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Characteristics of multi-pass narrow-gap laser welding of D406A ultra-high strength steel
摘要： A universal and applicable method to predict bonding quality in narrow-gap laser beam filler wire welding of D406A ultra-high strength steel was presented. Defect-free joint could be achieved under the predicted optimal welding condition, while the production efficiency of narrow-gap laser beam filler wire welding under optimized welding condition was about 3.75 times that of traditional tungsten arc welding currently used in practical industry. Compared with the tungsten arc welding joint, microstructure in the fusion zone of laser welded joint was more uniform, which brought out a less fluctuation in the microhardness of fusion zone along the thickness direction. The tensile strength of as-welded laser welding joint was slightly higher than that of as-welded tungsten arc welding joint while the elongation of the former increased by 15.9% over that of the latter. A binocular stereo three-dimensional scanning method was adopted to compare the residual distortion of D406A joints between laser welding and tungsten arc welding. Notably, the distortion of laser welded joint was about 21% of that of the tungsten arc welding joint. Narrow-gap laser filler wire welding is a feasible substitute for conventional tungsten arc welding in the fabrication of welded construction of D406A steel.
关键词： ultra-high strength steel,welding distortion,filler wire,narrow-gap laser beam welding,microstructure
更新于2025-11-28 14:24:20
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Hybrid laser-metal inert gas keyhole welding of thick steel/Al butt joints
摘要： Dissimilar joining of steel/Al joints has become more and more signi?cant in industrial applications with particular weight saving interest. However, directly welding of steel/Al joints even in thin thickness is very di?cult. In the present study, the hybrid laser-metal inert gas (MIG) source focused on the steel side in keyhole mode was introduced to weld steel/Al butt joints of 6 mm in thickness. E?ects of the laser o?sets on the weld shape, interface microstructures, and ultimate tensile strength (UTS) of the steel/Al joints were investigated. Sound steel/Al butt joints were obtained by using this hybrid laser-MIG keyhole welding process. By increasing the laser o?sets from 0.6 and 0.8 mm, the welds exhibited a better shape with a smooth appearance attributable to the reduced heat input. The positions through the thickness of the steel/Al joints played an important role in the morphology and thickness of the intermetallic compound (IMC) layers at the Al/weld interface. The IMC layers had a thick irregular morphology at the upper part and the lower part, while the layers at the middle part exhibited a relatively thin and uniform morphology. With some certain welding conditions, the Al/weld interface at the lower part of the steel/Al joints transformed to a welding-brazing mode from a fusion one. The island-shape structures were formed at the Al/weld interface, and the IMC layers were composed of Fe2Al5 layer and needlelike Fe4Al13 phases. The maximum UTS of 87.0 MPa was obtained at a laser o?set of 0.6 mm. Although the failure occurred in the IMC layers revealed a brittle fracture, the fracture morphology and locations were a mixed failure, which had a certain resistance to the crack propagation of the IMC layers.
关键词： laser-metal inert gas welding,ultimate tensile strength,keyhole welding,intermetallic compound,steel/Al joints
更新于2025-11-28 14:24:20
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Enhancement of weld strength of laser-welded joints of AA6061-T6 and TZM alloys via novel dual-laser warm laser shock peening
摘要： In this paper, an experimental study is presented on an investigation to improve the weld strength of laser-welded joints via post-processing by warm laser shock peening (wLSP). A dual-laser setup was utilized to simultaneously heat the sample to a prescribed temperature and to perform the wLSP process on the laser-welded joints of AA6061-T6 and TZM alloys. Joints in overlap and bead-on-plate configurations were created by laser welding by a high-power fiber laser and post-processed with wLSP. The tensile tests carried out on wLSP-processed AA6061-T6 samples demonstrate an enhancement in the strength by about 20% over as-welded samples and the ductility of samples processed by wLSP improved by 30% over as-welded samples. The bead-on-plate (BOP) welds of TZM alloy processed with wLSP demonstrated an enhancement in strength by about 30% and the lap welds processed with wLSP demonstrated an increase in the joint strength by 22%. Finite element analysis revealed that the depth and magnitude of compressive stresses imparted by wLSP were greater than room temperature laser shock peening (rtLSP), which contributed to the enhancement of the joint strength for processed samples.
关键词： Al6061,Warm laser shock peening,Strength improvement,Laser welding,TZM
更新于2025-11-28 14:24:20
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Influence of laser parameters on tensile shear strength of copper welds
摘要： The electrification of the power train in the automotive industry leads to the requirement of electrical connectors with high ampacities. These connectors are often realized using ultrasonic bonding technology. Substitution of ultrasonic welding by laser welding allows an increase of ribbon cross section by a factor of 5 and thus a similar increase of the maximum transferred current. The increased cross section leads to higher loads (at least by a factor of 5) applied to the weld seam during the process. To minimize the heat input, the weld seam strength in shear direction shall be maximized. The influence of different laser parameters on the ultimate tensile shear stress in lap joint configuration is investigated, based on representative specimen geometries (10 × 0.3 mm2). The variable parameters are: laser wavelength (IR around 1050 nm + frequency doubled 515 nm), focal diameters (42–300 μm), different temper conditions of the base material, process parameters (laser power 0.6–4 kW and feed rate 50–800 mm/s), and welding strategies (single pass welding, spatial beam modulation). The material used is Cu-ETP (>99.9% Cu). For all the investigated parameters, the observed failure mode is “fracture in the fusion zone.” The ultimate tensile shear stress for all experiments is around 188 N/mm2 even for parameter changes in the order of one magnitude. This is in contrast to the assumed relation between laser parameters and the mechanical properties. This contrast will be discussed.
关键词： load-carrying capacity,ductile welds,wobbling,fiber laser welding,shear strength
更新于2025-11-28 14:24:20
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Magnetic-Field-Induced Partial-to-Full Penetration Evolution and Its Mechanism During Laser Welding
摘要： The geometry and tensile strength of magnetic-?eld-assisted laser-welded Ti-6Al-4V joints have been studied. Due to the effects of the magnetic ?eld on the melt ?ow behavior during welding, the weld penetration depth increased from 4.27 mm (partial penetration) to 5.00 mm (full penetration) and the curvature of the weld cross-section decreased, improving the weld tensile strength. The fusion zone was enlarged, showing a maximum increase of 53.4% in area when the magnetic ?eld intensity was 90 mT. The increased penetration depth and fusion zone area suggest that application of a magnetic ?eld can improve the energy utilization of the laser during laser butt welding. The mechanism of the magnetic-?eld-induced penetration depth evolution is discussed. This study provides a new energy-saving method to obtain a full-penetration weld using laser welding at lower power.
关键词： Magnetic-field-assisted laser welding,Tensile strength,Energy utilization,Ti-6Al-4V,Weld geometry
更新于2025-11-28 14:24:20
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A comparison of microstructure and mechanical properties of laser cladding and laser-induction hybrid cladding coatings on full-scale rail
摘要： With the rapid development of high-speed and heavy-haul trains, the surface damages of rails are becoming more and more severe, and how to promote the surface strength of the rail and prolong its service life with high efficiency are becoming extremely important. Laser cladding (LC), with small heat affected zone (HAZ) and low dilution, is a promising novel way to hardface and repair the rail. However, there are two great barriers for the traditional LC to apply on full-scale rails: one is how to prevent the coating from cracking under the rapid heating and cooling cycle; the other is how to eliminate the martensite structure in HAZ, which may threaten the safety of railway transportation due to its high hardness and low fracture toughness and usually be forbidden in almost all the Railway Standards over the world. In this paper, laser-induction hybrid cladding (LIHC) was innovatively proposed to deposit Ni-based coatings on a full-scale rail. The cracking behaviors, microstructures and mechanical properties of the coatings and HAZs by LC, LIHC with induction pre-heating (pre-LIHC) and LIHC with induction post-heating (post-LIHC) were studied systemically. The results indicate that the cracking and martensite transformation occurred in the HAZ can only be prevented by post-LIHC, where fine pearlite with smaller pearlite block size and lower interlamellar spacing formed instead. Therefore, the abrupt change of microstructure and mechanical properties in the HAZ could be avoided by post-LIHC, and the hardness, strength and toughness of the rails can be improved significantly. The post-LIHC technology shows the potentiality to hardface and repair the full-scale rail.
关键词： Martensite,Microhardness distribution,Toughness,Laser-induction hybrid cladding (LIHC),Full-scale rail,Strength
更新于2025-11-28 14:24:20
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Interface characterization and mechanical properties of dual beam laser welding-brazing Al/steel dissimilar metals
摘要： The DP590 steel to AA7075 Al-alloy with lap configuration is successfully joined by dual beam laser welding-brazing without using filler metal. Through the introduction of the derived laser beam, the wetting angle, wetting distance and the thickness of intermetallic compound (IMC) layer are well improved and controlled. It is found that the wettability of liquid Al on steel improves with the increase of laser power, i.e. the wetting angle decreasing from 25.3° to 17.8° and the wetting distance increasing from 2.17 mm to 3.19 mm as the laser power increasing from 1.0 kW to 1.6 kW. Two kinds of IMC exist at brazing interface, one is η-phase (Fe2Al5) with flatten morphology closing to the steel side and the other is θ-phase (FeAl3) with needle-like morphology adjacent to the welding-brazing seam. The thickness of IMC layer increases from 8.37 μm to 12.12 μm with increasing laser power from 1.0 kW to 1.6 kW. Tensile test shows that both the wettability and the IMC thickness have influence on the welding-brazing joint strength. Poor wettability and too thick IMC layer will result in lower strength and fracture occurred in brazing interface. The optimal joint tensile strength of 123.7 MPa on average is achieved with the laser power of 1.4 kW.
关键词： Tensile strength,Welding-brazing,IMC,Dual beam laser,Al/steel dissimilar metals
更新于2025-11-28 14:24:20
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Development of a high strength Al–Zn–Si–Mg–Cu alloy for selective laser melting
摘要： Despite additive manufacturing processes are already widely used in several industrial applications, there are few materials that are specifically designed and optimized for these technologies. Currently, only few Al alloys are available on the market and employed for 3D printing of structural parts. In particular, SieMg bearing alloys are the most common Al alloys for additive manufacturing, featuring high processability but moderate mechanical properties. By this work, we studied the effect of Si addition on the hot cracking susceptibility of a high strength AleZneMgeCu alloy. A preliminary activity has been carried out by blending AleZneMgeCu and AleSieMg powders and analysing their microstructure and properties achieved after selective laser melting. Eventually a new AleZneSieMgeCu alloy has been designed, produced as powder alloy by gas atomization and tested. The microstructure and phase transformations of the new alloy has been investigated by synchrotron X-ray diffraction, differential scanning calorimetry and microscope analysis. The AleZneSieMgeCu alloy processed by selective laser melting featured a relative density of 99.8%, no hot cracks were noticed within the investigated microstructures. The ability of the new alloy to respond to aging starting from both as built and solution annealed conditions has been also evaluated. A good response to direct aging (directly from as built condition) was demonstrated, featuring yield strength and ultimate tensile strength of 402 and 449 MPa, respectively, and hardness of 174 HV after optimized aging at 165 (cid:1)C for 2 h.
关键词： Differential scanning calorimetry,Metal additive manufacturing,Mechanical properties,Synchrotron X-ray diffraction,High strength Al alloy
更新于2025-11-21 11:18:25
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SiC chip attachment sintered by nanosilver paste and their shear strength evaluation
摘要： In this study, a nanosilver paste was prepared by silver nanoparticles and organics, by which an SiC ship could be sintered on the direct bonding copper (DBC) substrate at 250–300 °C. The nanosilver paste firmly sintered the SiC chip and DBC substrate, and die attachment had an excellent bonding interface. Die-shear results showed that the shear strength increased with the increase of sintering temperature and was more than the value required by the MIL-STD-883J standard. When high assisted pressure was applied, the sintering temperature could be lowered and sintering time also could be shortened to realize attaching high bonding strength. The assisted pressure also influenced the porosity of the bondline. X-ray non-destructive method was used to measure the porosity of die attachment. The results showed that the shear strength of die attachment decreased with the increase of bondline porosity.
关键词： Nanosilver paste,Bondline,Die attachment,Shear strength
更新于2025-11-21 11:18:25
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Homogeneous Anodic TiO <sub/>2</sub> Nanotube Layers on Ti–6Al–4V Alloy with Improved Adhesion Strength and Corrosion Resistance
摘要： Hexagonal TiO2 nanotubes (TNTs) arrays are generally fabricated on Ti-based substrates for some biomedical purposes, but the TNT layers constructed on conventionally processed Ti alloys are usually inhomogeneous because the substrates typically contain both the α and β phases. In this work, high-pressure torsion (HPT) is applied to obtain a saturated single α-phase microstructure in Ti–6Al–4V alloys via strain-induced β phase dissolution. Homogeneous anodic TNT layers with three different morphologies, one-step nanoporous, one-step nanotubular, and two-step nanoporous structures, are electrochemically fabricated on the ultrafine-grained (UFG) Ti–6Al–4V alloy substrates after HPT processing, whereas the TNT layers prepared on coarse-grained substrates are normally inhomogeneous. More notably, the TNT layers show significantly improved adhesion strength to the UFG substrate as well as better corrosion resistance compared to those on the conventionally processed Ti–6Al–4V substrates. X-ray diffraction analysis, scanning electron microscopy in combination with electron backscatter diffraction, and transmission electron microscopy indicate that the improvement is due to a larger dislocation density in the UFG substrate as well as strain-induced β phase dissolution.
关键词： high-pressure torsion,homogeneity,TiO2 nanotubes,adhesion strength,strain-induced phase transformation
更新于2025-11-21 11:03:13