Weld Material Research Articles

Effect of thermophysical properties on porosity and microstructure of laser welded cast and wrought aluminum alloy dissimilar lap joints

The influence of thermophysical properties of materials on the porosity and microstructure of dissimilar lap joints between laser-welded Al–Si–Mg cast and Al–Mg–Si–Cu wrought aluminum alloys was investigated. The low thermal conductivity and viscosity of the weld would promote bubble escape, while the high electrical conductivity of the base material would increase the melt depth and reduce the convection intensity in the melt pool, thus increasing the difficulty of bubble escape. The variation in thermophysical properties did not significantly impact the distribution of elements, the type of precipitated phases, and the dislocation density, however, it did affect grain morphology. Differences in thermal diffusion coefficients between base materials created conditions for constitutional supercooling, increasing the likelihood of a columnar-to-equiaxed transition. Moreover, the temperature difference between the liquid phase lines of the weld and base materials facilitated the liquid base material flushed into the weld to solidify before mixing, resulting in an “island” formation. This “island” acted as a heterogeneous nucleation site, leading to equiaxed grain layer formation in the lowest zone of the weld. The variations in thermophysical properties exerted an influence on the tensile strength by impacting both the melt depth and the grain morphology of the weld but did not yield a significant impact on the average microhardness.

Epidemiological profile of occupational risks associated with artisanal burning of plastic materials in Parakou

Burning plastic releases toxic fumes and gases. More and more people engage in the professional activity of welding plastic parts by fusion in Benin. Hence the need for this study. To assess the frequency of the various occupational risks associated with the welding of plastic materials by burning in Parakou. A cross-sectional, descriptive, and analytical study focused on plastic welders in Parakou. The data was collected using a questionnaire. The variables studied were accidents at work, occupational diseases, and socio-professional characteristics. The data was analyzed by Epi info version 7.2.1.0. The significance level was set at p < 0.05. A total of 137 subjects were surveyed. They were all male. Almost all of them were victims of accidents at work. The lesions were mainly on the fingers (99%) and feet (99%). The most expressed morbid manifestations were musculoskeletal disorders (98%), rhinitis (87%), cough (79%), tearing (98%) and conjunctival hyperemia (93%). Plastic welding in Parakou is a high health risk activity for craftsmen. It is urgent to take protective measures for these craftsmen.

Ti3C2TX MXene@rGo Composite self-supporting membrane and its welding process

Ti3C2Tx MXene@rGo self-supporting film was prepared by HF etching and LiF/HCl etching method, and film welding was realized for the first time. The results showed that Ti3C2Tx MXene with typical accordion-like morphology was obtained by HF etching. In the Ti3C2Tx MXene@rGo self-supporting film welding test, it was found that in the time-sensitive period, Ti3C2Tx MXene@rGo self-supporting film can be welded with water as the medium, effectively ensuring the stability of the material welding. If beyond the time-sensitive period, the self-supporting film will lose weldability. This study is a significant advancement for the large-scale Ti3C2Tx MXene@rGo composites.

Microstructure and Pitting Corrosion Characteristics of Tig Welded Joints of Super 304HCu Austenitic Stainless Steel

Abstract Super 304HCu is an advanced ultra-super critical (A-USC) boiler grade austenitic stainless steel with the distinct addition of 3 wt.-% of Copper. A-USC power plants intended to operate in chloride rich environments (sea shore, feed water residues, etc.) are susceptible to chloride assisted corrosion failures. In this study, the pitting corrosion behaviour of the Super 304HCu parent material and tungsten inert gas weld joints was studied using a potentiodynamic cyclic polarization test in 3.5 % NaCl solution at three different pH levels (pH = 3, pH = 7, and pH = 11). The Epit values of the parent material is found to be much nobler than that of the weld joints. The micrographs of the pitted weld joints and the oxalic acid etched structure of Super 304HCu joints are presented. From the micrographs it is revealed that the heat affected zone is the most susceptible region to pitting corrosion.

Thermomechanical Modeling of Material Flow and Weld Quality in the Friction Stir Welding of High-Density Polyethylene.

A thermomechanical model of the friction stir welding (FSW) of high-density polyethylene (HDPE) was developed by incorporating a Coupled Eulerian-Lagrangian (CEL) approach. A Johnson Cook (JC) material model of HDPE was developed through experimentally generated strain-rate- and temperature-dependent stress strain data. Two sets of FSW process parameters with minimum and maximum weld defects were numerically modeled. The numerically calculated temperature distribution, material flow and flash and potential defects were validated and discussed with the experimental results. Tracer particles allowed to visualize the material movement during and after the tool had traversed from the specified region of the workpiece. Both numerical models presented similar maximum temperatures on the upper surface of the workpiece, while the model with high traverse speed and slow rotational speed had narrower shoulder- and heat-affected zones than the slow traverse, high rotational speed model. This contributed to the lack of material flow, hence the development of voids and worm holes in the high traverse speed model. Flash and weld defects were observed in models for both sets of process parameters. However, slow traverse, high rotational speeds exhibited smaller and lesser weld defects than high traverse, slow rotational speeds. The numerical results based on the CEL approach and JC material model were found to be in good agreement with the experimental results.

Resistance spot welding behaviour of novel medium manganese (M-Mn) steels - Role of welding parameters on weld microstructure and mechanical properties

Medium Mn (M-Mn) steels are classified as third-generation advanced high-strength steels (3G-AHSS) and have demonstrated outstanding mechanical properties. As a result, they are being considered as potential materials for use in the automotive industry. Spot weldability of materials is an essential requirement for the body in white (BIW) structures in automotive vehicles. Resistance spot welding (RSW) M-Mn steel can be challenging because it can lead to the formation of a fully martensitic microstructure. This work established the weld growth curve on M-Mn steel in the 4 to 8 kA current range. Based on this, single pulse (6 kA) and double pulse current (first pulse of 6 kA followed by the second pulse of 4 to 7 kA) were employed to investigate the microstructure, elemental segregation, cross-tensile strength (CTS), and fracture behaviour of the M-Mn steel welds. These welds, in all conditions, exhibited a martensitic microstructure with retained austenite content of <10 %. In all welding conditions, martensite softens along the heat-affected zone (HAZ) boundary, yielding tempered martensite and carbides. A study of chemical homogeneity using electron probe microanalysis (EPMA) demonstrated that Mn and Si segregate along the weld nugget (WN) edge during single (6 kA) and double (6–6 kA and 6–7 kA) pulsing. Mn and Si segregation is less prominent in double pulse welds at lower pulse currents (<6–6 kA). The elemental segregation at higher pulse currents is higher due to the more pronounced thermal gradient within the weld nugget, which promotes elemental segregation at the interface. Based on the cross-tension test results, the double pulse welds (6–7 kA) had the maximum CTS (1.26 kN) and energy absorption (2 J). The failure mode in this condition is a predominantly partial interfacial failure (PIF) with a plug ratio of about 50 %. This is attributed to the larger nugget diameter and refined martensitic structure. Complete interfacial failure (IF) leading to interdendritic fracture and a plug ratio of 0 % was observed when two equal pulse currents (6–6 kA) were applied. This can be attributed to remelting of WN and a high degree of Mn and Si segregation. From the above studies, we can conclude that M-Mn steel is weldable; however, further strategies are necessary to enhance the CTS of M-Mn steel welds.

Friction Stir Welding of Heat-Resistant Materials for Aircraft Engines

Friction Stir Welding of Heat-Resistant Materials for Aircraft Engines

A spiral slotted transducer with high longitudinal-torsional conversion rate

The longitudinal-torsional (L-T) composite piezoelectric transducer has wide applications in material processing, welding, and other fields due to its exceptional machining efficiency. This study introduces a spiral slotted L-T transducer, which is designed to achieve a high L-T conversion rate at low operating frequency. The equivalent spring concept is employed to derive the equivalent circuit of the L-T transducer, which provides a convenient study for the frequency characteristics of the transducer. A finite element model is developed to analyze the performance of the transducer and investigate the effect of the spiral slot parameters on the resonance frequency, amplitude, and the L-T conversion rate of it. Two prototype transducers are constructed and measured experimentally. Theoretical computation results, finite element simulation results, and experimental results are compared to each other. The comparison results demonstrate that the proposed computation model provides accurate prediction of the L-T coupling resonance frequency of the transducer. By adjusting the spiral slot parameters of the transducer, a higher L-T conversion rate can be achieved, which may have more applications in practical engineering.

X-ray analysis of welding parameters influence on pressure vessel steel P355 N

The paper presents a study on the influence of welding parameters that is done by radiographic interpretation of the X-ray analysis results collected from welded joins that had been realized by varying the welding current intensity, tension and welding speed. The base material of the experiment is a pressure vessel steel P355 N used for constructing railway tanks for transporting liquids by train. The welding method used is flux-cored arc welding, done by a semi-automatic welding machine using welding wire as joining material. The research aims to find connections between different material welding defects and the welding parameters involved in the process of flux-cored arc welding.

Research of the stress-strain state of the loaded assembly for friction welded device

This article presents the results of the study of methods for friction welding of dissimilar materials and the calculations to determine the structural strength of the most loaded part of a special friction welding device were made. The analysis showed that the friction welding method has wide technological capabilities and it is used in various industries. The designs of existing devices and machines for friction welding were also investigated. It was revealed that the method of friction welding in the conditions of machine-building plants of the Republic of Kazakhstan (RK) has not found application due to the little knowledge and high cost of technological equipment. The authors have developed a special device for friction welding of dissimilar materials. To optimize the parameters of the parts, in particular the bracket part, the stress-strain state calculations were performed using the ANSYS software package and the strength calculation by determining the acting external critical loads. The results of the calculation showed the applicability of the developed design of the bracket part.

Investigation on microstructure and mechanical properties of electron-beam-welded joint of reduced activation ferritic/martensitic steel fabricated by selective laser melting

The microstructure and mechanical properties of the complex low-activation ferritic–martensitic components of the China Fusion Engineering Test Reactor (CFETR) were examined in this study. The quenching–tempering treatment of CLF-1 steel formed by selective laser melting (SLM) (referred to as the QTed material) was carried out to analyze the effects of heat treatment on the microstructural and mechanical properties. Meanwhile, the microstructural and mechanical characteristics of CLF-1 steel electron beam welding (EBW) joints after quenching–tempering (referred to as the EBWed material) were investigated. Compared with the untreated sample (referred to as the SLMed material, with an ultimate tensile strength (UTS) = 979.8 ± 12.7 MPa and elongation (EL) = 3.7% ± 0.4%), the quenching–tempering treatment improved the EL of CLF-1 steel effectively (QTed material, 22.3% ± 0.1%), while it decreased the UTS correspondingly (505.6 ± 11.8 MPa), which mainly was due to the change in the grain size and structure during the heat treatment. The special microstructural distribution characteristics of the CLF-1 fabricated via SLM determined that the fracture mechanism was transgranular ductile/intergranular brittle mixed fracture. After electron beam welding of the QTed material, the tensile properties of the joint (UTS = 710.6 ± 21.4 MPa, EL = 9.7% ± 0.1%) were between those of the SLMed and QTed materials. The fracture appeared in the heat-affected zone (HAZ), proving that the strength of the weld was higher than that of the base metal. The microstructure of the weld was almost completely composed of coarse lath martensite, and the accumulation of dislocation clusters, precipitated M23C6-type carbides, and precipitated MX-type carbides contributed to the improvement of the yield strength (YS). The HAZ could be divided into three regions based on the different heating temperatures, and every region had different grain structures composed of mainly martensite and ferrite. The contributions of four strengthening mechanisms to the YS of CLF-1 steel were analyzed quantitatively, which lays a foundation for further improving the performance of CLF-1 steel and improving its application feasibility on the first wall of a fusion reactor.

The mechanical properties of dissimilar/similar polymer materials joined by friction stir welding

Joining dissimilar materials is important in engineering studies to reduce costs, lighten structures, and take advantage of the superior properties of the materials. However, the different chemical compositions, physical, and mechanical properties of dissimilar materials make the joining process difficult. To overcome the limitations of traditional joining techniques, there is an increasing interest towards innovative welding methods such as ultrasonic welding, laser welding, friction stir welding, and so on. In this study, friction stir welding was used to join different types of polymer materials. Polylactic acid (PLA Plus) plates were 3D printed and welded with High Density Polyethylene (HDPE) to create PLA Plus/PLA Plus, HDPE/HDPE, and PLA Plus/HDPE connection pairs. Two different pin profiles (triangle and square), rotational speed (1000 and 1500 rpm) and feed rate (30 and 50 mm/min) were used in the FSW process. Tensile tests were performed to determine the weld strength after FSW. In addition, the hardness changes in the heat-affected zone and in the weld zone were evaluated. Finally, optical inspections were made on the welded samples to identify welding defects. The results showed that the highest weld strength was obtained with the triangular pin profile in PLA Plus/PLA Plus and PLA Plus/HDPE material pairs, and while with the square pin profile in HDPE-HDPE pairs. PLA Plus has been found to be a more suitable material for Friction Stir Welding compared to HDPE. Welding defects caused by changes in welding speed and tool rotation speed were identified in the material pairs.

Fatigue crack propagation performance of Q690 high-strength steel and butt welds

The fatigue performance of high-strength steels is an important issue in bridge engineering. In this study, fatigue crack propagation rate tests and theoretical studies of high-strength steel Q690 base material and butt welds were conducted. Two types of compact tensile (CT) specimens—one for the Q690 compact tensile specimens and the other for the butt welds—were used for the test under stress ratios of R = 0.1, 0.3, and 0.5, with a loading frequency of 15 Hz. The fatigue crack length was measured using the flexural method with an extensometer, and the load value and the corresponding cycle number in the tests were also obtained. These results were processed using the seven-point polynomial method to obtain the fitting curve of log (da/dN) to log ΔK. Finally, the modified Paris formula of Q690 was presented, and the corrected values of the material parameters C and m were determined. The test results show that the fatigue crack propagation rate of Q690, both for the compact tensile specimens and those with butt welds, increased with the stress ratio R. The fatigue crack propagation rate of Q345qD was 1.8 times higher than that of Q690 high-strength steel. In addition, the fatigue resistance of Q690 was significantly higher than that of other standard steels. The fatigue crack propagation rate of the Q690 specimens with butt welds at a low-stress amplitude was lower than that of the Q690 compact tensile specimen. At a high-stress amplitude, the fatigue crack propagation rate of Q690 is greater than that of the Q690 compact tensile specimen.

Interfacial investigations on the microstructure evolution and thermomechanical behavior of explosive welded CLAM/316L composite

In this paper, a comprehensive study combined multiple characterizations and SPH numerical simulation was conducted to investigate the microstructure evolution, extreme thermomechanical behavior and consequences of the explosive welded CLAM/316L interface. The interfaces of the two welding materials underwent remarkable temperature rise and rapid cooling under high-speed collision conditions, forming a tight bond that presents a wavy structure with vortices. The SPH simulation adequately reproduced the heating and cooling process of the interface during explosive welding, revealing the high heterogeneity of the thermodynamic behavior during the impact process. Furthermore, the EBSD analyses showed the perplexing evolution of crystal structure at the bonding interface with vortex, including ultra-fine grains, columnar grains, equiaxed grains, deformed grains and serious lattice distortion. By correlating the temperature histories and grain characteristics at different positions of the interface, the formation mechanism of diverse grains was revealed, referring to crystallization from liquid, recrystallization from the solid and plastic deformation. The recrystallization at the interface was closely related to the material properties, and the significant variations in dislocation density and plastic strain values at the interface, as well as the thermal softening of the material, could be explained by different degrees of dynamic recovery and recrystallization.

An attractive attempt: Facile and direct adhesive of cellulose substrates using inorganic metal salt through partial welding

The development of cellulose-substrate remedies remains a technological challenge owe to their inability to self-heal and excessive dependence on petroleum-based adhesives, which is further hindered by the significant drawbacks of commercially unavailable welding materials and inconvenient manipulation. We herein describe a cellulose-substrate bonding technique achieved through partial dissolution using a low dosage of ZnCl2 aqueous solvent (ZS) and its dissolved cellulose (ZDC) gel as adhesives. This method demonstrates strong joint areas between strips without any failure, while shrinkage in the diffusion area remains the main cause of breakage. This shrinkage phenomenon can be alleviated by using ZDC instead of ZS, due to the water retention of hydrophilic hydroxyls on the macromolecular chains of dissolved cellulose. The well-maintained tensile strength of the ZDC-bonded strip (5.0% lower than the control) indicates that partially dissolved cellulose fills gaps between fibers, providing evidence for a mechanical interlocking adhesive mechanism in strip connections. ZDC gels exhibit favorable adhesive behavior for hand-sheets, art paper, and corrugated board, with welded joints demonstrating robust mechanical performance even after soaking in water for 6 h.

TARGET – Development of Submersible ROV System for BMN Inspection

Most PWRs have penetrations in the RPV lower heads for in-core nuclear instrumentation. These penetrations generally are made of nickel-based Inconel Alloy 600. Weld materials are typically Alloy 82/182. Operating conditions of PWR plants are causing nickel-based alloys cracking through a process called primary water stress corrosion cracking (PWSCC). In 2003, the licensee for the South Texas Project Unit 1 (STP-1) identified apparent boron deposits on the lower RPV head near two bottom mounted nozzles (BMNs). The NRC issued Bulletin 2003-02 to obtain information on licensee inspection activities and inspection plans for the RPV lower head. EPRI issued MRP-206 report that provides inspection and evaluation guidelines for BMNs for PWR plants, including guidelines for periodic bare metal visual examination for evidence of primary coolant leakage, or periodic non-visual nondestructive examinations for indications of service-induced cracking. The non-visual inspections (ultrasonic testing examination) may detect service-induced degradation before through-wall cracking, leakage, circumferential cracking below the bottom of the J-groove weld, release of loose parts, or incipient boric acid wastage of the low-alloy steel reactor vessel lower head material occurs. Therefore, periodic examinations will adequately manage potential for cracking by PWSCC and preserve structural integrity. INETEC developed TARGET system for BMNs inspection, consisted of submersible ROV and specially designed probe, composed of several UT probes. UT system and technique to detect, length and depth size the service-induced degradation in the BMN volume material is developed. The EPRI NDE Center performed a technical review and validated INETEC’s ultrasonic examination technique for BMNs. Aforementioned validation was done according to requirements defined by: 1) MRP-206, 2) MRP-411.

Simple inverse FEM based procedure of flow curve extraction applied to unirradiated and irradiated 73 W weld material

The H2020 FRACTESUS project is aimed to validate miniaturized compact tension specimens usage for fracture toughness characterization of irradiated materials. One of the tasks in the project is devoted to the numerical simulations of the 0.16T and 1T-CT specimens and comparison of their stress/strain fields in. For this purpose accurate material flow curves are necessary to derive comparable mechanical response between the numerical models and experiments. This paper presents a simple technique of flow curve extraction from the tensile test using engineering stress–strain data. The proposed method utilizes a coarse meshed Finite Element Model and a manual flow curve data optimization procedure without additional scripting. The robustness of the method was shown on the example of the 73 W weld material in the unirradiated and irradiated states, tested at various temperatures from −100 °C to 125 °C. The obtained numerical flow curves are in a very good agreement with the experimental results. Moreover, the advantages of the proposed method were shown over either the methods based on extrapolation of the predictions of popular models with parameters fitted to prior necking or the method based on fracture diameter measurements. The final validation of the proposed methodology was demonstrated by numerical simulations of fracture toughness tests on precracked Charpy specimens.

Effect of Weld Design of Transition Layer on Microstructure and Properties of Welded Joints of S32304/Q390C Composites

Due to the large difference in physical and chemical properties between the substrate and the cladding material, the welding of composite materials is much more difficult than that of single materials. In our work, S32304/Q390C composite material was considered as the research object. By adjusting the welding parameters, two kinds of joint geometry were obtained, namely, the transition layer weld lower (joint A) and higher the composite material interface (joint B). We studied the influence of the transition layer weld on the microstructure and properties of welded joints. The microstructure of the transition layer weld, the distribution of elements, the Schmidt factor of the interface between the transition layer and base layer weld, and the tensile strength of the joint were evaluated. The results show that with the increase of welding heat input, the microstructure of the transition layer weld changes from austenite and skeleton ferrite to austenite and lathy ferrite and austenite and acicular ferrite, while ferrite grows towards the weld center, showing a dendritic shape and a local network structure. At the side of the base layer weld of the interface between the transition and the base layer weld, the thickness of the low-carbon-content layer increased from 100 μm to 150 μm. Iron, chromium, and nickel elements on both sides of the interface were diffused, and the thickness of the diffusion layer increased from 3 μm to 10 μm. The tensile strength values of joints A and B were 648 MPa and 668 MPa, respectively, and the Schmidt factor values were 0.446 and 0.454, respectively. Combination with the analysis of the fracture morphology showed that when the transition layer weld was higher than the interface of the composite plate, the joint had better plastic deformation ability and higher tensile strength.

Nonlocal approach to fatigue analysis of a welded bicycle frame joint

AbstractThe paper attempts to predict the probabilistic fatigue strength scatter bands of a welded bicycle frame joint. The experimental data of the base material and the weld material were approximated by a nonlinear probabilistic model of the Weibull distribution. The fatigue strength for the material at the fatigue crack location was estimated considering the mean stress, residual stress, fatigue notch factor, and hardness profile. The output finite element numerical data of the real welded joint were compared with a nonlocal multiaxial fatigue criterion. The implementation of the volumetric method takes into account the stress gradient effect in the three‐dimensional geometry of the weld toe. The comparative localization of the minimum stress and the real crack indicates the validity of the numerical model. The predicted fatigue strength determines the possible failure of a welded joint at 5·105 cycles.

Preface

The 2023 4th International Conference on Advanced Materials and Clean Energy (ICAMCE 2023), supported by Jiangsu University School of Materials Science & Engineering, is to publish the latest results of research and development on the material and energy science and technology. The seminar has been held since 2020, therefore in 2023 is its fourth session.ICAMCE 2023 took place in Hangzhou, China during 17th to 19th February 2023 (virtual form) with about 60 attendees. The main objective of the Conference is to provide an international cooperation and exchange platform for experts and scholars in the field to deliberate latest developments and future directions in Advanced Materials and Clean Energy, and an opportunity for enterprise developers to discuss existing problems and challenges, and explore frontier science and technology.We have invited several resources persons from different parts of China and other about 10 countries to deliver expertise lectures by imparting the latest findings from their respective research domains. Hui Pan is a professor from the Institute of Applied Physics and Materials Engineering and Department of Physics and Chemistry in the Faculty of Science and Technology at the University of Macau, China. In his research, a combined computational and experimental method is used to design and fabricate novel nanomaterials for applications in green energy and environments (such as electro-/photo-catalysis, water splitting, CO2/N2 reduction, and fuel cells), electronic/quantum devices, and spintronics. He has published more than 230 papers in international peer-reviewed journals, such as Phys. Rev. Lett., Adv. Energy Mater., and Chem. Mater.. It was a great opportunity for the students, researchers and engineers to interact with the experts and specialists to get their advice or suggestions.The proceedings of the present Conference covers the following topics: New Semiconductor Materials, Optoelectronic Materials, Composite Materials for Wind Power Generation, Welding and Connection, Alternative Energy Technologies, Clean Energy Systems and Technologies, Thermodynamics and Energy Optimization, etc.. Arigorous peer review process was conducted to check the quality, originality, innovation point of the papers accepted in this proceedings which will be published in the format of printed books.We would like to express our sincere thanks to all the authors for their research contributions, and also to the organizers of the Conference for their valuable spadework. Also, our heartfelt thanks and appreciation to the Editors and Managers, Journal of Physics: Conference Series of IOP Publishing Ltd. for their help and kind cooperation during the preparation of the proceedings.We hope you will benefit from all the manuscripts of the proceedings and learn new and novel ideas!The Committee of ICAMCE 2023List of Committee Member is available in this Pdf.