High-strength Joints Research Articles

基于Ni中间层的铝合金与高强钢激光诱导TIG复合焊接

基于Ni中间层的铝合金与高强钢激光诱导TIG复合焊接

A Review of Using Response Surface Methodology in Friction Stir Welding

Friction Stir Welding (FSW) is a comparatively new joining process that has exhibited many advantages over traditional arc welding processes, including greatly reducing distortion and eliminating solidification. Friction stir welding used to join high strength joints aluminum pipes. The present work explains review and overview of Response Surface Methodology in Friction stir welding which contain the basic connotation of the process, mechanical properties and Suggested model in FSW process. This paper gives the review of basic concepts of response surface methodology in Friction Stir Welding for alloys on process parameters. It is established that response surface methodology in FSW of alloys is appropriate an increasingly overripe technology with many commercial applications.

Development of nickel-based filler metal for producing high-strength joints in critical products from heat-resistant materials

Development of nickel-based filler metal for producing high-strength joints in critical products from heat-resistant materials

고강도 강재를 적용한 겹침이음 접합부의 블록전단거동 및 강도

고강도 강재를 적용한 겹침이음 접합부의 블록전단거동 및 강도

Laser seal welding of end plug to thin-walled nanostructured high-strength molybdenum alloy cladding with a zirconium interlayer

The effects of micro-alloying method on microstructure and properties of laser-welded molybdenum alloy joints were investigated, and zirconium was selected as the additive material. In the fusion zone of the joint without zirconium addition, the segregation of MoO2 on the grain boundary were observed, leading to the brittle fracture of the joint. When zirconium ring was added into the fusion zone, ZrO2 was preferentially formed in the grain interior which alleviated the segregation of MoO2. The grains at fusion zone were refined under the effect of heterogeneous nucleation particles of ZrO2, thus it changes the fracture mechanism of welded joint from intergranular fracture to cleavage fracture. When zirconium foil was pre-placed at the overlapped interface of cladding tube and the end plug, a parasitic brazing zone was generated due to the high melting point and high thermal conductivity of molybdenum. Tensile strength of the welded joints matched that of the base metal. These results highlight possibilities for achieving high strength joints when joining refractory materials with intrinsic brittleness in complex joint configurations.

Scaling effects during friction stir welding of aluminum alloys with reduced tool aspect ratios

Friction stir welding (FSW) is a solid-state welding technique providing a number of unique advantages such as the weldability of various similar and dissimilar material combinations, the absence of process gases and filler materials, and high mechanical joint strengths. The operation principle is based on a rotating tool consisting of shoulder and probe. Due to friction-induced heat input, generated by the tool, the work pieces can be firmly bonded by dynamical deformation across the interface. However, the general application for this method is restricted by properties such as accessibility, high demands on the clamping technique, and in particular comparatively high process forces in the range of several kN. Process forces arise during the interaction between welding tool and the joining material and are decisively influenced by the dimensioning of shoulder and probe. In this study, a decrease of the process force could be achieved by tool scaling, which means the stepwise reduction of the shoulder and probe diameter. Furthermore, a method is developed to adapt the welding conditions for scaled FSW-tools. The study was carried out with a robotised FSW setup on 2-mm thick EN AW 6060 T66 sheets. The results show a decrease in process force of up to 60% and a spindle torque reduction of up to 80%.

Influence of cathodic dip painting on the mechanical strength of material-adapted composite/metal joints

The flow drill joining concept (FDJ) allows the load adjusted joining of continuous fiber reinforced thermoplastics (FRTP) and metallic sheets without auxiliary joining elements. As there is no scathe done to the fiber reinforcement, a radial realignment of the fibers leads to high-strength joints with high lightweight potential. In terms of their use in automotive lightweight construction, an important requirement for joining technologies is the resistance to temperature loads and chemicals, applied in the production processes, e.g., in vehicle lacquering. Therefore, force flux aligned FDJ-joints were investigated in cross tension and shear testings, after passing through a serial cathodic dip painting (CDP) process. The results show that the CDP-treatment does not adversely affect the quasi-static properties of the tested FDJ-joints, as they resist shear loads up to 2900 N and cross tension loads of about 1100 N, both, before and after the lacquering process.

Effects of minor Zr addition on the microstructure and mechanical properties of laser welded dissimilar joint of titanium and molybdenum

The capability to join molybdenum (Mo) and titanium (Ti) is of great interest for applications in aerospace and nuclear energy fields. Despite the importance, no effective methods have been developed to avoid the embrittlement problem of heat affected zone (HAZ) on the side of molybdenum plate to produce high strength joints. In this study, by adding zirconium (Zr) to the molten pool, ultimate tensile strength (UTS) of the joints were increased from about 350 MPa to about 470 MPa which reached more than 90% of that of the Ti base metal (BM). During this process, an ultra-fast diffusion behavior of Zr in HAZ on the side of a Mo plate (HAZMo) was observed. Electron back-scatter diffraction (EBSD) analysis revealed that diffusion distance of Zr in HAZMo was up to 0.75 mm, which was confirmed by the ZrO2 particles presented at both grain boundaries (GB) and the interior of the grains in HAZMo. Formation of ZrO2 particles not only inhibited the growth of recrystallised grains in HAZMo but also suppressed the precipitation of volatile MoO2 at GBs in HAZMo. These results highlight the possibilities for strengthening HAZ of refractory metals with intrinsic brittleness through fusion zone alloying.

Self-assembly of reduced Au atoms for vertical interconnections in three dimensional integrated circuits

Self-assembled Au atoms were employed to bond vertical interconnection for chip-stacking applications without pressure and at a temperature of 50 °C. In this process, Au ions in an electroless plating solution are forced through a thin gap between Si chips. The Au atoms, reduced from Au ions, self-assemble between pairs of Cu pillars, and void-free connections are achieved with high joint strength. In addition, it has been shown that the Au grains grow epitaxially with the Cu grains. This epitaxial growth offers a potential method to align the Au grains to enhance electrical performance for future high frequency applications.

Dissimilar joining of carbon/carbon composites to Ti6Al4V using reactive resistance spot welding

A 2D C/C composite with a high porosity (low strength) and a 3D C/C composite with a low porosity (high strength) were investigated for dissimilar joining to Ti6Al4V via reactive spot welding. It was determined that infiltration of melted metal into the composite and formation of a continuous thin TiC layer at the interface of the joints were the dominant joining mechanisms. The 2D C/C composite with a flat surface was successfully joined to Ti6Al4V due to the infiltration of the melted Ti6Al4V into its porous content. On the other hand, it was necessary to drill rectangular grooves onto the surface of the 3D C/C composite to facilitate the infiltration of the melted Ti into the composite, which produced high-strength joints. Surface patterning was determined to be necessary to join the components with mismatching coefficients of thermal expansion. The strength of the 2D C/C composite and Ti6Al4V joints was found to be 7 MPa, while the maximum strength of the groove-patterned 3D C/C composite and Ti6Al4V joints reached 46 MPa.

Investigation of mechanical properties of cold-rolled, annealed and welded semi-finished products from the test alloys of Al-Mg system, economically alloyed with scandium

The results of experimental investigation of mechanical properties of sheet metal from an experimental aluminum alloys Al–Mg system alloyed with scandium have been represented. It was established that the deformed and annealed semi-finished products of these alloys have higher strength properties. Testing of welded samples made from these semi-finished products showed high corrosion resistance and strength of welded joints.

Brazed Joint Interface Bonding Strength of AR500 Steel and AA7075 Aluminium Alloy

The joining of aluminium alloys to steels has been extensively studied, especially in the automotive sector. However, aluminium alloys are known to be difficult to join with steels when methods involving fusion welding are used because of the hot cracking problem. Hence, a high-strength joint between these dissimilar metals would be of benefit especially in reducing the weight of products. In this work, the torch-brazing method was applied to join AR500 steel with AA7075 aluminium alloy using Al–Si–Zn base filler metal at various flame times. The effects of the brazing work on the intermetallic phase formation and the mechanical strength of the joints were investigated. In this work, the maximum shear load obtained was 6460 N and the presence of the intermetallic phases had reduced the shear strength of the brazed joints. However, the torch-brazing process using Al–Si–Zn filler metal had successfully facilitated the joining of these dissimilar metals.

Experimental Study on the Laser Transmission Joining of Polystyrene and Titanium.

To address the difficulty of joining polystyrene (PS) and titanium by laser transmission joining, two methods—laser treatment of the titanium surface and oxygen plasma treatment of the PS surface—are used to compare the laser transmission joint strengths of the different treatment methods. The results of the experiments find that joining with titanium can be achieved only when PS is treated with oxygen plasma. When the laser-treated surface of titanium is jointed to the oxygen plasma-treated PS, the joint strength is the highest, reaching 6.5 MPa. The joining mechanism of oxygen plasma-treated PS and laser oxidation-treated titanium was investigated by joint tensile failure mode, joint micromorphology observation, contact angle and surface free energy experiments, and X-ray photoelectron spectroscopy (XPS). The results show that the failure mode of the joint is an interfacial failure; the size and amount of bubbles play an important role in the joining strength, and the joints with fine and uniform bubbles have the highest joint strength. The two surface treatment methods can improve the surface energy of the joints, improve the compatibility between the two joining surfaces, and enhance the joint strength. Ti–C and Ti–O chemical bonds are formed at the joints, which are the main reason for the increase in joint strength.

Solder-free electrical Joule welding of macroscopic graphene assemblies

Welding is an important convenient methodology to realize robust coalescence of individual metallic or polymeric objects through local melting of contact boundaries. However, how to firmly conjoin the refractory graphene-based materials via conventional welding remains an open question because of their non-melting nature. In this work, we report an efficient solder-free approach to weld individual macroscopic graphene assemblies via electrical Joule heating. Graphene-based materials with different architectures, including graphene fibers, films, and foams, are covalently welded together with high joint strength. The welding mechanism was studied by in situ transmission electron microscope and molecular dynamic simulations. We attributed the unique welding behavior to the defect-facilitated cross-linking between graphene layers at contact interface. The facile electrical Joule welding strategy provides a new reliable connection method for carbon materials, enabling the direct assembling of macroscopic graphene materials to sophisticated three-dimensional configurations.

Influence on the weld strength of high-strength fine-grained structural steels by thin-film-coated GMA welding electrodes

The increasing demand for high-strength fine-grain steels for the purpose of reducing the weight of steel structures and increasing payloads, is driving forward the development of fine-grain steels. However, with the currently available welding consumables, it is not possible to achieve the strengths of modern fine-grain steels with a grade of S1300QL in the weld metal. As a result, there is a need for novel welding consumables, which guarantee high-strength joints. The application of thin, functional layers on GMA welding electrodes by a PVD coating process makes it possible to influence the mechanical-technological properties to an extent which cannot be achieved by state-of-the-art technology. The sputtering of different elements on the substrate material of GMA electrodes and the layer thickness has an influence on the welding process and the welding metal. Especially, the influence on the microstructure by a niobium coating of different layer thickness is presented. Furthermore, the changes in the mechanical properties of the weld metal depending on the layer thickness or rather the niobium content are shown. In particular, the fine-grain and carbide-forming effect of niobium and the influence on the mechanical properties are presented. Here niobium contents between 0.5 wt.-% and 1.5 wt.-% are in the focus of investigations.

Double fillet lap of laser welding of thin sheet AZ31B Mg alloy

In this paper, we describe the experimental laser welding of thin sheet AZ31B using double fillet lap joint method. Laser welding is capable of producing high quality weld seams especially for small weld bead on thin sheet product. In this experiment, both edges for upper and lower sheets were subjected to the laser beam from the pulse wave (PW) mode of fiber laser. Welded sample were tested their joint strength by tensile-shear strength method and the fracture loads were studied. Strength for all welded samples were investigated and the effect of laser parameters on the joint strength and appearances were studied. Pulsed energy (EP) from laser process give higher effect on joint strength compared to the welding speed (WS) and angle of irradiation (AOI). Highest joint strength was possessed by sample with high EP with the same value of WS and AOI. The strength was low due to the crack defect at the centre of weld region.

Cyclic response analysis of high-strength self-compacting concrete beam-column joints

In this paper, finite element analysis software “DIANA” is implemented to simulate quasi-static cyclic loading test results of three full-scale beam-column joints cast with high-strength self-compacting concrete (HSSCC). The specimens were designed according to the New Zealand concrete standard (NZS3101 2006). Material models for concrete and steel were calibrated based on the physical characteristics of the materials derived either from laboratory tests or using expressions available in literature. Two-dimensional curved-shell elements were used in modelling the specimens. As the specimens were designed following the code requirements for seismic actions, bond between the reinforcement and concrete was assumed as perfect. In order to obtain a more representative prediction, both the longitudinal and transverse reinforcement were modelled in their actual locations. Pushover analyses were first conducted to check the mesh sensitivity; after which the modelled specimens were subjected to reversed cyclic loading histories applied in the experimental tests. Seismically important response parameters such as damping, stiffness, concrete and steel contributions in the joint shear resistance, joint shear deformation, strain development in the joint stirrups, elongation of the plastic hinge zone, development of compressive stress, and cracking pattern were extracted from the analytical predictions and compared to the experimental results. It was found that the adopted modelling and analysis approach was capable of predicting cyclic performance of HSSCC beam-column subassemblies with reasonable accuracy.

Closure to “Beam-to-CFT High-Strength Joints with External Diaphragm. II: Numerical Simulation of Joint Behavior” by Cristian Vulcu, Aurel Stratan, Adrian Ciutina, and Dan Dubina

Closure to “Beam-to-CFT High-Strength Joints with External Diaphragm. II: Numerical Simulation of Joint Behavior” by Cristian Vulcu, Aurel Stratan, Adrian Ciutina, and Dan Dubina

Discussion of “Beam-to-CFT High-Strength Joints with External Diaphragm. II: Numerical Simulation of Joint Behavior” by Cristian Vulcu, Aurel Stratan, Adrian Ciutina, and Dan Dubina

Discussion of “Beam-to-CFT High-Strength Joints with External Diaphragm. II: Numerical Simulation of Joint Behavior” by Cristian Vulcu, Aurel Stratan, Adrian Ciutina, and Dan Dubina

Friction stir lap welding of 6061-T6 Al to Ti-6Al-4V using low rotating speed

To obtain high joint strength, friction stir lap welding (FSLW) was used to join 6061-T6 aluminum alloy and Ti-6Al-4V alloy using low rotating speeds. The effect of tool rotating speed on the microstructure and lap shear failure loads of the joints was mainly discussed. Results showed that voids were easily observed at the lap interface when small penetration was used. The void was eliminated by decreasing the rotating speed. The hook acted as a “lock” during the lap shear test. At the inner side of hook, metallurgical bonding was formed due to the formation of intermetallic compounds. The joint failed through Al alloy and showed higher lap shear failure loads than other joints when the rotating speed of 300 rpm was used.