal is composed by Ag86Cu14 phase and Ag56Cu44 phase, while after Ti element be added in the Ag-Cu-Xwt%Ti filler metal, Cu-Ti intermetallic compounds will be formed. The different microstructures of the Ag-Cu-Xwt%Ti filler metals, especially the difference between the amounts and kinds of the intermetallic compounds, lead to the various viscosity and surface tension. Viscosity of the Ag-Cu-Xwt%Ti filler metal can be divided into low temperature zone and high temperature zone. At the low temperature zone, the viscosity increases obviously with the increasing Ti content, while at the high temperature zone, the viscosity for the four melting Ag-Cu-Xwt%Ti filler metals show little difference. With increase of the temperature, surface tension for the four melting Ag-Cu-Xwt%Ti filler metals all decrease firstly and then increase, and the temperature for the lowest surface tension is 975 °C. Moreover, with increase of the Ti content, surface tension of the melting Ag-Cu-Xwt%Ti filler metal increases gradually at both low temperature zone and high temperature zone, but the difference among them at low temperature zone is larger than that at high temperature zone. The non-reactive wetting experimental result confirms this conclusion very well.

Characteristics of Al2O3/diamond/c-BN/SiC grain steel brazing joints using Cu–Sn–Ti active filler powder alloys

Abstract Diamond, c-BN, Al2O3 and SiC abrasive crystals were brazed onto 0.45%C steel matrix using Cu–Sn–Ti active powder filler alloys in vacuum to develop a new superhard abrasive wheel. The brazing process was carried out in vacuum at the temperatures of 890 °C, 925 °C, and 960 °C for dwell durations from 10 to 30 min, respectively. The interface characteristics of the brazed joints between the abrasive grains and the filler alloys were investigated using optical microscope, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The results by microanalyses show that the element of Ti from the active powder filler was diffused preferentially to the surface of the grains, resulting in a Ti-rich reaction layer in the brazed joints. The microstructure phases of TiC, TiN, TiB, TiB2, TiO and TiSi2 in the grains/active filler interface and Cu–Ti in the active filler/steel interface were confirmed by XRD analysis. The joining of the grains to the 0.45%C steel was realized by the reaction products of Ti-based on the interface. The adhesive strength experiment of the joint interfaces was performed; the results suggest that the grains were not dislodged from the bond interface.

Brazing continuous carbon fiber reinforced Li2O–Al2O3–SiO2 ceramic matrix composites to Ti–6Al–4V alloy using Ag–Cu–Ti active filler metal

Abstract Cf/LAS composites and TC4 alloy were brazed successfully by vacuum brazing using Ag–Cu–Ti active filler metal. The interfacial microstructure was characterized by a scanning electron microscope, energy dispersive spectrometer and X-ray diffraction. The effects of brazing temperature on the interfacial microstructure and joint properties were investigated in details. Various phases including TiC, TiSi2, Ti3Cu4, Cu (s,s), Ag (s,s), TiCu and Ti2Cu were formed in the brazed joints. Interfacial microstructure varies greatly with the increase of brazing temperature, while the amount of Ti2Cu reduced, but no new phase is generated. The optimal shear strength of the joint is 26.4 MPa when brazed at 890 °C for 10 min. Shear test indicated that the fracture of the brazed joints went through the TiSi2 + TiC layer close to the Cf/LAS composites interface.

Microstructural characterization of diamond/CBN grains steel braze joint interface using Cu–Sn–Ti active filler alloy

In order to develop the new generation superhard abrasive tools of diamond and cubic boron nitride (CBN), the brazing joint experiments of diamond/CBN crystals and AISI 1045 steel matrix using Cu–Sn–Ti active filler powder alloy were investigated in vacuum furnace. The brazing temperature was 930°C and the dwelling time was 20min. Interfacial characteristics of the brazing joint among the diamond/CBN grains, the active filler layer and the steel substrate were analyzed using scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction techniques. The results indicated that Ti element in the Cu–Sn–Ti alloys diffused preferentially to the surface of diamond/CBN grits to form a Ti-rich reaction layer in the brazed joints by microanalyses. Moreover, the TiC, TiN and TiB2 phases in diamond/CBN interface and Cu–Ti phase in steel interface were confirmed by X-ray diffraction phase analysis. The wetting and bonding reactions on diamond/CBN by melting Cu–Sn–Ti alloy were realized through the interfacial reaction products like TiC, TiN and TiB2 compounds during the brazing process. The adhesive strength experiments of the joint interfaces revealed that the grains were not pulled out from the bond interface. The reliable bonding strength of brazed diamond/CBN grains to the steel substrate can meet the application requirements of high efficiency machining in the industrial field.

Microstructure and mechanical properties of Si3N4/42CrMo joints brazed with TiNp modified active filler

Si3N4 ceramic/42CrMo steel joints were obtained by employing TiNp modified Ag–Cu–Ti active filler and subsequently the effect of TiNp content on the microstructure and mechanical properties of the joints was investigated. Microstructural examination revealed that TiN+Ti5Si3 reaction layer was adjacent to the Si3N4 ceramic while a TiC reaction layer was close to the steel substrate. With the increase of TiNp content, more fine grains and less Ag–Cu eutectic appeared in the joint and the reaction layers near the two base materials became thinner. The flexural strength of the joint obtained by four-point bending test climbed about 100% with the optimum TiNp content of 5vol%, comparing with the case without TiNp. Thermal stress distributions in the joint were analyzed using finite element modeling computations, which accorded well with the bending test results.

Interfacial microstructure and mechanical property of SiO2-BN ceramics and Invar joint brazed with Ag–Cu–Ti active filler metal

Abstract SiO 2 -BN ceramics and Invar alloy were jointed by active brazing using Ag–21Cu–4.5Ti (wt.%) filler at 1113–1173 K for 5–30 min. Scanning and transmission electron microscopy studies revealed that the amorphous SiO 2 was not reacted during brazing while h-BN had strong tendency to react with Ti to formation a fine-grain layer adjacent to SiO 2 -BN ceramic. The composite TiN–TiB 2 fine-grain layer with the thickness of 100–150 nm was the key factor in achieving a good bond between SiO 2 -BN ceramic and Invar. Invar alloy dissolved into the molten filler and reacted with Ti to form Fe 2 Ti and Ni 3 Ti, which dispersed in Ag- and Cu-based solid solution. The shear strength of the joint decreases with the increase of Fe 2 Ti and Ni 3 Ti brittle compounds. The maximum shear strength reached 32 MPa when the joint brazed at 1153 K for 10 min. Cracks primarily propagated in the SiO 2 -BN ceramic and partially along the reaction layer.

Microstructure characteristics of CBN/steel joints brazed with TiB2 modified active filler

The joint of cubic boron nitride (CBN) grits to 0·45%C steel were obtained by using TiB2 modified Ag–Cu–Ti active filler at the brazing temperature of 920°C for the holding time of 5 min. The microstructure characteristics of the brazing interface were detected by means of optical microscope, scanning electron microscope, energy dispersion spectrometer, X-ray diffraction and microhardness measuring equipment as well. It has been found that the microstructure of Ag–Cu–Ti filler layer is significantly refined by TiB2 particles. The almost well proportioned distribution of TiB2 particles in the filler layer is realised. Negative influence of TiB2 particles has not occurred on the chemical reaction of CBN particles and the filler at elevated temperatures. Reliable joining of CBN grits to 0·45%C steel is accomplished dependent on the resultant reaction products at the brazing interface.

Role of Ti diffusion on the formation of phases in the Al2O3–Al2O3 brazed interface

Diffusivities of Ti, Cu, Al and Ag in the interface of Al2O3–Al2O3 braze joints using Ag–Cu–Ti active filler alloy, have been calculated by Matano–Boltzman method. The Matano plane has been identified for each elemental diffusion at various brazing temperatures. The diffusivities of Ag, Cu and Al are almost insignificant on formation of interface during brazing, whereas the diffusivity of Ti changes significantly with the brazing temperature and controls the formation of different reaction product in the interface. Presence of TiO and Ti3Cu3O phases in the interface has been confirmed by transmission electron microscopy (TEM).

Thermal cyclic test of alumina/kovar joint brazed by Ni–Ti active filler

Active brazing was used to join high purity alumina ceramic and Kovar alloy with nickel and titanium foils. A sandwich structure was observed in the solder, an α-Ti solid solution belt at mid part and two Ti2Ni intermetallics belts at sides. Thermal cyclic tests were undertaken for the brazed joints at temperature ranging from 200 to 600 °C. Shear strength of joints were tested before and after thermal cycles. The results showed that shear strength increased dramatically after 40 thermal cycles. The determination and calculation of residual stress in joints indicated that thermal cycles reduced residual stress in joints observably due to similar effects as annealing, and resulting in improved strength.

Brazing of Si 3N 4 ceramic to copper

Silicon nitride is one of the most promising structural ceramics for high temperature applications. There is an increasing demand for joining this ceramic to metal structures. Direct brazing using an active filler metal has been found to be a reliable and simple technique, capable of producing strong and reliable joints. Several factors affecting the strength of such joints have been investigated and are reported in the literature. This preliminary study is directed mainly towards investigating the effect of the surface preparation of the base metal and of the load applied to the joint during brazing on the strength of brazed joints. Experiments were conducted for brazing silicon nitride to copper using a commercial Ag–Cu–Ti active filler metal with and without applied load. The Si 3N 4/Cu joint shear strength and shear energy were determined for various brazing conditions. The initiation of the fracture was detected using acoustic emission sensing. The mechanism of bond formation is described, with emphasis placed on the active metal reaction with the joint materials. Both the interfacial adhesion and the microstructure were investigated. It was found that the smoother the surface finish of the copper base metal, the higher the joint shear strength attained. The shear energy of the joints increased substantially as a result of applying a light load on the joints during brazing.

Publication schedule

Diamond, c-BN, Al2O3 and SiC abrasive crystals were brazed onto 0.45%C steel matrix using Cu–Sn–Ti active powder filler alloys in vacuum to develop a new superhard abrasive wheel. The brazing process was carried out in vacuum at the temperatures of 890 °C, 925 °C, and 960 °C for dwell durations from 10 to 30 min, respectively. The interface characteristics of the brazed joints between the abrasive grains and the filler alloys were investigated using optical microscope, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The results by microanalyses show that the element of Ti from the active powder filler was diffused preferentially to the surface of the grains, resulting in a Ti-rich reaction layer in the brazed joints. The microstructure phases of TiC, TiN, TiB, TiB2, TiO and TiSi2 in the grains/active filler interface and Cu–Ti in the active filler/steel interface were confirmed by XRD analysis. The joining of the grains to the 0.45%C steel was realized by the reaction products of Ti-based on the interface. The adhesive strength experiment of the joint interfaces was performed; the results suggest that the grains were not dislodged from the bond interface.