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Welding Metallurgy of

01 Jan 1987-
About: The article was published on 1987-01-01 and is currently open access. It has received 991 citations till now. The article focuses on the topics: Welding.
Citations
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Journal ArticleDOI
TL;DR: In this article, the state of the art in selective laser sintering/melting (SLS/SLM) processing of aluminium powders is reviewed from different perspectives, including powder metallurgy (P/M), pulsed electric current (PECS), and laser welding of aluminium alloys.

1,172 citations


Cites background from "Welding Metallurgy of"

  • ...(......................................................3/)(16 33* VSL GSG ∆=∆ θπγ According to Kou [144] and Savage [145], growth of the solid in fusion welding is perceived as being initiated by epitaxial growth from the substrate and proceeds by competitive growth toward the center line of the weld....

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  • ...100 the predominant mechanism of solidification in fusion welding is the competitive growth in the weld fusion zone, Kou [144] identified and discussed the details of other mechanisms such as dendrite fragmentation, grain detachment, heterogeneous nucleation and surface nucl eatio that may tend can interrupt and/or dominate the solidification structure in fusion welding....

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  • ...According to Kou [144] and Savage [145], growth of the solid in fusion welding is...

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  • ...Whereas, the predominant mechanism of solidification in fusion welding is the competitive growth in the weld fusion zone, Kou [144] identified and discussed the details of other mechanisms such as dendrite fragmentation, grain detachment, heterogeneous nucleation and surface nucleatio that may tend can interrupt and/or dominate the solidification structure in fusion welding....

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Journal ArticleDOI
TL;DR: In this article, the authors show that the pre-existing dislocation network, which maintains its configuration during the entire plastic deformation, is an ideal modulator that is able to slow down but not entirely block the dislocation motion.

557 citations

Journal ArticleDOI
TL;DR: In this article, the fundamental understanding of structure-properties relationship in automotive steels resistance spot welds is discussed. And a brief review of friction stir spot welding, as an alternative to RSW, is also included.
Abstract: Spot welding, particularly resistance spot welding (RSW), is a critical joining process in automotive industry. The development of advanced high strength steels for applications in automotive industry is accompanied with a challenge to better understand the physical and mechanical metallurgy of these materials during RSW. The present paper critically reviews the fundamental understanding of structure–properties relationship in automotive steels resistance spot welds. The focus is on the metallurgical characteristics, hardness–microstructure correlation, interfacial to pullout failure mode transition and mechanical performance of steel resistance spot welds under quasi-static, fatigue and impact loading conditions. A brief review of friction stir spot welding, as an alternative to RSW, is also included.

369 citations


Cites background from "Welding Metallurgy of"

  • ...Despite the fact that Schaeffler diagram predicts two phases (austenite plus ferrite) in the FZ of AISI 304 weld nugget microstructure, under rapid solidification conditions such as laser beam welding, a shift in solidification mode may occur.(90) It is generally believed that the change in solidification mode can often result in a fully austenitic microstructure compared to the two phase (ferrite plus austenite) microstructure that is commonly found after primary ferrite solidification....

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  • ...In coarse grained region, which is beside the FZ, both high cooling rate and large austenite grain size coupled with the formation of the carbon rich austenite promote the formation of the martensite.(90) Figure 15 shows the microstructure gradient in TRIP780 RSW....

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  • ...The HAZ in carbon steel weldments can be divided into three distinct subregions: (i) upper critical HAZ (UCHAZ): This region experiences peak temperatures above Ac3 transforming BM microstructure into austenite.(90) Depending on the peak temperature the supercritical HAZ can be divided to the following zones: coarse grained HAZ (CGHAZ) and fine grained HAZ....

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  • ...It is generally believed that the change in solidification mode can often result in a fully austenitic microstructure compared to the two phase (ferrite plus austenite) microstructure that is commonly found after primary ferrite solidification.(90,95,96) Although the change in solidification mode of stainless steel in RSW has not been studied yet, very high cooling rate in RSW process can explain the formation of a fully austenitic weld nugget, as it is the case for laser beam welding....

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  • ...If this temperature is above Mf, there can be untransformed austenite left in the FZ and it can redecompose to untempered martensite upon cooling to room temperature after tempering.(90) For a particular tempering time and tempering current, there is a minimum cooling time to achieve PF mode....

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Journal ArticleDOI
TL;DR: In this article, a unified equation to compute the energy density is proposed to compare works performed with distinct equipment and experimental conditions, covering the major process parameters: power, travel speed, heat source dimension, hatch distance, deposited layer thickness and material grain size.

369 citations

Journal ArticleDOI
TL;DR: This study attempted to predict solidification defects by DNN regression with a small dataset that contains 487 data points and found that a pre-trained and fine-tuned DNN shows better generalization performance over shallow neural network, support vector machine, and DNN trained by conventional methods.

314 citations


Cites background from "Welding Metallurgy of"

  • ...Solidification crack is one of the most serious defects which occurs widely in welding [27,28], casting [29–31] and additive manufacturing (AM) [32,33], which occurs at the last stage of solidification when liquid films exist between dendrites boundaries where local strains cannot be accommodated by liquid feeding and solid deformation....

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References
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Journal ArticleDOI
TL;DR: In this article, the authors used the Gleeble® 3800 system equipment in the welding conditions to determine the temperature dependences of the mechanical properties of welded joints in 6005-T6 alloy, strengthened by heat treatment.
Abstract: Welded joints in 6005-T6 alloy, strengthened by heat treatment, are investigated. The temperature dependences of the mechanical properties are determined using the Gleeble® 3800 System equipment in the welding conditions. The unknown parameters of the volume heat source are determined by inverse modelling. Three-dimensional problems of thermal conductivity and thermal plasticity are solved numerically. Accumulated plastic strains are used as a criterion for the formation of liquation cracking. The proposed method can be used to predict the formation of liquation cracks in welding of 6005-T6 alloy.

6 citations

Book ChapterDOI
01 Jan 2019
TL;DR: In this paper, the additive manufacturing technique results in ultrafine microstructures with unique micron and submicron characteristics, and the microstructure of the as-built DMLS-Corrax was investigated using SEM, EBSD, and TEM.
Abstract: Martensitic hardenable (maraging) stainless steels are of interest due to their combination of high strength and ductility along with superior corrosion and stress corrosion cracking properties. Corrax maraging steel has been recently atomized in powder form for laser-based sintering applications. In the current study, Corrax with a nominal composition of 11–13% Cr, 8.4–10% Ni, 1.1–1.7% Mo, 1.2–2% Al and 0.05% C (in wt%) was additively manufactured through direct metal laser sintering (DMLS) process. This additive manufacturing technique results in ultrafine microstructures with unique micron and submicron characteristics. The microstructure of the as-built DMLS-Corrax was investigated using SEM, EBSD, and TEM. The result of the current study is the preliminary step to develop additively manufactured high strength Corrax stainless steels for various applications.

6 citations

Journal ArticleDOI
TL;DR: In this article, the stirring of the molten material during CO2 laser welding with a dynamic polarised laser beam (DP) was studied, where the key element of the set-up is a high power interference laser beam modulator for CW power rating up to 4 kW.
Abstract: The stirring of the molten material during CO2 laser welding with a dynamic polarised laser beam (DP) was studied. The key element of the set-up is a high power interference laser beam modulator for CW power rating up to 4 kW. Metallographic cross-sections and EDX analyses of the realised welds in St37 using the contrast material nickel proved the enhancement of melt pool stirring due to DP. Moreover, roughness measurements confirmed a smoothing of the top bead surface as well as a correlation between melt pool stirring and the formation of the top bead ripple structure.

6 citations

19 Dec 2007
TL;DR: In this paper, the authors investigate the weldability of a metal polymer sandwich structure and investigate three types of pulsed laser welding, single spot weld, overlapping spot weld and stitched welds.
Abstract: The purpose of this work is to investigate the weldability of a metal polymer sandwich structure. The welding of the sandwich material proceeds first by welding of the skin layer. The material selected for this research is Steelite, a sandwich structure developed by Corus, with 0.12 mm thick mild steel skin layers adhesively bonded to a 0.62 mm thick polypropylene core. The primary concerns when welding the skin layers of a metal polymer sandwich structure are degradation of the polymer core, and how this may affect the welding of the skin layer. For this reason low heat input pulsed laser welding was chosen, which enables precise control over the amount of energy delivered to the workpiece, and thus the heat build-up. Three types of pulsed laser welding were investigated, single spot welds, overlapping spot welds, and stitched welds. The single spot weld experiments reveal that it is possible to create almost defect free partial penetration spot welds in the skin layer of Steelite. The formation of the single spot welds occurs in three stages: initial heating where no melting occurs then melting and a rapid increase in size to a diameter dependant on the focal spot size of the laser beam, and finally growth proceeding at a decreased rate until the end of the pulse or until a blowhole is formed. Overlapping spot weld experiments were carried out with varying welding parameters. It was observed that an increase in heat input not only increases the width of the weld, as expected, but also changes the surface appearance. At low heat inputs the surface has a typical overlapping spot weld appearance. With an increase in heat input, a splash feature appears first with striking regularity. At the highest heat inputs where a weld is formed, the âsplashâ feature gives way to a rough and pocked appearance. The variation in surface appearance is of import as it is related to the depth of penetration and microstructure. The overlapping, discrete, spot weld appearance corresponds to partial penetration welds. The "splash" features appears once the welds are fully penetrated and indicate the presence and the location of flues, which have a different structure from the rest of the weld and a high carbon content. The last, pocked, surface appearance corresponds to high heat input full penetrations welds. These pocked welds have fully dendritic structures, carbon contents of approximately 5 wt.%, and Vickers hardnesses of up to 960 HV, the combination of which indicates a white cast iron structure. The absorption of carbon shifts the composition of the original mild steel towards the eutectic point on the iron carbon phase diagram, reducing the melting point. Stitching is a method of making a seam weld from overlapping spot welds while preventing the heat build up responsible for the degradation of the polymer core. Experiments show that the degradation under the stitched welds is significantly reduced in comparison to pulsed laser seam welds of comparable depth. Analytical and finite element modelling were carried out. The analytical model is based on Martin and Bowmans model which assumes a Gaussian heat source and a semi-infinite work piece. The results for the weld diameter of the single spot welds are quite accurate for short pulse times, however the results become less accurate with increasing pulse time. Finite element modelling proved more successful for predicting weld diameter for varying combinations of pulse parameters. Although the weld diameter can be predicted within 15%, the weld penetration is almost always over predicted. Despite this, the prediction for the degraded area in the core is reasonably accurate to first order.

6 citations

Dissertation
01 Jan 1993
TL;DR: Thesis (Ocean. E. E., Mass. Institute of Ocean Engineering, 1993, and Thesis (M.E.S.) as mentioned in this paper, Massachusetts Institute of Technology, Dept. of Materials Science & Engineering, 1992).
Abstract: Thesis (Ocean. E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1993, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science & Engineering, 1993.

6 citations