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Effect of graphene on corrosion resistance of Micro-arc oxidation coatings on 6061/7075 dissimilar laser-MIG hybrid welded joint
摘要： Corrosion behavior of a laser-metal inert gas hybrid (Laser-MIG) welded joint with dissimilar aluminum alloys was investigated. Micro-arc oxidation (MAO) coatings with and without graphenes were prepared on the surface of the welded joint. The effects of graphenes on the structure and corrosion resistance of the MAO coatings were studied. The welded joint was divided into five zones to investigate corrosion inducements in different zones. The heat-affected zone of 7075Al (7-HAZ) was found to be most susceptible to corrosion. Although the substrates in different zones had heterogeneous microstructures and phase compositions, the MAO coatings in different zones displayed relatively uniform surface morphology, structure, and phase composition. The MAO treatment significantly improved the corrosion resistance of welded joints. In addition, ceramic-graphene composite coatings exhibited slightly better corrosion resistance than a simple coating without graphenes due to structural changes in the coating.
关键词： Corrosion resistance,Aluminum,Graphene,Laser-MIG hybrid welding,Micro-arc oxidation
更新于2025-11-21 11:18:25
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Laser welding of electron beam melted Ti-6Al-4V to wrought Ti-6Al-4V: Effect of welding angle on microstructure and mechanical properties
摘要： Electron beam melting (EBM) is an established powder-bed additive manufacturing process for small-to-medium-sized components of Ti-6Al-4V. For further employing EBM on fabricating large-scale components, an effort has been made by joining EBM-built Ti-6Al-4V plates to wrought counterparts using laser welding, and the welding angles between EBM build direction and weld bead have been chosen as 0°, 30° and 45°. The influence of the welding angles on the microstructure, microhardness of base metals, fusion zone, and heat-affected zones, as well as the macro tensile test have been characterized. The microhardness of each zone is determined by the local microstructure, and the macro tensile properties largely depend on the EBM base metal due to the internal defects generated during the EBM process. The effect of welding angles on tensile strengths is not significant, while the elongation drops from 9.4% to 5.8% as the welding angle increases from 0° to 45°. The mechanism of stress during uniaxial tension on EBM base metal is discussed based on the stress state of columnar grains and the internal defects.
关键词： Defects,Microstructure,Mechanical properties,Additive manufacturing,Welding
更新于2025-09-23 15:23:52
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Preparation of graphene oxide with large lateral size and graphene/polyimide hybrid film via in situ “molecular welding” strategy
摘要： In this letter, we report an "ultrasonication-free" direct exfoliation method to obtain graphene oxide with large lateral size (LGO). The average size of LGO sheets is about 50 lm * 50 lm. The g-LGO film shows a superior in-plane thermal conductivity after the graphitization treatment. Furthermore, the in situ "molecular welding", using polyimide (PI) to weld up the GO sheets, is conducted to improve the performance of hybrid thermal conducting film. The thermal conductivity of g-LGO/PI film is 1053.975 ± 8.762 W m-1 K-1, superior to that of the g-LGO film and g-SGO/PI. The direct preparation method to obtain GO with large lateral size, followed by such an in situ "molecular welding" strategy by PI, provides a promising way to fabricate graphene-based film for efficient thermal management.
关键词： Molecular welding,In situ polymerization,Large lateral size,Thermal properties,Carbon material
更新于2025-09-23 15:23:52
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Laser impact welding: Investigation on microstructure and mechanical properties of molybdenum-copper welding joint
摘要： Due to their excellent properties, molybdenum and copper are widely used in the electronics industry. However, the welding of molybdenum and copper is difficult, which limits their application prospects in the field of microelectronics devices. This paper describes a novel method for Mo/Cu welding in micro devices: laser impact welding (LIW). The experimental results found that welding improved with the increase of laser energy. The springback and interface wave in the welding area were observed by optical microscope and scanning electron microscope (SEM) and the results showed that the shapes of the interface wave were flat and zigzag. Energy dispersive spectroscopy (EDS) showed little or no diffusion of elements at the welding interface. Tensile shear test results of the welded specimens showed that there were two kinds of failure forms: solder joint failure and solder joint edge failure. The nano-hardness of the materials in the welding area increased compared with the raw materials.
关键词： Laser impact welding,Springback,Interface wave,Molybdenum,Mechanical properties,Copper
更新于2025-09-23 15:23:52
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Microstructure and mechanical properties of Ti/Al dissimilar joints produced by laser-MIG welding–brazing
摘要： We butt-welded AA6061 aluminum alloy to Ti6Al4V titanium alloy, dissimilar light metals, by using laser-MIG hybrid welding–brazing without grooves. The parameters of the laser and arc were optimized to produce sound joints with good formation and mechanical properties. The microstructure of the layer of intermetallic compounds (IMCs) was investigated by scanning electron microscopy and energy dispersive spectroscopy. We also tested the tensile strength of the joints with and without reinforcement. The morphology and thickness of the IMCs varied throughout the joints. A continuous thin layer of TiAl3 appeared on the top surface of the Ti6Al4V, on which some rod-like IMCs grew toward the fusion zone. In the upper region of the butt plane, because more heat accumulated there from the high-power laser coupled with the MIG arc, double-layer IMCs with a thickness of ～ 10.0 μm formed, composed of TiAl (near the Ti alloy) and TiAl3 (near the fusion zone). In the lower region of the butt plane, the double-layer IMCs became continuous and uniform, the serrated morphology disappeared, and the thickness of the IMC layer decreased to 4.0 μm. On the backside of the joint, the thickness of the compound layer (TiAl3) was about 1.0 μm. The average tensile strengths of the reinforced and unreinforced joints were 226 MPa and 210 MPa, respectively, which are up to 88% and 81% of the AA6061 tensile strength, respectively.
关键词： dissimilar joint,titanium alloy,intermetallic compounds.,Laser-MIG hybrid welding–brazing,aluminum alloy
更新于2025-09-23 15:22:29
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Optimization of laser welding process parameters in dissimilar joint of stainless steel AISI316/AISI1018 low carbon steel to attain the maximum level of mechanical properties through PWHT
摘要： In this investigation, laser welding process parameters have been optimized for austenitic stainless steel (AISI316) and low carbon steel (AISI1018) materials by using Taguchi based grey relational analysis. Butt joint trials were carried out using 3.5 kW di?usion-cooled slab CO2 laser by varying laser power, welding speed, and focal distance. The optimum parameters have been derived by considering the responses such as tensile strength and microhardness. The optimal parameters are laser power 2600 W, welding speed 1.5 m/min and focal distance 20 mm. The responses of the optimized parameters obtained using the grey relational analysis has been veri?ed experimentally. Formerly, the e?ect of post weld heat treatment (860 °C and 960 °C) on the mechanical properties, microstructure and chemical composition of weld zone of the optimal welded joint was investigated by using tensile test, microhardness, bend test, optical microscope, SEM and EDS. The results show that the optimal welded joint had good mechanical properties after post weld heat treatment so that the best tensile strength 475.112 MPa was obtained at 960 °C. Due to the elimination of chromium carbide and reduce grain size, the heat treated samples show high corrosion resistance at 960 °C in comparison to 860 °C.
关键词： Metallurgical properties,Laser welding,Mechanical properties,Dissimilar metals,PWHT,GRA
更新于2025-09-23 15:21:21
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Microstructures and Mechanical Properties of Dissimilar Al/Steel Butt Joints Produced by Autogenous Laser Keyhole Welding
摘要： Dissimilar Al/steel butt joints of 6.0 mm thick plates have been achieved using fiber laser keyhole welding autogenously. The cross sections, interface microstructures, hardness and tensile properties of Al/steel butt joints obtained under different travel speeds and laser beam offsets were investigated. The phase morphology and thickness of the intermetallic compound (IMC) layers at the interface were analyzed by scanning electronic microscopes (SEM) using the energy-dispersive spectrometry (EDS) and electron back-scattered diffraction (EBSD) techniques. The results show that travel speeds and laser beam offsets are of considerable importance for the weld shape, morphology and thickness of IMC layers, and ultimate tensile strength (UTS) of Al/steel butt joints. This proves that the IMC layers consist of Fe2Al5 phases and Fe4Al13 phases by EBSD phase mapping. Increasing laser beam offsets from 0.3 mm to 0.7 mm significantly decreases the quantity of Fe4Al13 phases and the thickness of Fe2Al5 layers at the interface. During tensile processing, the Fe2Al5 layer with the weakest bonding strength is the most brittle region at the interface. However, an intergranular fracture that occurred at Fe2Al5 layers leads to a relatively high UTS of Al/steel butt joints.
关键词： laser keyhole welding,IMC layers,Al/steel joints,tensile properties,EBSD phase mapping
更新于2025-09-23 15:21:21
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Visualization of the molten pool of the laser beam submerged arc hybrid welding process
摘要： Submerged arc welding is currently the predominant industrial welding process for joining various steel grades in the plate thickness range of about 40 mm. A high energy input and the associated component distortion are unavoidable due to the high number of welding layers. By combining the conventional submerged arc welding process with the laser beam welding process to form a common hybrid welding process, this welding task can be mastered in only two welding layers by means of layer-counter-layer technology. This considerably reduces the welding time and thermally induced component distortion to a minimum due to the symmetrical energy input. A characteristic feature of a hybrid welding process is the formation of a common weld pool. In previous studies, the mixing of the molten pool has already been proven using chemical analysis methods. In the context of this paper, the shaping of the hybrid weld pool is also discussed. The molten material is expelled out of the joining zone by means of a gas pressure surge. Subsequently, a light section sensor was used to scan this area and produce a three-dimensional image from the formerly molten weld seam area. This shows that a single contiguous melt pool is produced. Finally, the first one-sided welds with full penetration and backing will be presented and discussed.
关键词： Hybrid welding,Submerged arc welding,Thick plate welding,Laser beam welding
更新于2025-09-23 15:21:01
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New approaches on laser micro welding of copper by using a laser beam source with a wavelength of 450 nm
摘要： Laser micro welding is specified with welding geometries below 1 mm and is used with increasing demand for contacting electronic components such as battery and fuel cells. Fiber lasers with a wavelength in the near infrared range (IR, λ ≈ 1 μm) have established themselves for this purpose. The laser welding process allows processing of parts in the micron range but reduces the surface quality of the processed parts at the same time. Furthermore, weld defects can occur due to process instabilities caused by the low absorptivity (<5%) of copper for infrared radiation. Therefore, alternative laser beam sources and processes have to be established, to avoid these negative effects on the weld seam quality. Laser beam sources in the visible wavelength range (VIS) prove to be an alternative due to an increased absorption of the laser energy in copper-based alloys. This paper presents the observation of laser micro welding of Cu-ETP and CuSn6 specimen with a thickness between 150 μm and 1 mm. The diode laser is specified by a wavelength of 450 nm and a nominal output power of 150 W. The surface roughness of the weld seam and the overall weld seam geometry for heat conduction welding are investigated. The laser energy absorption is measured using two integrating spheres to compare the results quantitatively to measurements conducted with laser sources of 1070 nm and 515 nm. For detailed observation high speed imaging is used to observe the melt pool dynamics. Simulations are conducted, to optimize the dimensioning of optics and laser beam source. Finally, the possible use of the novel laser beam source for various technical joining applications is discussed and evaluated and the influence of the use of protective gas is observed.
关键词： heat conduction welding,scanner system,laser micro welding,copper,modelling,450 nm
更新于2025-09-23 15:21:01
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Comparative Study on Microstructure and Aluminum Distribution Between Laser Beam Welding and Electron Beam Welding of Tia??6Ala??4V Alloy Plates
摘要： Ti–6Al–4V alloy plates with a thickness of 4 mm were joined by electron beam welding (EBW) and laser beam welding (LBW). The comparison of LBW and EBW was performed according to grain morphology, microstructure, aluminum distribution, and microhardness of the joints. Results indicate that compared with LBW joint, more equiaxed grains are observed around the central zone of the EBW joint. The microstructure in fusion zone (FZ) of EBW joint presents more uneven with obviously coarser acicular martensite α′. Moreover, the aluminum element content of EBW joint is substantially lower, which demonstrates a more significant burning loss behavior in EBW process. The lower aluminum content in the upper center areas of the joints is attributed to the more significant element burning loss caused by higher temperature, whereas more uniform aluminum distribution in the upper part of the joints is ascribed to stronger convection form within the upper part of the joint. In addition, the characteristics of convection and thermal field within the molten pool are recognized as vital factors influencing the aluminum distribution. The lower microhardness profile in FZ of the EBW joint is principally attributed to coarser acicular martensite α′ and lower aluminum element in EBW joint.
关键词： Electron beam welding,Microhardness,Microstructure,Burning loss,Titanium alloy,Laser beam welding
更新于2025-09-23 15:21:01