High-strength Joining Research Articles

Microstructural characterization and mechanical properties of inertia friction welded FGH96 joints

It is considerable to describe comprehensively the synergy effects of grain morphology and γ′ phase on mechanical properties in FGH96 inertia friction welded (IFWed) joints. Herein, the high-strength joining of the precipitation strengthened FGH96 superalloy was successfully realized by inertia friction welding. The evolution of grain morphology and γ′ phase, as well as the mechanical properties at room temperature (RT) and 750 ℃ were systematically investigated. It was discovered that fine equiaxed crystals were observed in the central of the bonding interface due to the dynamic recrystallization. The γ′ phase was progressively dissolved from the base material (BM) to the weld interface, resulting in the gradual flattening of grain boundaries. The evolution of the grain and γ′ phase exhibited a key role on the microhardness of IFWed joint. The impact toughness of joint at RT exceeded that of BM. The tensile strength of joint at RT reached 1514MPa, showing 94.8% of that of BM, with the fracture occurring in heat-affected zone. The tensile strength was 1223MPa at 750 °C, showing 96.3% of that of BM, with the fracture occurring in weld nugget zone. The tensile fractures subject to both RT and 750 °C were characterized by ductile fracture.

Achieving high-strength laser welding of quartz glass to titanium alloys via magnetron sputtering

In this study, a high-strength joining between quartz glass and titanium alloy was achieved by first depositing high-quality TiO2 film on the titanium alloy surface via magnetron sputtering, followed by a low-cost millisecond laser welding. Further research indicates that high-quality TiO2 films substantially enhance the surface energy of titanium alloys improving compatibility with quartz glass. The formation of the mixing zone during welding is attributed to the flow of the interfacial material after laser energy absorption, as well as the combined effects of recoil pressure and capillary forces. The formation of TiSi at the joint indicates that the two materials form a tight bond. The laser process parameters significantly influence the macromorphology, microstructure, and mechanical properties of the welded joint. By optimizing the process parameters, the shear strength of the joint reaches 30.63 MPa, which is 4-5 times greater than that achieved with conventional methods. Additionally, the optimized joints demonstrated reliable performance under high-temperature and high-pressure conditions.

High-strength joining of WC-Si3N4 composite via spark plasma sintering and functionally graded material (FGM) bonding

Joining of large aspect ratio WC-based cemented carbide and Si3N4-based ceramic at 1650 °C was achieved via spark plasma sintering by using functionally graded material (FGM) as a bonding layer. The influence of FGM layer numbers on the bonding quality of the large aspect ratio WC-FGM-Si3N4 composite materials was assessed based on thermal expansion coefficient and residual stress data. The microstructure analysis of the interface between adjacent layers revealed the formation of a structure with grain bidirectional anchoring, which promoted the enhancement of the bonding strength. High-strength joining of the large aspect ratio WC-FGM-Si3N4 composite rods with the average shear strength of 210.5 MPa was successfully realised. Furthermore, the rod was ground into an end mill, and the obtained end mill connection strength fulfilled the stringent machining conditions for dry milling of nickel-based superalloys.

Wettability and joining of reaction-bonded silicon carbide (RBSC) by Ti–Si eutectic alloy

The high-strength joining of reaction-bonded silicon carbide (RBSC) is pivotal for its application in the semiconductor field. In this paper, the wetting and joining mechanism of Ti–Si eutectic alloy on RBSC were investigated. The contact angles observed between Ti–Si eutectic alloy and RBSC were approximately 1.9°, indicating the favorable wettability and demonstrating the feasibility of bonding RBSC joints. The temperature bending strength of the joints initially increased and then decreased as the brazing temperature increased. Moreover, the shear strength of approximately 107.38 ± 5.56 MPa was achieved at 1350 °C for 30 min. Notably, the diffusion and amalgamation of atoms, lead to the establishment of stronger bonds between adjacent particles. Thus, the Ti–Si eutectic alloy brazing filler formed a direct connection with the RBSC matrix, with Si2Ti infiltrating into the base metal on both sides. The utilization of Ti–Si eutectic alloy brazing filler in RBSC joints exhibits promising prospects.

Advances in ultrasonic welding of lightweight alloys: A review

Abstract The lightweight alloy sheet materials have been widely used in industries such as automobiles, aviation, and aerospace. However, there are huge challenges in the structural joining process. Likewise, industries are probing new technologies and are rapidly adapting to more complex light alloy materials. The ultrasonic metal welding is a reliable solid-phase joining technology, which has incomparable development prospects in the high-strength joining of lightweight alloy sheet materials. This article summarizes the research progress of ultrasonic welding of aluminum alloy, magnesium alloy, and titanium alloy thin plates in recent years. The key features of this review article are the ultrasonic welding process, advantages, applications, and limitations. It introduces the welding process parameters to explore the breakthroughs for straightforward direction. Furthermore, to strengthen the phenomena, the current state of the ultrasonic welding of lightweight alloys and their future perspectives are also reflected.

High-strength joining of 6063Al alloys by an Zn–Sn hypereutectic interlayer in air based on liquid and solid phase diffusion

A high strength joint obtained at relatively low temperature and pressure by diffusion bonding has always been a challenge for manufacturing of aluminum alloy heat sinks. In this work, joining of 6063Al alloys was performed by a novel liquid and solid phase diffusion bonding method with an Zn–30Sn hypereutectic interlayer. It was achieved at a heating temperature of 360 °C and a pressure of 1 MPa. A 6063Al joint bonded was composed mainly of Zn–Al eutectoid phases and had a higher strength than the base metal. During the diffusion bonding process, the joint was constituted of Sn–Zn eutectic phases and η-Zn phases at initial diffusion stage. The proportion of Sn–Zn eutectic phases gradually decreased and Zn–Al eutectoid phases increased in a joint through inter-diffusion between base metal and interlayer with increasing of holding time. The η-Zn phases finally transformed into Zn–Al eutectoid phases with depleting of Sn–Zn eutectic phases, in which only 0.02 wt% Sn element was remained in the joint. The liquid and solid phase diffusion mechanisms were revealed. The penetration of Sn to the grain boundary of Al alloy happened under an assistance of the Zn diffusion. The Al originated from base metal interdiffused with η-Zn phases, forming Zn–Al eutectoid phases.

High-strength joining of silica glass and 2024 aluminum alloy by ultrasonic-assisted soldering with Sn-Bi low temperature solder

To alleviate the problem of residual stress in silica glass/2024Al soldered joints, ultrasonic-assisted soldering of silicon glass and 2024Al was carried out using SnBi low-temperature solders. The impact of the soldering temperature and Bi content of the solder on the soldered joints were studied. Powder-reinforced solders were utilized to further improve the joint shearing strength, and the stirring time of the composite solder was also researched. The results showed that the joint strength stabilized after the soldering temperature reached 260 °C. For solders with different Bi content, the highest joint strength (27.3 MPa) was achieved with Sn28Bi solder. The composite solder could further increase the joint strength to 32.1 MPa. In addition, 10 min of ultrasonic vibration and mechanical stirring were recommended to obtain a high-quality composite solder.

Effect of thermal condition on isothermal-pressing joined strength of silanized Al alloy/carbon fiber-reinforced polyamide-6

Carbon fiber-reinforced thermoplastics (CFRTPs) and lightweight metals are widely used in multi-material structures owing to their high strength and excellent corrosion resistance, thus stimulating research on various heat-assisted techniques to join them. Currently, the isothermal-pressing process has been developed to realize sound interface joining between CFRTP and Al alloy under relatively uniform thermal conditions. However, a quantitative investigation of the interaction between thermal conditions, chemistry reactions, and joining strength is still lacking. This current investigation analyzed chemical reaction state and resultant bonded strength of isothermal-pressing joined interface of silanized 5052 Al alloy and carbon fiber-reinforced polyamide-6 (CF/PA6) under various thermal conditions. X-ray photoelectron spectroscopy and Raman scattering analysis showed the increasing consumption of epoxy groups on silanized 5052 Al alloy side with the increase in joining temperature and residence time. This suggested higher temperatures and sufficient high-temperature duration times could efficiently promote the interface chemical reaction, increasing interface bonding strength. As the joining temperature or residence time increased, the fracture location gradually shifted from the silane coupling layer/re-solidified resin interface to the re-solidified resin close to interface, and even it directly passed through CF/PA6 along the thickness direction. Under the current adopted conditions, a critical high-temperature duration time of ∼6.0 s at least was recommended by optimizing the joining time to achieve high-strength joining between 5052 Al alloy and CF/PA6. The findings will guide optimizing the joining conditions in heat-assisted joining processes of Al/CFRTP hybrid structures.

Enhanced Ti3AlC2/Zircaloy-4 interfacial bonding by using copper as an interlayer

We propose a novel strategy for the high-strength joining of Ti3AlC2 and Zircaloy-4 by introducing copper as an interlayer. The interfacial microstructure reveals spontaneously formed Cu–Zr eutectic liquid phase wet Ti3AlC2 ceramic, generating a ZrC layer instead of brittle ZrxAly at the interface, enhancing the Ti3AlC2/Zircaloy-4 joint strength.

Experimental Study of the Impact of Glass Beads on Adhesive Joint Strength and Its Failure Mechanism.

The use of modern structural adhesives provides a lightweight, practical, and high strength joining methodology, which is increasingly being adopted in the automotive and aeronautical sectors, among many others. However, the strict mechanical performance standards that must be met in these applications require a constant search for ways of improving the adhesives’ behavior, which has led to the growing use of reinforcements as a way of improving the capabilities of bonded joints. The aim of this work was, thus, to analyze how the addition of inorganic fillers to the adhesive layer affects a joint’s strength and its failure mechanism. To this end, single lap joint specimens with mild steel and high strength steel substrates were tested, at quasi-static speeds, and with different amounts of glass microspheres reinforcing two different structural adhesives. The experimental results indicated that the addition of glass particles reduced the joint performance for both substrates under study. Furthermore, the failure pattern was found to evolve from adhesive failure to a cohesive type of failure as the amount of glass particles present in the adhesive was increased.

Sonotrodes for Ultrasonic Welding of Titanium/CFRP-Joints—Materials Selection and Design

Ultrasonic welding of titanium alloy Ti6Al4V to carbon fibre reinforced polymer (CFRP) at 20 kHz frequency requires suitable welding tools, so called sonotrodes. The basic function of ultrasonic welding sonotrodes is to oscillate with displacement amplitudes typically up to 50 µm at frequencies close to the eigenfrequency of the oscillation unit. Material properties, the geometry of the sonotrode, and the sonotrode tip topography together determine the longevity of the sonotrode. Durable sonotrodes for ultrasonic welding of high-strength joining partners, e.g., titanium alloys, have not been investigated so far. In this paper, finite element simulations were used to establish a suitable design assuring the oscillation of a longitudinal eigenmode at the operation frequency of the welding machine and to calculate local mechanical stresses. The primary aim of this work is to design a sonotrode that can be used to join high-strength materials such as Ti6Al4V by ultrasonic welding considering the longevity of the welding tools and high-strength joints. Material, sonotrode geometry, and sonotrode tip topography were designed and investigated experimentally to identify the most promising sonotrode design for continuous ultrasonic welding of Ti6AlV4 and CFRP. Eigenfrequency and modal shape were measured in order to examine the reliability of the calculations and to compare the performance of all investigated sonotrodes.

Dissimilar Metal Joining of Ti and Ni Using Ti-Al Powder Interlayer Via Rapid Thermal Explosion Method

To achieve the low energy consumption and high strength joining between Ti and Ni, a novel joining method (rapid thermal explosion, TE) was developed for joining dissimilar metals using Ti-Al mixture powders as flux. The TE reaction temperature of Ti-Al flux was measured, and the microstructure and mechanical properties of Ti/Ni joint were investigated. The results reveal that the combustion temperature of the Ti-Al powder interlayer is 1103 °C, which is higher than the joining temperature, and an obvious self-exothermic phenomenon lasts 20 s. The intermetallic compound diffusion layers formed at both interfaces mainly owing to the diffusion of Al and the growth activation energy of diffusion layers near both interfaces are 79.68 kJ/mol and 38.26 kJ/mol, respectively. Based on the sheer strength and diffusion layer, the formation mechanism of Ti/Ni joints is metallurgical bonding through atomic diffusion and formation of the diffusion layer.

A new strategy for high-strength joining of dissimilar materials

A new strategy that utilizes the multicomponent amorphous alloy as the filler metal to join the hard-to-weld dissimilar materials was proposed. The coexistence of multiple principal elements was envisaged to improve the role of mixing entropy and retard the atomic diffusion between the filler metal and base metals, inhibiting the formation of bulky directional intermetallic compounds. To give a theoretical analysis of the phase evolution of the joint and verify the feasibility of this strategy, vacuum brazing of TiAl- and Ni-based alloys with a high-entropy amorphous filler Ti20Zr20Hf20Cu20Ni20 as the filler metal was performed and the phase evolution was analyzed from the perspective of kinetics and thermodynamics. The experimental result showed that a circular solid solution phases firstly formed at high temperature, and fine phases were then precipitated from the solid solutions accompanied by a precipitation strengthening effect to the joint as the temperature decreased. The shear tests showed that a maximum shear strength of 319 MPa can be obtained, and the multiple principal elements filler metal proved to be a promising and feasible approach to solve the difficult joining of hard-to-weld dissimilar alloys.

Achieving high-strength joining of TiAl- and Ni-based alloys at room temperature and 750 ℃ via utilizing a quinary FeCoNi-based amorphous filler

High content of single element in TiAl- or Ni-based brazing filler metal always causes the formation of bulk, directional and brittle intermetallics in the TiAl/Ni brazed joints, which deteriorates the joint mechanical properties. In this study, a multicomponent FeCoNi-based amorphous filler was applied as the filler metal to vacuum braze γ-TiAl and Ni-based superalloy. The high mixing entropy derived from the multi-principle elements was envisaged to retard the atomic diffusion and slower grain growth. The experimental results showed that three different zones were formed in the TiAl/ Fe30Co30Ni15Si8B17/Ni joint: A diffusion zone Ⅰ composed of fine γ-(Fe, Ni) phase; a crystallization seam II containing dendritic α’-(Fe, Co) phase and nanoscale (Fe, Co, Ni)23B6, Fe2B in the inter-dendritic regions; a diffusion and reaction zone Ⅲ consisting of blocky τ3 and mixed (Fe, Co, Ni)23B6, τ, TiCo phases. The relationship between the microstructure and the mechanical property both at room temperature and high temperatures were discussed. The shear tests showed that the maximum shear strength at 30℃ and at 750℃ were 363MPa and 252MPa respectively when brazed at 1020℃ for 15min.

Scalable Process Chain for Flexible Production of Metal-Plastic Lightweight Structures

The demand for customised products leads to an increasing diversity of variants and batch sizes in production. Therefore, established high volume production technologies have become less profitable. This loss results primarily from high product-specific investments in mould-based manufacturing systems such as injection moulding and sheet metal forming whose amortisation is challenged by smaller batch sizes. The increasing number of components in multi-material design, especially from metal and plastics, calls for flexible production technologies. This paper introduces a new robot-based process chain for metal-plastic parts to close the existing gap between manual production of small batches and mould-based high volume production. The idea is to combine surface treatments with additive and subtractive manufacturing processes in a single workspace implementing an incremental process chain to realise a scalable production system. This will increase the manufacturing flexibility for customised products and reduce the cost per unit. As a first step in the process chain, the surface of a pre-produced metal part is structured for mechanical interlocking and high strength joining. Subsequently, an additive process is used to directly apply a plastic section onto the pre-structured metal part, thus producing a hybrid component. Finally, the hybrid component is machined to add individual holes or pockets and to finish the surface of the additively manufactured area. This paper presents a scalable process chain for metal-plastic components as well as concepts for its technological implementation. Furthermore, first experimental results from the fabrication of a metal-plastic part using additive and conventional processes are presented.

A multicomponent TiZr-based amorphous brazing filler metal for high-strength joining of titanium alloy

High contents of Cu and Ni in Ti-based brazing filler metals (BFMs) usually cause the formation of brittle intermetallics in titanium alloy brazed joints, which weakens the joint mechanical properties. In this work, a novel multicomponent Ti50Zr27Cu8Ni4Co3Fe2Al3Sn2Si1 (at.%) amorphous BFM with low total content of Cu and Ni and low liquidus temperature was designed and synthesized by melt spinning. The Ti–6Al–4V joints brazed with this amorphous BFM exhibited high shear strength up to ~413MPa, which is mainly attributed to the reduced amount of intermetallics in the braze zone due to the low contents of Cu and Ni in the BFM.

Wafer-scale titanium anodic bonding for microfluidic applications

We report the development of an anodic bonding process that allows, for the first time, high-strength joining of bulk titanium and glass substrates at the wafer-scale, without need for interlayers or adhesives. We demonstrate that uniform, full-wafer bonding can be achieved at temperatures as low as 250°C and that failure during burst pressure testing occurs via crack propagation through the glass, rather than the titanium/glass interface, thus demonstrating the robustness of the bonding. Moreover, using optimized bonding conditions, we demonstrate the fabrication of rudimentary titanium/glass-based microfluidic devices at the wafer-scale, and their leak-free operation under pressure-driven flow. Finally, we also demonstrate the monolithic integration of nanoporous titanium dioxide within such devices, thus illustrating the promise embodied in titanium anodic bonding for future realization of robust microfluidic devices for photocatalysis applications.

Seamless Joining of Silicon Nitride Ceramics

High‐strength joining of Si3N4 ceramics has been achieved by developing a process that effectively eliminates the seam, and may allow for fabrication of large or complex silicon nitride bodies. This approach to joining is based on the concept that when sintering aids are effective in bonding individual grains, they could be equally effective in joining bulk pieces of Si3N4. Optimization of the process led to Si3N4/Si3N4 joints with room‐temperature bend strengths as high as 950 MPa, corresponding to more than 90% of the bulk strength of the Si3N4. At elevated temperatures of 1000° and 1200°C joint strengths of 666 and 330 MPa, respectively, were obtained, which are the highest values reported to date for these temperatures. These bend strengths are also more that 90% of the strength of bulk Si3N4 measured at these temperatures.

６０６１アルミニウム合金管と丸棒のせん断接合

In the field of automobile manufacturing, in order to reduce car weight, the introduction of aluminum components is being promoted. Structural components such as suspension arms, which require high strength, are some components that are to be replaced by aluminum components. Under these circumstances, in this study, we investigated the possibility of obtaining high-strength joining of aluminum alloy parts of circular pipe and bar by the shear joining method, in which plastic deformation, without influence of heat and other factors, is utilized, using finite-element analysis and experiments. The results indicated that if 1) the amount of punch penetrating into the material, 2) the clearance between the punch and the hole, and 3) the curvature of the punch edge, which affect the joining strength, are optimized, we can obtain sufficient joining strength of suspension arms.