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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: The microstructure and fracture morphology of AISI 8630-IN625 and ASTM A182-F22-In625 dissimilar metal weld interfaces were compared and contrasted as a function of postweld heat treatment (PWHT) duration as discussed by the authors.
Abstract: The microstructure and fracture morphology of AISI 8630-IN625 and ASTM A182-F22-IN625 dissimilar metal weld interfaces were compared and contrasted as a function of postweld heat treatment (PWHT) duration. For both systems, the microstructure along the weld interface consisted of a coarse grain heat-affected zone in the Fe-base metal followed by discontinuous martensitic partially mixed zones and a continuous partially mixed zone on the Ni side of the fusion line. Within the partially mixed zone on the Ni side, there exists a 200-nm-wide transition zone within a 20-μm-wide planar solidification region followed by a cellular dendritic region with Nb-Mo–rich carbides decorating the dendrite boundaries. Although there were differences in the volume of the partially mixed zones, the major difference in the metal weld interfaces was the presence of M7C3 precipitates in the planar solidification region, which had formed in AISI 8630-IN625 but not in ASTM A182-F22-IN625. These precipitates make the weldment more susceptible to hydrogen embrittlement and provide a low energy fracture path between the discontinuous partially mixed zones.

44 citations

Journal ArticleDOI
TL;DR: In this paper, the laser metal inert gas (MIG) hybrid welded AZ31 magnesium alloy is discussed in weld shape, microstructure characteristics and mechanical properties in comparison of single laser and arc welding.
Abstract: The laser metal inert gas (MIG) hybrid welded AZ31 magnesium alloy is discussed in weld shape, microstructure characteristics and mechanical properties in comparison of single laser and arc welding. The stable MIG arc, reliable droplet transfer and regular weld that are hardly obtained in single MIG welding can be obtained in hybrid welding by laser arc synergic effects. The ultimate tensile strength and elongation of hybrid weld are far higher than those of laser weld and reach 97·8 and 87·5% of base metal respectively. Under this experimental condition, the efficiency of hybrid welding is 1·20 times faster than that of single laser welding. Between the wide upper part (arc zone) and the narrow lower part (laser zone), obvious difference is observed. Arc zone has coarser grain size and wider partial melted zone than laser zone. Finally, the porosity reduction mechanism of hybrid weld is discussed according to the weld pool shape and the acting forces on it.

43 citations

Journal ArticleDOI
TL;DR: In this article, a brief introduction to weld induced residual stresses and review of the current state of the art with regard to their current state-of-the-art is given.
Abstract: Self-equilibrating residual stresses may occur in materials in the absence of external loading due to internal strain inhomogeneity. While favourable distributions of residual stress can bestow an object with the appearance of superior material properties, most welding processes leave behind residual stresses in particularly unfavourable patterns, causing a greater susceptibility to fracture based failure mechanisms and unintended deformation. Currently, heat treatment is the primary means of removing these stresses, but since the formation of residual stress is dependent upon many material and process factors, there are several other viable mechanisms (using thermal, mechanical or phase transformation effects) by which it may be modified. It is only now, using relevant advances in numerical and experimental methods, that these techniques are being fully explored. This article gives a brief introduction to weld induced residual stresses and reviews the current state of the art with regard to their...

43 citations

Journal ArticleDOI
TL;DR: In this article, the influence of friction stir processing (FSP) on microstructure and mechanical properties of TIG welded joint of AA6061 and AA7075 was examined.
Abstract: In tungsten inert gas welding (TIG), micro-cracks, porosity, coarse grain structure and high residual stress distribution were found due to persisting thermal conditions. The TIG welded joint is processed using friction stir processing with input process parameters to avoid these defects. In present work, the experimental investigation was conducted to examine the influence of friction stir processing (FSP) on microstructure and mechanical properties of TIG welded joint of AA6061 and AA7075. Tensile test, Vickers hardness test, x-ray diffraction, microscopy and energy-dispersive x-ray test were performed for concluding the optimum set of parameters. The tensile test results shows that the hybrid TIG + FSP welded joint had higher tensile strength than TIG welded joint with filler ER4043, whereas the increment in the micro-hardness of TIG + FSP welded joint was observed. The grain size also decreases when tool pin rotates on TIG welding with different processing parameters. It was found that the maximum tensile stress, % elongation and micro-hardness at nugget zone for TIG + FSP welded joint are 255 MPa, 29.2, and 105 HV respectively. The present investigation demonstrates that the tool rotational speed and traverse speed are the dominating parameters to improve the mechanical properties of TIG welded joint.

43 citations

Journal ArticleDOI
TL;DR: In this paper, the Scheil equation was applied to the partially melted zone (PMZ), where grain boundary liquation occurs during welding, and the results indicated that liquation decreases in the order of 7075, 2024 and 6061, consistent with experiments.
Abstract: Aluminium alloys are susceptible to liquation cracking in the partially melted zone (PMZ), where grain boundary liquation occurs during welding. Alloys 2024, 6061 and 7075 were gas-metal arc welded with fillers 1100 and 4043, and liquation cracking near the weld root was examined. Curves of temperature (T) versus solid fraction (f S), based on the Scheil equation for Al‐ Cu‐ Mg‐ Mn‐ Si‐ Zn alloys, were calculated for the solidifying PMZ and weld metal at the fusion boundary. Judging from the freezing temperature range and the liquid fraction, these curves suggested that liquation decreases in the order of 7075, 2024 and 6061, consistent with experiments. They also suggested that 1100 increases the weld metal f S, thus promoting liquation cracking (by strengthening the solidifying and contracting weld metal that pulls the PMZ) and discouraging backfilling (by reducing the interdendritic liquid), while 4043 does the opposite except during PMZ terminal solidification in 7075 and 2024. These are consistent with experiments. STWJ/396

42 citations