Weld Quality Research Articles

Effects of welding parameter on the microstructure and mechanical properties of friction stir-welded non-heat treatable alloy AA5083

A non-traditional friction stir welding (FSW) is used to joint the materials that are challenging to join together by utilizing the fusion welding processes. This study investigated the influence of the welding speed ratio (υ) to rotating speed (ꞷ) on the weld quality and found the relationship between mechanical qualities and welding peak temperature. With increase in (ꞷ/υ), there was a corresponding rise in peak temperature, leading to the expansion of both the nugget zone (NZ) and the softened region within the joint. As (ꞷ/υ) increased because of the increased heat, as a result in the joint hardness decreased. The joint ultimate tensile strength (UTS) increased with increasing (ꞷ/υ), then decreased, with the maximum value reaching 84.75% of the base material at a (ꞷ/υ) of 9.6. As a result of the low (ꞷ/υ), a flexural crack formed. In comparison to the base material, the thermos mechanically affected zone (TMAZ) and the nugget zone (NZ) showed greater impact strength. The impact strengths first increased and subsequently dropped with an increase in (ꞷ/υ). The tensile specimens’ fracture surfaces showed dimples, signifying a ductile mode of fracture.

Optimising the quality of several welds in a metal-inert gas arc joining of AA6082 and AA7075 using the grey-based Taguchi technique

In recent times, welding procedures have become increasingly crucial for fabrication and manufacturing businesses. Gas metal arc welding, also known as metal inert gas (MIG) welding, has attracted much attention because of its versatility. Its benefits include low capital needs, high deposition rates, high productivity, and simplicity in adjusting to automation. It has drawn much interest because of its versatility in welding metallic materials and ease of automation. This work's objective is to maximise the multi-performance properties of the aluminium alloys AA6082 and AA7075's MIG-welded butt junction by using a hybrid grey-based Taguchi technique. During MIG welding, With the L9 Taguchi orthogonal array, the welding speed, gas flow rate, and current were optimised. Weld joint integrity has been evaluated using the fusion zone's Vickers microhardness, per cent elongation, tensile strength, and yield strength. The ideal welding current for the MIG process is 140 A, the perfect welding speed is 10 mm/min, and the excellent gas flow rate is 18 lit/min. The material showed 159.68 MPa of tensile strength, 112.79 MPa of yield strength, 16.79% of percentage elongation, and 70.95 HV of hardness under optimal conditions. With a 63.99% contribution to the process, welding speed greatly affected the weldments' overall performance. The confirmatory test confirmed the optimisation procedure also demonstrated that optimising numerous welded joint performance factors may be achieved effectively with the grey-based Taguchi approach.

Welding electrical connections between battery sheet metal materials and additively manufactured (AM) aluminum components: The effect of surface roughness

The integration of additive manufacturing's design versatility with a push for electrification can lead to unique innovations. In this context, when discussing welded joints, their quality and reliability play a significant role. The restricting factor for the use of laser powder bed fusion of metal (PBF-LB/M) additive manufactured (AM) parts is often their surface quality in the as-built state. In addition, the surface quality changes when part plane orientation changes. In this study, AlSi10Mg aluminum test samples were additive manufactured in seven different build angles. The AM samples were glass bead blasted after manufacturing, and the surface roughness of the joint surface area was optically measured. After the measurement, the AM samples were welded to nickel-plated copper and aluminum sheet metals. A continuous wave single-mode fiber laser with scanner optics was used to carry out the welding experiments in lap joint configuration. The structural and mechanical properties of the welds were evaluated by the macroscopic images of weld cross sections and tensile testing of the samples. The electric resistivity of the samples was also tested. Based on the measurement results of the samples, the impact of surface quality was discussed. The results indicated that there was no clear effect of building angle on the final weld quality. The worst surface quality in the joint area was on the test pieces in which the joint surface was facing down toward the build plate.

Influence of tool rotational speed in butt-joint friction stir welding (FSW): a thermo-mechanical simulation of AA6061

Friction Stir Welding (FSW) is a solid-state welding technique that involves joining two pieces of material by rotating a non-consumable pin at high RPM. This rotation generates heat through friction between the tool and the plates, enabling the welding process without the need for filler metal. Invented by the British Welding Institute (TWI) in 1991, FSW is renowned for creating strong welds and is widely used in the automotive and aerospace industries, in those industries the aluminum alloys are indispensable due to their unique combination of properties. This study focuses on how variations in rotational speed influence temperature distribution, the width of the heat-affected zone, and Von-Mises stress distribution in welded aluminum alloy 6061 sheets, this research aims to provide a comprehensive understanding of these effect, therefore the findings are expected to contribute to optimizing FSW parameters and enhancing weld quality. The analysis was conducted using the finite element method and ALTAIR software.

Performance analysis of various fluxes in different variants of the TIG welding process on the quality of welding

The tungsten inert gas (TIG) welding process is widely used in various industries for its ability to produce high-quality welds at a low cost. However, TIG welding struggles with welding thick stainless steel in a single pass, reducing production efficiency. To address this, new TIG variants such as activated TIG (A-TIG), flux bound TIG (FB-TIG), and flux zone TIG (FZ-TIG) have been developed to enhance penetration in austenitic stainless steel. This study investigates the effects of TiO2 and Fe2O3 flux on 304 stainless steels welded using A-TIG, FB-TIG, and FZ-TIG processes. Results show a slight increase in the depth-to-width (d/w) ratio for A-TIG and FB-TIG, while FZ-TIG achieved a 59% higher d/w ratio compared to autogenous TIG welding. The increased penetration is attributed to the reversal Marangoni convection and arc constriction. Microstructural analysis reveals a higher delta ferrite content in A-TIG and FZ-TIG welds due to increased heat input. Additionally, FZ-TIG welds exhibited an 11.5% higher microhardness compared to autogenous TIG welds. FZ-TIG welding enhances penetration and mechanical properties effectively.

Weld quality monitoring in friction stir lap joining of dissimilar Al6061 to polycarbonate using thrust–torque-based process stability signatures

The joining of dissimilar aluminium-based alloys to thermoplastic polymers is highly challenging which indicates the necessity of friction welding procedures. The present work addresses the degrees of steadiness in welding thrust-torque to monitor the lap weld contour of aluminium alloy (Al6061) overlapped on polycarbonate sheet or vice versa using friction stir welding. The primary objective was to compare the monitoring capability of the weld non-uniformity by using raw signals and stability signature of welding thrust and stirring torque. Further, these stability indices were used for the prediction of weld mechanical behaviour using response surface methodology. The stability signatures were found to be a better indicator of weld profile unevenness than raw signals as it was an amplified version of the local deviations in welding thrust-torque. Improved strength efficiency up to 49% was noticed in PC-Al welds due to improved process stability at intermediate tool traverse (55 mm/min) and revolving speeds (1100 rpm). The stability in stirring torque was better indicator of weld quality features than tool thrust steadiness in Al-PC lap while it was reversed in PC-Al lap. Thus, the thrust force instability was mostly indicated the joint ductility while combined steadiness in thrust-torque were essential for the prediction of weld strength. The higher stability index in tool thrust (≥7.5) with ample torque steadiness (5–8) can upgrade the Al-PC weld strength (≥20 MPa), whereas intermediate thrust stability (6–6.5) with high stable torque (≥7) can uplift the joint strength (≥25 MPa) in PC-Al welds.

The energy synergistic mechanism of coaxial heterogeneous-wavelength hybrid laser beam and its effect on welding molten pool dynamics for aluminum alloy

The coaxial heterogeneous-wavelength hybrid laser beam (HW-HLB) heat source featuring a “Gauss + Flat top” energy distribution, which integrates the 1080 nm and 915 nm laser beam, was employed in this paper to achieve excellent stability in the welding of aluminum alloy. The interaction mechanism between aluminum alloy and laser beams with different wavelengths was taken as a point cut to explore the synergistic enhancement mechanism of coaxial HW-HLB . A thermal-fluid coupling model for HW-HLB welding, considering the synergistic effect of dual lasers, was established according to the welding experiment results. The influence of fiber laser power (PF) and diode laser power (PD) on the molten pool flow behavior during welding process was investigated. The dynamic of the molten pool and the maintenance mechanism of the keyhole were elucidated through in-situ monitoring experiments and thermal-flow simulations. The results indicated that, in contrast to the single fiber laser beam (FLB), the power density of HW-HLB presents a significant increase, which results in the “avalanche-like” augmentation of the plasma plume, as well as deeper depth of the keyhole. The energy synergistic enhancement effect of coaxial HW-HLB with PF=2800 W and PD=2500 W performs stronger and thorough changes in the morphology and flow behavior of the molten pool. The introduction of 915 nm laser beam improves the multi-reflection behavior in the inner keyhole. The findings of our research provide a theoretical framework for improving the stability of the laser weld molten pool and the quality of welds in aluminum alloys through the implementation of HW-HLB.

Optimization and Analysis of Refill Friction Stir Spot Welding (RFSSW) Parameters of Dissimilar Aluminum Alloy Joints by FE and ANN Methods.

The quality of the refill friction stir spot welding (RFSSW) process is heavily dependent on the selected welding parameters that influence the resultant joint characteristics. Thermomechanical phenomena integral to the process were investigated using finite element (FE) analysis on two dissimilar materials. This FE analysis was subsequently validated through controlled experiments to ensure reliability. An artificial neural network (ANN) was employed to create a neural model based on an experimental setup involving 120 different sets of welding parameters. The parameters adjusted in the experimental plan included pin penetration depth, rotational speed, retention time, and positioning relative to material hardness. To assess the neural model's accuracy, outputs such as maximum temperature and normal stress at the end of the welding process were analyzed and validated by six data sets selected for their uniform distribution across the training domain.

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.

Alternatives to Reduce Hot Cracking Susceptibility of IN718 Casting Alloy Laser Beam Welds with a Mushroom Shape

Reducing hot cracking is essential for ensuring seamless production of nickel superalloys, which are extensively used in welded structures for aircraft engines. The prevalence of hot cracking in precipitation-strengthened alloy 718 is primarily governed by two factors: firstly, the chemical composition and the coarse microstructure formed during solidification, and secondly, the activation of hot cracking mechanisms, which is particularly critical in mushroom-shaped welding morphologies. In this study, different nickel-based superalloys welded using laser beam welding (LBW), more specifically bead on plate welding (BoP), specimens are compared. The cracking susceptibility of both wrought and two investment casting 718 alloys with tailored chemical compositions is examined through the application of both continuous and pulsed LBW. Additionally, various pre-weld treatments, including with and without Pre-HIP (hot isostatic pressing), are analyzed. The influences of chemical composition, LBW parameters and pre- and post-welding treatments on both internal and external cracks determined by conventional and advanced non-destructive tests are studied. A clear reduction of hot cracking susceptibility and overall welding quality improvement was observed in a tailored 718 alloy with relatively high Ni (55.6% wt) and Co (1.11% wt) contents.

Thick-wire GMAW for fusion welding of high-strength steels

The paper describes a high-current Gas Metal Arc Welding (GMAW) process using wire electrodes with diameters up to 4.0 mm for single-pass full penetration butt joint welding of 20 mm thick steel plates. Fundamental research aims to develop thick-wire GMAW into a high-efficiency method by identifying the limits of welding performance and achievable deposition rates. Current gaps in understanding include equipment requirements, process properties, application fields, and weld quality. The research project addresses these gaps through systematic investigations of basic technological analyses, application sample welding, and quality evaluations. The objective was to create a robust, cost-efficient gas-shielded high-performance welding technology with deposition rates comparable to Submerged Arc Welding. The fully mechanized, automatic welding setup included two parallel-connected welding power sources, one wire feeder and one high-power welding torch. Welding parameters and conditions were evaluated with the aim of achieving a high-quality weld. Optimal parameters were identified for one-sided single-pass welding on 20 mm thick plates. Validation of thick-wire GMAW for 20 mm thick high-strength steels was conducted via two-sided single-pass welding on S690Q grade plates. Testing of the weld joint included static tensile strength test (3x tensile specimen), a Charpy impact test at −40 °C (6x Charpy V-notch specimens respectively with notch position in weld metal, base material and heat-affected zone (HAZ)), microstructure examination and a hardness test. The lowest recorded impact energy was observed to be 50 J within the weld metal, in combination with hardness peaks in the HAZ reaching 415 HV1, and all tensile specimens failing outside the HAZ within the base material. The process achieved reliable, reproducible, and economical joint welding, meeting necessary mechanical-technological quality standards. The paper enhances the understanding of selected welding techniques tor thick plate joining and offers valuable industrial insights, demonstrating the technique's applicability and feasibility for high-strength applications.

Processing, experimental characterization and thermal analysis for friction stir welded joint of 2219Al alloy

ABSTRACT Present study aimed at thermal modelling and numerical analysis of dynamic heat flow behaviour, for friction stir welded (FSW) joint of 2219Al alloy, further experimentally correlated with microstructural evolution and microhardness profile through different weld zones. FSW was performed on cast 2219Al alloy, with varying process parameters of welding and rotational speed of the tool, and transient temperatures measured at different distances from weld line. From microstructural analysis, three different heat affected weld zones having separate grain morphologies were identified, namely Weld Nugget Zone (WNZ), Thermo-Mechanical Affected Zone (TMAZ) and Heat Affected Zone (HAZ). Vickers microhardness was evaluated at varying distances from weld line, through different weld zones. To investigate transient temperature profiles over the welded plate, a 3-D Finite Element (FE) thermal model was developed, incorporating volumetric heat source as heat generation. Transient temperature profiles computed from FEM analysis, were successfully compared and validated with experimental results, with fairly good accuracy within 4.86 %. Individual influences of welding parameters, on transient temperature profile, weld zones, microstructural and mechanical property were investigated, to optimise and achieve desired weld quality. Present study established structure-property correlation, along with thermal analysis, to validate and optimise the potential application of FSW on 2219Al alloy.

Study on penetration depth in laser welding: A process information database-based control strategy and OCT measuring verification

Penetration depth acts as a crucial indicator reflecting laser welding quality, thus the control of its stability and the perception of its fluctuation state are increasingly garnering attention. This paper proposes a process information database-based control strategy for penetration depth, and the control validity is verified through penetration depth detection utilizing optical coherence tomography (OCT). The process information database stores diverse expected penetration depth knowledge formed by a substantial quantity of varying welding speeds with fixed other process parameters under undisturbed welding conditions. In the database, the stable average values inside the standard penetration depth information and the corresponding heat input (HI) values are connected and mapped via an artificial neural network (ANN). In response to abnormal variations in the penetration depth curve caused by interferences during welding, according to the HI gap predicted by the trained ANN from the penetration depth gap arising from the curve deviation, the control unit can calculate the new welding speed required to feed the penetration depth curve back to within the steady fluctuation range. Based on OCT, the keyhole depth signal is acquired, and a deep belief network is built to predict the penetration depth curve via the correlation between the reconstructed keyhole depth obtained by ensemble empirical mode decomposition and the penetration depth. This detection method demonstrates that the penetration depth curve can be controlled accurately. Finally, a closed-loop real-time feedback control system for penetration depth is established.

Reaction mechanisms and mechanical properties of SiCf/SiC composite and GH536 superalloy joints using CoFeNiCrMn high-entropy alloy filler

To meet the service conditions and strength requirements of turbine stator blades and the inner and outer rings of aero engine casings, CoFeNiCrMn high-entropy alloy filler was used to braze SiCf/SiC/GH536 joints. This study investigated the effects of holding time on the joints' microstructure and mechanical properties. Key phases identified in the welded joints include MoNiSi, FCC, and Cr23C6 near the composites, with brittle Ni3Si and Fe2Si intermetallic compounds forming due to filler diffusion. Optimal brazing parameters were found to be 1220 °C for 30 min with a shear strength of 64.28 MPa. The study also highlighted that increased holding time at the same temperature enhances diffusion at the joint, increasing brittle intermetallic compounds, initially improving shear strength, which then declines. Microstructural and fracture morphology analyses revealed that insufficient insulation time leads to poor welding and stress concentration at pores, causing cracks. Excessive insulation time results in joint fractures due to the brittleness of Ni3Si and Fe2Si intermetallic. Thus, joint shear strength correlates with welding quality and intermetallic compound distribution.

Weld Quality Appraisal of AA1050/Cu FSWed Joints: A Novel Hybrid Taguchi-WASPAS-Alibaba and the Forty Thieves Algorithm

Weld Quality Appraisal of AA1050/Cu FSWed Joints: A Novel Hybrid Taguchi-WASPAS-Alibaba and the Forty Thieves Algorithm

Exploring the cutting edge: Recent trends in cold metal transfer welding

Cold metal transfer welding is known for its automated welding process, which is equipped with shortcircuit-based deposition of filler wire, which allows it to control its heat input parameter properly along with a wire feed rate. Cold metal transfer’s main characteristic, which greatly affected the manufacturing industries, is joining thin, similar, or dissimilar metal sheets as the processing heat input is minimal. This review paper (covering 104 studies) examines how joining different metals with varying welding parameters affects their weld appearance, microstructure, tensile strength, and the formation of joint failure. The main focus was on what additional methods, like hardfacing or post-heat treatment of material, must be adopted to enhance the joint's weld quality and appearance. The paper starts with the investigation of numerous dissimilar weld joints formed by the cold metal transfer technique, along with the effect of varying welding parameters and ultrasonic-assisted cold metal transfer hybrid welding on the weld quality and post–pre-weld heat treatment of materials. A comparison of different cold metal transfer arc modes employed in wire-arc additive manufacturing has also been discussed briefly. At the end of the analysis, it was noted that some metal joints had a positive impact, and some gained a negative effect while increasing the heat input. The research articles studied in this paper indicate that not every material would exhibit the same welding property when subjected to a specific set of varying welding parameters.

Penetration State Recognition during Laser Welding Process Control Based on Two-Stage Temporal Convolutional Networks.

Vision-based laser penetration control has become an important research area in the field of welding quality control. Due to the complexity and large number of parameters in the monitoring model, control of the welding process based on deep learning and the reliance on long-term information for penetration identification are challenges. In this study, a penetration recognition method based on a two-stage temporal convolutional network is proposed to realize the online process control of laser welding. In this paper, a coaxial vision welding monitoring system is built. A lightweight segmentation model, based on channel pruning, is proposed to extract the key features of the molten pool and the keyhole from the clear molten pool keyhole image. Using these molten pool and keyhole features, a temporal convolutional network based on attention mechanism is established. The recognition method can effectively predict the laser welding penetration state, which depends on long-term information. In addition, the penetration identification experiment and closed-loop control experiment of unequal thickness plates are designed. The proposed method in this study has an accuracy of 98.96% and an average inference speed of 20.4 ms. The experimental results demonstrate that the proposed method exhibits significant performance in recognizing the penetration state from long sequences of welding image signals, adjusting welding power, and stabilizing welding quality.

Heat Mapping and Plastic Strain Radius Modeling of Dual-Tool Friction Stir Welds 6061 Aluminum Alloy Plate Using FEM

This study investigates the effects of Dual-Tool Friction Stir Welding (DT-FSW) parameters on the weld quality of 8 mm thick 6061 aluminum alloy plates, specifically focusing on the elimination or minimization of the "pass-overlap zone" that’s a gap typically observed at the mid-section of the weld cross-section resembling characteristics of the Heat-Affected Zone (HAZ). To address ongoing debates regarding the optimal joint performance concerning this overlap, symmetric increases in the dimensions of both FSW tools were implemented to analyze resultant temperature fields and plastic strain adaptations at the weld interfaces. Simulation visualizations were conducted with tool density variations at intervals of 0.2 mm and 0.4 mm. Results indicate that increasing tool density, thereby reducing the distance between tool surfaces, leads to a decrease in peak temperatures generated during welding. This reduction in temperature correlates with a more uniform distribution of plastic strain rates across all layers of the material—upper, middle, and lower—with the leading edge exhibiting the most significant improvement in strain uniformity. Conversely, during the stabilization phase, a decrease in tool density (S) results in a reduction of the maximum equivalent plastic strain rate. These findings suggest that careful adjustment of tool density in DT-FSW processes can enhance weld quality by promoting more uniform mechanical and thermal properties across the joint.

Improved Femtosecond Laser Welding of Nonoptical Contact Glass by Pressure and a Water Intermediate Layer.

Ultrafast laser welding has emerged as a significant technology for the joining of transparent materials and has been extensively researched for the welding of glass materials in recent years. However, achieving a robust connection requires optical contact between the samples during laser processing, which complicates the welding process and increases its cost. To achieve high-strength welding of glass samples without optical contact, the samples are typically pressed together to minimize the gap, allowing the molten materials to completely fill it. In this study, two approaches are employed to facilitate high-strength welding of silica glasses: femtosecond (fs) laser welding with the assistance of pressure using a fixture and femtosecond laser welding aided by a water intermediate layer. The welding quality achieved by both methods is thoroughly examined and compared. The findings reveal that femtosecond laser welding with water assistance outperforms other methods in terms of welding uniformity and quality. Furthermore, the principle behind achieving high-quality welding is discussed to elucidate the success of this method.

The Impact of Welding Parameters on the Welding Strength of High Borosilicate Glass and Aluminum Alloy

This study adopts a new surface pretreatment method, Laser Surface Remelting (LSR). This experiment aims to establish a set of laser welding process parameters suitable for aluminum alloy and glass under this specific pretreatment. This experiment explores the impact of laser welding parameters on the welding strength between high borosilicate glass and aluminum alloy. The study specifically investigates the effects of four process parameters: defocus amount, laser power, frequency, and pulse width on the welding outcome. The results indicate that the welding quality between the aluminum alloy and glass reaches its optimum when the defocus amount is zero (i.e., when the laser converges at the interface between the glass and the metal) and the laser welding parameters are set to a power of 250 W, a welding speed of 1 mm/s, a welding frequency of 10 Hz, and a pulse width of 2.5 ms. The experiment also analyzes the fracture morphology under different parameters, summarizing the locations and causes of fractures, and establishing the relationship between the fracture location and the welding strength.