Search

Abstract: SiO2 glass ceramic has been successfully joined to Ti–6Al–4V alloy with AgCu/Ni composite interlayer. The brazing temperature varies from 950°C to 980°C, with the holding time ranging from 1min to 45min. AgCu eutectic foil melted first, followed by the Ti–Cu–Ni ternary eutectic reaction, then Ti reacted to SiO2 glass ceramic. All of Ti atoms came from Ti–6Al–4V alloy but not from braze alloy. The effects of brazing temperature and dwelling time on interface structure and joint strength were investigated in the present work. The largest shear strength of brazed joint could reach 110MPa when the brazing temperature was 970°C, holding time was 10min, and fracture occurred in the SiO2 glass ceramic part. While the thin reaction layer at SiO2 side is the weak part of the joint when the brazing parameter is not appropriate. [Copyright &y& Elsevier]

Abstract: TiAl-based intermetallics joined by vacuum induction brazing using Ag–Cu35.2–Ti1.8 filler alloy at 850–970°C for 1–10min was investigated. The interfacial microstructure and reaction kinetics across the brazed joint were comprehensively evaluated. The interfacial microstructure of brazed joints is TiAl/AlCuTi(TiCu)/AlCu2Ti(TiCu)/Ag solid solution/AlCu2Ti(TiCu)/TiC/35CrMo. According to the experimental observations, silver would not react with the TiAl substrate, but copper reacted strongly with the TiAl substrate, forming continuous reaction layer. The degree of interfacial reaction of TiAl/Ag–Cu35.2–Ti1.8 is related to the configuration of AlCu2Ti reaction layer and the amount of TiAl/Ti3Al phase interface in the TiAl substrate under the same technological conditions. The configuration and the size of AlCuTi phase have relation to the configuration and the amount of TiAl/Ti3Al lamellar colony. The visible acicular AlCuTi phase can be generated by the approximate lamellar structure with low Al content, which is beneficial to the joining of the TiAl substrate. [Copyright &y& Elsevier]

Abstract: The interfacial microstructure and properties of brazed joints of a Ti3Al-based alloy were investigated in this paper to meet the requirements of the use of Ti3Al-based alloy in the aeronautic and space industries. The effects of different brazing fillers on the interfacial microstructure and shear strength were studied. The relationship between brazing parameters and shear strength of the joints was discussed, and the optimum brazing parameters were obtained. The brazed joints were qualitatively and quantitatively analyzed by means of EPMA, SEM and XRD. The results showed that using a AgCuZn brazing filler, TiCu, Ti(Cu,Al)2 and Ag[s,s] were formed, the shear strength of the joint was decreased because of the formation of TiCu and Ti(Cu,Al)2; using a CuP brazing filler, Cu3P, TiCu and Cu[s,s] were formed at the interface of the joint, the former two intermetallic compounds decreased the shear strength. The analysis also indicated that using the TiZrNiCu brazing filler, the optimum parameters were temperature T=1323 K, joining time t=5 min, and the maximum shear strength was 259.6 MPa. For the AgCuZn brazing filler, the optimum parameters were joining temperature T=1073 K, joining time t=5 min, and the maximum shear strength was 165.4 MPa. To the CuP brazing filler, the optimum parameters were joining temperature T=1223 K, joining time t=5 min, and the maximum shear strength is 98.6 MPa. Consulting the results of P. He, J.C. Feng and H. Zhou [Microstructure and strength of brazed joints of Ti3Al-base alloy with NiCrSiB, Mater. Charact., 52(8) (2004) 309–318], relative to the other brazing fillers, TiZrNiCu is the optimum brazing filler for brazing Ti3Al-based alloy. [Copyright &y& Elsevier]

Abstract: Brazing of Ti3Al alloys with the filler metal TiZrNiCu was carried out at 1173–1373K for 60–1200s. The relationship of brazing parameters and shear strength of the joints was discussed and the optimum brazing parameters were obtained. When products are brazed, the optimum brazing parameters are as follows: brazing temperature is 1273–1323K, brazing time is 250–300s. The maximum shear strength of the joint is 250–260MPa. Four kinds of reaction products were observed to have formed during the brazing of Ti3Al alloys with the filler metal TiZrNiCu, namely Ti2Ni+TiCu intermetallic compounds formed close to the Ti3Al alloy. TiNi2Cu intermetallic compounds layer formed between Ti2Ni+TiCu intermetallic compounds and the filler metal and a Ti[s,s] (here s,s means super saturation) solid solution formed with the dispersed TiNi2Cu in the middle of the joint. The interfacial structure of brazed Ti3Al alloys joints with the filler metal TiZrNiCu is Ti3Al/Ti2Ni+TiCu/TiNi2Cu/Ti[s,s] solid solution+TiNi2Cu/TiNi2Cu/TiCu+Ti2Ni/Ti3Al and this structure will not change with brazing time once it forms. The formation of over many intermetallic compounds Ti2Ni+TiCu+TiNi2Cu results in embrittlement of the joint and poor joint properties. The thickness of Ti2Ni+TiCu+TiNi2Cu intermetallic compounds increases with brazing time according to a parabolic law. The activation energy Q and the growth velocity K0 of the reaction layer Ti2Ni+TiCu+TiNi2Cu in the brazed joints of Ti3Al alloys with the filler metal TiZrNiCu are 261kJ/mol and 0.0434mm2/s, respectively and the growth formula was y2=0.0434exp(-31392.83/T)t. Careful control of the growth of the reaction layer Ti2Ni+TiCu+TiNi2Cu can influence the final joint strength. [Copyright &y& Elsevier]

Brazing of Ti3Al alloys with the filler metal NiCrSiB was carried out at 1273–1373 K for 60–1800 s. The relationship of brazing parameters and shear strength of the joints was discussed, and the optimum brazing parameters were obtained. When products are brazed, the optimum brazing parameters are as follows: brazing temperature is 1323–1373 K, brazing time is 250–300 s. The maximum shear strength of the joint is 240–250 MPa. Three kinds of reaction products were observed to have formed during the brazing of Ti3Al alloys with the filler metal NiCrSiB, namely, TiAl3 (TiB2) intermetallic compounds formed close to the Ti3Al alloy. TiAl3+AlNi2Ti (TiB2) intermetallic compounds layer formed between TiAl3 (TiB2) intermetallic compounds and the filler metal and a Ni[s,s] solid solution formed in the middle of the joint. The interfacial structure of brazed Ti3Al alloy joints with the filler metal NiCrSiB is Ti3Al/TiAl3 (TiB2)/TiAl3+AlNi2Ti (TiB2)/Ni[s,s] solid solution/TiAl3+AlNi2Ti (TiB2)/TiAl3 (TiB2)/Ti3Al, and this structure will not change with brazing time once it forms. The formation of over many intermetallic compounds TiAl3+AlNi2Ti (TiB2) results in embrittlement of the joint and poor joint properties. The thickness of TiAl3+AlNi2Ti (TiB2) intermetallic compounds increases with brazing time according to a parabolic law. The activation energy Q and the growth velocity K0 of the reaction layer TiAl3+AlNi2Ti (TiB2) in the brazed joints of Ti3Al alloys with the filler metal NiCrSiB are 349 kJ/mol and 24.02 mm2/s, respectively, and the growth formula was y2=24.04exp(−41977.39/T)t. Careful control of the growth of the reaction layer TiAl3+AlNi2Ti (TiB2) can influence the final joint strength. [Copyright &y& Elsevier]

Residues and dissipation of the herbicide hexazinone in soil leachate were determined under a 3‐year‐old clear‐cut forest after a 1986 fall application of PRONONE 10G at 0, 2, and 1 kg ai/ha over a 448‐day period. Soil leachates were collected at depths of 30, 55, and 80 cm and were individually analyzed for hexazinone (ai) residues. There was no soil leachate collected up to 112 days after application and before ground freeze. Leaching of hexazinone was triggered by the snow melt in spring 1987 and continued until the end of November 1987. Detected amounts of residues were the highest in the first postwinter collection 227 days after treatment, reaching 205 and 61 ug at 30 cm depth in the 4 and 2 kg ai/ha treatment plots, respectively and reaching 89 and 39 ug at 80 cm depth; at the 55 cm depth, the peaks were 178 ug after 264 days and 28 ug after 351 days in the 4 and 2 kg ai/ha treatment plots. Hexazinone residues declined to less than 17 ug after 448 days in all depths and in both herbicide treated plots. There were no hexazinone residues detected in the 0‐treatment plot. The concentration of hexazinone in soil leachates was inversely related to the volume of leachate. The sample collected from the 4 kg ai/ha plot at a depth of 30 cm had the highest concentration (492 ppb) but the lowest volume (152 mL) 277 days after application, compared to samples collected at the same depth but at different times. In all cases the total amount of hexazinone residues (ug) in soil leachates increased with the rate of soil water percolation but declined over time. [ABSTRACT FROM PUBLISHER]

Direct bonding of ZrO 2 ceramic and SiC P /2A14 composite was successfully achieved in only a few seconds using ultrasonic waves at room temperature. A continuous void-free amorphous Al 2 O 3 interphase layer with an average thickness ranging from 60 to 70 nm was verified to be formed between ZrO 2 ceramic and SiC P /2A14 composite, which could be attributed to the significantly enhanced diffusion of O and Al atoms around the bonding interface due to a remarkable increase in defect density caused by the physical effects of ultrasonic vibration. The maximum average shear strength of the ZrO 2 –SiC P /2A14 joints was approximately 36.48 MPa. [ABSTRACT FROM AUTHOR]

Abstract: The nonisothermal dehydrogenation of TiH2 powders was studied using thermogravimetry and differential scanning calorimetry. The reaction model was established by estimating the activation energy. The results show the nonisothermal dehydrogenation occurred in a four-step process. The hydrogen released from the phase in the first step, which led to the decrease of activation energy. The second step was derived from the formation of in phase and the reaction model was Phase boundary reaction. In the third step, the hydrogen started to release from the phase, and then the phase transformation happened. So the activation energy underwent a decrease followed by a quick increase. The fourth step corresponded to the formation of in phase, and the slight oxidation resulted in the small fluctuation of activation energy. [Copyright &y& Elsevier]

For the first time, the wetting behavior of SiC ceramics modified by ion bombardment was studied and the interfacial microstructure was characterized. An amorphous layer was formed on the SiC surface, which has significant influence on the wetting behavior and the interfacial microstructure of SiC/AgCu–Ti wetting system. The interfacial reactions were accelerated when filler melted on the bombarded SiC surface, and the spreading on the bombarded SiC ceramics was controlled by interfacial reactions firstly and then by diffusion. The spreading rates, k r , were denoted as k r,i = 42.28exp (-456.2/RT) for bombarded SiC, and k r,0 = 28.62exp (-329.9/RT) for the original one. Ion bombardment improved the bonding quality of ceramics/droplet interface effectively, a mixed reaction layer containing TiC and Ti 5 Si 3 was formed and no reactant stratification was occurred at the interface of SiC/droplet. [ABSTRACT FROM AUTHOR]

• Surface modification of SiC ceramics induced by Ar ion bombardment was investigated. • An amorphous layer was formed at SiC surface after ion bombardment for fluence of 1 × 1017ions/cm2 at 50 keV. • Beneath the amorphous layer, high-density dislocations and twin crystals were formed by ion bombardment. • Ion bombardment improved bonding quality of ceramics/filler interface effectively, and no reactant stratification occurred. • The shear strength of SiC brazed joints was improved with Ar ion bombardment. Ar ion bombardment was conducted to modify the SiC surface microstructures, which had a vital effect on the interfacial microstructure and shear property of brazing joints. The amorphous layer with thickness of ∼120 nm was formed on the bombarded surface, accompanied with plenty of dislocations and twins beneath the amorphous layer. Reliable SiC/AgCu-Ti/SiC joints were brazed in vacuum at 900 °C for 10 min, and the interfacial microstructure was investigated by SEM, EDS and TEM in detail. When the ion bombarded SiC was used as substrates, the microstructure of brazing beam was optimized as SiC / Ti 5 Si 3 + TiC mixed layer / Ag(s,s) + Cu(s,s) containing TiCu / Ti 5 Si 3 + TiC mixed layer / SiC, in which the interfacial stratification was eliminated compared to the conventional SiC brazing. The shear strength was improved to 30.9 MPa with ion bombardment, which was ∼72.6 % higher than that of the original SiC joints without ion bombardment. The proposed Ar ion bombardment method provides a novel way to modify the brazability of ceramics. [ABSTRACT FROM AUTHOR]

CaO-Al 2 O 3 -SiO 2 (CAS) glass ceramics were designed and prepared using a melt-quench approach. The coefficient of the thermal expansion (CTE) of the synthesized CAS (4.12 × 10−6 K−1) matched perfectly with that of the SiC ceramic (4.01 × 10−6 K−1). Thermal analysis of the CAS was conducted. Then the joining of the SiC ceramics by the CAS glass ceramics under various process parameters were conducted. The bonding temperature affects the fluidity of the CAS glass and the oxidation of the SiC substrate. The holding duration decides the infiltration of the CAS glass into the SiC substrate. The optimal bonding parameter is 1400 ℃/10 min and the corresponding highest shear strength of the SiC/CAS/SiC bonded joints in average was 56 MPa. Fracture observation was also conducted to help analyze the relationship between the interfacial microstructure and the joint strength. Finally, the formation mechanism of the SiC/CAS/SiC bonded joints was proposed. [ABSTRACT FROM AUTHOR]

Due to the poor wettability of the AgCuTi alloy on the quartz fiber reinforced composite (QFSC), a reliable joining of the QFSC to itself or to other metals can be hardly achieved. In this study, vertically aligned carbon nanotube (VA-CNT) composed of multi-wall carbon nanotube (MWCNT) was synthesized on the QFSC surface by a plasma enhanced chemical vapor deposition method. As a result, the final contact angle decreased from 96.5° (without VA-CNT modification) down to 30.6° (with VA-CNT modification) at 870 °C with 10min holding duration. Besides, the reaction layers at the AgCuTi/QFSC interface transformed into continuous ones and the infiltration effects became more obvious after the VA-CNT modification. Finally, a possible mechanism how VA-CNT enhanced the wettability of the AgCuTi alloy on the QFSC surface was proposed. Defective sites on the MWCNT surface with a high chemical reactivity and the nanoscale capillary structure of the VA-CNT turned out to be the essential factors to promote the wetting process. This novel surface modification approach can offer new insights on addressing the wetting issues in composites preparation, brazing and soldering, etc.. Image 1098128 [ABSTRACT FROM AUTHOR]

Abstract Brazing C/SiC composites to Ti6Al4V alloy is associated with the problem of high residual stress inducing low joining strength. To overcome this problem, negative thermal expansion Zr 2 P 2 WO 12 (ZWP) nanoparticles were introduced into AgCu brazing alloy to obtain robust C/SiC-Ti6Al4V joints. Microstructures and mechanical properties of the joints brazed with different ZWP contents were investigated. Results indicated that 3 wt% ZWP nanoparticles dispersed homogeneously among brazing seam and compatible with brazing alloy. The width of reaction layer at C/SiC side was reduced sharply. Meanwhile, the finite element analysis showed that residual stress was reduced by 52.9 MPa and stress concentration among reaction layer was eliminated. The average shear strength of the joints brazed with AgCu + 3 wt% ZWP increased to 146.2 MPa, which was 70.8% higher than that of joints brazed without ZWP. [ABSTRACT FROM AUTHOR]

Abstract To address the thermal stress issue in the brazed SiO 2f /SiO 2 -Invar joints, a novel nano-TiO 2p (p: particle) modified braze filler was developed. Wetting of the SiO 2f /SiO 2 composite by AgCuTi-based composite braze filler with different TiO 2p contents were conducted first and a TiO 2p content lower than 5 wt% was fixed. Then the microstructure evolution and mechanical performance of the SiO 2f /SiO 2 -Invar joints brazed with different TiO 2p additions and different brazing parameters were discussed. The highest shear strength of 30 ± 8 MPa was obtained at 910 °C/10 min. After using the TiO 2p modified braze filler, the fracture probability of the SiO 2f /SiO 2 -Invar joints dropped down by 75% (Taking 22 MPa as an example). Finally, a FEM was employed to get an in-depth understanding of the stress relief effects when using a TiO 2p modified braze filler. Results show that the compressive stress on the SiO 2f /SiO 2 side dropped down by 30% after using a 2 wt% TiO 2p modified braze filler. The in-situ formed Cu x Ti 6-x O (x = 2, 3) phases played a key role in relieving the residual stress of the brazed joints. The development of the novel TiO 2p modified braze filler was particularly suitable for the joining of the oxide ceramics and oxides-based composites. [ABSTRACT FROM AUTHOR]

In this study, Ni particle was validated as an effective grain refiner for the Cu-Sn solid-liquid interdiffusion (SLID) wafer bonding joints, which induced a dispersive non-interfacial nucleation of intermetallic grains, effectively preventing the grain mergence phenomenon. With increasing the Ni particle addition, there were significant reductions in both the (Cu, Ni) 6 Sn 5 grain size and the Cu 3 Sn layer thickness, 6 wt% addition of Ni particles even led a formation of the intermetallic joints only consisted of (Cu, Ni) 6 Sn 5 grains with an average grain size of 1.3 μm. (Cu, Ni) 6 Sn 5 grain refinement could notably enhanced the shear strength of the intermetallic joints. [ABSTRACT FROM AUTHOR]

Abstract For active brazing, excessive formation of brittle intermetallics in the brazed seam is always a big issue, which has an adverse effect on the joint property. Herein, an innovative vertical few-layer graphene (VFG) buffer layer was directly grown on the Invar surface prior to brazing. SiO 2 -BN ceramic and the Invar alloy with and without the VFG were first brazed using a Ag-Cu-Ti braze alloy. Interfacial microstructure and fracture morphologies of the brazed joints were then put into comparison. Results show that there is a 20% increase in shear strength after the VFG modification. To further discuss the effect of the interfacial microstructure variation on the joint property, Invar alloy was self-brazed. The fracture path and the tensile-shear strength of the Invar/Invar joints were discussed. Finally, the interaction between the VFG and Ti was characterized and the controlling mechanism of the intermetallic compounds formation by the VFG was proposed. This novel surface modification approach reported in this paper was promising particularly for the active brazing associated with the brittle IMCs formation issue. [ABSTRACT FROM AUTHOR]

Abstract In this study, the SiBCN ceramic and TC4 alloy were successfully brazed using TiB 2 reinforced AgTi composite filler in a vacuum furnace. The typical interfacial microstructure of the joint and the reaction products were identified through EDS, SEM and XRD. The effect of the TiB 2 content and brazing temperature on the joint microstructure and property were investigated. During the brazing process, the filler reacted with the SiBCN to form TiC + TiB + TiN + Ti 5 Si 3 reaction layer adjacent to the SiBCN. With the increase of the TiB 2 content in the composite filler, the diffusion of Ti in the brazing seam was restrained, and the reaction layer became thinner. Meanwhile, the TiB 2 volume fraction in the brazing seam increased. The increase of the brazing temperature promoted the reaction of the braze filler and the base materials. Thick reaction layer adjacent to the SiBCN and lots of Ti (s.s) and Ti 2 Ag in the brazing seam were obtained at high brazing temperature. When the SiBCN and TC4 were brazed using 6 wt% TiB 2 reinforced AgTi composite filler at 980 °C for 10 min, the maximum shear strength of the joint reached 32 MPa. Highlights • The SiBCN and TC4 were vacuum brazed using TiB 2 reinforced AgTi composite filler. • The typical microstructure of the SiBCN/TC4 joint was investigated. • Both of the TiB 2 content and brazing temperature affects the microstructure and property of the joint significantly. • The maximum strength of the joint reached 32 MPa when the joint brazed using AgTi-6TiB 2 at 980 °C for 10 min. [ABSTRACT FROM AUTHOR]

Abstract Carbon fiber reinforced carbon matrix (C f /C) composite and Ni base superalloy were brazed in vacuum using MBF 20 filler. By varying brazing temperatures and holding times, the effects of brazing parameters on the microstructure as well as its evolution and mechanical properties of the joints were investigated. The results show that the microstructural evolution of joints experiences three stages. With the rising of brazing process parameters, the dissolution of C f /C turns strong, leading to the formation of rough composite/filler interface and the increasing of amount of Cr 7 C 3 and MC complex metal carbides. The residual stress concentration in joint changes consequently. The maximum shear strength of the joint can reach 35 MPa (which is up to 92% of the shear strength of C f /C substrate), 15 MPa and 9 MPa at room temperature, 800 °C and 1000 °C, respectively. The fracture initiates and propagates in C f /C composite. Highlights • C f /C composite and GH99 superalloy were successfully brazed using MBF 20 filler in vacuum. • The microstructural evolution experiences three stages: the substrates dissolving and elements diffusing; the carbides forming; the carbides layer forming and growing. • With the rising of brazing parameters, the interfacial reaction is promoted and carbides grow into a continuous layer adjacent to C f /C. • The maximum shear strength of the joint reaches 35 MPa at room temperature, 15 MPa at 800 °C and 9 MPa at 1000 °C. [ABSTRACT FROM AUTHOR]

For the active brazing of ceramic/metal couples, formation of brittle intermetallics in the brazed seam is often a big issue that needs to be addressed. Herein, a novel vertical few-layer graphene (VFG) modified Cu-23Ti braze filler was developed to join the SiO 2f /SiO 2 composite and the Invar alloy. Microstructures of the wetting interfaces and the SiO 2f /SiO 2 -Cu23Ti-Invar brazed joints with and without the VFG modification were put into comparison. Results show that the formation of intermetallics in the brazed seam are greatly suppressed and the joint strength improves by 2 times after using a VFG-modified Cu-23Ti braze filler. Typical microstructure of the SiO 2f /SiO 2 -Invar joint brazed using a VFG-modified Cu-23Ti braze filler was characterized and the joint formation mechanism was proposed finally. [ABSTRACT FROM AUTHOR]

Joining of graphite materials is problematic primarily due to the poor wettability of non-active filler metal on these materials. In an attempt to overcome this problem, magnetron sputtering deposition of Cr film on graphite was performed to modify the surface of the graphite. The wetting and brazing of graphite are carried out using non-active AgCu eutectic filler metals after deposition. The results indicated that surface modification enables wetting and joining of graphite with non-active filler. Cr film reacted with graphite forming Cr-C interfacial reaction layer, which resulted in the decrease of contact angle. Reliable graphite/graphite joints were obtained at temperature from 1113 K to 1233 K for 10 min. The typical interfacial microstructure of the brazed joint is graphite/Cr-C layer/Ag(s,s) + Cu(s,s) eutectic phase/Cr-C layer/graphite. The optimal shear strength of the joint was 13.6 MPa when the brazing parameters were 1173 K for 10 min. [ABSTRACT FROM AUTHOR]

Brazing SiO 2 -BN ceramic to Ti6Al4V is often associated with the problem of brittle continuous phases and high residual stress at the reaction layer of SiO 2 -BN, inducing low joining strength. To overcome these problems, SiO 2 -BN ceramic modified with in situ synthesized carbon nanotubes (CNTs) were joined to Ti6Al4V by TiZrNiCu alloy. Results show that CNTs can improve the wettability of TiZrNiCu on SiO 2 -BN rapidly, and break the continuous reaction layer of SiO 2 -BN into fine sizes. Residual stress can also be reduced by low CTE of CNTs and fine size phases among reaction layer. The shear strength of SiO 2 -BN/Ti6Al4V joints with CNTs modified is 35.3 MPa at 970 °C for 10 min, which is 3 times higher than that of the joints without CNTs modified. [ABSTRACT FROM AUTHOR]

TZM alloy and ZrC particle reinforced W composite (ZrC p -W) were vacuum brazed using Ti-61Ni eutectic brazing alloy. The typical interfacial microstructure of the brazed joint consisted of three zones: a Mo solid solution layer, a brazing seam consisting of TiNi phase, TiNi 3 phase and (Ti, Zr)Ni 2 phase, and a diffusion layer composed of W particles, (Ti, Zr)C particles and (Ti, Zr)Ni 2 phase. The results revealed that brazing temperature affected the interfacial morphologies of the joint, the phase constituents of the brazing seam, the element contents of these phases and the mechanical properties of the brazed joint. The optimal shear strengths at room temperature and at 800 °C reached 124.8 MPa and 82.3 MP respectively when brazed at 1240 °C for 10 min. Meanwhile, the fracture paths located at the TZM substrate and the fracture surface exhibited inter-granular fracture characteristics. [ABSTRACT FROM AUTHOR]

An AgCu-4.5 wt.%Ti/W/AgCu-1 wt.%Ti composite interlayer was designed to braze the Invar-SiO 2f /SiO 2 joints. Ti contents in the interlayer between the tungsten foil and the Invar alloy was optimized. The effects of the tungsten-foil thickness on the microstructure, elemental distribution and mechanical properties of the brazed joints were investigated. Compared with a single AgCu-4.5 wt.%Ti interlayer, a sufficient metallurgical reaction happened on the SiO 2f /SiO 2 composite side and the formation of Fe 2 Ti, Ni 3 Ti compounds which are detrimental to the joint properties, was greatly inhibited by using a low-expansion composite interlayer (LECI). The tungsten interlayer can reduce the CTE (coefficient of thermal expansion) mismatch in the Invar-SiO 2f /SiO 2 joint. The highest shear strength of joints brazed with an LECI was 33 MPa, which was 1.75 times higher than the joints brazed with a single AgCu-4.5 wt.%Ti interlayer. [ABSTRACT FROM AUTHOR]

In this study, transparent alumina and TiAl alloy were successfully brazed at 860°C-940 °C using Ag-21Cu-4.5Ti (wt%) filler metal. The microstructure and mechanical properties of the joints were investigated. SEM and TEM analysis showed the typical interfacial microstructure of the joints brazed at 900 °C for 5min was TiAl/β-Ti + AlCuTi/AlCu 2 Ti + AlCuTi/AlCu 2 Ti + Ag(s,s) + Cu(s,s)/(Cu,Al) 3 Ti 3 O/transparent alumina. The effects of brazing temperature and holding time on the microstructure and mechanical properties of TiAl/transparent alumina joint were studied. In addition, the effects of the dissolution and diffusion of TiAl on the microstructural evolution of the brazing seam were discussed. Shear strength analysis reveals that the shear strength of the joint increases at first and then decreases when brazing temperature rises. The maximum shear strength is 49 MPa when the joint is brazed at 900 °C for 5 min. [ABSTRACT FROM AUTHOR]

ZrC-SiC ceramic and TC4 alloy were successfully brazed using a self-prepared Ti-15Cu-15Ni filler. The microstructure and mechanical property of the joints obtained at different brazing temperatures were investigated. The results indicated that Ti from the Ti-15Cu-15Ni and the TC4 reacted with the ZrC-SiC to form TiC phase adjacent to the ZrC-SiC ceramic. In the brazing seam, Ti 2 (Ni, Cu) intermetallic compounds zone (IMCs Zone), Hypoeutectic Zone and Hypereutectoid Zone formed. The brazing temperature affected the dissolution of TC4 into the braze filler significantly, and then determined the microstructure of the joint. The formation of α-Ti in the brazing seam could decrease the hardness and the brittleness of the brazing seam, which was beneficial to the property of the brazed joint. The joint strength reached a maximum value of 43 MPa when the joint was brazed at 970 °C and cracks propagated in the ZrC-SiC substrate near the brazing seam. [ABSTRACT FROM AUTHOR]

Plasma bombardment was applied to remove the surface oxide film of 7075 alloy and the deposited Cu layer with thickness of ∼20 μm was attached closely to the surface of 7075 alloy by magnetron sputtering process. The brazing of 7075 alloy using Cu foil was carried out at 580 °C as the contrast test. The results showed that the brazed joints using deposited Cu layer have better microstructure and higher mechanical properties than that of using Cu foil. As brazing temperature increased to 570 °C, the deposited Cu layer was dissolved into the substrate gradually and formed intermetallic compounds. Further increasing brazing temperature, the intermetallic compounds were reduced and the homogenization of microstructure of brazed joints was enhanced. The shear strength of brazed joints increased firstly and then decreased with the increasing of brazing temperature. The maximum shear strength of 38.7 MPa was obtained when brazing temperature was 600 °C. [ABSTRACT FROM AUTHOR]

Laser welding-brazing process was developed for joining 5052 aluminum alloy and H62 brass in butt configuration with Zn-15%Al filler. Effect of welding speed on microstructural characteristics and mechanical properties of joints were investigated. Acceptable joints without obvious defect were obtained with the welding speed of 0.5–0.6 m/min, while lower and higher welding speed caused excessive back reinforcement and cracking, respectively. Three reaction layers were observed at welding speed of 0.3 m/min, which were Al 4.2 Cu 3.2 Zn 0.7 (τ′)/Al 4 Cu 9 /CuZn from weld seam side to brass side; while at welding speed of 0.4–0.6 m/min, two layers Al 4.2 Cu 3.2 Zn 0.7 and CuZn formed. The thickness of interfacial reaction layers increased with the decrease of welding speed, but varied little at different interfacial positions from top to bottom in one joint. Tensile test results indicated that the maximum joint tensile strength of 128 MPa was obtained at 0.5 m/min, which was 55.7% of that of Al base metal. All the joints fractured along the weld seam/brass interface. Some differences were found regarding fracture locations with three and two reaction layers. The joint fractured between Al 4 Cu 9 and τ′ IMC layer when the interface had three layers, while the crack occurred between CuZn and τ′ phase in the case of two layers. [ABSTRACT FROM AUTHOR]

Reliable brazing of TZM alloy and ZrC particle reinforced (ZrC p ) W composite was achieved in this study by using Ti-28Ni eutectic brazing alloy. The typical interfacial microstructure of TZM/Ti-28Ni/ZrC p -W brazed joint consisted of a Ti solid solution (Ti(s, s)) layer, a continuous Ti 2 Ni layer and a diffusion layer mainly composed of W particles and (Ti, Zr)C particles. With an increase of brazing temperature, more ZrC particles and W particles entered the molten brazing alloy, which broadened the brazing seam and diminished the Ti 2 Ni layer, resulting in the disappearance of the Ti 2 Ni layer eventually. Meanwhile, more Ti(s, s) stripes were observed on the TZM side. The presence of continuous Ti 2 Ni intermetallic phase and Ti(s, s) stripes structure in joints deteriorated the joining properties, which resulted in the formation of brittle fracture under shear test. In addition, the fracture path was related to the brazing temperature, and cracks initiate and propagate in the continuous Ti 2 Ni layer at lower temperatures. However, the fracture path tended to be located at the TZM substrate close to the interface between TZM and the brazing seam when the brazing temperature exceeded 1040 °C. The optimal room temperature shear strength reached 120.5 MPa when brazed at 1040 °C for 10 min and the fracture surface exhibited cleavage fracture characteristics, and the shear strength at high temperature of 800 °C for the specimens with highest shear strength at room temperature reached 77.5 MPa. [ABSTRACT FROM AUTHOR]

The multilayer Ti and Ni foils were designed to braze SiO 2 -BN diphase ceramic with Nb at 1140 °C for 5min. The interfacial microstructure was examined using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), transmission electron microscope (TEM) and X-ray diffraction (XRD) methods, respectively. Experimental results and thermodynamical calculations showed that the interfacial microstructures between Nb and SiO 2 -BN ceramic were (βTi,Nb)-TiNi eutectic structure/TiNi + TiNi 3 /TiN + Ti 3 O 5 + TiB 2 + Ti 5 Si 3 . The effects of the Ti content in the Ti-Ni braze alloy on the microstructures of the joints were investigated. With the increase of the Ti content, less Ni 3 Nb formed in the joint and TiNi 3 phase successfully turned into TiNi and Ti 2 Ni. The effects of the Ti content in the Ti-Ni braze alloy on the shear strength of the joints showed that the optimum thickness of the TiN + Ti 3 O 5 + TiB 2 + Ti 5 Si 3 reaction area was about 13 μm and the maximum shear strength of 52 MPa was achieved when the Ti content was 45 wt.%. [ABSTRACT FROM AUTHOR]

Laser welding-brazing of dissimilar metals 5052 aluminum alloy and H62 brass in butt configuration was performed with Zn-15%Al filler metal. Laser beam offset was defined as the deviation from the center of the laser beam to the butted joint face. Influence of laser offset (defined Al side (−) and brass side (+)) on microstructure and mechanical properties of welded-brazed joints were investigated. Satisfied and defect-free joints were obtained when laser beam was irradiated at Al side, while poor wetting at the bottom, interfacial cracks and lack of penetration occurred when laser offset was shifted to brass side. When the laser offset was −0.6–0 mm, the interfacial microstructure mainly consisted of serrated layer Al 4.2 Cu 3.2 Zn 0.7 adjacent to the weld seam and continuous layer CuZn close to the brass substrate. When the laser offset moved towards brass side (0.3 mm), Al 4 Cu 9 phase formed in between CuZn and Al 4.2 Cu 3.2 Zn 0.7, due to more melting and dissolution of brass. Tensile test indicated that joint strength increased first and then reduced with laser offset from Al side to brass side, and the maximum tensile strength of 128 MPa was obtained at laser offset of −0.3 mm, which was 55.7% of that of Al base metal. All the joints fractured along the bottom of brass side with brittle fracture surface and fracture location extended into the weld seam at the upper of the joints. [ABSTRACT FROM AUTHOR]

A novel nano-Si 3 N 4 particle reinforced AgCuTi composite filler (AgCuTi C ) was used to braze Ti6Al4V and Si 3 N 4 ceramic in the study and brazing cycles that peak at 880 °C for 0–20 min. Effects of holding time on interfacial microstructure and mechanical property were studied by scanning electron microscopy, energy dispersive spectrometer, transmission electron microscopy, and universal testing machine. TiN and Ti 5 Si 3 were identified as the main product of the reaction between Si 3 N 4 and Ti. The interfacial microstructure evolved considerably with joining time, eventually leading to a high degree of inhomogeneity across the length of the joint, and the maximal shear strength of 78.3 MPa was obtained when the joint was brazed at 880 °C for 10 min. A limited number of Si 3 N 4 /Si 3 N 4 and Ti6Al4V/Ti6Al4V joints using AgCuTi C with different content of Ti particles were also studied to clarify the influences of diffusion and dissolution behaviors of element Ti on interfacial microstructure. In terms of characterizing the interfacial phases, efforts were made to understand the microstructural evolution mechanism of Si 3 N 4 /Ti6Al4V brazed joints. [ABSTRACT FROM AUTHOR]

A novel composite interlayer with a reinforced network was designed using a SiC ceramic with a network structure and Ti-Ni-Nb composite filler foils, to which the Nb and BN-SiO 2 ceramic were successfully brazed under vacuum. For a brazing temperature of 1160 °C and holding time of 10 min, the interfacial microstructure of the Nb/BN-SiO 2 ceramic joint was Nb/(βTi,Nb)-TiNi eutectic structure+(βTi,Nb) 2 Ni+SiC+TiC/TiN+Ti 2 N+TiB+Ti 5 Si 3 +TiO/BN-SiO 2 ceramic. In addition, the shear strength and nano-hardness were analyzed to evaluate the effect of the composite interlayer with a network reinforcement architecture on the mechanical properties of the joint. During brazing, the Ti-Ni-Nb filler metal infiltrated and reacted with the SiC to form the network reinforcement architecture, resulting in the residual stress being relieved and the mechanical performance of the joint being significantly improved. A maximum shear strength of 102 MPa was achieved, which was 60 MPa (142%) higher than that of the joint brazed without the network reinforcement architecture. A reduction in the residual stress on the BN-SiO 2 ceramic side from 328 MPa to 210 MPa was observed with the network reinforcement architecture, and the fracture path of the joint changed from the surface of the BN-SiO 2 ceramic to the interfacial reaction zone. [ABSTRACT FROM AUTHOR]

Real-time electric signal data, metal transfer images and weld appearances at different alumino-thermic additions in underwater wet flux-cored arc welding (FCAW) were obtained. The electric signal results showed that the thermite addition would improve the stability of the wet welding process while the weld appearances at larger content of thermite displayed numerous tiny spatters. The shock in weld pool due to metallurgical reaction was responsible for the tiny spatters. Two typical modes of metal transfer process, globular repelled transfer mode and surface tension transfer mode, were observed. The aluminum flux addition changed the droplet diameter, transfer time and relative proportion of metal transfer mode. When the thermite addition increased from 0 to 50%, the weld penetration depth increased from 2 mm to 4 mm, and the weld dilution rate increased from 22% to 37%. [ABSTRACT FROM AUTHOR]

Vacuum brazing of copper to SiO 2 electroceramics was carried out using commercially obtained Ag-Cu-Ti filler alloy. The effects of brazing temperature and bonding time on the interfacial microstructure and mechanical properties were investigated. The microstructure observation revealed that the typical interfacial structure could be expressed as SiO 2 ceramic/Ti 5 Si 3 + Ti 4 O 7 /Ti 2 Cu + Ti 3 Cu 3 O/Ag (s,s) + Cu (s,s)/Copper. The migration of Ti in brazing seam, which promoted the reaction of Ti with the SiO 2 ceramic, was a positive factor on the interfacial microstructure and mechanical properties. With increased the brazing temperature or holding time, the thickness of Ti 5 Si 3 + Ti 4 O 7 reaction layer thickened, meanwhile, the amount of AgCu eutectic structure decreased. The shear strength firstly increased and then decreased with brazing temperature increasing or bonding time prolonging. The maximum shear strength of 22 MPa was obtained at 850 °C for 5 min. Its fracture occurred both along the ceramic substrate adjacent to the bonding interface and along the reaction layer, showing a mixture fracture mode. [ABSTRACT FROM AUTHOR]

A defect-free Sn-based metallization layer was prepared successfully on the surface of graphite at 950 °C for 30 min using Sn0.3Ag0.7Cu- 9%Cr (wt. %) metal powders. The typical interfacial microstructure of the metallization interface was β-Sn/Cr 3 C 2 /graphite. The formation mechanism of Cr 3 C 2 reaction layer was investigated in detail. Reliable soldered joint of metallized graphite to copper was achieved using Sn3Ag0.5Cu solder paste at 250 °C for 60 s in air, and the average shear strength of soldered joint reached 25 MPa. The novel metallization method provides a neoteric way for joining graphite and copper. [ABSTRACT FROM AUTHOR]

The SiO 2f /SiO 2 composite and the Invar alloy were brazed at 860 °C from 5 min to 25 min using an AgCuTi alloy. Scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS) was employed to examine the elemental distribution in the joint. X-ray diffraction (XRD) and transmission electron microscopy (TEM) was selected to accurately identify the species, morphologies and crystal structures of the reaction products. The effect of the holding time on the interfacial microstructure evolution of the joint was studied in detail. The shear strength of the joints and the fracture morphologies were closely related to the thickness of the whole reaction layer, as well as the thickness ratio of the Ti 5 Si 3 + TiO 2 layer to the Cu x Ti 6-x O layer. The maximum shear strength was 26 MPa obtained at 860 °C for 10 min. Finally, the formation of the reaction products in the joint was analyzed by thermodynamic calculations. A brazing mechanism was proposed based on the experimental results. [ABSTRACT FROM AUTHOR]

Underwater wet welding of 316L stainless steel was performed with specially designed nickel-based tubular wire at shallow water. Microstructural observations showed that fully austenitic weld metal without cracks and pores was achieved by the nickel-base filler materials. The ultimate tensile strength of welded joints was 508 MPa and the average elongation of the joints was up to 32%. The impact test results indicated that all specimens exhibited ductile fracture and Charpy impact toughness value of weld metal at 0 °C was 159 J/cm 2 . The average hardness of weld metal was 156 HV. There was a sharp increase of hardness occurred in fusion zone due to more ferrite formation. [ABSTRACT FROM AUTHOR]

A kind of novel composite filler was designed using FeCoNiCrCu high entropy alloy and pure Ti foil. ZrB 2 SiC C ceramic and GH99 superalloy were brazed with the composite filler. The interfacial microstructure as well as brazing mechanism was investigated. The mechanical properties were also assessed. The results show that the high entropy mixing effect of the Ti/FeCoNiCrCu composite filler keeps the activity of Ti and Cr. The solid solution forms as the matrix of brazing seam. The phase structure of (TiB + Cr B)/solid solution promise a good bond between ZSC and GH99. The interfacial reaction is affected greatly by the brazing parameters, because the activity of Ti and Cr is changed. The maximum shear strength reaches 71 MPa when the joint is brazed at 1180 °C for 60 min. Cracks primarily propagate in the ZSC away from the reaction zone. [ABSTRACT FROM AUTHOR]

Vacuum brazing of Titanium–Zirconium–Molybdenum (Abbreviated as TZM) alloy using Ti–28Ni (wt%) eutectic brazing alloy was successfully achieved in this study. Reliable TZM brazed joints were obtained at the temperatures ranging from 1000 °C to 1160 °C for 600 s. The interfacial microstructure of TZM joints was characterized by employing SEM, EDS and XRD. The effects of brazing temperature on interfacial microstructure and joining properties were investigated in details. TZM brazed joints mainly consisted of δ-Ti 2 Ni phase and Ti-based solid solution (Ti(s,s)). The interfacial microstructure of TZM joints was influenced obviously by brazing temperature. Both the thickness of brazing seam and the amount of δ-Ti 2 Ni phase was reduced with the increasing brazing temperature, while the Ti(s,s) layer did not change significantly. The maximum average shear strength of TZM joints reached 107 MPa when brazed at 1080 °C. The presence of δ-Ti 2 Ni intermetallic phase and crack-like structure in joints deteriorated the joining properties, which resulted in the formation of brittle fracture after shear test. In addition, fracture locations were related to the brazing temperature. When the brazing temperature was relatively low, cracks initiated and propagated in the continuous δ-Ti 2 Ni layer. However, the fracture locations preferred to locating at the interface between TZM substrate and brazing seam when brazing temperature exceeded 1080 °C. [ABSTRACT FROM AUTHOR]