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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: Tailor welded blanks (TWBs) as mentioned in this paper were originally used at mass production level in Germany in the early 1980s and have since seen rapidly increasing engineering applications worldwide.
Abstract: Tailor welded blanks (TWBs) – pressing blanks arranged to combine, by welding, multiple steel sheets of different thicknesses and properties, and which may or may not have been surface-treated – are now extensively used in the automotive industry for fabrication of car body panels. TWBs were initially used at mass production level in Germany in the early 1980s and have since seen rapidly increasing engineering applications worldwide.1, 2 TWBs were originally viewed as a way of boosting material yields through reuse of pressed-off edge material as well as of cutting manufacturing costs by reducing the number of component spot welds, number of welding operations, and number of pressing dies through integral forming of multiple pressings after pre-welding of blanks from conventional spot welding production.

26 citations

Journal ArticleDOI
TL;DR: In this paper, the authors exploited low heat input characteristics of laser welding to effectively control grain coarsening in the fusion zone (FZ) and in the heat affected zone (HAZ).
Abstract: One of the major factors influencing weldability of stabilized 17 wt% Cr ferritic stainless steels is extensive grain coarsening in the fusion zone (FZ) and in the heat affected zone (HAZ). This study aimed at exploiting low heat input characteristics of laser welding to effectively control grain coarsening in the FZ and HAZ of 1.2-mm thick stabilized 17 wt% Cr ferritic stainless steel weldment. The study demonstrated that as compared with gas tungsten arc welding (GTAW), laser welding brought about significant grain refinement in the FZ and HAZ. Laser weldments exhibited superior ductility over their GTA counterparts. An important observation of the study was that, in contrast to GTA weldment, laser weldment was associated with weaker interfaces along columnar grain boundaries in the FZ that served to arrest crack propagation normal to them.

26 citations

Journal ArticleDOI
TL;DR: In this paper, a study of the power beam welding of two precipitation strengthened nickel base superalloys, Waspaloy and Udimet 720Li, which are widely used in the gas turbine industry is presented.
Abstract: A study is presented of the power beam welding of two precipitation strengthened nickel base superalloys, Waspaloy and Udimet 720Li, which are widely used in the gas turbine industry. Processing was carried out on 4·3 mm thickness rectilinear sections using (i) an electron beam welding apparatus operating at 150 kV and 12 mA, and (ii) a Nd-YAG laser capable of delivering 3·5 kW at the workpiece. The laser beam welds yielded 'hourglass shaped' fusion profiles, due to the blooming of the laser beam; conversely, the profiles of the electron beam welds were very much more uniform. Radiography indicated considerable porosity in the laser welds, which was attributed to the entrapment of gases due to keyhole collapse. In Waspaloy, the fusion zone was about 40% softer than the baseplate following welding; in contrast, the Udimet 720Li fusion zone was about 15% harder. This was attributed to the different equilibrium fractions of the γ' phase, and the lack of any detectable in weld γ' precipitation in Wasp...

26 citations

Journal ArticleDOI
TL;DR: In this paper, the nickel-plated carbon nanotubes composite inconel718 alloy coatings were prepared on 304 stainless steel by laser melting deposition and its properties of microstructure, wear resistance and corrosion resistance were studied.
Abstract: Nickel-plated carbon nanotubes composite inconel718 alloy coatings were prepared on 304 stainless steel by laser melting deposition. Its properties of microstructure, wear resistance and corrosion resistance were studied. In the inconel718 coating, the phases are γ-(Ni, Fe), γ′-Ni (Al, Ti) and Fe3Ni2. Compared with the coating without nickel-plated carbon nanotubes, the new phases are C, (Fe, C), C70 and Fe5C2, the grain structure is more uniform, the number of cracks is less and the length of cracks is shorter, the hardness is reduced by 21%, the self-corrosion potential is decreased by 4.4%, the corrosion current density is increased by 47%, the polarization resistance is decreased by 44%, the friction coefficient increases by 18% and the mass wear increases by 83%.

26 citations

Journal ArticleDOI
TL;DR: In this article, a small addition of scandium to the commercial 7010 alloy reduces the hot cracking susceptibility during solidification of welds produced by the gas tungsten arc welding process.
Abstract: The commercial 7000 series aluminium alloys are based on medium strength Al–Zn–Mg and high strength Al–Zn–Mg–Cu systems. The medium strength alloys are weldable, whereas the high strength alloys are non-weldable. This is because the amount of copper present in these alloys gives rise to hot cracking during solidification of welds. As a result, the high strength Al–Zn–Mg– Cu base alloys are not used for applications where joining of components by welding is an essential step. In the present study, using a combination of qualitative Houldcroft test and quantitative Varestraint test, it is shown that a small addition of scandium to the commercial 7010 alloy reduces the hot cracking susceptibility during solidification of welds produced by the gas tungsten arc welding process. The improvement in weldability is found to be the result of the considerable grain refinement in the weld structure following the scandium addition. The results of microhardness and tensile tests are further described within the...

26 citations