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Showing papers on "Welding published in 2012"


Journal ArticleDOI
TL;DR: A light-induced plasmonic nanowelding technique is demonstrated to assemble metallic nanowires into large interconnected networks and opens new avenues to control light, heat and mass transport at the nanoscale.
Abstract: Flexible electronics and other nanoscale devices require simple yet reliable assembly procedures. An optical welding technique for metal nanowires, based on surface plasmon resonances, is now used to fabricate interconnected nanowire networks with enhanced electrical properties for use as transparent electrodes in solar cells and other electrical devices.

1,036 citations


Journal ArticleDOI
TL;DR: In this paper, the relationship between the laser process conditions and the dimensions and quality of the seam was investigated by means of optical and phase-contrast microscopy, which revealed a tensile strength of greater than 80% of the bulk material strength.
Abstract: Absorber-free transmission and butt-welding of different polymers were performed using thulium fiber laser radiation at the wavelength 2 μm. The relations between the laser process conditions and the dimensions and quality of the seam were investigated by means of optical and phase-contrast microscopy. Mechanical properties of the weld joints were studied in tensile strength tests. Laser-welded polyethylene samples revealed a tensile strength of greater than 80% of the bulk material strength. Transmission welding of different polymer combinations featured the formation of different joint classes depending on the spectral properties. The experiments demonstrate new application areas of mid-IR fiber laser sources for materials processing.

256 citations


Journal ArticleDOI
TL;DR: In this article, the optimal process parameters were determined with reference to tensile strength of the joint and confirmed by conducting the confirmation run using the predicted optimal parameters using optimum parameters, which were optimized using Taguchi L16 orthogonal design of experiments.

255 citations


Journal ArticleDOI
TL;DR: In this article, the effect of tool rotational speed and pin profile on the microstructure and tensile strength of the joints were studied, and the results showed that the tool speed and the pin profile considerably influenced the micro-structure of the joint.

244 citations


Journal ArticleDOI
TL;DR: In this paper, an integrated modeling framework for friction stir welding of 6xxx series Al alloys has been established and applied to the 6005A and 6056 alloys.

234 citations


Journal ArticleDOI
22 Feb 2012
TL;DR: In this paper, inclined and horizontal wall features have been built using an inclined torch position and a range of travel speeds has been investigated to better understand the effect of travel speed on part quality for angled walls.
Abstract: Wire and arc additive manufacture enables us to build fully dense metallic parts by depositing material in layers using a welding process. Conventionally, in this process, the welding torch is always maintained in a vertical orientation, but this can cause accessibility problems and may require that the part is moved during the deposition process. The aim of the research presented in this article is to investigate the production of geometrical features using wire and arc additive manufacture with positional welding. Positional welding is particularly useful for building features with limited accessibility without having to manipulate the part. In the current work, inclined and horizontal wall features have been built using an inclined torch position. The knowledge obtained from these experiments has been further applied to build enclosed features. Additionally, a range of travel speeds has been investigated to better understand the effect of travel speed on part quality for angled walls. Factors that hind...

200 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of welding speed and laser power on weld quality of 16mm thick Ti−−6Al−−4V sheets autogenously laser beam welded in butt configuration using a Nd-YAG laser was studied The joint quality was characterized in terms of weld morphology, microstructure and mechanical properties.

174 citations


Journal ArticleDOI
Yahya Bozkurt1
TL;DR: In this article, the Taguchi approach of parameter design was used as a statistical design of experiment technique to set the optimal welding parameters to obtain the influence of the friction stir welding parameters on the weld strength.

170 citations


Book ChapterDOI
TL;DR: In this paper, microstructural and physical properties of the Ni-based superalloy CM247LC were investigated by using a stereological study of scanning electron microscope (SEM) micrographs.
Abstract: The use of a selective laser melting (SLM) powder-bed method to manufacture Ni-based superalloys components provides an economic approach for low production run components that operate under a high-temperature and stress environment. A major concern with the SLM of precipitation hardenable Ni-based superalloys is their high susceptibility to cracking, which has been heavily documented in the field of welding. Weld cracking may occur either during processing (hot cracking, liquation cracking and ductility-dip cracking) or during the post weld heat-treatment stage (strain-age cracking). Due to the complex thermal history of SLM fabricated material there is the potential for all of these mechanisms to be active. In this investigation, cuboidal coupons of the Ni-based superalloy CM247LC were fabricated by the SLM of argon gas atomised powder. Parametric studies were performed to investigate the influence of the process parameters (laser scan speed, power and scan spacing) on the cracking density and morphology through conducting a stereological study of scanning electron microscope (SEM) micrographs. Further microstructural evidence is presented, illustrating the different crack morphologies observed as well as suggesting the responsible mechanisms. Finally a postfabrication Hot Isostatic Pressing (HIP) treatment was performed to investigate its utility in ‘healing’ the internal cracks, and providing a route to retro-fix the cracking problem in the heat treatment stage of production. The findings highlight the need for process models of the SLM method in order to understand the thermal history and the laser fabricated structures observed. Introduction The discipline of additive layer manufacture (ALM) has been steadily growing since the 1980’s and now encompasses a wide variety of technologies. They all share the common feature of producing a three dimensional shape by combining two dimensional ‘slices’ of a predetermined thickness. In recent years, ALM technologies have been developed to push the field forward from ‘rapid-prototyping’ towards ‘rapid-manufacturing’ and the production of fully dense and functional metallic components. In terms of laser fabrication there are now two key technologies for the rapid manufacture of fully-dense metallic components; Direct Laser Fabrication (DLF or any ‘Blown Powder’ system) and ‘Selective Laser Melting (SLM) Powder-Bed’ manufacturing. Comprehensive reviews of the different ALM methods can be found elsewhere [1-4]. SLM powder-bed technology has attracted the interest of aerospace manufacturers for several key reasons including: The elimination of the need the expensive tooling associated with forging and investment casting; the immediate recyclability of the unused metal powder, and the significant reduction in the ‘design-to-component’ time thus allowing for actual physical testing and many design iterations. The present study aims to assess the microstructural and physical characteristics of the SLM fabricated Ni-based superalloy for high-temperature application. Weld Cracking Laser fabrication process can be considered analogous to a continuous laser welding process. Due to this, an alloy weldability can be used as an indication as to its processability by SLM. Figure 1 [5] shows a number of typical Ni-based superalloys plotted according to their Al and Ti contents (γ′ forming elements). The alloys lying above the dotted line show a high volume fraction of the γ′ phase and are typically considered unweldable due to their cracking susceptibility. This relationship between the cracking susceptibility and γ′ fraction is attributed to the precipitation hardening that occurs within the aging temperature of the alloy; reheating the material to within this region (either in the welding process or as part of a post-weld heat treatment (PWHT)) results in hardening accompanied by a reduction in ductility leaving the material prone to cracking [5]. A review of the relevant literature highlighted four potential cracking mechanisms associated with welding and reheating of Ni-based superalloys, which are: Figure 1. Plot showing increasing cracking susceptibility with γ′ forming elements (Al and Ti) [5]. Alloys lying above the dotted line are particularly susceptible to cracking during welding or PWHT. Solidification Cracking Also referred to as ‘Hot-Tearing’, is reported to occur within the solidifying melt pool (or the mushy zone) where the material is in

164 citations


Journal ArticleDOI
TL;DR: In this article, the influence of welding parameters on the microstructure and the heat affected zone has been studied, and an evaluation of the opportunities for an automatized repair process is made.

161 citations


Journal ArticleDOI
TL;DR: In this article, two different grades of high strength steel (HSS), with different microstructures and strengths, were joined to AA6181-T4 Al alloy by FSW.
Abstract: The use of light-weight materials for industrial applications is a driving force for the development of joining techniques. Friction stir welding (FSW) inspired joints of dissimilar materials because it does not involve bulk melting of the basic components. Here, two different grades of high strength steel (HSS), with different microstructures and strengths, were joined to AA6181-T4 Al alloy by FSW. The purpose of this study is to clarify the influence of the distinct HSS base material on the joint efficiency. The joints were produced using the same welding parameter/setup and characterised regarding microstructure and mechanical properties. Both joints could be produced without any defects. Microstructure investigations reveal similar microstructure developments in both joints, although there are differences e.g. in the size and amount of detached steel particles in the aluminium alloy (heat and thermomechanical affected zone). The weld strengths are similar, showing that the joint efficiency depends foremost on the mechanical properties of the heat and the thermomechanical affected zone of the aluminium alloy.

Journal ArticleDOI
TL;DR: The results of the welding experiments have demonstrated the effectiveness of the proposed method of seam tracking monitoring during high-power fiber laser welding to improve the accuracy of weld detection.
Abstract: This paper proposes a method of seam tracking monitoring during high-power fiber laser welding. A visual sensor system was employed to capture the infrared images of molten pools and the surroundings in the laser welding process. A weld seam position variable was extracted by the image difference and centroid algorithms. The state and measurement equations for weld seam position were established based on an eigenvector derived from the weld seam position variable. A Sage-Husa adaptive Kalman filter (AKF), as an estimator of the noise statistical characteristics, was applied in order to enhance the filtering precision. By embedding an Elman neural network into the AKF, an error estimator was used to compensate for the filtering errors. The results of the welding experiments have demonstrated the effectiveness of the proposed method to improve the accuracy of weld detection.

Journal ArticleDOI
TL;DR: In this article, a mathematical model was developed to predict the tensile properties of friction stir welded AA 6061-T4 aluminum alloy joints at 95% confidence level with three welding parameters: tool rotational speed, welding speed and axial force.

Journal ArticleDOI
TL;DR: In this paper, the interfacial reaction between Al, AA6111, and Mg AZ31 alloys has been studied as a function of welding energy, and it was shown that the reaction layer thickness was already ∼5μm thick.
Abstract: High power ultrasonic spot welding (USW) is a low heat input solid-state joining process that may offer a solution for welding difficult dissimilar-material couples, like magnesium (Mg) to aluminium (Al) for automotive body applications. However, the high strain rate dynamic deformation in USW has been claimed to accelerate inter-diffusion rates in dissimilar joints. The interfacial reaction between Al, AA6111, and Mg AZ31 alloys has been studied as a function of welding energy. For the optimum welding condition of 600 J (0.4 s) the reaction layer thickness was already ∼5 μm thick. Intermetallic reaction centres were found to nucleate within microwelds at the interface at very short welding times and spread and grow rapidly to form a continuous layer, composed of two sub-layers of Al 12 Mg 17 and Al 3 Mg 2 . Interface liquation was also found for longer welding times at temperatures below the recognised lowest eutectic reaction temperature in the Al–Mg binary system. Modelling has been used to show that the solid state reaction kinetics were over twice the rate expected from parabolic growth predictions made using rate constants obtained under static test conditions. The reasons for this discrepancy and the depressed melting reaction are discussed.

Journal ArticleDOI
TL;DR: In this paper, the use of submerged friction stir welding (SFSW) under water as an alternative and improved method for creating fine grained welds, and hence, to alleviate formation of intermetallic phases.

Journal ArticleDOI
Han-Sur Bang1, Hee-Seon Bang1, GeunHong Jeon1, Ik-Hyun Oh2, Chan-Seung Ro 
TL;DR: In this paper, the potential for using the gas tungsten arc welding (GTAW) assisted hybrid friction stir welding (HFSW) process to join a stainless steel alloy (STS304) to an aluminum alloy (Al6061) in order to improve the weld strength was evaluated.

Journal ArticleDOI
Yanling Xu1, Huanwei Yu1, Jiyong Zhong1, T. Lin1, Shanben Chen1 
TL;DR: In this article, a real-time seam tracking method was proposed to overcome the deficiencies of teaching-playback welding robots in seam tracking during gas tungsten arc welding (GTAW) process.

Journal ArticleDOI
TL;DR: In this article, the effect of different beam scanning patterns on the microstructure and mechanical properties of Ti-6Al-4V alloy joints by electron beam welding was investigated, and the results showed that the weld metal is full of cross-cross acicular α′ martensitic structure, while the base metal is of equiaxed structure.

Journal ArticleDOI
TL;DR: In this paper, the shape metal deposition (SMD) was used to produce dense, near net-shaped parts with columnar grains with fine dendritic microstructure, and the interdendritic boundaries were decorated by small Laves phase precipitates and by MC carbides.
Abstract: INCONEL 718 parts have been manufactured by shaped metal deposition (SMD), an additive layer manufacturing technique applying wire-based tungsten inert gas welding. This technique is aimed toward mass customization of parts, omitting time- and scrap-intensive, subtractive fabrication routes. SMD results in dense, “near net-shaped” parts without pores, cracks, or fissures. The microstructure of the SMD parts exhibit large, columnar grains with a fine dendritic microstructure. The interdendritic boundaries are decorated by small Laves phase precipitates and by MC carbides. Tensile tests were performed with different strain rates (10−4, 10−3, and 2 × 10−3 1/s), but no dependency on strength or strain at failure was observed. The ultimate tensile strength was 828 ± 8 MPa, the true plastic strain at failure 28 ± 2%, the micro Vickers hardness 266 ± 21 HV200, and the dynamically measured Young’s module was 154 ± 1 GPa.

Journal ArticleDOI
TL;DR: A high strength Al-Zn-Mg alloy AA7039 was friction stir welded by varying welding and rotary speed of the tool in order to investigate the effect of varying welding parameters on microstructure and mechanical properties as mentioned in this paper.

Journal ArticleDOI
TL;DR: This work-site based study among welders demonstrates a high prevalence of parkinsonism compared to nonwelding-exposed workers and a clinical phenotype that overlaps substantially with PD.
Abstract: Objective Manganese (Mn), an established neurotoxicant, is a common component of welding fume. The neurological phenotype associated with welding exposures has not been well described. Prior epidemiologic evidence linking occupational welding to parkinsonism is mixed, and remains controversial.

Journal ArticleDOI
TL;DR: In this paper, the authors show that maximizing the extent of interpenetration and hence promoting mechanical interlocking between the metallic phases, is the key to attaining reasonable transverse strength in Al-Mg dissimilar metal welds.
Abstract: Extruded Al–0.5Mg–0.3Si (6063) aluminum and rolled Mg–3Al–1Zn (AZ31B) magnesium alloy sheets were joined by Friction Stir Welding. The dissimilar metal weld joints exhibit tortuous interfaces. The nugget grain size on both the Al and Mg sides monotonically increase as the tool rotational speed increases. The midplane microhardness traverses show fluctuating hardness peaks due to the presence of different microstructural phases in the nugget zone. The maximum tensile strength of the dissimilar weld joint is 68% of the 6063-T5 base metal with a maximum elongation of 1%. The low ductility is attributed to the formation of brittle intermetallic phases at the Al–Mg interface in the weld joint. Transverse tensile test results are correlated with several interface features: (1) actual interface length, (2) extent of interpenetration between the aluminum and magnesium base metals, (3) maximum intermetallic layer thickness, and (4) area fraction of micro-void coalescence on the tensile fracture surfaces. Results indicate that maximizing the extent of interpenetration and hence promoting mechanical interlocking between the metallic phases, is the key to attaining reasonable transverse strength in Al–Mg dissimilar metal welds. The welding process control variables that promote higher mechanical interlocking of the weld joints are discussed. The process response variables (welding torque, power, x-axis force and the nugget grain size) are presented for a range of welding parameters.

Journal ArticleDOI
TL;DR: In this article, the microstructure of Mg/Al CMT weld joint was studied by means of Optical Microscopy, Scanning Electron Microscope (SEM), Energy Dispersive Xray (EDX), X-ray Diffraction (XRD).

Patent
12 Jul 2012
TL;DR: A method and system to weld or join workpieces employing a high intensity energy source to create a weld puddle and at least one resistive filler wire which is heated to at or near its melting temperature and deposited into the weld puddles is described in this article.
Abstract: A method and system to weld or join workpieces employing a high intensity energy source to create a weld puddle and at least one resistive filler wire which is heated to at or near its melting temperature and deposited into the weld puddle.

Journal ArticleDOI
TL;DR: Direct evidence of lithium-assisted welding between physically contacted silicon nanowires (SiNWs) induced by electrochemical lithiation and delithiation is presented, indicating that a strong bond is formed at the junction of two SiNWs.
Abstract: From in situ transmission electron microscopy (TEM) observations, we present direct evidence of lithium-assisted welding between physically contacted silicon nanowires (SiNWs) induced by electrochemical lithiation and delithiation. This electrochemical weld between two SiNWs demonstrates facile transport of lithium ions and electrons across the interface. From our in situ observations, we estimate the shear strength of the welded region after delithiation to be approximately 200 MPa, indicating that a strong bond is formed at the junction of two SiNWs. This welding phenomenon could help address the issue of capacity fade in nanostructured silicon battery electrodes, which is typically caused by fracture and detachment of active materials from the current collector. The process could provide for more robust battery performance either through self-healing of fractured components that remain in contact or through the formation of a multiconnected network architecture.

Journal ArticleDOI
TL;DR: In this paper, the static and fatigue strength of mechanically clinched and self-pierce riveted joints in aluminium alloy sheets were compared with those of a resistance spot welded joint.

Journal ArticleDOI
TL;DR: In this article, the microstructure of the base metal is composed of primary α phases and the lamellar bimodal structure, and the fracture locations of all the EBW tensile specimens are in base metal.

Journal ArticleDOI
TL;DR: In this paper, the effect of important welding parameters and tool properties that are effective on static strength in friction stir spot welds of polyethylene sheets were studied, including tool rotational speed, tool plunge depth and dwell time.

Journal ArticleDOI
TL;DR: In this article, the dissimilar friction stir welding of pure copper/1350 aluminum alloy sheet with a thickness of 3 mm was investigated, where most of the rotating pin was inserted into the aluminum alloy side through a pin-off technique and sound welds were obtained at a rotation speed of 1000 r/min and a welding speed of 80 mm/min.

Journal ArticleDOI
TL;DR: A comparative study on the influence of gas tungsten arc welding (GTAW) and carbon dioxide laser beam welding (LBW) processes on the size and microstructure of fusion zone FZ then, on the mechanical and corrosion properties of duplex stainless steel DSS grade 2205 plates of 6.4mm thickness was investigated as mentioned in this paper.
Abstract: A comparative study on the influence of gas tungsten arc welding (GTAW) and carbon dioxide laser beam welding (LBW) processes on the size and microstructure of fusion zone FZ then, on the mechanical and corrosion properties of duplex stainless steel DSS grade 2205 plates of 6.4 mm thickness was investigated. Autogenous butt welded joints were made using both GTAW and LBW. The GTA welded joint was made using well established welding parameters (i.e., current ampere of 110 A, voltage of 12 V, welding speed of 0.15 m/min and argon shielding rate of 15 l/min). While optimum LBW parameters were used (i.e., welding speed of 0.5 m/min, defocusing distance of 0.0 mm, argon shielding flow rate of 20 l/min and maximum output laser power of 8 kW). The results achieved in this investigation disclose that welding process play an important role in obtaining satisfactory weld properties. In comparison with GTAW, LBW has produced welded joint with a significant decrease in FZ size and acceptable weld profile. The ferrite–austenite balance of both weld metal WM and heat affected zone (HAZ) are influenced by heat input which is a function of welding process. In comparison with LBW, GTAW has resulted in ferrite–austenite balance close to that of base metal BM due to higher heat input in GTAW. However, properties of LB welded joint, particularly corrosion resistance are much better than that of GTA welded joint. The measured corrosion rates for LBW and GTAW joints are 0.05334 mm/year and 0.2456 mm/year, respectively. This is related to the relatively small size of both WM and HAZ produced in the case of LBW. In other words, properties of welded joints are remarkably influenced by FZ size rather than the produced austenite–ferrite balance.