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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 paper, a laser microwelding was used to join superelastic NiTi to biomedical PtIr, which can be used in multicomponent biomedical devices, and the NiTiPt phase inside the fusion zone had a strong metallurgical bonding with NiTi base material due to the smooth transition of its grain orientation towards B2 NiTi.
Abstract: Laser microwelding was used to join, for the first time, superelastic NiTi to biomedical PtIr which can be used in multicomponent biomedical devices. By process optimization, it was possible to control the formation of the B2 NiTiPt, with no intermetallic compounds being formed. The NiTiPt phase inside the fusion zone had a strong metallurgical bonding with the NiTi base material due to the smooth transition of its grain orientation towards B2 NiTi. The major finding of the present work is the preservation of the NiTi superelastic response in the welded joint as evidenced by the load/unloading cycling up to 6% strain, significantly higher than typically required for biomedical applications.

9 citations

Journal ArticleDOI
Rihong Han1, Shanping Lu1, Wenchao Dong1, Dianzhong Li1, Yiyi Li1 
TL;DR: In this article, the columnar to equiaxed transition (CET) in the weld is used to refine the grain structure and improve the mechanical properties of the weld.
Abstract: Fusion welding has a wide range of applications in the manufacturing industry field.1) The morphology of the solidification structure in the molten pool controls the ultimate mechanical properties of the weld.2) The columnar to equiaxed transition (CET) in the weld produce the continuous equiaxed grain zone in the weld as shown in Fig. 1,3) which can obviously refine the grain and improve the mechanical properties of the weld. Therefore, in order to obtain the finer equiaxed grain structure and the better mechanical properties of the weld, the study on the CET phenomenon during welding should be performed to provide the useful information for the welding parameter optimization. The various grain structure morphologies in the weld is directly determined by the competitive growth of microstructures with different preferential orientations in the molten pool. The welding parameters exert an important influence on the grain structure evolution through changing the solidification conditions. As a result, to better understand the CET process during welding, it is necessary to investigate the competitive growth of microstructures in the molten pool. However, owing to the complicated welding process, it is difficult to observe the highly dynamic solidification behavior. With the development of the numerical technique, the solidification structure morphology in the molten pool could be simulated directly by the Phase field (PF) and the cellular automata (CA) methods. Pavlyk4) simulated the dendrite Multi-scale Simulation for the Columnar to Equiaxed Transition in the Weld Pool

9 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of a preweld solution annealing, heat input, interpass temperature and type of filler metal on the weldability of two alloys were investigated.
Abstract: Dissimilar welding of the aged alloy 800 and the as cast 25Cr–35Ni (wt-%) heat resistant steel was investigated. Microstructures, mechanical properties and weldability of the dissimilar welds were characterised using optical microscopy, scanning electron microscopy and transition electron microscopy equipped by energy dispersive X-ray spectroscopy, and Varestraint test. Since such dissimilar welding was susceptible to crack formation in the heat affected zone of the aged part, the effects of a preweld solution annealing, heat input, interpass temperature and type of filler metal on the weldability of two alloys were investigated. It was found that during the solution treatment, the precipitates produced in the service stage were decomposed and that TiC was formed. In addition, tensile strength and hardness were reduced, but ductility and toughness increased. It was concluded that the most important step to improve weldability and to reduce cracking susceptibility was solution annealing. A suitable...

9 citations

Journal ArticleDOI
TL;DR: In this article, a high-oriented fine microstructure was achieved through laser melting of electrospark layer of a precipitation hardened nickel based superalloy using electron back scattered diffraction analysis, it was found that the new layer has preferred orientation toward the surface.
Abstract: Highly oriented fine microstructure was achieved through laser melting of electrospark layer of a precipitation hardened nickel based superalloy. Using electron back scattered diffraction analysis, it was found that the new layer has preferred orientation toward the surface. This microstructure grows epitaxially on the electrospark layer, which consists of very fine grains. Having lower elemental segregation and finer grain size, this new modified microstructure has higher hot cracking resistance compared to the conventional autogenous laser weld microstructure on cast alloy.

9 citations

Journal ArticleDOI
TL;DR: In this paper, a combination of phase field and cellular automata methods is used to study the effect of initial grain size and laser power density on heat-affected zone (HAZ) formation during laser surface melting.
Abstract: A combination of phase-field and cellular automata methods is used to study the effect of initial grain size and laser power density on heat-affected zone (HAZ) formation during laser surface melting. Also, an analytical model is developed to estimate the depth of HAZ as a function of initial grain size and process parameters. Both analytical and numerical results indicate that the size of HAZ, as measured with respect to the changes in the grain structure, is inversely proportional to the initial grain size. They also show how increasing the laser power leads to an increase in the extent of HAZ. The proposed models thus provide a basis for the prediction and control of HAZ in laser surface melting.

9 citations