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This work investigated the influence of friction stir welding (FSW) parameter on forming the dissimilar T-joint of aluminum alloy 6061 (AA6061) to pure copper (C1100). The experimental outcomes indicated that the hook formation trended to move toward the center of welding line at low welding and/or high rotational speeds. In all cases, the kissing bond (KB) defects were significantly observed in advancing (AS) compared to retreating sides (RS). The thickness of diffusion and intermetallic compound (IMC) layers decreased with increasing welding and/or decreasing rotational speeds. A highest joint efficiency was attained with approximately 74% at 500/125 rev/mm of the skin test and 34% at 500/100 rev/mm of the stringer tests. The fracture process under the stringer test initiated from the AS to the RS along the interface while that of the skin test cracked in the heat affected zone. Improving dissimilar T-joint of AA6061/C1100 was impacted not only by controlling the KB defect but also the IMC layer thickness. [ABSTRACT FROM AUTHOR]

The article explores the microstructure, mechanical, and fractographic behavior of diffusion welded joints of AA2219 and Ti-6Al-4V for aerospace applications. The study focuses on the challenges and advancements in welding technologies for joining aluminum and titanium alloys, emphasizing the importance of welding reliability and intermetallic formation. Various welding techniques, such as vacuum diffusion welding, are discussed for joining dissimilar metals with low heat input conditions to ensure bonding joint integrity. The research findings highlight the relationship between holding time, diffusion zone thickness, hardness, shear strength, and fracture morphology of the welded joints, providing insights into optimizing the welding process for aerospace applications. [Extracted from the article]

In this paper, the effect of ER2209 multi-stranded wire compared to single wire on the microstructure and pitting resistance of 2205 duplex stainless steel submerged arc welded joints was studied using electron backscatter diffraction, scanning electron microscopy, energy spectrum analysis, electrochemistry and other detection techniques. Compared with single-wire welding of duplex stainless steel, the multi-stranded wire deposited more metal and doubled the welding efficiency with the same heat input, while increasing the elemental concentration of Ni in the weld metal and the proportion of austenite in the heat-affected zone. Compared with single-wire welding, multi-stranded wire welding promotes the diffusion of the main alloying elements (Cr, Mo, Ni, N) in the welded joint and improves the mechanical properties and pitting resistance of the welded joint. [ABSTRACT FROM AUTHOR]

Vacuum diffusion welding of magnesium alloy MA2-1 is considered in the paper. It was found that welding of the magnesium alloy without using intermediate layers does not ensure formation of high-quality joints. Separate flat pores, elongated along the joint line, are observed in the joint, causing low mechanical properties of the joints. Using intermediate layers made of low-alloy nickel or titanium alloys and forming matrices during welding, which increase plastic deformation on the contact surfaces of the samples during the thermal-deformation welding cycle, allows producing joints without defects. Metallographic studies show significant plastic deformation of the intermediate layer (Ni or Ti), which is a harder material compared to the magnesium alloy. The mechanical properties and microhardness of the welded joints were determined. [ABSTRACT FROM AUTHOR]

Using BNi as the interlayer material, transient liquid phase diffusion welding experiments were conducted on Q355 steel at a welding temperature of 1050 °C under different holding times (10, 15, 20, 25 min). The welded joint microstructure, element diffusion migration, and phase composition were analyzed by using modern analytical testing instruments such as optical microscope (OM), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). The mechanical properties of the joint were tested and analyzed by using a microhardness tester, universal testing machine, and impact testing machine. The electrochemical corrosion property of the welded joint was analyzed and studied by using an electrochemical workstation. The results showed that under the conditions of 1050 °C and 6 MPa pressure, the Q355 steel TLP welded joint with better property could be obtained with a 20-min holding time. With the increase of holding time, the width of the bonding interface layer increased first and then decreased, and the microstructure tended to be more uniform. The shear strength gradually increased, reaching a maximum of 496.7 MPa (25 min), but the impact toughness increased first and then decreased, with a maximum of 250.61 J/cm2 (20 min). The corrosion resistance of the joint also improved first and then weakened. [ABSTRACT FROM AUTHOR]

The diffusion welded joint of oxide dispersion strengthened tungsten (ODS-W) and Mo-Ti-Zr-C alloy (TZC) was successfully fabricated with the use of spark plasma sintering (SPS) at a vacuum level of 10 Pa. This study systematically investigates the microstructure, mechanical performance, and thermal shock resistance of the ODS-W/TZC connector at four different temperatures, ranging from 1300 to 1600 °C. The diffusion distance between the W and Mo atoms at the interface of ODS-W/TZC joint raises as the sintering temperature increases, with a maximum diffusion distance of up to 2 μm at 1500 °C, but then slightly decreases at 1600 °C. The ODS-W/TZC connector bonded at 1500 °C exhibits the best tensile performance, with tensile strengths of 459 MPa and 786 MPa at room temperature and 500 °C, respectively. A maximum hardness of 446 HV is obtained at the interface when the sample is sintered at 1600 °C. Thermal shock tests are conducted on the surface and interface of the ODS-W/TZC connector sintered at various temperatures. ODS-W/TZC samples prepared below 1500 °C were severely damaged, leading to exfoliation after laser thermal shock, while samples prepared above 1500 °C produced fewer damage cracks. Confocal laser scanning microscope (CLSM) analysis demonstrated that the ODS-W/TZC joint fabricated at 1500 °C exhibited substantially reduced height perturbation of both its surface and interface compared to that of ODS-W, providing evidence for its superior thermal shock resistance. [ABSTRACT FROM AUTHOR]

Diffusion welding of heat-resistant alloys has attracted interest in the manufacturing of components with complex configurations. Controlling secondary precipitates along the interface is necessary to enhance the quality of the diffusion welding. Surface treatment to increase the solubility product (Ksp) of Ti-rich carbide is proposed to accomplish such an enhancement. The reduction of secondary precipitates along the interface induced grain boundary migration across the interface. The chemical compositions at/near the interface satisfied the material specifications. The mechanical properties of the diffusion weldment were similar to those of Alloy 800H that underwent the same thermo-mechanical processes in the range of 25–700 °C. At 25 °C, the tensile strength was 553 MPa, which satisfied the minimum specified tensile strength described in ASTM B: 409-22. The location of failure was random in the gauge section, and dimples, the evidence of the macroscopic plastic deformation, were observed on the fracture surface. [ABSTRACT FROM AUTHOR]

The paper gives the results of investigations on vacuum diffusion welding of МА2-1 magnesium alloy. Different technological measures were used in welding: unsupported welding, welding with application of forming matrices, welding without interlayers and with a zinc interlayer. It is found that it is not possible to produce the joint in unsupported welding without an interlayer at 400 °С temperature and process duration less than 60 min. Increase of welding temperature or time leads to considerable grain growth. Application of 250 ~m zinc interlayer and of the following welding mode: Т = 320 ºС, Р = 10 MPa, t = 30 min allows producing the joint. Analysis of chemical composition in different areas of the joint zone shows that development of diffusion processes in the butt during welding results in pore formation with magnesium content on the level of 17.8 – 20.12 wt. % in the zinc interlayer at 2 – 3 ~m distance from magnesium/zinc contact line. In the central part of the joint zone the metal chemical composition is close to pure zinc composition. Application of forming matrices and an interlayer of zinc in the solid-liquid state in welding in the following mode: Т = 340 ºС, Р = 10 MPa, t = 30 min. allows producing sound joints due to localisation of plastic deformation in the butt joint. Results of metallographic investigations showed formation in the butt joint of common grains and remains of the interlayer in the form of dispersed particles of 15…50 ~m size, with chemical composition of Mg–4.53Al–0.20Mn–63.49Zn, wt. %, having an irregular elongated shape. [ABSTRACT FROM AUTHOR]

The paper gives the results of investigations on vacuum diffusion welding of MA2-1 magnesium alloy. Different technological measures were used in welding: unsupported welding, welding with application of forming matrices, welding without interlayers and with a zinc interlayer. It is found that it is not possible to produce the joint in unsupported welding without an interlayer at 400 ℃ temperature and process duration less than 60 min. Increase of welding temperature or time leads to considerable grain growth. Application of 250 μm zinc interlayer and of the following welding mode: T = 320 ℃, P = 10 mpa, t = 30 min allows producing the joint. analysis of chemical composition in different areas of the joint zone shows that development of diffusion processes in the butt during welding results in pore formation with magnesium content on the level of 17.8-20.12 wt.% in the zinc interlayer at 2-3 μm distance from magnesium/zinc contact line. In the central part of the joint zone the metal chemical composition is close to pure zinc composition. application of forming matrices and an interlayer of zinc in the solid-liquid state in welding in the following mode: T = 340 ℃, P = 10 mpa, t = 30 min. allows producing sound joints due to localisation of plastic deformation in the butt joint. Results of metallographic investigations showed formation in the butt joint of common grains and remains of the interlayer in the form of dispersed particles of 15-50 μm size, with chemical composition of mg-4.53al-0.20mn-63.49Zn, wt.%, having an irregular elongated shape. [ABSTRACT FROM AUTHOR]

The effects of various process parameters on microstructure, tensile strength, temperature distribution, and weld quality were investigated during friction stir welding (FSW) of Al-Si alloys. The weld process factors altered the microstructure, with non-uniform grains seen at lower tool rotation rates and enhanced mixing at higher speeds. During force balancing, hyper eutectic alloys generated a substantial amount of heat, resulting in increased temperatures. The tool had difficulties while progressing through hyper eutectic alloys, resulting in greater temperatures and a reduction in weld quality. The study emphasised the need of selecting the right process parameters, such as plunging force, mixing, and plastic flow, to achieve the necessary weld quality and joint strength. Overall, this study emphasises the importance of accurate process parameter control to obtain optimal microstructures, tensile strength, and weld quality in Al-Si alloy FSW. Further optimisation can result in improved weld joint characteristics, which will improve the performance of these alloys in actual applications. [ABSTRACT FROM AUTHOR]

Diffusion bonding is a sort of solid-state joining that allows the joining of metals with similar and dissimilar compositions by allowing them to diffuse into one another. The current study investigated the impact of process parameters on the bonding strength of AA5083. The process parameters were considered as bonding temperature, holding time, and bonding pressure. Because of micro-constituent diffusion in the interface, the bonding and shear strengths increased as pressure and temperature were raised in the sample. By increasing the temperature of the Al3Mg2 particles from 490 °C to 520 °C and the bonding pressure from 5 MPa to 15 MPa, the dispersion of secondary phase particles is improved, and pores/defects in bonded joints are reduced. Furthermore, microstructural characterization reveals that the achieved strength is contingent on boundary grain growth and grain boundary migration through the bonding process, respectively. The light optical microscope was used to characterize the microstructural test and diffusion layer configuration at the boundary. [ABSTRACT FROM AUTHOR]

ERNiCr-3 nickel-based welding wire was used as the solder of T91/TP347 H dissimilar steel welding joints, The phase composition, microstructure, elements, and microhardness of T91/TP347 H dissimilar welding joints in original state, service for 6×104 h and service for 105 h were characterized by X-ray diffraction analyzer, optical microscope, scanning electron microscope and microhardness tester.The results showed that with the increase of service time, the grain size of T91 base metal, TP347 H base metal and weld zone increased to a certain extent.T91 base metal had precipitated phases M23C6,and TP347 H base metal had precipitated phases M23C6 and Nb（C,N）,there is a small amount of M23C6 in the weld area.The diffusion of Fe and Ni elements occurred during service.The welded joints in the three states have the highest microhardness in the T91 heat-affected zone, and the microhardness of the TP347 H base metal was the lowest.With the increase of service time, the microhardness of the weld bottom layer was basically unchanged, while the microhardness of the weld cover layer and filler layer rise sharply, the microhardness of other areas decreased. [ABSTRACT FROM AUTHOR]

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In this work, good bonding between the high-entropy alloy (HEA) CuCoCrFeNi and TC4 titanium alloy was obtained through vacuum diffusion welding at a joining temperature of 1000  °C for 60 min under a pressure of 5 MPa. The results showed that the typical interfacial microstructure of the CuCoCrFeNi/TC4 joint was TC4/diffusion layer/island structure/dendritic structure/diffusion layer/HEA. Compared with Ti atoms, atoms such as Cr and Co from the CuCoCrFeNi substrate were prone to diffuse into the other material. Intermetallic compounds Cu0.5Fe0.5Ti and Co0.15Ni0.85Ti, solid solutions Ti(Fe, Cr)ss and amorphous materials were produced in the joint. The self-diffusion activation energy formula Q = 18 R T m e l t ≈ 15.2 Δ H m e l t can be used to approximate the order of diffusion capacity of elements, which follows in Cr >Fe> Co > Ni. [ABSTRACT FROM AUTHOR]

In this paper, partial transient liquid phase (PTLP) diffusion bonding between Si3N4 ceramics and Ht250 cast iron was carried out by using an Ti/Cu/Kovar/Cu/Ti interlayer. The effects of the heating temperature and holding time on the microstructure, formation mechanism, and mechanical properties of Si3N4/Ht250 cast iron joints were studied. The results show that the maximum shear strength of the joint is 112 MPa when the welding temperature is 1000 °C and the holding time is 1 h. In addition, the problems of Ti/Cu/Ti intermetallic compound formation and Cu/Si3N4 ceramic residual thermal stress in the joint can be effectively alleviated. [ABSTRACT FROM AUTHOR]

Investigations on vacuum diffusion welding of nichrome powder alloy Ni-20Cr--(3--4)Fe--(0.40--0.6)Al--(0.25--035)Ti--0.5Y (% wt.), are presented. As shown, welding nichrome alloy directly in the temperature range of 800-1100°C under vacuum of 1.33 10-3 Pa does not provide sound joints. As found, during nichrome alloy heating, oxidation of its contact surfaces takes place, which makes it more complicated to produce the welded joint. The possibility of protection of the alloy surfaces from oxidation by coating them with nickel is studied. Deposition of a nickel interlayer by EBPVD method in the form of 5-7 µm thick coating allows avoiding oxidation of the contact surfaces. The influence of heat treatment in vacuum on the coating chemical composition is investigated. As shown, annealing of the coated samples at T = 1100°C for 10 min. under vacuum of 1.33 10-3 Pa promotes enhancement of the diffusion processes between the base metal and deposited nickel layer and ensures equalizing of the chemical composition in the zone of contact of the coating and the alloy. As shown, the microstructure of the samples, produced in the following mode: T = 1200°C, P = 40 MPa, t = 20 min is characterized by absence of defects in the joint zone. Distribution of chemical elements in the welded joint is monotonic. Diffusion of elements from nichrome alloy into the nickel coating ensures formation of the diffusion zone, is similar, in its chemical composition to nichrome alloy. Mechanical properties of the welded joints are studied. As demonstrated, application of an intermediate nickel layer at vacuum diffusion welding of a nichrome powder alloy enables producing joints with the microhardness on the level of that of the base metal after annealing. [ABSTRACT FROM AUTHOR]

The direct welding of alumina and zirconia ceramics by ultrashort pulse laser is presented for the first time. Compared to traditional dissimilar ceramic joining techniques such as brazing and diffusion welding, this method shows various advantages, including operation at room-temperature, higher welding efficiency, and negligible impact on base materials. The joint microstructure consists of a combination of Al 2 O 3 and ZrO 2 phases, without new phases detected. By adjusting the laser focal point position, the phase content within joint is effectively regulated, successfully preventing crack formation in alumina substrate. The influence of laser power and welding speed on joint morphology and mechanical property is fully investigated. The highest four-point bending strength of 365.5 MPa and shear strength of 33.4 MPa are achieved. After experiencing thermal cycling test at 1000°C, the joint strength and microstructure does not exhibit significant changes, demonstrating the excellent high-temperature durability of the sample. [ABSTRACT FROM AUTHOR]

Zircaloy-4, which is used as a structural material for nuclear cladding, requires precise bonding at low temperature in nuclear power applications. We achieved this using diffusion bonding with Ni plating on the surface of Zircaloy-4. We evaluated the performance of joints at temperatures between 650 and 780 °C. At 650 °C, the joint was successfully bonded. The joint exhibited a maximum shear strength of 207 MPa at 780 °C, which was twice as high as that produced by direct diffusion bonding at 700 °C under the same parameters. The interface was analyzed by using a combination of SEM and TEM to identify the presence of multilayered intermetallic compound layers in the joints. We investigated the mechanism of interface generation and determined the sequence of phase formation by Gibbs free energy calculations to be NiZr, Ni 10 Zr 7 , NiZr 2 , Ni 7 Zr 2 , and Ni 3 Zr. Through X-ray diffraction and cross-section elemental analysis of the fractures, we observed that, at lower temperatures, the joint fracture tended to occur in the Ni layer, whereas at higher temperatures, it occurred between Ni 7 Zr 2 and Ni 3 Zr. The utilization of diffusion welding with Ni plating applied to the surface of Zircaloy-4 reduces the joining temperature and enhances the properties of the joint. • Achieving Zr-4/Ni/Zr-4 joint through Ni plating on the surface. • The temperature of vacuum diffusion bonding decreases after Ni plating. • Using Gibbs free energy to determine the generation order of the phases. [ABSTRACT FROM AUTHOR]

In the present study, super-duplex stainless steel (SDSS) and zirconium alloy (ZrA) was vacuum welded using nickel alloy (NiA) interlayer by the diffusion welding process. The welded joints were processed from 800 to 950 °C in steps of 50 °C using 4-MPa compressive load for 75 min. The joints were characterised using optical microscopy, scanning electron microscopy, electron probe micro-analyser, and x-ray diffractometer. The SDSS│NiA interface is planar in nature for all welding temperatures; however, layer-wise Ni 5 Zr, Ni 10 Zr 7 , NiZr, and NiZr 2 reaction products were observed at the NiA│ZrA interfaces. The reaction products and width of these products increase with welding temperature. At both the interfaces, hardness values gradually increase with an increase in welding temperature. NiA│ZrA interface exhibited higher hardness as compared to the SDSS│NiA interface due to the presence of layer wise intermetallics. Joints reached a maximum tensile strength of ∼370 MPa (with an elongation of ∼7.9 %) when the joints were processed at 900 °C due to optimal reaction zone width and the least embrittling effect of the respective intermetallics. At lower temperatures, fracture surfaces of welded assemblies showed featureless morphology and voids present due to the poor coalescence of mating surfaces. At higher welding temperatures, the fracture surface of the transition joint preferred brittle fracture mode due to the cleavage planes with different alignments with insignificant volume fraction of voids on the fractography. • People's material and nuclear material joined using interlayer engineering. • Study reported diffusion-welded joints (DWJs) with sound metallurgical interfaces. • Study is the first type to report tensile properties of DWJs of Zr alloy & SDSS. • DWJs processed at 900 °C favoured the highest tensile strength (∼370 MPa). • Equiatomic Ni–Zr intermetallic (NiZr) requires the least activation energy for growth. [ABSTRACT FROM AUTHOR]

Changes in the material properties of alloys subjected to diffusion welding need to be analyzed to increase the adoption of compact heat exchangers in American Society of Mechanical Engineers standards. Hastelloy X was diffusion-welded in this study following a procedure recently developed by the authors. A metallographic study showed that the interface was discernible with some grains migrated across the interface. Satisfactory tensile properties were obtained at 25 °C, but the tensile samples were fractured at/near the interface with ∼40 % of tensile elongation in the tensile tests. The minimum strength reduction factors of the yield strength and tensile strength were 0.799 and 0.843, respectively. Dimples were extensively observed on the fracture surfaces, but the fracture surfaces were predominantly flat owing to the remnant Mo-rich M6C carbides (stringers). [ABSTRACT FROM AUTHOR]

The regularities of joint structure formation in diffusion pressure welding through multilayer interlayers based on AL-Si and Al-Cu aluminum systems with eutectic, obtained by electron beam deposition in vacuum, were studied, using SiCp-AMg5 aluminum composite, as an example. It is shown that the intermediate multilayer layers of eutectic ‘composition provide permanent joints without degradation of the properties of the base material at a temperature of 500 °C, which corresponds to the beginning of intensive plastic deformation of the interlayer under pressure. It is established that the nature of the diffusion interaction of the components of the interlayer and the composite and the phase composition of the eutectic affect the structure and the chemical composition of the joint. Conditions that prevent the formation of barrier layers at the interlayer/composite interface, namely layer alloying or intermetallic particle formation in it before the welding process, promote intensive mass transfer of interlayer and composite components, ensuring homogeneity of the structure and microhardness of the joint. Mechanisms for forming SiCp-AMg5 composite joint through multilayer intermediate layers based on aluminum systems with eutectic of different types — simple, consisting of system components (for example AI-Si) and one containing an intermetallic based on components (for example AL-Cu) are proposed. [ABSTRACT FROM AUTHOR]

Proceeding from the results of literature analysis, the good prospects for application of pressure welding methods, namely diffusion, ultrasonic, and roll welding, when joining elements from magnesium alloys, are shown. Comparative evaluation of welding modes was performed. The main directions for producing sound joints were determined. It is shown that the main ways to improve the welding processes are application of the following approaches: monitoring the temperature-time parameters of welding, application of interlayers in the form of separate layers from similar materials, based on copper, nickel, zinc or silver, or of eutectic mixtures, butt joint strengthening through application of nano- or finely-dispersed particles, intensification of plastic deformation through superposition of ultrasonic oscillations, increase of plastic deformation intensity, as well as application of heat treatment before and after welding. 31 Ref., 1 Tabl., 10 Fig. [ABSTRACT FROM AUTHOR]

The structural material of the water-cooled ceramic breeder (WCCB) blanket is reduced activated ferrite/martensite (RAFM) steels. The first wall (FW) of one of its components is realized by hot isostatic pressure (HIP) diffusion welding and vacuum electron beam welding (EBW). In order to study the performance difference of electron beam welded joint of RAFM steels before and after heat treatment, the EBW test of RAFM steels was carried out, and the welded joint was quenched and tempered treatment. The properties of welded joints before and after quenched and tempered treatment were studied. The results show that the microstructure of the weld is composed of $\delta $ ferrite and coarse lath martensite. After quenching and tempering treatment, the microstructure of the joint changes into tempered martensite with no obvious martensite characteristics. Moreover, $\delta $ ferrite disappears, and carbide precipitates out at the original austenite grain boundaries. Here, the type of precipitated carbide is M23C6 as characterized by the electron backscatter diffraction analysis. [ABSTRACT FROM AUTHOR]

As an example of alloy OT4 it is shown, that at diffusion welding of titanium alloys with the original globular (equiaxed fine-grained) microstructure, the accumulated strain value of the welded blanks can be reduced (more than 2 times) if the welding process is performed in the temperature range of polymorphic transformation (∼950 °С). In such a case, use the welding pressure only at the first stage to form a physical contact with an area of at least 50% of the nominal, and then produce an isothermal annealing without pressure, the duration of which is temperature dependent. When using a temperature higher than the end of polymorphic transformation (∼1000 °C), the duration of annealing is reduced by almost 10 times compared with annealing at 950 °C. [ABSTRACT FROM AUTHOR]

This study investigates the interface, microstructure, and mechanical properties of layered Ni/Ni-Ni3Al/Ni composite, fabricated by spark plasma sintering (SPS). Crack propagation behavior and joining mechanisms of particles in this layered composite were comprehensively studied and discussed. Ni3Al powders were first synthesized using mechanical alloying. Particulate Ni-Ni3Al composite was then produced by mixing 60 wt.% Synthesized Ni3Al and 40 wt.% Ni powders. The layered composite was then synthesized by SPS. Samples were held at 970°C for 10 minutes to do sintering. Results showed that a uniform interface has been formed between different layers of composite, without any obvious evidence of delamination, cracks, or flaws in-between layers. Moreover, there was hardly any sharp boundary/interface and necking between particles is discernible, inferring that applied sintering has resulted in rather complete densification. Based on the obtained results, interfaces were categorized into three different interface types: Ni-Ni, Ni3Al-Ni3Al, and Ni-Ni3Al. Results showed that intermetallic joints were less diffused and were less sintered, while metallic interfaces were much more diffused. Overall, complete sintering and diffusion for metal and kiss bonding or even cavities for intermetallic interfaces are more usual. The attribution of different interface structures to the mechanical properties and fracture behavior of the fabricated composite was thoroughly discussed. Results showed that a sample with a mixed Ni/Ni3Al mid-layer has an improved shear strength, when compared to the case where pure Ni3Al is used as the mid-layer. [ABSTRACT FROM AUTHOR]

Joints of VT6 and VT20L titanium alloys are prepared by diffusion welding in an autoclave (at a temperature of 920°C, a pressure of 4 MPa, and holding time of 4 h) and during hot isostatic pressing (at a temperature of 930°C, a pressure of 100 MPa, a holding time of 2 h). Alloy Ti6Al4V components are prepared in two different ways, i.e., by rolling and selective laser melting methods. After welding in an autoclave, defects are found in the microstructure of the specimens in the diffusion joint area. No defects are found within the microstructure of the specimen prepared by hot isostatic pressing. Welded specimens have a high level of strength properties corresponding to the VT20L base alloy material level. [ABSTRACT FROM AUTHOR]

Joining of similar metal sheets of Al-2024 with and without hematite ore particulates in between the sheets was performed through the solid-state diffusion bonding process by means of compression testing machine. During joining process, heat was applied to the specimen through the customized die in which electric heating elements were inserted. The specimens were subjected to continuous compressive plastic deformation by using compression testing machine for different holding times. Microstructural analysis confirms that solid-state bonding depends on the process parameters used. Tensile testing result shows that, strength of the joint increases with increase in holding pressure and time. [ABSTRACT FROM AUTHOR]

Diffusion bonding of Ti2AlNb alloy using pure titanium (Ti) foil as an interlayer was carried out on superplastic forming and diffusion bonding special equipment by gas pressure loading method. The microstructure of Ti-Ti2AlNb interface was observed using scanning electron microscope and energy-dispersive spectrometer while the mechanical properties of the joints were evaluated by shear test. The results show that the thickness of Ti foil interlayer has a great influence on the microstructure and shear strength of the interface diffusion region. When the thickness of the intermediate layer is thin (25 µm), Ti, aluminum (Al), and niobium (Nb) elements are fully diffused with uniform element distribution through the diffusion region. The diffusion layer region presents uniform, fine, and disordered lamellar α-Ti + β-Ti dual-phase structure with high shear strength. When the thickness of Ti foil interlayer is thick (50 mm), the distribution of Al elements is relatively uniform through the diffusion region due to its smaller radius and faster diffusion speed, and Ti and Nb elements present gradient distribution from the middle to both sides. The diffusion layer region presents a coarse and long strip shape α-Ti + β-Ti dual-phase structure in the middle part and a fine needle-like or irregular α-Ti + β-Ti dual-phase structure in both side parts, with slightly lower shear strength. Temperature has a great influence on the microstructure and mechanical properties of the diffusion bonding joints. The diffusion region presents a black α-Ti strip area in the middle part with the width of about 10 mm at lower temperature (910°C) with poorer property, due to the grain growth of the parent metal, the property is slightly poorer when the temperature is too high (960°C), and the optimal temperature is 930°C with a higher shear strength. [ABSTRACT FROM AUTHOR]

Vacuum diffusion bonding of Zircaloy-4 (Zr-4) and 304L stainless steel by using pure Ti and pure Ag as multiple interlayers was carried out at the bonding temperatures of 800900° C for the bonding time of 30 min under the bonding pressure of 12 MPa. The effect of the bonding temperature on the interfacial microstructure and mechanical properties of the joints was studied. The results showed that the interface zone of the joints was transited from 304L/Ag/¡-Ag+TiAg/Ti/Ti(Zr)/Zr(Ti)/Zr-4 to 304L/Ag/¡-Ag+TiAg/Ag(Ti, Zr)2/Ti(Zr, Ag)/Ti(Zr)/Zr(Ti)/ Zr-4 with the bonding temperature increased to 900°C while the TiAg content of ¡-Ag+TiAg layer decreased. Shear strength of the joints increased with the increasing of the bonding temperatures, and the maximum shear strength of 111.2 MPa was reached at 900°C. The fracture occurred in the Ag layer, which was mainly due to the low mechanical properties of Ag. [ABSTRACT FROM AUTHOR]

In this study, a laser high-velocity impact welding of Ta/Cu metal foil was successfully realized under different laser energies and flight distances. The morphology, microstructure, and mechanical properties of welded specimens were investigated via systematic experiments. Results indicated that the plastic deformation of the welded specimens was further pronounced with the increase in laser energy or flight distance. The welding area was ring-shaped, and the variation laws of the effective welding area under different laser energies and flight distances were summarized. The transition of the interface waveform was different when changing the laser energy and flight distance. Energy dispersive spectroscopy results showed that a trace element diffusion formed at the welding interface and intermetallic compounds were absent. Nanoindentation hardness tests showed that the hardness value increased with the decrease in distance from the welding interface. Two main failure modes of the Ta/Cu welding specimens occurred in the tensile shear tests, and the trend of the maximum tensile force under different process parameters was concluded. [ABSTRACT FROM AUTHOR]

Aluminum foam joints were fabricated via liquid diffusion welding with zinc‐aluminum alloy solder aided with ultrasonic vibration at 520 °C. Zinc‐aluminum alloys with different compositions (10 % aluminum, 20 % aluminum, 30 % aluminum) were used as solder material. The control group was fabricated under the same conditions but without ultrasonic assistance. The microstructure of aluminum foam joints was analyzed by optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. Among the different soldering alloys, those with the zinc‐20aluminum solder had the widest diffusion area and the most continuous interface. The tensile strength of metallurgic alloy joined aluminum foams was tested. Zn20Al samples had the best performance among all samples, including the low‐density substrate aluminum foam (0.3 g/cm3 and 0.4 g/cm3), but it still showed a lower performance than the high‐density substrate aluminum foam (0.6 g/cm3). Therefore, ultrasonic vibration remarkably improved the tensile strength and impact toughness of joints. Samples with ultrasonic assistance had better tensile strength and impact toughness than high‐density substrate aluminum. [ABSTRACT FROM AUTHOR]

This article provides a comprehensive review of the advancements made in the diffusion bonding of titanium and its alloys to other advanced materials such as aluminium, stainless steel, and magnesium. This combination of advanced alloys has received considerable attention in different industries, including aerospace, petrochemical, and nuclear applications due to high specific strength, lightweight, corrosion resistance, and moderate to high mechanical properties. The mechanisms of bond formation are discussed based on the type of microstructures formed and the mechanical properties achieved. The scientific literature identifies various methods/processes for controlling the volume of intermetallic compounds formed within the joint regions, as well as ways of maximising the strength of the weld/joints. This paper discusses the relationship between weld/bond properties and bonding parameters such as time, temperature, surface roughness, pressures, interlayer composition, and thickness. The scientific literature also shows that the bonding mechanisms and microstructural evolution of the bond zone can be significantly affected by suitable optimization of the bonding parameters. Additionally, this is a method of maximising bond strength. [ABSTRACT FROM AUTHOR]

The development of semiconductor integrated circuits has been limited by the low utilization rate of refractory metal sputtering targets. Spark plasma sintering (SPS) technology has shown great superiority in the sintering and joining of materials, which can be applied to the repair of waste targets and improve the utilization rate. In this study, SPS technology was used to sinter-join the high-purity refractory metal W 30Si sputtering powder and the target for integrated circuits to determine the optimal repair process and repair mechanism. The morphological characteristics, grain size, relative density, and Vickers hardness of the repair layer (powder-sintered body) and the target under different joining times were analyzed, and the interface structure and properties of the W 30Si joint were also studied. It was found that the W 30Si joint was composed of WSi 2 and Si phases. The grain size, relative density, and Vickers hardness of the W 30Si powder-sintered body and targets increased with the joining time. When the joining time was 10 min (1200 °C), the W 30Si joint formed a "zigzag" joining interface, and the bending strength, relative density, grain size, Vickers hardness, and thermal conductivity of the joint were similar to those of the pristine target. In addition, the physical model of SPS sintered and joined refractory metal powders and targets was constructed. Studies have shown that the sinter-joining consists of three stages: early stage, middle stage, and late stage. Among them, the middle stage included two steps that may occur simultaneously, namely the sintering of refractory metal powders and the joining of refractory metal powders with the target, involving pressure welding, micro-arc welding, resistance welding, and diffusion welding mechanisms. This work can provide theoretical guidance for the optimal design of the SPS repair process for refractory metal W 30Si sputtering targets. • The sinter-joining of W 30Si powders and target was realized by SPS technique, and the best repair process was determined. • The repair mechanism of W 30Si target was revealed. After repair, W 30Si joint formed a zigzag connection interface. • The physical model of sinter-joining of W 30Si powders and target was established. [ABSTRACT FROM AUTHOR]

Abstract Conducting the diffusion brazing cycle at 1120 °C for 45 min led to the completion of isothermal solidification and formation of a single-phase Ni-rich γ -solid solution at the joint centerline. Chromium-rich boride precipitates with blocky and acicular morphologies were detected in the diffusion affected zone (DAZ) of all the bonds. The post bond heat treatment of the brazed joint (HT-3 sample) resulted in complete elimination of DAZ boride precipitates and obtaining high levels of homogeneity across the joint region. Performing the brazing cycle between the solution treatment and the double aging cycle (HT-1 sample), as well as after the full heat treatment of the base metal (HT-2 sample), had a minor effect on the morphology of the joint region. While all the heat treatment sequences raised the microhardness values across the bonding regions, the HT-2 sequence reduced the microhardness levels in the isothermally solidified zone (ISZ). The HT-3 sequence improved the joint efficiency up to the remarkable value of 91%. In the as-brazed sample, the fracture path was observed in the ISZ and a dimple-like morphology was detected in the fracture surface. In HT-1 sample, the fracture occurred within the hard DAZ precipitates and a semi-cleavage morphology was detected in the fracture surface. [ABSTRACT FROM AUTHOR]

Abstract Hydrogenation of niobium foil was achieved by cathodic charging and its application as the interlayer facilitates a sound joint of TiAl/Ti 2 AlNb. The microstructure and mechanical properties of hydrogenated niobium were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), nano-indentation and thermogravimetry (TG) analysis. It is demonstrated that the plasticity of the surface of niobium interlayer is improved and dislocation density in niobium crystal lattice increases significantly, owing to the process of niobium interlayer hydrogenation and subsequent dehydrogenation. To investigate the effect of the hydrogenation of the niobium interlayer on the TiAl/Ti 2 AlNb diffusion bonding joint, the pure niobium foil was also applied as the interlayer for comparison. The effect of the bonding parameters on the interfacial microstructure evolution and mechanical properties of the joints were systematically analyzed by SEM coupled with an energy-dispersive spectroscopy (EDS) and shear test. The typical microstructure of the joint is found to be TiAl/B2 phase/Nb/δ phase/β phase/Ti 2 AlNb. With the increase of the hydrogen content, bonding temperature, holding time and bonding pressure, the bonding defects decreased and the thickness of the diffusion layer increased correspondingly. The shear strength of joint reached 258.9 MPa at 950 °C for 40 min under a pressure of 5 MPa with the hydrogenated niobium interlayer of 1.0 wt% hydrogen content. Highlights • Hydrogenated niobium foils are obtained by electrochemical charging technique. • Novel hydrogenated niobium was applied to achieve a sound joint of TiAl/Ti 2 AlNb. • Mechanisms for hydrogen-induced enhancement of diffusion bonding are proposed. [ABSTRACT FROM AUTHOR]

Abstract Three different thicknesses of pure Zn interlayers were used in the two-step diffusion bonding between ZK60 magnesium (Mg) alloy and 5083 aluminum (Al) alloy. The effect of Zn interlayer thickness on the microstructure and the mechanical properties of the joints were investigated. The results showed that with the thickness of Zn interlayer increased, the width of the diffusion layers increased and the phase formed in the diffusion layer changed from Mg-Al-Zn ternary compounds to Mg-Zn binary compounds and Al-Zn solid solution. The microhardness of the Mg/Zn/Al joints was lower than that of the Mg/Al joint and the shear strength of the joint was improved by Zn interlayer addition. The maximum shear strength of 38.65 MPa was obtained from the Mg/Zn 50 /Al joint in which the laminar structure of MgZn 2 layer resisted the rapid propagation of cracks. Highlights • Two-step diffusion bonding of ZK60Mg and 5083Al were carried out using different thickness of Zn interlayer. • The bonding process was carried out under solid state conditions. • Mg-Zn IMCs formed in Mg/Zn/Al joints, but its influence on the strength of joints was less than that of Mg-Al IMCs. • The maximum shear strength of bonding sample was 38.6 MPa and the microhardness value of was lower than Mg/Al joint. [ABSTRACT FROM AUTHOR]

Three-mm-thick AA 6061 plate and 2-mm-thick Ti6Al4V plate were friction stir lap welded using a W-Re pin tool. Defect-free joints were obtained at various rotation speeds ranging from 800 to 1400 rpm with a constant welding speed of 100 mm/min. The influence of rotation speed on the microstructure and mechanical properties of the Al/Ti friction stir lap welding (FSLW) joints was investigated. At low rotation speed within 1000 rpm, the obtained joint has no obvious mechanical Al/Ti intermixing at the interface. However, a significant mechanical mixture of Al and Ti alloys accompanied by hooks could be found in the joint welded at a rotation speed over 1000 rpm. Only diffusion layer was observed in the joint obtained at low rotation speed. Further, IMCs could be found in the Al/Ti mixture and hook when the rotation speed increased to 1400 rpm. The highest microhardness was measured at the interface due to the formation of IMCs. The tensile shear load of the welded joints reached the maximum at 1000 rpm and the specimens failed along the interface during the test. [ABSTRACT FROM AUTHOR]

In the present study, dissimilar TC4 alloy and 1060Al alloy were successfully diffusion-bonded at a very low temperature about 410 °C by improving the effective physical contact area. A sound joint with a crack-free interface and a high shear strength (128 MPa) is obtained with a combination of TC4 surface roughness of 109.90 μm (Sa) and 1060Al surface roughness of 101.43 μm (Sa), and customized parallel surface scratches. Under this condition, the two parent metals share the largest contact area during the physical contact stage of diffusion bonding process, which is consistent with the theoretical calculation. The results show that no Ti-Al binary intermetallic compounds are observed at the interface of the joints. The maximum shear strength of the joint reaches 128 MPa with optimized bonding parameters (410 °C for 120 min with a pressure of 20 MPa), which is higher than the shear strength of 1060Al (80 MPa) base metal. The fractography analysis indicates the joints failed with a ductile fracture at the 1060Al side. [ABSTRACT FROM AUTHOR]

The development of lightweight high-temperature materials and their processing methods are receiving increasing attention as the need for improved performance and energy efficiency in aero-engines increase. In this study, the γ-TiAl alloy was successfully soundly bonded to Ti 2 AlNb alloy by pulsed high current (PHC) diffusion welding. The effect of different high level (HL)/low level (LL) of composite pulse current on the microstructure and mechanical properties of the joints have been studied. The representative interface microstructure of PHC-950 °C TiAl/Ti 2 AlNb joint was γ-TiAl substrate/diffusion bonding zone/Ti 2 AlNb impacted zone/Ti 2 AlNb substrate. The diffusion bonding zone was composed of continuous equiaxed α 2 grains and a small amount of B 2 and O phases. The α 2 phase in the diffusion bonding zone was mainly transformed from the γ phase in γ-TiAl substrate and the B 2 and O phase in Ti 2 AlNb substrate. The composite pulse current has a significant promoting effect on the diffusion of elements and joint formation. The diffusion coefficients of D Al and D Nb in hot-pressing (HP, without current effect) diffusion welding joint at interface were 2 × 10−14 m 2/ s and 0.92 × 10−14 m 2/ s , respectively. In the representative PHC-950 °C joint with HL/LL = 12/2 cycles (single cycle duration 3.3 ms), diffusion coefficients of D Al-12/2 , D Nb-12/2 at interface were 19.62 × 10−14 m 2/ s , 13.34 × 10−14 m 2/ s , respectively. Increasing the duration of LL would weaken the current effect. The current waveform parameters were tuned to HL/LL = 12/4 and 12/6 cycles, the diffusion coefficients of D Al-12/4 , D Nb-12/4 D Al-12/6 and D Nb-12/6 were reduced to 15.69 × 10−14 m 2/ s , 12.49 × 10−14 m 2/ s , 15.31 × 10−14 m 2/ s and 10.99 × 10−14 m 2/ s , respectively. The PHC-950 °C joints have the highest shear strength of 257.3 MPa at HL/LL = 12/2 cycles, reaching 83.3% of the base material strength. The HP-950 °C TiAl/Ti 2 AlNb joint has a shear strength of 230.5 MPa, reaching 74.6% of the base material strength. The shear strength of PHC-950 °C joints at HL/LL = 12/4 and 12/6 reduced to 205.3 MPa, 195.8 MPa due to insufficient element diffusion and damages the bonding quality. This work provides a strategy that contributes to reduce the thermal damage of base metal and improve the joint forming efficiency. • Pulse high current diffusion welding was demonstrated for the soundly joining of dissimilar materials of γ-TiAl and Ti 2 AlNb alloys. • The effect of the high-level/low-level ratio of the pulse current on the TiAl/Ti 2 AlNb joints has been studied for the first time. • Elemental diffusion coefficient in TiAl/Ti 2 AlNb joints under pulsed current conditions is numerically analyzed. [ABSTRACT FROM AUTHOR]

Tantalum (Ta) coated tungsten (W) targets were prepared by hot isostatic pressure (HIP) diffusion welding in the temperature range from 1250 °C to 1550 °C. The mechanical tensile properties displayed that the bonding strength of the W Ta interface reached the maximum value of 138.3 MPa at 1450 °C. The value of nanoindentation hardness of the W Ta interface are between the values of W and Ta substrates indicating the diffusion layer. W Ta diffusion layers were formed during the HIP, and the thickness of diffusion layers increased with the increase of the HIP temperature. TEM results show that the diffusion layer consists of W Ta solid solution, and crystal plane distances of the diffusion layers were slightly enlarged due to the W Ta solid solution. • Using HIP process to prepare solid Ta cladded W targets for spallation neutron sources. • • A diffusion layer was found at the interface of the W‑Ta composite material. The diffusion layer is a sub-grain with a size of about microns. The thickness of the diffusion layer increases with the increase of the HIP temperature. [ABSTRACT FROM AUTHOR]

Abstract This study presents an electrically assisted diffusion bonding (EADB) process as a variation of solid-state diffusion bonding to obtain a wider dissemination of this technique. This concept is an experimental adaptation inspired by the rapidly increasing Joule heat during welding that has already been placed into practice. EADB was studied for a Ti 2 AlNb alloy sheet using a commercially pure titanium (CP-Ti) foil interlayer. An in-house built experimental setup was assembled to implement the EADB concept. The nonuniform temperature profiles of the Ti 2 AlNb alloy sheets under different electric current densities were imaged for reference in the subsequent discussion. Common characterization techniques were used to observe the interfacial microstructures, and the shear property and surface Vickers hardness were tested to assess the joint quality. The results showed that bonding interfaces consisted of the interlayer zone and the transition zone, and the Ti 2 AlNb alloy sheets were completely bonded under high electric current densities in the central zone of the sheet. When the density was increased to 4.58 A/mm2, the average room-temperature shear strength and Vickers hardness value reached the maximum values of 641 MPa and 493 HV, respectively. [ABSTRACT FROM AUTHOR]

Abstract The interfacial microstructure and mechanical properties of SiC ceramic joints diffusion bonded via spark plasma sintering with a powder mixture of Ti 3 SiC 2 and B 4 C were investigated. The content of B 4 C ranging from 0 to 20 wt% was added into Ti 3 SiC 2. Microstructure analysis results indicated that B 4 C in-situ reacted with Ti 3 SiC 2 to form fine-sized TiB 2 , TiC, SiC, and carbon in the joint. The volume fraction of these reaction formed phases and coefficient of thermal expansion of the composite interlayer were calculated. The proper addition of B 4 C (5–15 wt%) was beneficial for the improvement of joint strength. The optimal amount of B 4 C addition was 7.5 wt%. The shear strength of the joint bonded with 7.5 wt% B 4 C addition reached 112.5 ± 8.3 MPa, which was 53.9% higher than that bonded without B 4 C addition. Vickers hardness of the composite interlayer was enhanced with the B 4 C addition. Toughening mechanisms including delamination and kinking of Ti 3 SiC 2 , crack deflection, crack bridging, and crack branching were observed in the composite interlayers. [ABSTRACT FROM AUTHOR]

A self-nanocrystallization layer was prepared on the surface of a Ti alloy sample via shot peening to investigate its influence on the follow-up diffusion bonding between a titanium alloy and a TiAl-based alloy. The experiment results show that surface self-nanocrystallization treatment can accelerate the interface reaction between a Ti alloy and a TiAl alloy, lowering the bonding temperature of the sound joints by more than 50 K. Moreover, the thickness of the interface reaction layer plays an important role in the interfacial bonding strength. In this work, the maximum shear strength of the joint appears to have a thickness of about 1.8 μm. As a consequence, it is found that surface self-nanocrystallization treatment is helpful for optimizing the diffusion bonding process. [ABSTRACT FROM AUTHOR]

Microstructural characterization of TiAl to Ti6Al4V dissimilar diffusion bonds assisted by reactive Ni/Al nanolayers was performed in this study. The nanolayers (alternated Al and Ni) were deposited onto the base material surfaces. Diffusion bonding was performed at 700 and 800 °C under pressures from 5 to 40 MPa and dwell times between 60 and 180 min. Microstructural characterization was performed using high-resolution transmission and scanning electron microscopies. The observations revealed that dissimilar TiAl to Ti6Al4V joints assisted by Ni/Al reactive nanolayers can be obtained successfully at 800 °C during 60 min using a pressure of 20 MPa. The bond interface is thin (less than 10 µm) and is mainly composed of NiAl grains. Thin layers of Al-Ni-Ti intermetallic compounds were formed adjacent to the base materials. [ABSTRACT FROM AUTHOR]

SiC ceramic was successfully diffusion bonded to itself with a powder mixture of TiH 2 , Si and graphite by spark plasma sintering in the temperatures from 1150 °C to 1450 °C. The microstructure, phase formation and evolution, and the mechanical properties of the joints were evaluated. In-situ reaction in the powder mixture produced fine-grained Ti 3 SiC 2 and TiC x (TiC and TiC 0.625 ) composite in the joint. The grain morphology and size of carbides were determined. No reaction between the carbides and SiC ceramic was observed. The fraction of Ti 3 SiC 2 in the composite joint had a strong effect on the joint strength, which increased with the increasing of Ti 3 SiC 2 content. The highest shear strength of 80.5 ± 7.4 MPa was obtained at 1350 °C, due to the uniform distribution and inherent toughening characteristic of Ti 3 SiC 2 phase. The decomposition of Ti 3 SiC 2 occurred at 1450 °C led to the formation of TiC x and TiSi 2 , thereby lowering the shear strength. The hardness of the interlayer was dependent mainly on the fraction of TiC x phase. [ABSTRACT FROM AUTHOR]

In the present study, diffusion bonding of two dissimilar materials TC6 and copper alloy was investigated in vacuum chamber by directly bonding and using Ni foil as interlayer. Interface quality of the joints was evaluated by mechanical property and microstructure. The maximum shear strength of directly bonding was found to be 64 MPa for the speciemen bonded at 850 °C, 5 MPa for 30 min; and the maximum shear strength with Ni foil interlayer was 113 MPa under the same bonding parameters. The bonding interfaces and fracture surfaces were analyzed by energy disperse spectrometer, scanning electron microscopy and X-ray diffraction. The results show that the diffusion region of directly bonding specimen generated several IMCs (Ti2Cu and Ti5CuSn3, etc.). Fracture morphology showed that brittle fracture present at the Ti5CuSn3 IMCs, which was the weak point of the joint. While the diffusion zone of the specimen with Ni foil interlayer consists of various phase including Ti2Ni, TiNi, TiNi3 at TC6 side, and Cu-Ni solid solution at ZQSn11-4-3 side, and fracture surface of joint present a mixture of brittle and ductile characteristics, and fracture initiated at the TiNi3/Ni interface. [ABSTRACT FROM AUTHOR]

Dissimilar W/steel metals were successfully joined by diffusion bonding process with the help of a Ti/Ni composite interlayer. The effect of bonding temperature and holding time on interfacial microstructure and mechanical properties of the bonded joints were investigated. Metallographic and compositional analyses show that no intermetallic compound was observed at the W/Ti and Ni/steel interfaces, but Ti 2 Ni, TiNi and TiNi 3 were formed at the Ti/Ni interface at 850–1050 °C for 0.5–2 h. Tensile test showed that variations in the strength of the joint were strongly related to the intermetallic compounds in the diffusion zone of the Ti/Ni interface. The maximum tensile strength of ∼267 MPa was obtained for the joint diffusion bonded at 950 °C for 1 h, and the failure took place at both the W/Ti interface and W substrate. With further increase of the joining temperature, the holding time or both, the joint strength dropped as a function of the increase in the width of Ti–Ni intermetallic compounds, and the failure occurred at intermetallics layers of the Ti/Ni interface. [ABSTRACT FROM AUTHOR]

The paper describes the design and examination of Ti/Cu double interlayer to produce a joint between tungsten and steel. Partial transient liquid phase diffusion bonding was performed by a double stage bonding process. To join tungsten to steel, the brazing of steel to a Cu interlayer (500 μm) was carried out at 1050 °C followed by transient liquid phase diffusion bonding to tungsten using an active Ti interlayer (25 μm) at 1000 °C. Microstructural evolution was studied at different bonding times (5, 15, 30, 60 and 180 min) to reveal the diffusion behavior of Ti atom in the interfacial zone between W and Cu. With the increase of the bonding time, the inserted active Ti interlayer and the formed Ti–Cu base intermetallic phases tend to be molten and consumed by the formed liquid alloy in the W-steel joint, while the tensile strength of the joint increases. The strength of the bonded specimens is as high as 412 MPa at the bonding time of 180 min. This technique provides a reliable method of bonding W to steel. [ABSTRACT FROM AUTHOR]