Search Results (65)

An ultra-high-strength press-hardening steel (PHS) and a high-strength dual-phase steel (DP) were butt-joined by the gas metal arc welding (GMAW) process, aiming to assess the effects of a high heat input welding process on the structure-property relationship and residual stress. The post-weld microstructure, the microhardness profile, the tensile behavior, and the experimentally obtained residual stresses (by x-ray diffraction) of the steels in dissimilar (PHS-DP) and similar (PHS-PHS, DP-DP) pair combinations have been analyzed. Results indicated that the ultimate tensile strength (UTS) of the dissimilar pair PHS-DP achieves a similar strength to the DP-DP joint, whereas the elongation was similar to that of the PHS-PHS weldment. The failure location of the tensile specimens was expected and systematically observed at the tempered and softer sub-critical heat-affected zone (SC-HAZ) in all welded conditions. Compressive residual stresses were consistently observed along the weldments in all specimens; the more accentuated negative RS were measured in the PHS joint attributed to the higher volume fraction of martensite; furthermore, the negative RS measured in the fusion zone (FZ) could be well correlated to weld restraint due to the sheet anchoring during the welding procedure, despite the presence of predominant ferrite and pearlite microstructures. Full article

The future of the automotive industry appears to hinge on the integration of dissimilar materials, such as aluminum alloys and carbon steel. However, this combination can lead to galvanic corrosion, compromising the structural integrity. In this study, laser-welded joints of 6013-T4 aluminum alloy and DP980 steel were evaluated for their morphology, microhardness, and corrosion resistance. Corrosion resistance was assessed using the electrochemical noise technique over time in 0.1 M Na₂SO₄ and 3.5% NaCl solutions. The wavelet function was applied to remove the DC trend, and energy diagrams were generated to identify the type of corrosive process occurring on the electrodes. Corrosion on the electrodes was also monitored using photomicrographic images. Analysis revealed an aluminum–steel mixture in the melting zone, along with the presence of AlFe, AlFe₃, and AlI₃Fe₄ intermetallic compounds. The highest Vickers microhardness was observed in the heat-affected zone, adjacent to the melt zone, where a martensitic microstructure was identified. The 6013-T4 aluminum alloy demonstrated the highest corrosion resistance in both media. Conversely, the electrochemical noise resistance was similar for the DP980 steel and the weld bead, indicating that the laser welding process does not significantly impact this property. The energy diagrams showed that localized pitting corrosion was the predominant form of corrosion. However, generalized and mixed corrosion were also observed, which corroborated the macroscopic analysis of the electrodes. Full article

This paper delves incto the tungsten inert gas (TIG) welding process, renowned for its efficacy in creating robust metal joints and widely employed in diverse industries for fusing similar or dissimilar materials. The focus of this study is the welding of mild steel with stainless steel, showcasing the method’s ability to amalgamate exceptionally sturdy metals and alloys. The resultant welded joints exhibit a meticulously refined microstructure and an impressive strength-to-weight ratio. The primary aim is to scrutinize TIG-welded joints, specifically those connecting mild steel with stainless steel, to elucidate their metallurgical and mechanical attributes. Notably, joints formed between distinct materials, such as mild steel and stainless steel, manifest commendable mechanical and metallurgical properties. This paper extensively investigates the metallurgical microstructures and tensile characteristics of both comparable and dissimilar metal junctions, contributing valuable insights to the field. Full article

Over the past decade, friction stir spot welding (FSSW) has gained increasing attention, making it a competitor to conventional welding methods such as resistance welding, rivets, and screws. This type of welding is environmentally friendly because it does not require welding tools and is solid-state welding. This study attempts to demonstrate the importance of pin geometry on temperature distribution and joint quality by using threaded and non-threaded pins for similar and dissimilar alloys. To this end, thermal analysis of the welded joints was conducted using real-time monitoring from a thermal camera and an infrared thermometer, in addition to finite element method (FEM) simulations. The thermal analysis showed that the generated temperatures were higher in dissimilar alloys (Al-Cu) than in similar ones (Al-Al), reaching about 350 °C. In addition, dissimilar alloys show more pronounced FSSW stages through extended periods for each plunging, dwelling, and drawing-out time. The FEM simulation results are consistent with those obtained from thermal imaging cameras and infrared thermometers. The dwelling time was influential, as the higher it was, the more heat was generated, which could be close to the melting point, especially in aluminum alloys. This study provides an in-depth experimental and numerical investigation of temperature distribution throughout the welding cycle, utilizing different pin geometries for both similar and dissimilar non-ferrous alloy joints, offering valuable insights for advanced industrial welding applications. Full article

TC4 titanium alloy and 5083 aluminum alloy with different groove shapes were joined by laser-MIG hybrid welding–brazing using ER4043 filler wire. The effects of groove shape on the weld formation, intermetallic compounds and tensile property of the Ti/Al butt joints were investigated. The welds without obvious defects could be obtained with grooves of I-shape and V-shape on Ti side, while welds quality with grooves of V-shape on Al side and V-shape on both sides were slightly worse. The interfacial intermetallic compounds (IMCs) on the brazing interface were homogeneous in the joints with groove of V-shape on Ti side, and V-shape on both sides, which had similar thickness and were both composed of TiAl₃. Unlike the IMCs mainly composed of TiAl₃ at the I-shape groove interface, TiAl₃, TiAl, and Ti₃Al constituted the IMCs at the V-shape on Al side interface. The average tensile strength of Ti/Al joints with groove of I-shape was the highest at 238 MPa, and was lowest at 140 MPa with groove of V-shape on Al side. The tensile samples mainly fractured at IMCs interface and the fractured surfaces all exhibited mixed brittle–ductile fracture mode. Based on the above research results, I-shape groove was recommended for laser-arc hybrid welding–brazing of 4 mm thick Ti/Al dissimilar butt joints. Full article

The demand for electric mobility has driven the development of advanced laser welding technologies such as dual beam welding and beam shaping. Nevertheless, some intrinsic characteristics present challenges to exploring all its benefits. In this sense, this study investigates the effect of the laser welding parameters employed on the weld quality in busbar–battery interconnects. Dual beam and beam shaping strategies were applied in Al-Al (AA1050 H24) and Al-Cu (AA1050 H24 and C11000) overlap joint configurations adopting statistical methods. For Al-Al joints, welding speed was the most significant parameter influencing interface width, whereas in Al-Cu joints, core power was the only significant parameter affecting both interface width and penetration in the studied configuration. Common defects, such as porosity and cracks, were observed in both material combinations. In Al-Al joints, higher welding speeds resulted in up to a 16% (65.6 HV) increase in hardness, while, in Al-Cu joints, the peak value reached around 900 HV in the interface zone due to the formation of intermetallic compounds (IMCs). In addition, IMCs with complex structures and significant compositional variations, including Cu₉Al₄ and CuAl₂ were identified. Full article

The current study investigates the thermal, metallurgical, and mechanical results in similar and dissimilar weldments of Monel 400 and AISI 316L. Infrared thermography (IRT) was employed to record thermal cycles, while X-ray diffraction (XRD) was used to analyze the residual stresses post-welding. Mechanical properties were assessed through tensile and microhardness tests, and microstructural evolution was examined using energy-dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). IRT results showed peak temperatures of 1788 °C for Monel 400 and 1750 °C for AISI 316L. Residual stress analysis revealed compressive stresses of 293 MPa in dissimilar welds, compared to 235 MPa in Monel 400 and tensile stresses of 57 MPa in AISI 316L. Ultimate tensile strength (UTS) values were 543 MPa for dissimilar welds, 533 MPa for Monel 400, and 556 MPa for AISI 316L, with corresponding microhardness values of 207 HV, 203 HV, and 168 HV, respectively. Microstructural analysis identified coarse Ni-Cu phases in the Monel 400 heat-affected zone (HAZ), austenitic structures in AISI 316L, and intermetallic compounds in dissimilar welds. The findings highlight the impact of thermal distribution, residual stress, and microstructural evolution on weld performance, providing insights into optimized welding parameters for improved joint integrity and mechanical properties. Full article

Despite the significant economic and environmental advantages of friction stir spot welding (FSSW) and its amazing results in welding similar and dissimilar metals and alloys, some of which were known as unweldable, it has some structural and characteristic defects such as keyhole formation, hook defects, and bond line oxidation. This has prompted researchers to focus on these defects and propose and investigate techniques to treat or compensate for their deteriorating effects on microstructural and mechanical properties under different loading conditions. In this experimental study, sheets of AA6061-T6 aluminum alloy with a thickness of 1.8 mm were employed to investigate the influence of reinforcement by graphene nanoplatelets (GNPs) with lateral sizes of 1–10 µm and thicknesses of 3–9 nm on the static and fatigue behavior of FSSW lap joints. The welding process was carried out with constant, predetermined welding parameters and a constant amount of nanofiller throughout the experiment. Cross-sections of as-welded specimens were tested by optical microscope (OM) and energy-dispersive spectroscopy (EDS) to ensure the incorporation of the nanographene into the matrix of the base alloy by measuring the weight percentage (wt.%) of carbon. Microhardness and tensile tests revealed a significant improvement in both tensile shear strength and micro-Vickers hardness due to the reinforcement process. The fatigue behavior of the GNP-reinforced FSSW specimens was evaluated under low and high cycle fatigue conditions. The reinforcement process had a detrimental effect on the fatigue life of the joints under cyclic loading conditions. The microstructural analysis and examinations conducted during this study revealed that this reduction in fatigue strength is attributed to the agglomeration of GNPs at the grain boundaries of the aluminum matrix, leading to porosity in the stir zone (SZ), the formation of continuous brittle phases, and a transition in the fracture mechanism from ductile to brittle. The experimental results, including fracture modes, are presented and thoroughly discussed. Full article

Resistance spot welding (RSW) is now the primary joining process used in the automobile and aerospace sectors. Mechanical parts, when put into service, often undergo cyclic stress. As a result, avoiding fatigue failure should be the top priority when designing these parts. Given that spot welds are a type of localised joining that results in intrinsic circumferential notches, they increase the likelihood of stress concentrations and subsequent fatigue failures of the structure. Most of the fatigue failures in automotive parts originate around a spot weld. To that end, this study seeks to examine the mechanical properties and fatigue behaviour RSW joints made of titanium (Ti) grade 2 alloy and AISI 304 austenitic stainless steel (ASS) with equal and unequal thicknesses of 0.5 and 1 mm. Based on the mechanical properties and fatigue life results, the maximum tensile shear strength and fatigue life for the RSW titanium joint were 613 MPa and 7.37 × 10⁵ cycles for the 0.5–0.5 mm case, 374.7 MPa and 1.39 × 10⁶ cycles for the 1–1 mm case, and 333.5 MPa and 7.69 × 10⁵ cycles for the 1–0.5 mm case, respectively. The maximum shear strength and fatigue life of ASS welded joints were 526.8 MPa and 4.56 × 10⁶ cycles for the 1–1 mm case, 515.2 MPa and 3.35 × 10⁶ cycles for the 0.5–0.5 mm case, and 369.5 MPa and 7.39 × 10⁵ cycles for the 1–0.5 mm case, respectively. The assessment of the shear strength and fatigue life of the dissimilar joints revealed that the maximum shear strength and fatigue life recorded were 183.9 MPa and 6.47 × 10⁵ cycles for the 1 mm Ti–0.5 mm ASS case, 115 MPa and 3.7 × 10⁵ cycles for the 1 mm Ti–1 mm ASS case, 156 MPa and 4.11 × 10⁵ cycles for the 0.5 mm Ti–0.5 mm ASS case, and 129 MPa and 4.11 × 10⁵ cycles for the 0.5 mm Ti–1 mm ASS case. The fatigue life of titanium and stainless steel welded joints is significantly affected by the thickness, particularly at maximum applied stress (0.9% UTS), meaning that similar thicknesses achieve a greater fatigue life than unequal thicknesses. Conversely, the fatigue life of the dissimilar joint reached the greatest extent when an unequal thickness combination was used. The ductile failure of similar Ti and ASS welded joints was demonstrated by the scanning electron microscopy (SEM) examination of fatigue-fractured surfaces under the high-cycle fatigue (HCF) regime, in contrast to the brittle failure noticed in the low-cycle fatigue (LCF) regime. Brittle failure was confirmed by the SEM fatigue of dissimilar joint fractured surfaces due to interfacial failure. The Ti and ASS fractured surfaces presented river-like cleavage facets. On the Ti side, tiny elongated dimples suggest ductile failure before fracture. The topography results showed that the roughness topography parameters of similar and dissimilar fractured specimens made from Ti grade 2 and AISI 304 for the HCF regime were lower than those of the fractured specimens with LCF. The current study is expected to have practical benefits for the aerospace and automotive industries, particularly the manufacturing of body components with an improved strength-to-weight ratio. Full article

Facing the global energy crisis and increasingly stringent environmental protection regulations, automotive lightweighting has become a core issue for the sustainable development of the automotive industry. In particular, the qualified combination of steel and aluminum alloy has become a promising development direction to achieve the aim of lightweight design. As an innovative solid-phase welding technique, magnetic pulse welding (MPW) exhibits unique advantages in joining these dissimilar metals. The 6061 Al alloy and 20# steel tubes were joined by the MPW technique in this study. The microstructure and interface morphology of the MPW steel/Al tube were characterized using optical microscopy (OM), scanning electron microscopy (SEM), and an electro-probe microanalyzer (EPMA). The microstructure in the region adjacent to the interface was similar to that of the base metals (BMs). The element transition zone could be observed at the interface. The thickness of the transition layer was approximately 6 μm. The transition layer did not possess high hardness and brittleness like the Fe–Al binary IMC layer. Therefore, the interface bonding quality and long-term stability of the MPW steel/Al joint were relatively good. The welded joint interface could be divided into three zones: the bonded zone in the center and unbonded zones on both sides. In particular, an obvious wavy interface with gradually increased amplitude was detected in the bonded zone. The interaction between the reflected wave and the welding collision point could promote the initiation of the wavy interface. In addition, the formation of the wavy interface depended on the impact velocity and angle of the MPW process. The qualified mechanical properties of the joint could be attributed to the formation of the wavy interface. The microhardness at the interface was higher than that on both sides, owing to work hardening, at approximately 226 HV. Full article

Rotary friction welding is a solid-state welding process that can manufacture high-integrity joints between similar and dissimilar materials with short weld times. However, access to expensive and complex industrial-grade friction welding machines is not always possible. This study explores the design process and functionality of a laboratory-scale friction welding setup following the fundamentals of large-scale machinery. The proposed setup is designed to be easily manufactured, employing the use of a calibrated drill press and load cell, thus ensuring welding parameters such as rotational speed and applied axial load are monitored. The decision to investigate rotary friction welding of aluminium bronze Ca104 to austenitic stainless steel AISI316 was taken to explore the limitations of this bespoke friction welding machine for prospective applications in the nuclear energy sector. The workpieces were friction welded at four sets of rotational speeds with constant friction and forging pressures. The microstructural evolution and mechanical properties of the dissimilar material welds were investigated via optical and scanning electron microscopy with energy dispersive spectroscopy, 4-point bend testing and microhardness measurements. Results show a change in the hardness along the weld interface and evidence of metallic diffusion between the dissimilar materials, demonstrating the successful application of the small-scale experimental setup. Full article

Friction-stir-welded dissimilar AA2024/AA7075 joints have an apparent influence on grain and texture development at the weld interface due to differences in physical and chemical properties between the two aluminum alloys. In this work, the effect of tool shoulder profile on grain structure and texture evolution in the center interface zone (CIZ) and bottom interface zone (BIZ) of dissimilar AA2024/AA7075 joints were quantitatively studied by electron back-scattering diffraction (EBSD). The results indicate that abundant fine and coarse equiaxial grains are produced in the CIZ and BIZ of the joints produced with a concentric circle shoulder (CCS) and three-helix shoulder (THS), and the average grain size of the BIZ is lower than that of the CIZ for the same CCS or THS joint. A higher degree of recrystallization occurs in the CIZ of the joint with a CCS than that of the joint with a THS, while a similar degree of recrystallization is presented in the BIZ of the two joints. For the distribution of local misorientation angle between the two sides of the interface in the same CCS or THS joint, the CIZ manifests relatively uniform behavior, while the BIZ presents the characteristics of uneven distribution. Tool shoulder profile has a significant impact on the texture components at the weld interface, which results in different types of shear textures generated in the CIZ and BIZ of the two joints. It is beneficial to make out the microstructural evolution mechanism at the weld interface in dissimilar FSW joints for engineering applications in this study. Full article

(FeCoNi)₉₆A_l4 high-entropy alloy (HEA) is a new material with a strength similar to that of commercial Q235 structural steel, and its elongation is nearly three times greater than that of Q235 steel. Studying the welding process of the (FeCoNi)₉₆Al₄ HEA and Q235 steel is expected to further expand the application range of commercial Q235 structural steel and provide a foundation for the engineering application of the (FeCoNi)₉₆Al₄ HEA. This study focuses on the dissimilar welded components of (FeCoNi)₉₆Al₄ HEA and Q235 steel and analyzes the forming quality, microstructure, and mechanical properties of dissimilar welded samples under different currents. The results show that when the welding current is above 170 A, the 3 mm sheet metal is completely penetrated, and a well-formed weld seam is obtained. The base metal of the (FeCoNi)₉₆Al₄ HEA has an FCC structure, whereas the fusion zone of the weld seam is almost entirely a BCC structure. The microstructure of the weld seam exhibits needle-like and block-like grains that are different from those of the base metal. Owing to the difference in microstructure between the weld seam and the base metal, the average microhardness of the welded joint is twice that of the base metal. The strength of the dissimilar welded components reached 460 MPa, maintaining the tensile strength of the (FeCoNi)₉₆Al₄ HEA, which is similar to that of the Q235 structural steel. The elongation reached over 30%, which was significantly greater than that of the Q235 structural steel. Full article

Resistance spot-welded joints are crucial parts in contemporary manufacturing technology due to their ubiquitous use in the automobile industry. The necessity of improving manufacturing efficiency and quality at an affordable cost requires deep knowledge of the resistance spot welding (RSW) process and the development of artificial neural network (ANN)- and machine learning (ML)-based modelling techniques, apt for providing essential tools for design, planning, and incorporation in the welding process. Tensile shear force and nugget diameter are the most crucial outputs for evaluating the quality of a resistance spot-welded specimen. This study uses ML and ANN models to predict shear force and nugget diameter responses to RSW parameters. The RSW analysis was executed on similar and dissimilar AISI 304 and grade 2 titanium alloy joints with equal and unequal thicknesses. The input parameters included welding current, pressure, welding duration, squeezing time, holding time, pulse welding, and sheet thickness. Linear regression, Decision tree, Support vector machine (SVM), Random forest (RF), Gradient-boosting, CatBoost, K-Nearest Neighbour (KNN), Ridge, Lasso, and ElasticNet machine learning algorithms, along with two different structures of Multilayer Perceptron, were utilized for studying the impact of the RSW parameters on the shear force and nugget diameter. Different validation metrics were applied to assess each model’s quality. Two equations were developed to determine the shear force and nugget diameter based on the investigation parameters. The current research also presents a prediction of the Relative Importance (RI) of RSW factors. Shear force and nugget diameter predictions were examined using SHapley (SHAP) Additive Explanations for the first time in the RSW field. Trainbr as the training function and Logsig as the transfer function delivered the best ANN model for predicting shear force in a one-output structure. Trainrp with Tansig made the most accurate predictions for nugget diameter in a one-output structure and for shear force and diameter in a two-output structure. Depending on validation metrics, the Random forest model outperformed the other ML algorithms in predicting shear force or nugget diameter in a one-output model, while the Decision tree model gave the best prediction using a two-output structure. Linear regression made the worst ML predictions for shear force, while ElasticNet made the worst nugget diameter forecasts in a one-output model. However, in two-output models, Lasso made the worst predictions. Full article

The need for combining dissimilar materials is steadily increasing in the manufacturing industry, and the resulting products are expected to always have high performance. While there are various methods available for joining such material pairs, one of the commonly preferred techniques is fusion welding. In this study, three different steel materials (Protection 600T, DP450, and S275JR) were joined using gas metal arc welding (GMAW) in different combinations (similar/dissimilar). The microstructure and mechanical properties of the joints were evaluated. Tensile test, Vickers microhardness (HV 0.1), bending, Charpy V-notch impact testing, and microstructure examinations were conducted to analyze the weld and heat-affected zone. The tensile strengths of the base metal materials Protection 600T, DP450, and S275JR were found to be 1524.73 ± 18.7, 500.8 ± 10.4, and 508.5 ± 9.5 MPa, respectively. In welded samples of similar materials, the highest efficiency was found to be 103.05% for DP450/DP450, while in dissimilar welded joints, it was 105.5% for the DP450/S275JR pair. Hardness values for the base materials Protection 600T, DP450, and S275JR were measured as 526.5 ± 10.5, 153.8 ± 1.8, and 162.5 ± 5.2, respectively. In all welded samples, there was an increase in hardness in the weld zone (due to the welding wire) and the heat-affected zone (due to grain size refinement). While the impact energy values of similar material pairs were close to the base material impact energy values, the impact energy values of dissimilar material pairs varied according to the base materials. In addition, in joints made with similar materials, the bending force was close to the base materials, while a decrease in bending force was observed in joints formed with dissimilar materials. As a result, the welding of DP450 and S275JR materials was carried out efficiently. Protection 600T was welded with other materials, but its welding strength was limited to the strength of the material with low mechanical properties. Full article