Subjects -> METALLURGY (Total: 58 journals)
Showing 1 - 10 of 10 Journals sorted alphabetically
Acta Metallurgica Slovaca     Open Access  
Advanced Device Materials     Open Access   (Followers: 3)
American Journal of Fluid Dynamics     Open Access   (Followers: 47)
Archives of Metallurgy and Materials     Open Access   (Followers: 8)
Asian Journal of Materials Science     Open Access   (Followers: 5)
Canadian Metallurgical Quarterly     Hybrid Journal   (Followers: 20)
Complex Metals     Open Access   (Followers: 1)
Corrosion Communications     Open Access   (Followers: 5)
Energy Materials : Materials Science and Engineering for Energy Systems     Hybrid Journal   (Followers: 19)
Handbook of Magnetic Materials     Full-text available via subscription   (Followers: 2)
Indian Journal of Engineering and Materials Sciences (IJEMS)     Open Access   (Followers: 10)
International Journal of Metallurgy and Alloys     Full-text available via subscription   (Followers: 3)
International Journal of Metals     Open Access   (Followers: 6)
International Journal of Minerals, Metallurgy, and Materials     Hybrid Journal   (Followers: 8)
International Journal of Mining and Geo-Engineering     Open Access  
Ironmaking & Steelmaking     Hybrid Journal   (Followers: 4)
ISIJ International - Iron and Steel Institute of Japan     Full-text available via subscription   (Followers: 23)
Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional’nye Pokrytiya (Proceedings of Higher Schools. Powder Metallurgy аnd Functional Coatings)     Full-text available via subscription   (Followers: 2)
JOM Journal of the Minerals, Metals and Materials Society     Hybrid Journal   (Followers: 32)
Journal of Advanced Joining Processes     Open Access  
Journal of Central South University     Hybrid Journal   (Followers: 1)
Journal of Cluster Science     Hybrid Journal  
Journal of Heavy Metal Toxicity and Diseases     Open Access  
Journal of Iron and Steel Research International     Hybrid Journal   (Followers: 7)
Journal of Materials & Metallurgical Engineering     Full-text available via subscription   (Followers: 1)
Journal of Materials Processing Technology     Hybrid Journal   (Followers: 18)
Journal of Metallurgical Engineering     Open Access   (Followers: 2)
Journal of Sustainable Metallurgy     Hybrid Journal   (Followers: 3)
Materials Science and Metallurgy Engineering     Open Access   (Followers: 7)
Metallurgical and Materials Engineering     Open Access  
Metallurgical and Materials Transactions A     Hybrid Journal   (Followers: 42)
Metallurgical and Materials Transactions B     Hybrid Journal   (Followers: 31)
Metallurgical and Materials Transactions E     Full-text available via subscription   (Followers: 2)
Metallurgical Research & Technology     Full-text available via subscription  
Metallurgical Research and Technology     Full-text available via subscription   (Followers: 6)
Metallurgy and Foundry Engineering     Open Access  
Mining, Metallurgy & Exploration     Hybrid Journal  
Powder Diffraction     Full-text available via subscription   (Followers: 1)
Powder Metallurgy     Hybrid Journal   (Followers: 33)
Powder Metallurgy and Metal Ceramics     Hybrid Journal   (Followers: 7)
Powder Metallurgy Progress     Open Access   (Followers: 5)
Rare Metals     Hybrid Journal   (Followers: 1)
Revista de Metalurgia     Open Access  
Revista del Instituto de Investigación de la Facultad de Ingeniería Geológica, Minera, Metalurgica y Geográfica     Open Access  
Revista Remetallica     Open Access  
Russian Metallurgy (Metally)     Full-text available via subscription   (Followers: 4)
Science and Technology of Welding and Joining     Hybrid Journal   (Followers: 4)
Soldering & Surface Mount Technology     Hybrid Journal   (Followers: 1)
Stainless Steel World     Full-text available via subscription   (Followers: 17)
Transactions of the IMF     Hybrid Journal   (Followers: 14)
Transactions of the Indian Institute of Metals     Hybrid Journal   (Followers: 4)
Tungsten     Hybrid Journal  
Universal Journal of Materials Science     Open Access   (Followers: 1)
Welding in the World     Hybrid Journal   (Followers: 4)
Welding International     Hybrid Journal   (Followers: 7)
Вісник Приазовського Державного Технічного Університету. Серія: Технічні науки     Open Access  
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Welding in the World
Journal Prestige (SJR): 0.533
Citation Impact (citeScore): 2
Number of Followers: 4  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0043-2288 - ISSN (Online) 1878-6669
Published by Springer-Verlag Homepage  [2469 journals]
  • Effect of process parameters and heat treatments on delta-phase
           precipitation in directed energy deposited alloy 718

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      Abstract: This article outlines a detailed study of solution treatments and delta precipitation treatments carried out on laser-directed energy deposited (DED) alloy 718 specimens. Two different sets of DED process parameters were used in high and low energy conditions that yield different microstructural features to study the effect of process parameters on delta precipitation. These two conditions were subjected to solution treatment at 1010 °C and 1050 °C each for 1 h, which improved homogeneity and altered grain texture with introduction of annealing twins. The as-built and solution-treated specimens served as the initial reference condition for subsequent delta processing treatments (DPT) performed at three temperatures of 850 °C, 900 °C, and 950 °C to study the effect of short- and long-term exposures ranging from 1 to 48 h. When as-built specimens were subjected to DPT, interdendritic delta precipitates were observed at Nb-rich regions. In contrast, solution-treated specimens under short-term exposure to DPT resulted in intergranular delta phase precipitates whereas under long-term exposures to DPT yielded predominantly intragranular delta precipitates, which grew denser and longer with increased time of treatment. For longer exposure times of 24 and 48 h, a continuous film of intergranular delta phase was noticed. The morphology, location, and volume fraction of delta phase precipitates studied in this research are imperative for designing the performance of alloy 718 built by DED process.
      PubDate: 2022-01-24
       
  • Investigation of carbide precipitations on microstructure and hardness of
           medium carbon Cr-Ni austenite stainless hardfacing deposit with high wear
           resistance properties

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      Abstract: Generally, the Cr-Ni austenite stainless steels have high corrosion resistance and good weldability, but are not used as wear-resistant material due to their low hardness. The studies were carried out to enhance the wear resistance of deposited hardfacing metals of the stainless steel by shielded metal arc welding, maintaining its superior properties at high levels. The hardfacing metals of the medium carbon Cr-Ni austenite stainless steel were deposited, using electrodes coated with flux including C and strong carbide-forming elements (Cr, Mo, V) on 18Cr-8Ni stainless steel wire. In an as-welding state, the matrix phases and precipitation of carbides in hardfacing metals were investigated, using X-ray diffraction, scanning electron microscopy, and energy-dispersive spectrometry. The surface hardness (HB) and microhardness (HV) of the metals were measured. It was found that carbides formed by Cr, Mo, and V were precipitated a lot in the austenite matrix and at the grain boundaries; thus, the surface hardness of deposited hardfacing metals was about HB 300–500, enough for high wear resistance while maintaining austenite (γ) phase as the matrix, and the effectiveness investigated by simple corrosion wear experiments.
      PubDate: 2022-01-22
       
  • Influence of the rotation speed on the interface microstructure and
           joining quality of aluminum alloy 6061/CF-PPS joints produced by refill
           friction stir spot welding

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      Abstract: The application of lightweight materials in automotive industry creates the demand to develop reliable and cost-effective solutions for joining hybrid material parts and assemblies. In this work, the microstructure and mechanical properties of the dissimilar joint between aluminum alloy 6061 (AA6061) and carbon fiber-reinforced polyphenylene sulfide (CF-PPS) processed by refill friction stir spot welding (RFSSW) were investigated. The results show that the joining between AA6061 and CF-PPS is attributed to the combined effect of mechanical interlocking and adhesive bonding. The rotation speed affects the porosity at the AA6061/CF-PPS interface which is the governing factor of the joints’ peak load during the lap-shear test. Varying rotation speed from 1000 to 1400 rpm, it illustrated that the lap-shear joints produced under 1200 rpm possess the highest peak load of 1460 N. Besides, it is observed that the joints produced with 1200 rpm have a thicker adhesive layer, which possess a strong mechanical interlocking effect. The failure mechanism for the joints includes cohesive and adhesive fracturing. Under the optimized rotation speed, the fracturing surface of the sample possess dimples with fiber pull-outed fibers, which infers a ductile failure.
      PubDate: 2022-01-22
       
  • Effects of solder thickness on interface behavior and nanoindentation
           characteristics in Cu/Sn/Cu microbumps

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      Abstract: The thickness of the solder, for Cu/Sn/Cu microbumps with dimensions of tens of microns or even a few microns (such as 40 µm, 15 µm, 10 µm, and 6 µm), can have a significant effect on the interfacial transfer and the performance. During the reflow stage, it was found that the grains of Cu6Sn5 showed “staggered growth” phenomenon in some areas of the microbumps with the solder thickness of 6 µm and the thickness of intermetallic compounds’ (IMCs) layer grew the fastest; that the second fastest growth of 40 µm; that the third fastest growth of 15 µm, and that the slowest growth of 10 µm. After thermal aging at 160 °C for 80 h, the thickness of the IMC layer in descending order was the microbumps with the solder thickness of 15 µm, 10 µm, 40 µm, and 6 µm. These results were caused by the difference in the element concentration. In addition, there were four main components in the microbumps: Cu, Sn, Cu6Sn5, and Cu3Sn. The hardness of Cu and Sn was about 1.37 ± 0.3 Gpa and 0.13 ± 0.03 Gpa, respectively. And the hardness of Cu6Sn5 and Cu3Sn was about 6.7 ± 0.3 Gpa and 6.2 ± 0.4 Gpa, respectively. The nanoindentation hardness analysis showed a general increase in the hardness of the microbumps after thermal aging for 80 h, compared with that after reflow. And the thinner the solder thickness was, the more obvious the hardness improvement was.
      PubDate: 2022-01-22
       
  • Comparison of the core–shell and mechanical mixing of the Ni–Cr-P-Cu
           composite filler metal

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      Abstract: The Cu@BNi-7 core–shell structure composite filler metal prepared by the electroless plating method and the mechanical mixing BNi-7 + 5%Cu composite filler metal is applied for the improvement of the uniform distribution of the element Cu in the brazing seam. The microstructure and the mechanical properties of the joint brazed with Inconel 718 using the two types of composite filler metals are investigated. Compare to the joint brazed using the mechanical mixing filler metal, the core–shell structure composite filler metal is beneficial for the formation of the Ni(Cu, Fe, Cr)ss solid solution, which is evenly distributed in the joint. The brazing temperature influences the element diffusion and results in the formation of the incomplete diffused granular structure with large numbers in the joint when the temperature is lower. The nanoindentation and the shear strength test of the joints are conducted, and the large-area distributed Ni(Cu, Fe, Cr)ss solid solution could release the residual stress and make the crack expand around the solid solution. Consequently, the core–shell structure Cu@BNi-7 composite filler metal shows better performance. The maximum shear strength of the brazed joint using Cu@BNi-7 composite filler metal is 220 MPa, which is 53% higher than the brazed joint using the BNi-7 + 5%Cu composite filler metal.
      PubDate: 2022-01-22
       
  • Development and implementation of a software for wire arc additive
           manufacturing preprocessing planning: trajectory planning and machine code
           generation

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      Abstract: To overcome a shortage of flexible and low-cost solutions for wire arc additive manufacturing (WAAM) preprocessing, this work’s objective was to develop and validate an in-house computational programme in an open-source environment for WAAM preprocessing planning. Algorithms for reading STL (stereolithography) files and implementing rotation, slicing, trajectory planning, and machine code generation were elaborated and implemented in the Scilab environment (free and open-source). A graphical interface was developed to facilitate user interaction, with 5 options for path planning. The functionality of each work step is detailed. For validation of the software, single and multiple-layer prints, with different geometrical complexity and printing challenges, were built in a CNC table geared by the generated machine code. The validation criteria were deposition imperfection, morphological, and dimensional tolerances. The outputs showed that the parts were successfully printed. Therefore, this work demonstrates that Scilab provides the necessary resources for companies and universities to implement and/or develop algorithms for planning and generating trajectories for WAAM. Moreover, emerging ideas can be reasonably easily implemented in such software, not always possible in commercial packages.
      PubDate: 2022-01-21
       
  • Study on mechanical properties and microstructure development of Inconel
           718 ultrathin-walled capillary-and-plate brazed structure using BNi-5
           filler metal

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      Abstract: The fuel indirect precooled turbine combined cycle engine is the promising power to realise more green environmental protection intercontinental navigation and hypersonic aerospace transportation in the future. The compact, lightweight precooler arranged in the front of the inlet is a critical component of the advanced heat management system, which could improve the fuel efficiency and flight range of the turbine engine. This paper mainly focuses on the high-temperature brazing process of Inconel 718 ultrathin-walled capillary-and-plate brazed structure using the BNi-5 brazing filler metal. In this investigation, a testing method for tensile strength of ultrathin-walled structures was proposed; the effects of different brazing parameters on the mechanical properties and microstructure evolution of different types of brazed structures were studied to investigate the particularity of ultrathin-walled capillary-and-plate brazed structure. The brazed joint was mainly composed of γ-Ni solid solution, Ni5Si2, G-phase, Ni3Si, and Cr3Ni5Si2. The results showed that the higher brazing temperature and longer holding time were beneficial to improve the mechanical properties of the conventional lap brazed structure; however, the mechanical properties of the ultrathin-walled capillary-and-plate structure decrease significantly. The optimised brazing process for the ultrathin-walled structure was 1150 °C for 3 min; dissolution behaviour of the ultrathin-walled capillary and the deeper position of the precipitates induced by the acute diffusion phenomenon play an important role in the tensile strength of the ultrathin-walled structure. And the failure mechanism was analysed in detail; the result indicated that ultrathin-walled capillary-and-plate brazed structure was mainly affected by the eutectic structure of the brazing fillet; the Nb-rich precipitates in the diffusion affected zone and the dissolution behaviour of the ultrathin-walled base metal.
      PubDate: 2022-01-21
       
  • Effects of welding defects on the fatigue properties of spot welded
           automobile steel sheets and the establishment of a fatigue life evaluation
           method

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      Abstract: The welded areas of spot welding of actual vehicles are confirmed welding defects such as blowholes between steel plates. However, most of studies on the strength reliability of spot welded structures do not consider welding defects, and it is necessary to clarify the effects of weld defects on the strength reliability of spot welded structures. This study investigated the effect of the size and location of through holes simulating welding defects on the fatigue properties of tensile-shear-type spot welded joints using automobile steel sheets. Moreover, the effect of the loading type both tensile-shear and cross-tension type on the fatigue properties of the spot welded joints was investigated, and a unified evaluation of the fatigue life for different loading type joints was established. The size and location of a welding defect do not affect the fatigue strength or the fatigue fracture morphologies of tensile-shear-type spot welded joints. This is because the slit tip of spot welded joints is in the singularity stress field under mixed-mode condition, regardless of the welding defect of the joint. Therefore, the equivalent stress intensity factor at the slit tips of joints can uniformly evaluate the fatigue life of joints with different loading types.
      PubDate: 2022-01-21
       
  • Determination of notch factors for transverse non-load carrying stiffeners
           based on numerical analysis and metamodeling

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      Abstract: Stress concentration factors (SCFs) at weld toes and weld roots as required for the effective notch stress concept (see [1, 2]) are usually computed using finite element analysis (FEA) which requires a certain amount of effort for model generation, the solving process, and postprocessing. Regression functions of many FEAs within given parameter bounds provide the possibility of a fast prediction of SCFs. This paper provides new and accurate regression formulae for the estimation of notch stresses at idealized weld geometries on the basis of multiple linear-elastic FEAs for the transverse stiffener (non-load carrying T-joint) under tension and bending of the load carrying slab. Regression of sampled finite element results has been performed using (a) second-order polynomial regression with coupling terms (PRC) and (b) artificial neural networks (ANN). The presented formulae are compared with several existing estimations of stress concentration factors. The new methods appear to show a higher quality of prognosis as well as apply to significant larger ranges of the geometrical parameters of the weld joint. The formulae presented here for the transverse stiffener add another welded joint to a series of similar surrogate models presented from Munich University of Applied Sciences in earlier publications and made available for use by the web-based tool SCF-Predictor.
      PubDate: 2022-01-21
       
  • Effect of pulsed power ultrasonic vibration on keyholing/penetrating
           capability in waveform-controlled plasma arc welding

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      Abstract: Enhancing the keyholing capability of the plasma arc is of great significance for the welding of medium-thick plate structures. A novel new process of pulsed power ultrasonic vibration assisted plasma arc welding was proposed to realize the effective use of ultrasonic energy and the effective improvement of the plasma arc keyholing ability. Three kinds of plasma arc welding (PAW) experiments without ultrasonic vibration (UV), with continuous power UV and with pulsed power UV were conducted on stainless steel plates to compare the difference of keyholing/penetrating capability of plasma arc. It was found that under the same welding conditions, PAW without UV could not form open keyhole, UV-assisted PAW (U-PAW) could not produce sustainable open keyhole, and pulsed power UV-assisted PAW (PU-PAW) could ensure establishment of open keyhole. And compared to PAW, PU-PAW was able to form an open keyhole even if the welding speed was increased by 10%. The pulsed power UV induced further constriction of plasma arc, and the plasma arc pressure was increased from 955 Pa in PAW to 1391 Pa in PU-PAW, so that the keyholing/penetrating ability of plasma arc was enhanced.
      PubDate: 2022-01-21
       
  • In situ detection of welding defects: a review

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      Abstract: Weld defect detection is a crucial aspect for improving the productivity and quality of the welding process. Several non-destructive methods exist for the identification of defects post weld deposition. However, they only help assess the quality of the component and offer no inputs while the welding process is being performed. Real-time or in situ weld defect detection aids in the detection of defects during the welding process, allowing to take corrective measures or halt the welding to avoid further wastage of time and material. The current paper provides a brief description of various types of weld defects and the commonly used non-destructive testing (NDT) techniques used for identifying weld defects. It then proceeds to provide a detailed review of various methods available for in situ weld defect detection, classifying them based on their input signals. It also classifies the methods based on the type of algorithm used, along with an intuitive explanation of the commonly used algorithms in weld defect detection. The methods covered in this manuscript make use of different input signals that include audio, welding current and voltage, and optical signals also highlighting methods that use a combination of the abovementioned signals for in situ prediction of weld defects. A critical analysis of the efficacy, advantages, and drawbacks of each method is presented. Further, this work highlights a few research gaps identifying avenues for future research in this area.
      PubDate: 2022-01-21
       
  • Expansion of laser–arc hybrid welding to horizontal and vertical-up
           welding

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      Abstract: Laser–arc hybrid welding (LAHW) is an advanced welding method that combines arc welding and laser welding and can achieve deep penetration and the reduction of welding deformation compared with conventional arc welding. As with other welding techniques, it is common to target the flat position (PA) as the welding position. However, the expansion of the applicable positions enables the application of high-quality welded joints fabricated by LAHW to many welded joints in large steel structures. This study used the LAHW system with a robot manipulator to establish weldability in the horizontal position (PC) and the vertical-up position (PF) to expand the applicable range of LAHW in large steel structures. Suitable LAHW conditions for fabricating the butt-welded joint with a welding length of 1,000 mm for these positions were established through various investigations, including molten pool observation. Finally, the quality of these joints was evaluated in accordance with the laser–arc hybrid welding guidelines (ClassNK) of Nippon Kaiji Kyokai, and it was confirmed that the joints satisfy the required standards.
      PubDate: 2022-01-21
       
  • On the interaction of axial and bending loads in the weld root fatigue
           strength assessment of load-carrying cruciform joints

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      Abstract: Current design standards and recommendations incorporate the nominal stress system for assessing the fatigue strength capacity of load-carrying cruciform (LCX) joints with the fillet welds and failing from the weld root. Thus far, bending-loaded joints have not been addressed in these standards. The aim of the present study is to investigate the fatigue performance of LCX joints subjected to cyclic axial and bending loads. Firstly, fatigue test data sets of such joints subjected to axial loading and bending loads in the adjoined plate component are extracted from the literature, and statistical analyses are carried out to evaluate the fatigue strength capacity using the nominal weld stresses (NWSs). Secondly, experimental fatigue tests are carried out on LCX joints made of ultra-high-strength steel (UHSS) grade using constant amplitude loading and subjected to combined axial and bending load to study the load interaction effects on the fatigue strength capacity. The results showed that the FAT36 detail category for the weld root failures is applicable for bending-loaded joints when applying NWSs calculated on the basis of effective throat thickness of weld and assuming linear-elastic stress distribution over the joint section. The effective notch stress analyses showed unconservative results for the tested joints, when applying FAT225 design curve with the reference radius of rref = 1.0 mm.
      PubDate: 2022-01-21
       
  • Obituary: David J. Landon

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      PubDate: 2022-01-18
       
  • Fatigue assessment of weld seams considering elastic–plastic material
           behavior using the local strain approach

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      Abstract: In this contribution, the notch strain approach is applied to seam welds including butt welds and filet welds. This allows the fatigue assessment for all regimes of fatigue life, including the low cycle fatigue regime (N > 10). Linear-elastic finite element analyses are used to determine the local stresses. The modeling of the geometry to be assessed is similar to that of the effective notch stress concept. Necessary input values besides linear-elastic stresses are estimated from the hardness of the heat-affected zone. Subsequently, the elastic–plastic stresses and strains are estimated, and a service life calculation is carried out. The used algorithm for the notch strain approach is based on the German FKM-guideline “nonlinear” and includes the influence of stress gradients, highly stressed surfaces, and the influence of surface roughness. Up to now, this FKM-guideline has only been approved for non-welded components. However, this article shows that, with a few modifications, it can also be applied to welds.
      PubDate: 2022-01-18
       
  • Nature of nonmetallic inclusions in electrogas weld metal

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      Abstract: An electrogas weld metal deposited with an approximately 20 kJ/mm heat input was examined to investigate the chemical and microstructural characteristics of nonmetallic inclusions related to the weld microstructure. The inclusions in this weld were found to be very active for ferrite nucleation, and the larger inclusions tended to be more effective for multiple-nucleation. Experimental evidence demonstrated that the high nucleation potency of inclusions was attributable to the TiO layer formed on the inclusion surface and that the multiple-nucleation was due to the polycrystalline nature of the TiO layer. In addition, small patches of the TiN phase were present on the outer surface of inclusions. From the morphological and chemical composition, this phase was believed to be formed from the steel matrix by the precipitation reaction upon cooling.
      PubDate: 2022-01-17
       
  • Hybrid laser-arc welding of laser- and plasma-cut 20-mm-thick structural
           steels

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      Abstract: It is already known that the laser beam welding (LBW) or hybrid laser-arc welding (HLAW) processes are sensitive to manufacturing tolerances such as gaps and misalignment of the edges, especially at welding of thick-walled steels due to its narrow beam diameter. Therefore, the joining parts preferably have to be milled. The study deals with the influence of the edge quality, the gap and the misalignment of edges on the weld seam quality of hybrid laser-arc welded 20-mm-thick structural steel plates which were prepared by laser and plasma cutting. Single-pass welds were conducted in butt joint configuration. An AC magnet was used as a contactless backing. It was positioned under the workpiece during the welding process to prevent sagging. The profile of the edges and the gap between the workpieces were measured before welding by a profile scanner or a digital camera, respectively. With a laser beam power of just 13.7 kW, the single-pass welds could be performed. A gap bridgeability up to 1 mm at laser-cut and 2 mm at plasma-cut samples could be reached respectively. Furthermore, a misalignment of the edges up to 2 mm could be welded in a single pass. The new findings may eliminate the need for cost and time-consuming preparation of the edges.
      PubDate: 2022-01-14
       
  • On the nondestructive testing and monitoring of cracks in resistance spot
           welds: recent gained experience

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      Abstract: The current paper addresses the challenge of steel and modern automotive industries in the detection of liquid metal embrittlement (LME) crack when occurring during resistance spot welding of advanced high strength steel. While progress has been made to understand and prevent LME crack occurrence, its detection and characterization are still the main concern. Unfortunately, these aspects have received scarce attention in the literature. In this study, various non-destructive testing solutions (NDT) for crack detection and characterization (in particular depth estimation) were developed using novel algorithms and hardware. Despite the complex features of LME crack, its detection and characterization are promising: acoustic emission testing (AT) was found to be efficient for crack detection using a novel criterion based on Shannon entropy. Unprecedented AT tests have even been carried out in serial automotive production environments to assess deployment feasibility. The machine vision algorithm was implemented for magnetic inspection to assess crack detection automation. For crack depth estimation, three solutions are discussed using pulsed thermography, Eddy current array, and industrial large scale tomography (RoboTom). This paper focuses on gained experience and recommendations that would help the research community to increase the technology readiness of LME crack detection and characterization.
      PubDate: 2022-01-13
       
  • Numerical simulation method of the multi-field coupling mechanism for
           laser cladding 316L powder

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      Abstract: Laser cladding is a non-equilibrium physical–chemical metallurgical process, and there are complex metallurgical phenomena such as the heat conduction, convection, mass transfer, and solid/liquid interface diffusion. The multi-field coupling in cladding determines the microstructure and morphology of the cladding layer. Quantitatively revealing the mechanism of multi-field coupling is the key to improve the quality of the cladding layer, which can provide an essential theoretical basis for process optimization. In this paper, a multi-field coupled three-dimensional finite element model of ASTM 1045 laser cladding 316L powder is established, considering the temperature field, stress field, and flow field. Combining the tracking technology of the solid–liquid solidification interface and the Arbitrary Lagrangian–Eulerian dynamic grid method, the influence mechanism of the laser power on the dynamic evolution of multi-field coupling in the laser cladding is revealed. The transient evolution law of the cladding temperature, flow rate, and laser power stress is quantitatively studied. The calculations show that under the influence of the laser heat source, an “ellipsoid” molten pool is formed, and the temperature field is distributed in a “teardrop” shape. As the laser heat source sweeps through the substrate, the temperature curves at different locations periodically move forward with a peak distribution, showing a heat accumulation phenomenon. An obvious Marangoni flow is formed in the molten pool. Perpendicular to the laser scanning direction, the stress is distributed in a “half-moon shape”. The Zeiss-ƩIGMA field emission SEM was used to observe the micromorphology of the cladding layer, which verified the model validity.
      PubDate: 2022-01-11
       
  • Interpretation of evaluation indices based on solidification cracking
           behavior by in situ observation in Trans-Varestraint test

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      Abstract: The Varestraint test has been used in various fields for evaluating hot cracking susceptibility and has significantly contributed to studies associated with the hot cracking susceptibility of materials. Evaluation indices obtained from the Varestraint test include number of cracks, total crack length, maximum crack length, minimum nominal strain, brittle temperature range, and critical strain rate for temperature drop; however, the detailed significance of the evaluation indices is yet to be elucidated. In this study, the strain related to the initiation and propagation of solidification cracking is quantitatively evaluated by observing the solidification cracking behavior during the Trans-Varestraint test using an in situ observation method. In practice, the strain loaded onto the weld metal in the Varestraint test increases with the nominal strain. Solidification cracks occur near the solid–liquid interface and then propagate away from the weld pool. The initiation strain to solidification cracking occurrence is constant regardless of the nominal strain, and the strain for the propagation increases with the nominal strain. This suggests that a change in the nominal strain in the Varestraint test affects the solidification crack length; however, the initiation strain of the solidification crack is constant at all nominal strains and is independent of the crack length. Therefore, it is concluded that initiation strain of solidification cracking cannot be evaluated based on the conventional arrangement of the Varestraint test.
      PubDate: 2022-01-11
       
 
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