Active Filler Metal Research Articles

Effect of Composition in Active Filler Metals in Joining of Alumina to Spheroidal Graphite Cast Irons

Effect of Composition in Active Filler Metals in Joining of Alumina to Spheroidal Graphite Cast Irons

Joining of Alumina to Spheroidal Graphite Cast Irons Using Active Filler Metal

Joining of Alumina to Spheroidal Graphite Cast Irons Using Active Filler Metal

Joining of High Chromium White Cast Irons to Ceramics by Using Active Filler Metal and Aluminum

Joining of High Chromium White Cast Irons to Ceramics by Using Active Filler Metal and Aluminum

Brazing C/SiC composites and Nb with TiNiNb active filler metal

C/SiC composites and Nb were vacuum brazed with the Ti39·4Ni39·4Nb21·2 alloy being the active filler metal. The mechanical properties of the filler material, the microstructure and the strength of brazing joints were investigated. The results showed that the filler TiNiNb alloy has a tensile strength of 860 MPa, an elongation of 51% and an elastic modulus of 78 GPa. Both Ti and Nb elements in the filler reacted with C/SiC during the brazing process, and a well bonded C/SiC–Nb joint was obtained. The ductile filler metal released the thermal stress in the joint. When the brazing was performed at 1220°C for 20 min, the shear strength of brazed joints reached 149, 120 and 73 MPa at 20, 600 and 800°C respectively.

Brazing a Graphite Composite to Molybdenum Alloy TZM Using Active Copper-Based Filler Metals with Chromium Additive

Brazing a Graphite Composite to Molybdenum Alloy TZM Using Active Copper-Based Filler Metals with Chromium Additive

Effect of Brazing Process on Alumina/Carbon Steel Interface Microstructure and Joining Strength

Al2O3 ceramics and carbon steels were brazed using Cu-Ti active filler metal. The weld interface was characterized using scanning electron microscopy, energy spectrometer and X-ray diffraction instrument. Effects of brazing temperature on interface microstructures and the shear strength of the joint were investigated. The results show that the optimum brazing process is brazing temperature of 1323K, holding 30 min. The brazed joints with good microstructure morphology and higher interface shear strength can be obtained under the optimum brazing process. Interface bonding zone consists of three layers: reaction layer close to the ceramic, brazing alloy layer and diffusion layer close to the steel. And Cu3Ti3O, TiFe and TiFe2 are confirmed to form in the interface bonding zone. The shear strength of the joint reaches 99MPa.

Effect of Ti Addition on Shear Strength of Brazing Diamond and Ag Based Filler Alloy

The shear strength samples of brazed single crystal diamond with the (72Ag–28Cu)–xTi (x=2, 4, 7wt.%) active filler metal were prepared, using vacuum brazing methods. Microstructure evolution of interfacial reaction product and shear strength of the brazed diamond and Ag based filler alloy were studied. The results show that there exits a layer of TiC on the surface diamond in different Ti additions, and the thickness of TiC layer increases with the increase of Ti addition. With the increase of Ti addition, the shear strength of the brazed joint decreases due to the increase of TiC layer thickness and amount of intermetallics. From the results, it was seen that mutual diffusion of C and Ti was effective on the morphology of the interface zone that affected the shear strength of the bonds. To achieve a reliable brazed joint, the Ti content must be controlled under 4wt.%.

Active brazing carbon/carbon composite to TC4 with Cu and Mo composite interlayers

Active filler metal (TiZrNiCu) was used to increase the wettability and Cu and Mo composite interlayers were added to release residual stress and increase the mechanical properties of TC4–C/C composite joints. The mechanical properties of the brazed joints were measured by shear strength testing. The effects of brazing parameters on the microstructures of the brazed joint were investigated by SEM, EDS and XRD. It is shown that the maximum shear strength of the joints is 21 MPa brazed at 900 °C for 5 min, which is about 3 times greater than brazing alloy alone. When the brazing temperature is low, the interface structure of C/C composite/Cu brazed joint is Cu/Cu 51Zr 14/Ti 2(Cu,Ni) + Ti(Cu,Ni) + TiCu + Cu 2TiZr/(Ti,Zr)C/C/C composite. With the increased brazing temperature, Ti 2(Cu,Ni), Ti(Cu,Ni), TiCu and Cu 2TiZr reaction phases disappear. Cu(s.s) and Ti(Cu,Ni) 2 appear. The thicknesses of Cu 51Zr 14 and (Ti,Zr)C reaction layers increase. When the brazing temperature is high, the interface structure change to Cu/Cu 51Zr 14/Cu(s.s) + Ti(Cu,Ni) 2/(Ti,Zr)C/C/C composite.

Determination of Liquidus Temperature in Sn–Ti–Zr Alloys by Viscosity, Electrical Conductivity and XRD Measurements

Abstract The Sn – Ti – Zr system is an important subsystem for Cu based active brazing filler metals. Experimental results on this system, however, are rather scarce. The diagram is rather uncertain regarding most of the liquidus, especially on the Sn rich side. In this work, the atomic structure and temperature dependence of structure-sensitive physical properties (dynamic viscosity and electrical conductivity) of liquid Sn – Ti – Zr alloys in the Sn-rich corner were investigated in a wide temperature range with special attention to the melting – solidification region. The results allowed the liquidus line position to be specified.

Effects of Mo Interlayer on Suppressing Cracks in Al2O3/Kovar Brazed Joint

Abstract In order to avoid the formation of cracks in Al2O3/Kovar joint, Mo was coated on the Kovar surface by magnetron sputtering method. Meantime, Ti-Cu-Ni active filler metal was employed to braze Al2O3 and Kovar. The interfacial microstructure and element distribution were analyzed by SEM and EDS methods. It can be found that the cracks were avoided when the Mo layer was 14.2 μm in thickness. Meanwhile, the results also show that Mo interlayer decreased the reaction rate between Fe element from the base material and Ti element from the filler metal. That is, fewer FexTiy intermetallic compounds were formed at the interface, and therefore the formation of cracks at the reaction interface were suppressed.

Pressureless Brazing of Zirconia to Stainless Steel Using Active Filler Metal with TiH<sub>2</sub> Powder

The ZrO 2 ceramic/stainless steel joints were fabricated by pressureless brazing using Ag-Cu brazing solder with TiH 2 powder. Microstructure and microchemistry of ceramic/filler interface and brazing interlayer on the joint cross section were characterize and analyzed by means of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Joint strength was tested by shear-loading method. The effects of brazing conditions on the joint strength were investigated. The results show that three main zones are formed in the brazing interlayer. A thin reaction layer and a Ti-rich sublayer are produced at the ceramic/filler interface. In the experimental condition ranges, the joint strength increases firstly and then falls, and the influence of brazing temperature on joint strength is more remarkable than that of holding time. The maximal shear strength is about 90MPa, and the average is over 75MPa with the optimized technologic condition. Most of the joints fracture in the ceramic matrix adjacent to the joint, only several in the reaction layer. The lower the temperature or the shorter the holding time is, the greater the possibility which joints fractured in reaction layer is. Diffusion, enrichment and interreaction of diversified elements, act the key role in the formation of the brazing interlayer, and finally affect the joint mechanical properties.

Microstructure in the Interface between CVD Diamond Thick Film and a Ag-Cu-Ti Braze Alloy

CVD diamond thick film was brazed to cemmented carbide using a Ag-Cu-Ti active filler metal. The brazing process was performed in a vacuum furnace under different processing condition. The interfacial microstructure and characterization between diamond and Ag-Cu-Ti filler metal were studied by SEM, EPMA and EDX. The morphology and distribution of new compound are shown for the first time (Figs). Results illustrate that a small amount of new compound TiC, TiCu compound exist in the interface. TiC layer exists in the interface and it's thickness is variational with the varying of processing condition such as peak heating temperature, keeping time and so on. New compound TiC accretes with the surface atoms of diamond in a special section, and particular orientation relationships are occasionally observed by examining the fracture section. TiCu layer near TiC exists in the interface. It is worth notice that too much TiC and TiCu in interface could weaken join strength because TiC and TiCu are brittle.

Experimental investigation of the Cu–Ti–Zr system at 800 °C

The Cu–Ti–Zr system has attracted increasing interest in recent years due to its good glass-forming ability and the use of its alloys as active brazing filler metals. However, only limited phase diagram data are available in the literature. In the first part of this work we describe experimental investigations. Samples were investigated by means of EPMA and DSC. At 800 °C an isothermal section was determined by the diffusion couple technique and individual alloy compositions. This combination of methods is deemed to be effective, as it only involves limited experimental effort. The binary systems Cu–Ti and Cu–Zr show a series of intermetallic phases. One of these – Cu(Ti,Zr) 2 – forms an isomorphous solid solution. The binary phases in the Cu–Zr system, in particular Cu 51Zr 14, show remarkable solubility for Ti. One ternary compound (Cu 2TiZr) in this system is known to be in thermal equilibrium with nearly all binary intermetallic phases and therefore dominates the isothermal section. Based on current data and data in the literature a thermodynamic description of the Cu–Ti–Zr system was obtained which is described in the second part of this work.

Selection and Design of Brazing Fillers for Metal-Ceramic Joints

Three different approaches for metal to ceramic brazing are compared using the example of Si3N4/TiN-steel joints: the use of an active filler metal (single layer brazing system), the metallisation of the ceramic and brazing with a non active filler (two-layer brazing system), the use of a composite brazing filler system (three layer brazing system). Different aspects are analysed: the development of the joint’s microstructure in the as-brazed state, the thermally induced residual stresses and the resulting bend strength of the joint’s strength. With two layers and three layers brazing system, bend strength of about 400 MPa, about 15% higher then single filler metal, were achieved. The three layer brazing system has two advantages: firstly one step processing secondly lower scattering of joint bend strength compared to two layers brazing system. The key factors in all cases are the selection of the brazing fillers and the braze design. In all cases a careful selection of the brazing fillers and the braze design are the key factors. The first criteria for the selection of the brazing fillers for joints of dissimilar materials can be done by considering only the main filler characteristics like titanium content, processing temperature and yield stress. It’s necessary to simulate the joint behaviour by finite element simulation for verifying the final selection of filler metals. It was clearly seen that the plasticity of the filler metal is the main factor affecting residual stresses for the joint geometry in this current work.

Comparison of Three Different Active Filler Metals Used for Brazing Ceramic‐to‐Ceramic and Ceramic‐to‐Metal

Three active filler metals were studied to determine their suitability for joining Si3N4‐TiN composite ceramics. The evolution of the bend strength in the different setups could be explained using microstructural analysis, micro‐hardness measurement and finite element modelling. It was observed that residual stresses in ceramic‐to‐metal joints can be decreased more effective with plastic deformation than by reducing the brazing temperature.

Relief of the Residual Stresses in Ceramic‐Metal Joints by a Layered Braze Structure

The potential of active brazing filler metal modification by ceramic particle addition, with the aim of reducing the stresses in ceramic‐metal joints is studied. A layered braze structure is proposed: layers of reinforced and un‐reinforced filler are combined in an optimal manner to minimize residual stress. The joints are tested in 4‐point bend tests. The evaluation of residual stresses and the optimization of the braze layout are carried out by FE modelling.

Thermodynamic Assessment of the Sn–Ti System

The knowledge of phase equilibria and thermodynamic properties in the ternary Cu-Sn-Ti system is of technical importance for active brazing filler metals. Thermodynamic descriptions of the binary systems Cu-Ti and Cu-Sn are well established. In this work a self-consistent thermodynamic description of the Sn-Ti binary system has been obtained by fitting critically reviewed thermochemical and phase diagram data. The newest and most consistent lattice stability has been used, and all the intermetallic phases and recent experimental information have been taken into account. The equilibrium measurement on the Sn-rich side and more experimental thermodynamic properties are required for a better thermodynamic description of this system. The evaluated thermodynamic description of the Sn-Ti binary system will serve as part of the thermodynamic database for Cu-Sn-Ti brazing alloys.

Joining of SiC fibre reinforced borosilicate glass matrix composites to molybdenum by metal and silicate brazing

The brazing of SiC fibre reinforced borosilicate glass matrix composites with Mo plates has been investigated. Molybdenum was chosen as the metallic partner under consideration of system requirements, e.g. thermomechanical stability at temperatures of interest (500–750∘C), and physical properties, e.g. coefficient of thermal expansion close to that of the glass matrix composite. Two brazing filler materials were investigated: a glass braze (Schott G018-174) and an active filler metal (Incusil ABA, brazing temperature = 740∘C). When using the glass braze the surface of the metal had to be roughened to ensure a bond of significant strength. Vacuum brazing with the active filler metal resulted in joints with high strength, which allows to fully utilise the mechanical competence of the glass matrix composite when the joint configuration is adapted to the relevant loading conditions. A novel design of a tool for hot glassware handling, made of glass matrix composite/Mo joints, is presented.

The Role of Binder Content on Microstructure and Properties of a Cu‐base Active Brazing Filler Metal for Diamond and cBN

Melting experiments of Cu‐Sn‐Ti‐Zr filler metal powder containing cellulose nitrate and graphite, respectively, resulted in the formation of nanosized TiC particles in both Cu‐rich phase and CuSn3Ti5 intermetallic regions of the alloy (see figure). The variation of the binder type and content allows to tailor the properties of the filler metals in terms of erosion resistance, decisive for a new generation of superabrasive tools.

Interfacial Microstructures and Bonding Strength between Aluminum Nitride and Silver Brazing Filler Metals Containing Various Active Elements

Effect of active element on interfacial microstructures and bonding strength of brazed AlN/AlN joints has been investigated and compared with the case of brazed Si3N4/Si3N4 joints. Brazing was carried out at 1173 to 1473 K for 3.6 ks in a vacuum using Ag-Cu filler metals containing Ti, Zr, V and Nb as an active element. The obtained joint had no defects such as un-bonded areas, regardless of active element and bonding temperature. Four kinds of active elements were divided into two groups by shear tests and microstructural observations. One was Ti and Zr, and the other was V and Nb. The bonding strength of the former was higher than that of the latter. In particular, the joint with Ti addition showed an excellent strength of about 200 MPa. Main fracture position in the joints with Ti and Zr additions was within the AlN, while most joints with V and Nb additions broke at the interface between the active filler metal and the AlN. In the former, TiN and ZrN layers consisting of fine grains were observed adjacent to the AlN. On the other hand, the joint with Nb addition had roundish grains of Nb2N in similar locations. It was considered that the existence of fine grains contributed to the enhancement of bonding strength due to the increase of contact area and to the formation of complicated interface. These tendencies were essentially consistent with those of the brazed Si3N4/Si3N4 joints.