Hybrid Welding Technique Research Articles

Effects of Nano-modification on the Microstructural Evolution and Mechanical Properties of AA7075/AA6061 Aluminum Alloy Joints Fabricated by Laser-MIG Hybrid Welding Technique

Effects of Nano-modification on the Microstructural Evolution and Mechanical Properties of AA7075/AA6061 Aluminum Alloy Joints Fabricated by Laser-MIG Hybrid Welding Technique

Effects of ultrasonic vibration on residual stress distribution and local mechanical properties of AA6061/Ti6Al4V dissimilar joints by resistance spot welding

The joining of dissimilar titanium and aluminum alloys has potential applications in railway and aerospace industries, owing to substantial weight reduction and better economic viability. In this study, the residual stress distribution and local mechanical performance of ultrasonic-assisted resistance spot welding (UaRSW) welds were investigated. The welding current, welding time, and electrode force of the RSW process were set as 9.0 kA, 350 ms, and 1.0 kN respectively, and the frequency and power of ultrasonic vibration were 20 kHz and 800 W. The residual stress was evaluated by X-ray diffraction (XRD) method and numerical simulation, and these methods showed a reasonable match. There was tensile residual stress distributed on RSW welds and UaRSW welds, but the value of residual stress was reduced by about 30% at welding nugget and 20% at heat affected zone (HAZ) with the ultrasonic vibration, the reduction of residual stress in UaRSW welds was attributed to the more uniform temperature distribution and lower plastic deformation resistant of AA6061. The welding peak temperature was decreased from 1673.4 °C to 1584.2 °C with the ultrasonic vibration, resulted from the modified Al/Ti contact surface and reduced contact resistance. The miniature tensile test results showed the improvement of mechanical performance by ultrasonic vibration. The maximum load of welding nugget region increased from 19.6 N to 22.3 N, and the elongation obtained 10% increase. This hybrid welding technique shows a potential to improve the quality of welds with ensured efficiency, which is also simple to realize automation in the manufacturing industry.

A novel method for fully penetrated U-rib-to-deck joints: Single-sided oscillating laser arc hybrid welding

U-rib-to-deck (RTD) joints represent one of the most critical and vulnerable welding details of orthotropic steel decks. Aiming for full penetration and high-level service performance, a novel method with single-sided oscillating laser-arc hybrid welding (OLAHW) technique was proposed for the RTD joint. The weld formation, microstructure and mechanical properties were extensively investigated. The results indicated that the porosity and lack of fusion (LoF) defects effectively suppressed with the beam oscillation during LAHW process. The OLAHW technique has good spatial accessibility with larger laser beam incidence angle of 20° Beam oscillation led to an increase in acicular ferrite in the fusion zone (FZ) while simultaneously a reduction of martensite in the heat effected zone (HAZ). This was related to the cooling time, and the thermal simulation results revealed that the OLAHW sample demonstrated comparable cooling times in both the Laser-FZ and arc-FZ. Consequently, beam oscillation can generated more homogeneous microstructures and microhardness. Although the microhardness of the OLAHW sample in the FZ was increased compared to the conventional arc welding (CAW) and LAHW sample, the highest microhardness value remained within acceptable limits (380 HV). Moreover, the ultimate tensile strength of the OLAHW weld sample increased by 7 % compared to the CAW weld sample. The application of the OLAHW technique demonstrates its feasibility for engineering applications in orthotropic steel decks manufacturing.

Enhancing all-position weldability and weld quality via an innovative laser-GMAW hybrid welding technique with copper liner

The change in welding position results in varied effects of gravity on the weld pool behavior. Conventional welding methods face difficulties when adjusting to welding in different positions. To address these challenges, a novel all-position welding technology, laser-GMAW hybrid welding with copper liner (CL), was introduced. CL serves a dual purpose. First, from flat to vertical welding, it supports the weld pool across various positions, thereby preventing root sagging or burn-through defects at the root of the weld in this range. Second, it facilitates accelerated weld pool solidification and inhibits its downward movement during vertical to overhead welding positions, forming the back continuous reinforcement. To quantitatively analyze the impact of CL on the temperature field during welding, finite element software was employed in this study. Moreover, the study also explored the effects of the size of the forming groove, welding current, and laser power on the weld appearance during overhead welding. As a result, with constant welding parameters, ideal welds with continuous back reinforcement were successfully achieved at five representative positions within the 0–180° range.

High-strength and crack-free welding of 2024 aluminium alloy via Zr-core-Al-shell wire

The 2000 series aluminium alloys are qualified for widespread use in lightweight structures, but solidification cracking during fusion welding has been a long-standing issue. Here, we create a zirconium (Zr)-core-aluminium (Al)-shell wire (ZCASW) and employ the oscillating laser-arc hybrid welding technique to control solidification during welding, and ultimately achieve reliable and crack-free welding of 2024 aluminium alloy. We select Zr wires with an ideal lattice match to Al based on crystallographic information and wind them by the Al wires with similar chemical components to the parent material. Crack-free, equiaxed (where the length, width and height of the grains are roughly equal), fine-grained microstructures are acquired, thereby considerably increasing the tensile strength over that of conventional fusion welding joints, and even comparable to that of friction stir welding joints. This work has important engineering application value in welding of high-strength aluminum alloys.

Fatigue inhomogeneity of thick 316L stainless steel joints fabricated by ultra-high power laser-MIG hybrid welding

The ultra-high power laser-MIG hybrid welding technique provides an effective method for thick-walled components joining, but the fatigue properties of joints are rarely reported. This research aims to unveil the fatigue behavior evolution of thick weldments along penetration direction. The fitted S-N curves are derived and results show that the fatigue strength presents a downtrend and failure location is transferred from heat affected zone to weld center in depth direction. The mechanism of fatigue crack initiation and propagation are discussed, and find that the shrinkage cavity in lower layer will reduce fatigue performance. The research results provide theoretical guidance for the service of ultra-high power laser-MIG hybrid welded joints.

Experimental and numerical investigation of laser-FSW hybrid welding technique for high strength materials

Friction stir welding (FSW) of high-strength materials and thicker plates has a number of challenges that are preventing widespread industry application such as (i) premature tool failure, (ii) selection of tool material and design, and (iii) weld productivity. A finite element (FE) based analysis for Laser-FSW hybrid welding technology is carried out in ABAQUS, commercially accessible FE software, to solve these typical difficulties. The thermal analysis of Laser-FSW hybrid technique is done using two moving heat sources for the case of 3.2 mm thick S45C steel plate. A negative moving heat source is placed as a replacement of the backing plate material in the high contact pressure region under the FSW tool. It was shown that the laser heat source needs to be 10 mm ahead of the FSW tool for achieving the duplex phase (Ferrite + Bainite/Martensite) microstructure.

Improving the mechanical property of dissimilar Al/Mg hybrid friction stir welding joint by PIO-ANN

Ultrasonic-stationary shoulder assisted friction stir welding (U-SSFSW) is a novel hybrid welding technique, which reveals promising prospect in joining Al/Mg dissimilar alloys. A thorough understanding of U-SSFSW process is imperative for the further application of this technique. Pigeon-inspired optimization (PIO) is a swarm intelligent optimization algorithm and is proposed in mathematical modeling and process optimization by artificial intelligence. In this study, PIO optimized artificial neural network (PIO-ANN) was firstly established to acquire the relationships between the inputs and output of the Al/Mg welding process by U-SSFSW technique. A reliable PIO-ANN was achieved and the joint with a tensile strength of 161 MPa was acquired under the PIO optimized parameters. This tensile strength is higher than any ever-reported results with the similar welding condition. The joint formation, microstructure, microhardness and fracture behaviors were systemically investigated based on the reported studies and the confirmation experiment of this study to explore the enhancing mechanism of U-SSFSW Al/Mg joint.

Interactive Phenomena in Hybrid KPAW–GMAW-P

A hybrid welding technique formed by combining keyhole plasma arc welding (KPAW) and pulsed gas metal arc welding (GMAW-P) is characterized by the complex interactions of the arc, droplet, keyhole, and weld pool. With the help of a high-speed video camera, zirconia particles, and a thermal camera, the complex interactive phenomena of the hybrid KPAW–GMAW-P process was analyzed. Owing to the formation of a direct-current path between the KPAW cathode (tungsten electrode) and the GMAW anode (welding wire), the ionized plasma arc was extended to the GMA side, causing an expansion of the GMA. The current at the GMAW droplet was diverged; thus, the Lorentz force promoted a more stable one pulse one droplet metal transfer mode compared with that of GMAW-P. The strong backward flow from the keyhole was suppressed because of the pull-push flow pattern on the top surface of the weld pool be-tween the two arcs. As the heat and molten metal in the weld pool were transported from the region near the GMA (high temperature) to the region near the plasma arc (low temperature), the weld pool temperature decreased.

Research on Laser-TIG Hybrid Welding of 6061-T6 Aluminum Alloys Joint and Post Heat Treatment

The 6061-T6 aluminum (Al) alloys was joined by the laser induced tungsten inert gas (TIG) hybrid welding technique. It mainly studied the influences of welding parameters, solution, and aging (STA) treatment on the microstructure and tensile properties of Al alloy hybrid welding joints. Microstructures of the joints were also analyzed by optical microscopy and transmission electron microscopy. Results showed that the laser induced arc hybrid welding source changed the microstructure of the fusion zone and heat effect zone. STA treatment effectively improved the mechanical properties of the softening area in the hybrid welding joint, whose values of the tensile strength and elongation were on average 286 MPa and 20.5%. The distribution of the reinforcement phases and dislocations distributed were more uniform, which improved the property of STA treated joint.

Research on the Microstructure Characteristic and Tensile Property of Laser-MIG Hybrid Welded Joint for 5A06 Aluminum Alloy

Laser-metal inter gas (MIG) hybrid welding technique provides higher overall productivity over the traditional fusion welding processes for joining medium-thick aluminum alloy. In this paper, laser-MIG hybrid welding experiment was performed by the TruDisk 12003 Laser and KUKA robot. The second fusion line, the laser-dominated region and laser-MIG hybrid-dominated region were introduced to this study to discuss the microstructure distribution. A three-dimensional finite element model was established by MSC. Marc to study the thermal field distribution of laser-MIG hybrid welding process. It found that the temperature in the laser-MIG hybrid-dominated region was much higher than the laser-dominated region. The formation of the second fusion line in the welded joint is mainly owing to the different heat effect of laser-arc hybrid-dominated region and laser-dominated region. The crystalline size of equiaxed dendrite grains in the laser-MIG hybrid-dominated region is finer than the laser-dominated region. In addition, the tensile property was measured to dissect the failure mechanism of the laser-MIG hybrid welding joints. The element content in fractured surface at the position of dimple and pore wall were comprehensively analyzed. The element content of Mg and O in pore wall are higher than dimple. In the solidification process, the growth of equiaxed dendrite grains is in part hindered by the existence of coarse pores in the laser-MIG hybrid-dominated region.

An Experimental Investigation of Magnetically Impelled Arc Butt Welding of Pipes: A Review

This paper describes a new development of circumferential welding of pipes. Circumferential butt welds are commonly used to join pipes in various industries, including power plants and automobile industries. Magnetically impelled arc butt welding process is a hybrid welding technique. It uses a rotating electric arc as its heat source and is known as efficient method for pipe welding. In this process heat is evolved prior to forging by an arc generated between two coaxially aligned pipes, this arc rapidly rotates along the circumferential edges of the pipes to be welded due to the electromagnetic force exerted by the interaction of arc current and magnetic field generated by the external magnetic system. The entire weld over the full joint thickness is made in one single operation, instead of using several passes as in conventional welding. The main emphasis of this review is to describe the different works carried out in the past which help full for providing the information for the future development of research work. Present study exposes the different works that has been done in the past for improving the weld quality.

Measurement of Strain During Tension Test of Welded Joint Using Multi-camera 3D Correlation System

This work concerns experimental research on the determination of deformation during uniaxial tension test of samples made of laser-arc hybrid welded joints. Steel sheet made of S355 steel with thickness 5 mm is butt-welded without gap using hybrid welding technique involving GMAW method with Yb:YAG laser beam. Samples used to the tension test are made from welded joints and base material. Universal strength machine Zwick&Roel Z100 is used with extensometer Multisens in all performed tension tests. The machine works with Dantec Q-400 Istra multi-camera 3D correlation system. System of three cameras mounted on a beam line is used for accurate measurement of the spatial deformations. Presented results of the research include strain fields measured for the entire tension cycle at the frequency 40Hz.

Microstructure and mechanical properties of laser-MAG hybrid welded thick-section weathered steel joint

Weathered steel (S355J2W) joint was prepared by laser-metal active gas hybrid welding technique. The microstructures of the joint were examined with an optical microscope and a scanning electron microscope. Microhardness measurement, tensile test, side bend test, and Charpy impact test were conducted to examine the mechanical properties of the joint. Experimental results show that S355J2W steel joint has a nail head shape with three different zones: weld metal, heat-affected zone (composed of overheated zone, normalized zone, and incomplete normalized zone), and base metal. The highest microhardness of the joint is 280 HV. All the joint specimens failed in the base metal. Average tensile strength of 502.6 MPa and yield strength of 380.9 MPa were achieved. A bending angle of 180° was obtained for all the joint specimens, and a crack less than 3 mm was detected. The average values of absorbed energy for the weld are 198.7 and 79.1 J at −40 and −20 °C, respectively. All the specimens exhibited a level of toughness as indicated by deformation at the fracture surface.

Influence of laser power on microstructure and mechanical properties of fiber laser-tungsten inert gas hybrid welded Mg/Cu dissimilar joints

Fiber laser-tungsten inert gas (TIG) hybrid welding technique has been developed for lap joining of dissimilar metals AZ31B Mg alloy to pure copper (T2). The influence of laser power on microstructure and mechanical properties of joints was investigated. The results indicated that acceptable joints could be obtained by adjusting the laser power to the range of 2000–3000 W. In particular, at the laser power of 2500 W the average tensile shear strength reached a maximum of 45.3 MPa, representing a 57% joint efficiency relative to the Mg sheet. Greater or less than 2500 W would cause over or under reaction at the interface, which resulted in the poor joint strength. The different morphologies including Mg–Cu eutectic structure, Mg–Cu intermetallic compound and Mg–Al–Cu ternary intermetallic compound were identified at the Mg/Cu interface. All the joints fractured at the Mg/Cu interface. However, the fracture mode was found to differ. For 2500 W the surface was characterized by tearing edge, while that with poor joint strength was almost dominated by smooth surface or flat tear pattern.

Hybrid Welding of AA5754-H111 Alloy Using a Fiber Laser

The new generation of high power fiber lasers presents several benefits for industrial application. Nevertheless, due to the small spot size of the laser, the fiber laser has difficulties in some welding applications. These shortcomings can be overcome by laser-arc hybrid welding technique such as laser-gas metal arc welding or laser-gas tungsten arc welding. In this work, a high power fiber laser was coupled to an arc welder and the AA5754-H111 magnesium aluminum alloy was welded. The trials were carried out using laser leading configuration. A new generation of high power fiber laser was used. The experimental trials included process parameters such as laser power, welding speed and arc current. Microstructure, microhardness and weld appearance were analyzed. The experimental results showed that laser leading configuration produces full penetration for some welding parameters. The obtained results worth a larger investigation based on the experimental design technique.

Analysis of droplet transfer mode and forming process of weld bead in CO 2 laser–MAG hybrid welding process

In this paper, CO 2 laser–metal active gas (MAG) hybrid welding technique is used to weld high strength steel and the optimized process parameters are obtained. Using LD Pumped laser with an emission wavelength of 532 nm to overcome the strong interference from the welding arc, a computer-based system is developed to collect and visualize the waveforms of the electrical welding parameters and metal transfer processes in laser–MAG. The welding electric signals of hybrid welding processes are quantitatively described and analyzed using the ANALYSATOR HANNOVER. The effect of distance between laser and arc ( D LA ) on weld bead geometry, forming process of weld shape, electric signals, arc characteristic and droplet transfer behavior is investigated. It is found that arc characteristic, droplet transfer mode and final weld bead geometry are strongly affected by the distance between laser and arc. The weld bead geometry is changed from “cocktail cup” to “cone-shaped” with the increasing D LA . The droplet transfer mode is changed from globular transfer to projected transfer with the increasing D LA . Projected transfer mode is an advantage for the stability of hybrid welding processes.

Phase Matching Mode Between Laser Pulse and TIG Arc in Hybrid Welding Process

In previous work, the low-power laser/arc hybrid welding technique was used to weld a magnesium alloy, and high-quality weld joints were obtained. For the pulsed laser and alternating current (ac) tungsten inert gas (TIG) arc, there are two typical phase matching modes between the laser pulse and the ac TIG arc: laser pulse acting on the positive wave, during which the tungsten electrode is the cathode, and laser pulse acting on the negative wave of ac TIG arc, during which the tungsten electrode is the anode. The welding plasma behaviors, welding penetrations, and weld bead appearances of the two phase matching modes are studied. The result shows that both the welding penetration and the weld appearance with laser pulse acting on the negative wave of TIG arc are better than those with laser pulse acting on the positive wave. The differences of the welding quality induced by the two phase matching modes are analyzed from the aspects of power input and spot force. Following this, the pulsed triggering and controlling system of pulsed laser and ac TIG arc was designed to control the phase matching mode in order to improve the welding quality in pulsed laser/ac TIG arc hybrid welding process.

Improvement of laser keyhole formation with the assistance of arc plasma in the hybrid welding process of magnesium alloy

In the previous work, low-power laser/arc hybrid welding technique is used to weld magnesium alloy and high-quality weld joints are obtained. In order to make clear the interactions between low-power laser pulse and arc plasma, the effect of arc plasma on laser pulse is studied in this article. The result shows that the penetration of low-power laser welding with the assistance of TIG arc is more than two times deeper than that of laser welding alone and laser welding transforms from thermal-conduction mode to keyhole mode. The plasma behaviors and spectra during the welding process are studied, and the transition mechanism of laser-welding mode is analyzed in detail. It is also found that with the assistance of arc plasma, the threshold value of average power density to form keyhole welding for YAG laser is only 3.3×10 4 W/cm 2, and the average peak power density is 2.6×10 5 W/cm 2 in the present experiment. Moreover, the distribution of energy density during laser pulse is modulated to improve the formation and stability of laser keyholes.

Friction Stir Lap Welding of Magnesium Alloy and Zinc-Coated Steel

AZ31 Mg alloy and zinc-coated steel were lap welded using friction stir welding technology. The microstructures and mechanical properties of the joints were examined. The lap shear tensile test results showed that the welding speed had a significant effect on the failure loads of the joints at the rotation speed of 1500 rpm. The maximum failure loads of 3.4 kN, 65% of that of the zinc-coated steel base material, could be obtained when the welding speed was 150 mm/min. Microstructure analysis showed that the intervention of zinc coat promoted the formation of Mg-Zn low-melting-point eutectic structure at the interface. The joining mechanism and the role of Zn coat on friction stir lap welding of Mg alloy and zinc-coated steel were put forward. (doi:10.2320/matertrans.M2009022) Magnesium alloys, the lightest of the structural metals, with a density two-thirds that of aluminum alloy are a promising structural material in vehicle fabrication. Zinc- coated steel with excellent corrosion resistance and good durability is a promising structural material in vehicle applications. In order to achieve combined properties of magnesium alloys and zinc-coated steel, development of reliable joints between magnesium alloy and zinc-coated steel is necessary. As a solid state welding technology, friction stir welding (FSW) process 1) can be used to join Mg alloys 2-6) and steel 7-14) and gets high quality joints than fusion welding technology. Such good merits are also expected for joining dissimilar metal materials. Watanabe et al. 15) studied the weldability of FSW AZ31 magnesium alloy/SS400 steel, and reported that the rotation speed, the position of the pin axis had a significant effect on the strength and the microstructure of the joint. The maximum tensile strength of a butt joint reached about 70% of that of the magnesium base metal and the fracture path was along the joint interface. Liu et al. 16) studied the lap joining of the dissimilar alloys of AZ31B Mg alloy and 304 steel by a laser-GTA hybrid welding technique. A transitional zone formed at the interface of the Mg-Fe during laser-GTA hybrid welding and Mg diffused into the matrix of Fe in the form of oxides and reacted in the transitional zone. During tensile testing, the joints fractured at the interface between the Mg alloy and the steel. The metallic oxides produced at the Mg-Fe interface deteriorated the mechanical properties of the joints. Up to date, current studies only report the weldability of FSW or a laser-GTA hybrid welding of magnesium alloy/ steel and the preliminary results of mechanical properties and microstructure evolution of the joints. 15,16) Investiga- tions on FSW of magnesium alloy and zinc-coated steel have not yet been reported. The object of the present study is to examine microstructure evolution and mechanical properties in FSW magnesium alloy and zinc-coated steel. In this study, AZ31 magnesium alloy and low carbon zinc- coated steel are selected for friction stir lap welding. The magnesium alloy sheet is put on the zinc-coated steel sheet. The inserting depth of the tool, being strictly controlled, is less than the thickness of the magnesium alloy. That is, the probe tip of the tool does not reach the surface of the zinc- coated steel sheet during welding. The emphasis is to study the interface microstructure evolution and clarify the joining mechanism.