Laser Welding Method Research Articles

Analysis and Optimization of Laser Beam Welding Parameters for Aluminium Composite (Al-Zn-Cu Alloy) by Grey Relational Optimization

Aluminium and its composites are widely used in production to enhance the strength of lightweight objects. In this study, an AA7075/SiC composite was fabricated using a stir casting route. Multi-objective optimization and finite element analysis were performed with various process parameters on a manufactured aluminium composite (AA7075 + SiC) undergoing a laser beam welding process. Four welding parameters, i.e., pulse frequency, power, welding speed (transverse), and wire size were taken for laser welding as per the L-9 orthogonal array for experimental study. Tensile strength, deflection, temperature distribution, Rockwell hardness (fusion zone), and Rockwell hardness (heat affected zone) were taken as output parameters after welding. The standard deviation objective weighting–grey relational optimization method optimized the process parameter. ANSYS APDL 23 software was utilized to simulate the entire laser welding method with a cylindrical heat source to predict the temperature distribution in the butt-welded plates. This software uses finite element analysis and gives a deviation of only 5.85% for temperature distribution with experimental results. This study helps to understand the effect of various parameters on the welding strength of the aluminium composite.

Mechanism analysis of dual wavelength laser welding AlN-PC joint based on microtexture treatment

High-strength interfacial bonding between ceramics and transparent polymers is hardly to be achieved, especially in the field of optical packaging of biochips. This paper proposes a novel laser welding method that enhances the joint strength between aluminum nitride (AlN) ceramic and polycarbonate (PC) by laser surface microtexturing. The study investigates the influence of welding methods and microtextures on welding effectiveness, elucidating the bonding mechanisms of the joints. The obtained results showed that dual wavelength laser welding effectively achieves the connection between AlN ceramic and PC. Laser microtexturing increases surface roughness and contact area, leading to stronger mechanical interlocking and overall joint strength. The highest shear strength reached up to 14.66 MPa with longitudinal grooves microtexture. The laser microtexturing improves the hydrophilicity of the AlN surface, facilitating more effective bonding between the materials. The bonding mechanisms at the joint interface include both mechanical interlocking and chemical bonding. Microtexturing improves the stress distribution at the joint interface. The formation of C-O-Al chemical bonds at the interface effectively enhances the joint strength. Longitudinal grooves microtexture exhibit a higher substrate fracture rate due to stress concentration and capillary pores. In contrast, staggered square holes microtexture provide superior mechanical performance through uniform stress distribution and robust mechanical interlocking.

Enhancing strength performance of laser welded 7075 aluminum alloy joints with TiC nanoparticle-mixed filler powder

Precipitation-strengthened 7075 aluminum alloy (AA 7075) is a crucial structural material widely utilized in the aerospace industry. Nevertheless, the achievement of highly strengthened joints of this alloy remains a challenge because of its susceptibility to composition dilution and defect formation during welding. In this study, the method of powder-filled laser welding was employed to weld AA 7075-T6 plates, utilizing both AA 7075 powder and a mixed powder of AA 7075 and 5 wt % TiC nanoparticles as the filler. To investigate the impact of the filler on the mechanical properties of the welded joints, their microstructure, phase constitution and tensile strength were measured and analyzed. Moreover, the transient temperature and the forming process of the joints during laser welding were captured. The results indicate that the joints are heat-treatable when the filler contains the AA 7075 powder. The ultimate tensile strength (UTS) of the joints can reach 500 MPa as a result of the η′ phase precipitated during heat treatment. The incorporation of TiC nanoparticles into the AA 7075 powder led to a refinement of grains, a reduction in porosity within the joints and an increase in the UTS by up to 540 MPa, which is 91.5 % of the base metal. Further theoretical estimation suggests that Orowan strengthening as well as grain size strengthening due to the Hall-Petch effect are the main strengthening mechanisms for the improved tensile performance. The powder-filled laser welding method also provides a flexible approach for designing compositions of filler material.

Comparative investigation on the microstructure and corrosion properties of surfacing cobalt alloys by various methods

This study applies three different welding methods, namely tungsten inert gas (TIG) welding, laser welding, and plasma arc welding, to perform cobalt alloy surfacing on austenitic stainless steel substrates, and compares their microstructure and corrosion properties. The results reveal that samples obtained through all three methods exhibit excellent metallurgical bonding between the austenitic stainless steel substrate and the cobalt alloy surfacing layer, with no observed defects such as cracks, pores, or inclusions. Among them, the cobalt alloy surfacing layer produced by laser welding shows a finer and more uniform microstructure, displaying a distinct growth direction along the surfacing direction away from the interface. Additionally, electrochemical polarization curve testing demonstrates that the corrosion resistance of the laser-welded surfacing layer surpasses that of TIG welding and plasma arc welding, exhibiting a lower corrosion rate. This study offers valuable insights into the selection of cobalt alloy surfacing welding methods on austenitic stainless steel substrates and the evaluation of the corrosion properties for the cobalt alloy surfacing layer, providing essential guidance for engineering practices in the power plant valves.

In-situ monitoring method of femtosecond laser welding between glass and copper with acoustic emission

The use of femtosecond laser welding has created new possibilities for connecting glasses and metals, revolutionizing the fabrication and assembly of advanced electronic components. However, monitoring the connection process during femtosecond laser welding is challenging due to the small heat-affected zone and brief interaction time. This study utilizes acoustic emission to monitor femtosecond laser welding and introduces the “Sum of Relative RMS” feature to correlate connection formation with acoustic emission signals in glass-copper welding. The mechanism and signal occurrence trends during welding are explained through in-situ signal monitoring and offline scanning electron microscopy characterization. Additionally, a Convolutional Neural Network is enhanced by increasing the convolutional kernel size, integrating multi-dimensional features, and incorporating prior knowledge via a customized loss function, resulting in an increase in the accuracy of successful welding detection from 89% to 95%. This research provides new insights into the monitoring of femtosecond laser glass-metal heterogeneous welding.

Experimental analysis of the effect of ultrasonic vibration on porosity suppression in narrow gap laser welding

Abstract The welding process has a wide range of applications in aerospace, military manufacturing, machinery, and other fields, and with the continuous improvement of welding technology requirements, the inhibition of porosity in the welding process is also increasing. This study, through the narrow gap laser welding characteristics and porosity formation mechanism of the depth of analysis, for the existing narrow gap laser welding method exists in the side wall of the weld fusion is poor porosity, poor uniformity of organizational properties and other issues, proposed ultrasonic-based welding method to achieve effective inhibition of porosity. The experimental analysis of ultrasonic vibration on the formation of porosity is carried out based on narrow-gap laser welding. The peak sound pressure of narrow gap welding increases when the ultrasonic current amplitude changes from 24A to 32A. Under different ultrasonic vibration conditions, the number of welds without applied ultrasound was as high as 95, while the number of porosities gradually decreased to 48 with the increase of applied ultrasound amplitude from 12% to 37%. Furthermore, as the ultrasonic amplitude increased, the residual height decreased by 0.45 ml. In addition, at fixed ultrasonic amplitude, with the increase of laser power, the porosity increased from 0.89% to 2.21%, and the average diameter of the porosity increased from 0.29 mm to 0.43 mm. The porosity for the porosity diameter of less than 200 μm was reduced to 0.020%. The percentage of stomata with a diameter greater than or equal to 200μm increased to 2.098%. This study analyzes the inhibition effect of ultrasonic vibration on porosity to a certain extent. Moreover, the inhibition effect of ultrasonic vibration in narrow gap laser welding is significant and the smaller the laser power under the same amplitude, the better the inhibition effect, which provides a valuable reference for the research of the narrow gap laser welding process.

A comparative study of microstructure and corrosion resistance in DP980 steel joints under different laser welding method

Three different laser welding methods were used to welding 2 mm DP980 steel butt joint, which were laser welding, laser-TIG hybrid welding and laser powder feeding (CoCrNi) welding respectively. An observational analysis was carried out in terms of microstructure, mechanical properties and corrosion resistance. It was discovered that a central microstructure of laser welding and laser-TIG hybrid welding the weld was dominated by slatted martensite. The laser powder feeding welding has resulted in a remarkable reduction of cylindrical crystals and an increased number of isometric crystals in weld center due to the addition of CoCrNi powder. Microstructure was further refined in incomplete phase transition zone by three different laser welding methods. The tempered martensite was also formed in the tempering zone, which softened the joint. The hardness values decreased considerably and tensile samples were also fractured at this location. Comparison with corrosion resistance of their joints through polarization curves and impedance spectra shows that laser powder feeding joint > laser joint > laser-TIG hybrid joint. The corrosion resistance of laser and laser-TIG hybrid joints in the base metal (BM) > heat affected zone (HAZ) > weld zone (WZ) is shown based on scanning vibrating electrode technique (SVET) localized area testing data at different time intervals. The laser powder feeding welding enhances the density of passivation film by reacting Cr to form Cr2O3, thereby improving corrosion resistance of entire joint.

Design and study of an autonomous linear welding robot with mechanical referencing system

The biggest challenge for welders is the byproduct of welding, like smoke, heat, and ultraviolet light. It is the process of melting two or more metal pieces to the point of fusion, allowing them to cool, and then connecting the pieces. Arc welding, Metal Inert Gas (MIG) Welding, Tungsten Inert Gas (GTAW or TIG) Welding, gas welding, resistance welding, laser welding, and other methods can all be used to complete the procedure. The welder has many health hazard issues, so the modal is designed to convert the manual welding operation to a fully automatic welding operation. A four-wheeled linear welding robot with a mechanical arm can perform the task. The detection method of the robot is to reference and analyze the structure of the welding job mechanically. There are many options for welding to make it effective. Like the welder can change the thickness of the welding, the thickness of the welding will be uniform. There is one more option for stitch welding for the initial welding operation. This process will enhance the product quality and quantity and minimize health issues as the person is not in direct contact with smoke, heat, or ultraviolet light. The primary purpose of the research is to automate the linear welding process economically so that it can get into the market and workers can be protected from industrial pollution. In addition, the parameters of welding are optimized so that the wastage of material can be reduced. Further, an experimental study is presented, which demonstrates that the robot successfully performs the welding operation continuously without human intervention.

Fiber laser beam welding of additive manufactured 316L austenitic stainless steel with wrought 2507 super duplex and wrought 904L super austenitic stainless steels: Crystallographic texture, microstructure, and mechanical properties

In this study, 316L parts were produced by selective laser melting (SLM) method, one of the additive manufacturing (AM) processes. Since the size limits of the SLM system prevent large parts from being produced in one piece, there is a need to weld the parts produced with SLM to each other in a final process as an alternative option. For this reason, AM 316L parts are joined with full penetration by fiber laser welding. Welded joints of metals with different properties are widely used in various industries. Accordingly, welding combinations of AM 316L and wrought (W) 2507 super duplex stainless steel (W2507) and wrought (W) 904L super austenitic stainless steel (W904L) sheets, which are stainless steel types with superior mechanical properties, were carried out. Weldability, microstructure, texture, and mechanical properties of AM316L-AM316L, AM316L-W2507, and AM316L-W904L stainless steels welded by fiber laser welding method were investigated in detail. According to the results obtained, it was observed that the as-built AM 316L microstructure consists of cellular grains, and the AM316L-AM316L, AM316L-W2507, and AM316L-W904L laser welded joints are composed of a fine microstructure. While no pores and porosity were observed in As-built AM 316L, nano-sized particles were seen in welded joints' transmission electron microscope (TEM) images. According to EBSD analysis, epitaxial solidification was observed in the weld center of all samples, while grain orientations were mostly random. According to the kernel average misorientation (KAM) analysis, a high dislocation density was detected, especially at the weld metal grain boundaries of the AM316L-W2507 sample. Again in this sample, the lowest grain orientation spread (GOS) value and the highest Taylor Factor value were determined. Depending on the laser welding process, it was determined that some grains in the weld metal center of all samples showed a relatively strong texture (<011>//welding direction). In contrast, the grains in other parts of the weld metal (WM) showed a weaker texture. According to the mechanical test results, the welded joints' mechanical properties were generally lower than the as-built AM316L, W904L, and W2507 base metals. Among welded joints, the highest tensile and yield strength was found in the AM316L-W2507 sample, while the highest ductility was found in the AM316L-W904L sample. It has been determined that the toughness results are very close to each other. As a result of the tensile and impact tests, it was seen that the fractures took place in the ductile mode.

Experimental study on the fatigue crack growth rates of welded ultra-high strength steel plates

The assessment of the fatigue crack growth rate behavior of welded structural components made of ultra-high strength steels (UHHS) is very important to gain a comprehensive understanding of these materials under high-cycle fatigue loadings and to enhance their applications in the construction industry. The literature on the fatigue crack growth rates of welded ultra-high strength steel plates with nominal yield strengths higher than 690 MPa is very scarce and only very limited research has been done thus far to provide the Paris’ Law fatigue material constants for welded UHSS components in terms of the base metal (BM), the weld metal (WM), and the heat-affected zone (HAZ) regions, which are essential for fatigue life prediction. Hence, the fatigue crack growth rates of butt-welded UHSS plates with three grades (S700, S960, and S1100) are experimentally investigated in this study using Paris’ Law for these three different regions of the welded components. Gas metal arc welding (GMAW) and laser welding (LW) methods are adopted to analyze the influence of welding methods on each steel grade with respect to their static and fatigue strength, microstructural changes, and hardness. In the fatigue crack growth rate test, it was observed that the S700 base material shows the lowest fatigue crack propagation resistance amongst these three grades. In welded components, laser welding outperforms gas welding in terms of the fatigue crack growth resistance. Comparisons of fatigue crack growth behaviors are made among all three tested UHSSs as well as with those from the literature.

Microstructure and Mechanical Properties of TA2/Q235 Laser Weld Joint with Copper Interlayer.

For the dissimilar metal welding needs of TA2 titanium and Q235 steel, preliminary trials were conducted using laser welding methods, and the results showed that the addition of a copper interlayer and the bias of the laser beam toward the Q235 side allowed for an effective connection. The welding temperature field was simulated using the finite element method, and the optimum offset distance of 0.3 mm was obtained. Under the optimized parameters, the joint had good metallurgical bonding. Further SEM analysis showed that the microstructure of the bonding area between the weld bead and Q235 was a typical fusion weld pattern, while that of the bonding area between the weld bead and TA2 was in brazing mode. The microhardness of the cross-section showed complex fluctuations; the microhardness of the weld bead center was higher than that of the base metal due to the formation of a mixture microstructure of copper and dendritic Fe phases. The copper layer not involved in the weld pool mixing had almost the lowest microhardness. The highest microhardness was found at the bonding site of TA2 and the weld bead, mainly due to the formation of an intermetallic layer with a thickness of about 100 μm. Further detailed analysis revealed that the compounds included Ti2Cu, TiCu and TiCu2, showing a typical peritectic morphology. The tensile strength of the joint was approximately 317.6 MPa, reaching 82.71% of that of the Q235 and 75.44% of the TA2 base metal, respectively. The fracture occurred in the unmixed copper layer.

A new laser welding method of two transparent plastic parts based on reflector assisted method

It is a challenging work to joint two transparent plastic parts using traditional laser welding because the absorptivity of transparent plastic on short wavelength (800–1000 nm) laser energy is very low. During the laser welding of two transparent plastic parts, although laser absorber and long wavelength (1600–2000 nm) laser can obtain the high-strength weld joint, the problems of unattractive weld joint or pollution will occur when laser absorber is used, and the laser energy utilization coefficient is about 70% when long wavelength laser energy is used. To address this issue, this paper proposes a new production method for the absorber-free laser welding of two transparent plastic parts based on reflector assisted method. From three-dimensional thermal model, it can be found that the simulation data of the modified Gauss cylindrical body heat source show better agreement with the experimental result than those of Gauss surface heat source and Rotary-Gauss body heat source. In addition, for the same the weld joint width on the contact surface, the reflector assisted laser welding method can decrease the laser energy consumption by about 20%. Moreover, the maximum shear force of weld joint can be up to 1315 N. Under the same process parameters, the reflector assisted method can increase the shear strength of weld joint by 15.3%. Hence, the reflector assisted method has good application and promotion value in laser welding two transparent plastic parts.

Research on the hybrid joining process and failure mode of laser welding and riveting on QP980 steel/CFRP

Combining the advantages of riveting and laser welding methods, and the characteristics of stepped rivets, excellent QP980 steel/CFRP weld-rivet hybrid joint joints were obtained and the effects of different laser powers on the welded joints were investigated. It was found that this welding method can reduce the damage to CFRP by heat input and obtain joints with favorable mechanical properties with maximum tensile shear load over 10 kN. Three failure characteristics of joints with this hybrid joining process were found: failure of steel joint, failure of CFRP, and failure of both steel joint and CFRP. The stress distribution characteristics in case of CFRP failure were simulated with ABAQUS. Different heat inputs resulted in different melting amounts of steel and CFRP, and these melted materials entered the assembly gap due to thermal expansion, thus changing the load-bearing characteristics of the hybrid joint. This load-bearing structure is not just a simple riveted and welded structure, but also forms a mechanical interlocking effect.

Mechanical Properties of Laser Welded Joint of Copper and Steel Dissimilar Metals

In this research project, copper and stainless steel were connected by two laser welding methods: straight seam welding and swing welding. Then, electronic tensile test machine, X-ray diffractometer, scanning electron microscope and metallographic microscope were used to analyze the tensile properties, macroscopic and microscopic structure morphology and phase of the welded joint. Based on the experimental results, we determined that the strength of the straight seam welded joint was higher. Because of the intermetallic compound near the weld in the swing welding process, it leads to stress concentration, crack cracking and strength reduction. In addition, the oscillating laser beam also leads to the disorderly direction of columnar crystal and coarse structure, which makes the joint strength decrease.

Multi-scan picosecond laser welding of non-optical contact soda lime glass

Nowadays, ultrafast laser welding has been widely used in chip labs, microelectronic systems (MEMS), and micro-medical implantable devices, etc. The welding of the non-optical contact transparent materials has become a new challenge to promote the practical application of ultrafast laser welding, and the existing research mostly through spatially and/or temporally shaping the laser under the single scanning. In this context, we adopt a multi-scan picosecond laser welding method to weld the non-optical soda lime glass that has a gap up to ∼5 μm. A welding region of 12 × 1 mm2 and a welding strength of 6.5 MPa is achieved by using a 1064 nm, 13 ps, 50 kHz picosecond laser. In addition, the effects of the scanning number (0–35), laser power (0–3.2 W), focus position (-113.4 µm- +18.9 µm) on the welding performance are systematically studied, while the intrinsic mechanism of multi-scan welding of the non-optical contact sample is also revealed. Finally, the optimal welding parameters of the multi-scan (scanning number 15, laser power 2.5 W, focus position −37.8 µm) is used in welding of cylinder samples with a radius of 12.7 mm and the results shows a well welding strength and sealing performance. The welding method proposed in this paper is simple and can provide a new technical solution for the practical application of ultrafast laser welding.

Study of the properties of high silicon aluminum alloy by laser welding

High silicon aluminum alloy is a kind of high-performance electronic packaging material, due to its excellent thermal conductivity, low thermal expansion coefficient, and low density. The heat affected zone (HAZ) of conventional welding techniques is too wide to weld the high silicon aluminum alloy, as wide HAZ will improve risk of cracking. Laser welding with narrow HAZ, high joint strength, and good morphology, has been considered as a promising method to weld high silicon aluminum alloy. Herein, the surface morphology, microstructure, and microhardness of laser welding joint between Al-50wt.%Si and Al-27wt.%Si alloys were investigated. It has been found that welding speed at 3 mm–5 mm/min can significantly reduce the hydrogen pores and cracks in laser welding joints. Also, the key paraments of laser welding to control the quality of joints are power and pulse width, while the former one is mainly controlling the joint width and the latter one is significantly changing the joint depth. Along the horizontal direction of laser welding joints, the microhardness increases firstly and then decreases, with the highest microhardness of 167 HV in the weld zone. Because the laser welding method could produce uniform microstructure of joints, the microhardness of joints is uniform along the longitudinal direction. The tensile properties of welding samples are almost the same with the properties of the Al-50wt.%Si base materials.

Effect of Microalloying on Microstructure and Mechanical Properties of Laser Weld of PHS Steel

The laser welded joint of 2000MPa cold rolled annealed hot pressed steel (PHS) is easy to break during cold rolling. In this paper, the laser welding method is used to butt weld four kinds of PHS2000 with a thickness of 3.5mm. The four kinds of PHS2000 steel are added with elements of 0% Nb, 0.04% Nb, 0.06% Nb + Cr and 0.08% Nb + Cr. The microstructure of the four kinds of welded joints is compared and analyzed. The mechanical properties of the four kinds of joints are compared through hardness test and tensile test. The results show that after adding 0.04% Nb, residual austenite appears in the weld zone and fully quenched zone, the width of columnar crystal decreases, the average hardness of the weld zone decreases from 595HV to 408HV, and the tensile strength increases from 608MPa to more than 800MPa. For chromium containing steel, the increase of niobium content can reduce the size of columnar crystal in weld zone.

Effects of powder feeding rate on porosity and tensile strength of powder feeding laser welded Al-30wt.% B4C composite with the addition of Al powder

Al-B4C metal matrix composite is an advanced neutron absorption material. In order to obtain a wider application in spent nuclear fuel storage and transport, the welding technique is essential for Al-B4C composites. In this paper, powder feeding laser welding (PFLW) method was used to weld Al-30wt.% B4C composite. During the experiments, Al powder was used as the filler metal, the effects of powder feeding rate on porosity, neutron shielding ratio and tensile strength of the joints were investigated by using micro-CT (micro computed tomography), OM, SEM and TEM. It is found that PFLW has a significant weld porosity suppression effect, and a joint efficiency (UTS) of 87% is obtained in PFLW of Al-30wt.% B4C composite with the powder feeding rate of 1.2 g/min. The neutron shielding ratio of the joint reduced by 3% due to the volume ratio of AlB12C2 (a B-rich reaction product) reduced by 7.6% when the powder feeding rate is 1.2 g/min. The results illustrate the great potential of PFLW in welding Al-B4C composites.

Optimization of processing parameters for pulsed laser welding of dissimilar metal interconnects

An experimental and numerical investigation is performed into the optimal processing parameters for the fabrication of aluminum and copper dissimilar lap joints using a pulsed laser welding (PLW) method with a wobble strategy. A circle packing design algorithm is first employed to select 43 representative combinations of the peak laser power and tangential welding speed. The selected parameters are then supplied to a computational fluidic dynamics (CFD) model of the PLW process to predict the melt pool geometry (i.e., interface width and penetration depth) and copper concentration. The simulation results are used to train three surrogate models to predict the melt pool geometry and copper concentration for any combination of the PLW parameters within the design space. Finally, the processing maps constructed using the surrogate models are filtered in accordance with three quality criteria to determine the PLW parameters that produce dissimilar joints with no cracks or pores in the fusion zone and enhanced mechanical and electrical properties. The validity of the proposed optimization approach is demonstrated by evaluating the shear strength, intermetallic compound (IMC) formation, and electrical contact resistance of experimental samples produced using the optimal welding parameters. The results confirm that the optimal parameters yield a high shear strength of 1209 N and a low electrical contact resistance of 86 µΩ. Moreover, the fusion zone is free of defects, such as cracks and pores.

Comparative Study on the Behavior of Keyhole in Analogy Welding and Real Deep Penetration Laser Welding.

In deep penetration laser welding, the behavior of the keyhole has an important influence on the welding quality. As it is difficult to directly observe the keyhole and detect the pressure inside the keyhole during metal laser welding, theoretical analysis and numerical simulation methods are commonly used methods in studying keyhole behavior. However, these methods cannot provide direct real information on keyhole behavior. In this paper, a method of analogy welding is proposed, in which high speed gas is used to blow the liquid to generate the keyhole. Relevant process experiments were conducted to explore keyhole behavior in analogy welding and real deep penetration laser welding. The pressure balance of the keyhole, both in analogy welding and real deep penetration laser welding, were analyzed. The laws obtained in analogy welding and real deep penetration laser welding are similar, which indicates that studying keyhole formation and the maintenance principle using the analogy welding method proposed in this paper may be helpful for deep understanding of the keyhole formation and maintenance mechanisms in real deep penetration laser welding.