Welding Energy Research Articles

Enhancement of 3D printability and mechanical properties of polylactic acid/lignin biocomposites via interface engineering

Very recently, the additive manufacturing of lignin-based composites has shown promising results toward the sustainable development of green materials. However, the high brittleness and poor 3D printability of the composites restrict their printing, caused by lignin’s weak compatibility with polymers and its high viscosity. In this study, a high-performance, printable lignin-based polylactic acid (PLA) composite was investigated through copolymerizing 2-ethylhexyl acrylate at the interface. It was shown that 10 wt% modified lignin (e-lignin) composites exhibit significantly enhanced toughness from 1.16 to 3.84 MJ/m3 and also impact energy from 2.12 to 6.36 KJ/m2 relative to the pure PLA. The responsible toughening effect was interpreted by plasticization and the bridging effect of e-Lignin. The low melt viscosity of the dispersed e-Lignin phase caused local thermo-rheological relaxation and promotes the mobility of PLA molecular chains, showing desirable melt viscosity for fused deposition modeling 3D printing. Notable that the adhesion strength between deposited layers during additive manufacturing was increased due to high interfacial diffusion of composites, where an approximately 138% improvement of weld energy was achieved in 10 wt% e-lignin composites compared to those of pure PLA. This study shows the great promise to utilize lignin extracted natural materials particularly in additive manufacturing by replacing petroleum-based thermoplastics.

Assessment of the Laser Beam Welding of Galvanized Car Body Steel with an Additional Organic Protective Layer.

This study discusses the effect of laser beam welding parameters on the structure, mechanical properties and corrosion resistance of 1.2 mm thick galvanized sheets made of low-carbon steel DC04 provided with a ZE36/36 GardoprotectOC2BU organic coating. The test laser beam butt welded joints were made without the filler metal, using a variable welding rate, where linear welding energy was restricted within the range of 30 J/mm to 90 J/mm. The joints were subjected to non-destructive tests, destructive tests and corrosion resistance tests. The tests revealed the possibility of making joints meeting the criteria specified in the ISO 15614-11 standard. Regardless of the value of linear welding energy applied in the process, all the joints were characterised by high mechanical and plastic properties. It was noticed that an increase in linear welding energy from 30 J/mm to 90 J/mm was accompanied by the widening of the weld and that of the heat-affected zone (HAZ). In addition, an increase in linear welding energy was accompanied by a decrease in the maximum weld hardness to approximately 250 HV0.2. In the HAZ, hardness was restricted within the range of 190 HV0.2 to 230 HV0.2 and decreased along with increasing linear welding energy. In the static tensile test, regardless of the value of linear welding energy, the test specimen ruptured in the base material. In the bend test, regardless of the value of linear welding energy, a bend angle of 180° was obtained without partial tear or scratches; unit elongation was restricted within the range of 29% to 42%. The electrochemical tests and experiments performed in the salt spray chamber revealed the very high effectiveness of the corrosion protections against aggressive chloride ions.

Microstructural investigations on laser welded Al-30wt.% B4C composite

In order to tailor the microstructures and mechanical properties of laser welded Al-B4C composite, it is necessary to elucidate the chemical reactions between B4C reinforcement and Al matrix during laser welding process. In this study, 3 mm thick Al-30wt.% B4C plates were laser welded using different parameters. Then the microstructure, reaction products, tensile properties and fracture surface of welded joint were studied. The results show that the reaction products of the weld zone can be controlled by varying the welding energy input, but the full penetration welded joint requires high energy input (120 KJ/m in this paper). For the full penetration welded joint, all B4C particles and part Al matrix react to form irregularly particle-like AlB2C2 and coarse needle-like Al4C3 phases, the joint efficiency is 67%. The failure mechanism of AlB12C2 is cleavage fracture, and the failure mechanism of Al4C3 is interfacial decohesion and pull out. The interfacial decohesion between Al4C3 and Al matrix results in crack initiation due to their weak bonding interface. The cracks propagate, connect and penetrate the brittle AlB12C2 phase and eventually lead to brittle fracture of the joint.

Microstructural Evolution and Mechanical Properties of Cu/Ti Joints Welded by Ultrasonic Spot-Welding with Zn Interlayer

Cu/Ti dissimilar metals were joined together utilizing ultrasonic spot welding with a Zn interlayer. The threedimensional finite element analysis model was established to simulate the temperature field of the interface of Cu/Ti ultrasonic welding joint under different welding energies. The interface forming, microstructure, and mechanical properties of the Cu/Zn/Ti ultrasonic spot-welded joints were studied systematically. Results showed that the temperature distribution of the interface of the Cu/Zn/Ti ultrasonic welding joint was inhomogeneous, and the temperature of the interface below the indentation reached the highest and decreased gradually to the surrounding. With the increase of welding energy, the maximum temperature and the corresponding high-temperature region of Cu/Zn/Ti joint interface gradually increased. The interface of Cu/Zn/Ti ultrasonic welding joint was well formed, and the thickness was different, and the local position had wavy undulation morphology. When the welding energy was low, the interface microstructure was mainly composed of copper solid solution and titanium solid solution. As the welding energy increased, the microstructure of the joint interface was composed of CuZn compound, copper solid solution and titanium solid solution. When the welding energy was increased to 2000 J, the joint interface microstructure was composed of CuZn, Zn15Ti compound and copper solid solution. In comparison, Cu/Ti joints welded with a Zn interlayer in-between displayed the maximum shearing force about 33.5% greater than those of joints without a Zn interlayer.

Study on the SPCC and CFRTP Hybrid Joint Performance Produced with Additional Nylon-6 Interlayer by Ultrasonic Plastic Welding

Due to the high degree of dissimilarity in physicochemical properties between metal and carbon fiber, it presents a tremendous challenge to join them directly. In this paper, cold rolled steel (SPCC) and carbon fiber reinforced thermoplastic (CFRTP) chopped sheet hybrid joints were produced with the addition of Nylon 6 (PA6) thermoplastic film as an intermediate layer by the ultrasonic plastic welding method. The effect of ultrasonic welding energy and preheating temperature on the hybrid joint microstructure and mechanical behavior was well investigated. The suitable joining parameters could obtain a strong joint by adding the PA6 film as an intermediate layer between the SPCC and bare carbon fibers. Microstructural analysis revealed that the interface joining condition between the PA6 film and the SPCC component is the primary reason for the joint strength. The crevices generated at the interface were eliminated when the preheating temperature arrived at 200 °C, and the joint strength thus significantly increased. The lap shear test results under quasi-static loading showed that the welding energy and preheating temperature synergistically affect the joint performances. At 240 °C, the joint strength value reached the maximum. Through the analysis of the microstructure morphology, mechanical performance, and the failure mechanism of the joint, the optimized joining process window for ultrasonic plastic welding of SPCC-CFRTP by adding an intermediate layer, was obtained.

Experimental Investigation on Vibro-Acoustic Characteristics of Stiffened Plate Structures with Different Welding Parameters

Varied welding process parameters result in different welding energy inputs and welding residual stresses, significantly impacting the vibro-acoustic characteristics. This work investigated the influence of different welding energy inputs on the vibro-acoustic characteristics of the stiffened plate structure. Several experiments on the stiffened plate structure with different welding energy inputs were conducted regarding modal, underwater vibration, and acoustic radiation. The results revealed that welding energy input had the most significant impact on the first-order natural frequency, and the impact first becomes higher and subsequently decreases as welding energy input increases. The welding energy input had relatively little effect on the peak point distribution of vibration and acoustic radiation curves but could affect the peak point amplitude. With the increase in welding energy input, the overall vibration acceleration level and sound radiation level in each frequency band decreased and then increased. The best result was obtained when the welding energy input was 167 J/cm with a welding current of 200 A, a welding voltage of 25 V, and a welding speed of 3.02–3.06 mm/s. Based on construction technology, this research can provide some instructive insights for enhancing the acoustic stealth performance of ships and marine structures.

Evaluation of the Properties and Microstructure of Thick-Walled Welded Joint of Wear Resistant Materials.

The research was conducted on a thick-walled welded joint between the HTK 900H wear-resistant steel plates and the A6 cast profile. The aim of the experiment was to produce a joint with the relevant performance requirements, i.e., a good abrasion resistance joint in the weld face area while ensuring its proper plasticity. The welded joint was made using the MAG PULSE and the high-performance MAG TANDEM methods under automated conditions using the linear welding energy ranging from 1.2 to 2.2 kJ/mm for the different joint regions. The scope of the research included both non-destructive and destructive testing. The non-destructive visual (VT), magnetic-particle (MT), and ultrasonic (UT) tests revealed a good quality of the welded joint with no significant welding imperfections. The microstructure of the welded joint in the weld zone was characterized by a dominant volume fraction of martensite/bainite. The measurement of hardness near the face of the weld confirmed obtaining similar values for this parameter. The HTK 900H steel was characterized by hardness at the level of 383 HV10, whereas the A6 cast-328 HV10, and the weld-276 HV10. At the same time, the analyzed joint showed high ductility in the range of 86 to 159 J. The tests carried out showed that the linear energy control allowed a welded joint with the required performance characteristics to be obtained.

Influence of welding parameters and surface preparation on thin copper–copper sheets welded by ultrasonic welding process

Ultrasonic welding is increasingly used in industry. In this paper, the influence of ultrasonic welding parameters (USW) on the joint strength and quality was analysed. The properties of the USW joints depend on many factors. The work focuses on the influence of the technological parameters and the surface properties of welded EN Cu-ETP copper sheets with a thickness of 1 mm. The impact of the process parameters, such as welding time, pressure, vibration amplitude and the surface roughness on the lap shear strength and the metallographic weld properties was analysed. The welding energy for each variant was also determined. The research was conducted on the basis of a full factorial design of experiments. The optimal process parameters were determined to obtain high-quality joints in terms of strength and weld quality. Based on the presented experimental study, it was demonstrated that the ultrasonic vibration amplitude has the greatest impact on the joint strength. A surface preparation with acetone resulted in the highest tensile strength and welding energy and, making any additional surface treatment prior to welding unnecessary.

Near-Net Shape Manufacture of Ultra-High Strength Maraging Steel Using Flow Forming and Inertia Friction Welding: Experimental and Microstructural Characterization

Abstract Flow forming and inertia friction welding (IFW) have been widely used as manufacturing processes that produce high-value engineering components. Combining these two advanced processes facilitates the fabrication of near-net shape components leading to optimized designs. This study introduces the joining of flow-formed seamless tubes of MLX®19 maraging steel using the IFW process to fabricate a near-net shape component used in landing gears and missile parts. The as-received material was initially provided ≈30% reduction in thickness from the flow forming trials and then welded at four varying weld energies while maintaining constant friction and forge pressures. The mechanical behavior of the weldments was characterized, and the optimized weld parameters were determined. The concomitant microstructural evolution of the optimized weld was also examined to comprehend the underlying deformation mechanisms. The weld strength, axial shortening, and width of dynamic recrystallization (DRX) displayed an increasing trend with an increase in the weld energy. The weld-zone (WZ) and thermomechanical affected zone (TMAZ) showed the presence of martensite, whereas in the HAZ presence of intermetallic precipitates and reverted austenite was confirmed along with tempered martensite. Based on microstructural evidence, it was concluded that the peak temperature attained in the WZ was above Ac3, whereas in the TMAZ it was in-between Ac1 and Ac3. The evolution of crystallographic texture implied that WZ was subjected to pure shear deformation during the welding whereas the TMAZ experienced a combined shear and compressive deformation.

Understanding formation mechanisms of intermetallic compounds in dissimilar Al/steel joint processed by resistance spot welding

This paper confirmed the formation mechanism of intermetallic compounds (IMCs) in Al/steel resistance spot welds with transmission electron microscopy, electron backscatter diffraction, nanoindentation and thermodynamic calculations. In particular, the formation of AlFe with BCC_B2 structure, which is not commonly seen in welds, was identified. The formation mechanism of IMCs at the high welding energy region is described as follows. Al13Fe4 first nucleates from the Al side, followed by Al5Fe2 growth with Fe atoms accumulating at the Al13Fe4 grain boundaries. Then, Al5Fe2 grains grow continuously to coarse columnar grains, and AlFe forms at the interface of Al5Fe2 grains and the ferrite phase. Lastly, the needle-like Al13Fe4 forms in the cooling process. At the middle welding energy region, only equiaxed Al5Fe2 and small Al13Fe4 grains are formed at the interface because of the lower diffusion rates of Al and Fe, hence postponing the growth of Al5Fe2 and Al13Fe4. At the low welding energy region, only sporadic Al5Fe2 and Al13Fe4 grains are formed surrounded by the Al phase.

Detection of Microstructural Changes in Metastable AISI 347, HSS Z-M4 and Tool Steel Ferrotitanit WFN by Mechanical Loss Coefficient at Ultrasonic Frequencies.

Ultrasonic processes such as ultrasonic welding or ultrasonic fatigue testing use power ultrasound to stimulate materials with amplitudes in the range of 1–100 µm. The ultrasonic welding process is sensitive to any changes in the system or even the environment that may result in lower joint quality. The welding tools, so called sonotrodes, have to be accurately designed to endure high mechanical and thermal loads while inducing a sufficient amount of welding energy into the joining zone by oscillation with the Eigenfrequency of the whole system. Such sonotrodes are often made of thermally treated metals where the heat treatment is accompanied by microstructural changes. During ultrasonic stimulation, the material may further change its properties and microstructure due to cyclic loading. Both are expected to be recognized and identified by loss coefficients. Therefore, the loss coefficient was determined by modal analysis of rods and fatigue specimen made of different materials to correlate microstructural changes to attenuation. The determined loss coefficients indicated microstructural changes in all materials investigated, confirming results from previous investigations that showed an increasing attenuation due to cyclic loading for AISI 347. For the sonotrode materials Z-M4 PM and Ferrotitanit WFN, the loss coefficients decreased due to thermal treatments. Technically most relevant, changes in elastic modulus due to thermal treatments were quantitatively related to frequency changes, which can significantly simplify future sonotrode development.

Sensitivity analysis and multi-objective optimization of tungsten inert gas (TIG) welding based on numerical simulation

In welding processes, many factors contribute in achieving a required quality of the welds. Those factors are numerous and they may interact with each other, affecting response parameters such as welding penetration and the heat-affected zone (HAZ) size. Some factors are more important while the influence of others is negligible. To find an optimum factor combination in order to maximize penetration and minimize the HAZ is not an easy task. This contribution is aimed to evaluate the influence of welding energy (E) versus the influence of current (I) and welding speed (Vw) on the penetration and HAZ volume in the autogenous tungsten inert gas welding process. For this purpose, two numerical models are proposed. The first considers an in-house finite volume numerical model, and the second is based on response surface method. A sensitivity analysis of the proposed numerical model using two strategies is also performed. In addition, to determine the best-operating conditions, a multi-objective optimization problem is proposed and solved. The presented numerical models were found to provide good concordance in terms of coefficient of determination and p-value, indicating its significance. Each model (with one or more independent variables) represents detailed information about the physical process and can be used for optimization. The sensitivity analysis demonstrates that the current affects penetration and HAZ volume much stronger than the welding speed does. Physically, this is due to the fact that the current has linear (arc coupling) and non-linear (Joule effect and pressure gradient) influence, and the welding speed contributes linearly, modulating the heat conduction. Finally, it was demonstrated a compromise between the penetration and the HAZ volume by addressing multi-objective optimization. In this context, point C (I = 250 A; Vw = 24.8 cm/min) of the Pareto curve is the optimal option for operation since it provides a lower relative HAZ volume while keeping the same penetration and higher productivity (welding speed).

A Hybrid Algorithm Based on GRNN and Grasshopper Optimization Algorithm for Welding Nugget Diameter Prediction

Abstract Resistance spot welding (RSW) is applied extensively by automotive manufacturers for assembling the structural and body components of vehicles. The current method of welding quality inspection is off-line inspection after welding, which cannot provide real-time feedback on welding quality and cannot meet the rhythm of modern production. Therefore, the online non-destructive testing technology of welding quality is worth studying. In this study, an RSW quality prediction model is developed using the improved grasshopper optimization algorithm combined with the generalized regression neural network (GRNN) algorithm, in which the actual process parameters including welding current, welding voltage, energy, power, and pulse width are used as inputs to predict the nugget diameter. During the network training process, the optimization algorithm is used for finding the optimum smoothing factor σ of GRNN, chaotic mapping, and non-uniform mutation are added to the traditional grasshopper optimization algorithm to enhance the optimization ability of the algorithm. Through bootstrap sampling, a comparison experiment about the prediction effect of the proposed quality prediction model with earlier methods is carried out, and the analysis of the experimental results leads to a conclusion that the accuracy of the proposed welding quality prediction model is higher.

Process and strength analysis of joining CF/PA6 composite plates without energy director by a servo-driven ultrasonic welder

A servo-driven ultrasonic welding (USW) offers a good control for joining carbon fiber reinforced thermoplastic composites (CFRTP) with a constant plunging speed, a dynamic applied force and adjusting power in real time. This study focuses on the process and strength analysis during servo-driven USW of CF/PA6 composites without energy director (ED) to obtain the correlation between the operation parameters and joint strength. The results show that a servo-driven welder benefits in USW without ED due to the initial intimate contact between workpieces without horn retraction. It is also found that a typical vibration process can be divided into four stages following the heat evolution and characteristic temperature of CFRTP, i.e., “initial stage”, “soften stage”, “melting stage” and “steady stage”. High energy and amplitude bring enough total energy and high power to melt materials; while a low trigger force and a slow plunging speed can mitigate the excessive squeeze-out with a result of the increase in weld strength. Thus, as the melted material remained in the weld region decides the bonding efficiency, the desired joints can be obtained under the enough welding energy (≥400 J) and amplitude (≥80%), not too high welding force (≤800 N) and plunging speed (≤0.8 mm/s). Meanwhile, weld quality can be online inspected and judged based on welding force evolution, and the measured displacement relative to the set value. This work contributes to the optimal parametric selection for USW of CFRTP plates without ED applying a servo-driven welder.

Optimization of Friction Stir Welding Operation using Optimal Taguchi-based ANFIS and Genetic Algorithm

The friction stir welding (FSW) process is an effective approach to produce joints having superior quality. Unfortunately, most published investigations primarily addressed optimizing process parameters to boost product quality. In the current work, the FSW operation of the aluminum alloy has been considered and optimized to decrease the specific welding energy (SWE) and enhance the jointing efficiency (JE) as well as micro-hardness at the welded zone (MH). The parameter inputs are the rotational speed (S), welding speed (f), depth of penetration (D), and tool title angle (T). The optimal adaptive neuro-based-fuzzy inference system (ANFIS) models were utilized to propose the welding responses in terms of the FSW parameters, while the Taguchi method was applied to optimize the ANFIS operating parameters. The neighborhood cultivation genetic algorithm (NCGA) was employed to determine the best solution. The obtained results indicated that the optimal values of the S, f, D, and T are 560 RPM, 90 mm/min, 0.9 mm, and 2 deg, respectively. The SWE is decreased by 17.0%, while the JE and MH are improved by 2.3% and 6.4%, respectively at the optimal solution. The optimal ANFIS models for the welding responses were adequate and reliably employed to forecast the response values. The proposed optimization approach comprising the orthogonal array-based ANFIS, Taguchi, and NCGA could be effectively and efficiently utilized to save experimental costs as well as human efforts, produce optimal predictive models, and select optimum outcomes. The observed findings contributed significant data to determine optimal FSW parameters and enhance welding responses.

Ultrasonic welding of polyetheretherketone for dental applications

ObjectiveDue to its favorable properties, the high-performance polymer polyetheretherketone (PEEK) is used as a metal-free alternative for the fabrication of denture frameworks. For dental applications, PEEK is available in different colors, such as red or white, by compounding with different fillers. In order to permanently bond such different dental PEEK types together in a denture framework, ultrasonic welding could be a viable process.Therefore, the aim of this study was to determine the optimum processing welding parameters for welding different dental PEEK grades in terms of maximum weld strength. MethodsRectangular plates from three PEEK compounds were prepared according to the dimensions of a removable partial denture (RPD) of PEEK. These were combined in a way that four groups resulted, whereas the combination of pure PEEK served as control. In each group, 5 samples were ultrasonically welded at one of four welding energies using a microprocessor-controlled ultrasonic welder, where the welder was activated only once. Afterwards, the samples were subjected to tensile tests to evaluate the shear bond strength (SBS) of the joint. ResultsIncreasing the welding energy resulted in an increase in the welding time. Accordingly, the increase in the welding energy increased the surface deformation for all tested samples. The shear bond strengths ranged from 4.8 ± 0.68 MPa for samples welded with 50 Ws to 16.37 ± 1.69 MPa for samples welded with 90 Ws. Excessive weld energy of 130 Ws led to a significant decrease of SBS due to a severe indentation and perforation induced by the sonotrode. SignificanceThe SBS and topography of the welded samples were systematically studied and the optimal welding parameters were determined. This could serve as a reference and instruction for clinical applications.

Assessment of the Corrosion Resistance and the Mechanical Properties of Laser Welded Joints Made of Steel DOCOL 1200M

The article presents test results concerning the corrosion resistance of laser beam welded joints made of steel DOCOL 1200M. The thickness of the joints subjected to the tests amounted to 1.8 mm. The joints were welded in the flat position (PA), without the use of the filler metal; the linear welding energy was restricted within the range of 25 J/mm to 55 J/mm. The non-destructive tests revealed that the joints represented quality level B in accordance with the ISO 13919 standard. The results of mechanical tests demonstrated the possibility of obtaining joints, the strength of which equalled that of the base material, which is unobtainable when welding such high strength steel (1200 MPa) using arc welding. The corrosion resistance tests were performed using the gravimetric method in alkaline, inert and acidic environments (0.1 M solution of sodium hydroxide (NaOH), the 3.5% solution of sodium chloride (NaCl) and the 0.1 M solution of sulphuric acid (VI) (H₂SO₄)). The material subjected to analysis was characterised by varied corrosion resistance, resulting from the test environments. The test joints contained various forms of corrosion-triggered damage including cracks, pits, swells and material losses. The above-presented corrosion resistance tests revealed that welded joints made of steel DOCOL 1200M were characterised by the highest corrosion resistance in the alkaline solution and the lowest corrosion resistance in the acidic solution.

Constructional Features and Energetic Parameters Influence on Structure Formation and Sealed Welded Joints Properties in the Production of Capsules for Hot Isostatic Pressing

The features of the formation of the structure of welded joints for various welding modes and energy parameters of welding capsules for hot isostatic pressing are given. Mechanical properties are investigated for each of the modes.

Projection-capacitor discharge resistance welding of 430 stainless steel and 14YWT

Efforts to advance structural materials with improved properties and service life in support of next generation designs for nuclear reactor components have recently led to development of nano-ferritic alloys (NFAs) containing nano-oxides such as 14YWT. A key enabling technology to realizing the useful properties of NFAs during service involves preservation of the oxide dispersions during joining. Solid-state welding processes, such as projection-capacitor discharge resistance welding (P-CDRW) used here, are well suited for joining NFAs while retaining the oxides. Due to limitations in the supply of 14YWT NFA material, initial experiments were conducted using 430 stainless steel as an inexpensive surrogate material. The goal of the surrogate experiments was to scale suitable parameters from 430 welds to 14YWT using ratios of key properties for the two materials including flow stress at temperatures and strain rates relevant to hot working. Results indicated that weld displacement increased with increasing weld force and increasing weld energy for all other variables held constant. Weld energy appeared to have a larger effect on displacement than weld force for the sample geometry used here. Appropriate process parameters (no melting) were established for the two materials. The process window for the 430 material extended from 350 J to 600 J of energy for weld forces of 2.2 kN and 3.1 kN. Suitable parameters for 14YWT were similar in terms of energy but for force levels of 3.1 kN and 4.0 kN. Displacement for both materials ranged from 150 μm to 300 μm for welds that did not experience melting. Simple heat flow analysis confirmed that the extent of displacement was limited by the characteristic thermal distance determined from thermo-physical properties and the weld current rise time. The higher flow stresses of 14YWT relative to 430 were apparently offset by greater heating due to higher electrical resistivity near the projection tip and lesser heat conduction from the projection tip owing to lower thermal conductivity. Based on the results presented here and in our companion paper. The P-CDRW process appears capable of successfully joining the 14YWT NFA while retaining the microstructures and properties of the original material.

Ultrasonic welding of short carbon fiber reinforced PEEK with spherical surface anvils

Ultrasonic welding of carbon fiber reinforced thermoplastic (CFRTP) has attracted increased attentions from researchers in the automotive and aerospace industries. This paper proposes a novel ultrasonic welding method for focusing the welding energy at the desired location without using the energy director (ED). An anvil with a spherical surface is used in the welding system instead of a conventional flat anvil. Short carbon fiber reinforced polyether ether ketone (CF/PEEK) is employed as the research material. The effects of spherical radius and welding energy on the weld formation are investigated. The microstructure, tensile-shear property, and fracture characteristics of the joints are also analyzed. The results show that the using of a spherical surface anvil can effectively concentrates the welding energy and therefore, reduces the scattered welds.