Welding Metallurgy of

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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.

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Journal Article•DOI•

A review on selective laser sintering/melting (SLS/SLM) of aluminium alloy powders: Processing, microstructure, and properties

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E. O. Olakanmi¹, E. O. Olakanmi², Robert F. Cochrane¹, Kenneth Dalgarno³•Institutions (3)

University of Leeds¹, Federal University of Technology Minna², Newcastle University³

01 Oct 2015-Progress in Materials Science

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.

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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 Article•DOI•

Dislocation network in additive manufactured steel breaks strength–ductility trade-off

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Leifeng Liu¹, Qingqing Ding², Yuan Zhong¹, Ji Zou³, Jing Wu³, Yu-Lung Chiu³, Jixue Li², Ze Zhang², Qian Yu², Zhijian Shen¹ - Show less +6 more•Institutions (3)

Stockholm University¹, Zhejiang University², University of Birmingham³

06 Dec 2017-Materials Today

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.

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557 citations

Journal Article•DOI•

Critical review of automotive steels spot welding: process, structure and properties

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Majid Pouranvari¹, S. P. H. Marashi²•Institutions (2)

Islamic Azad University¹, Amirkabir University of Technology²

18 Nov 2013-Science and Technology of Welding and Joining

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.

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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.

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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 Article•DOI•

Revisiting fundamental welding concepts to improve additive manufacturing: From theory to practice

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João Pedro Oliveira¹, Telmo G. Santos¹, Rosa Maria Mendes Miranda¹•Institutions (1)

University of Lisbon¹

01 Jan 2020-Progress in Materials Science

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.

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369 citations

Journal Article•DOI•

Using deep neural network with small dataset to predict material defects

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Shuo Feng¹, Huiyu Zhou¹, Hongbiao Dong¹•Institutions (1)

University of Leicester¹

15 Jan 2019-Materials & Design

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.

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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 Article•DOI•

Hot cracking of welds on heat treatable aluminium alloys

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Ching-min Cheng¹, Chang-Pin Chou¹, I-Che Lee¹, H. Y. Lin¹•Institutions (1)

National Chiao Tung University¹

01 Jun 2005-Science and Technology of Welding and Joining

TL;DR: In this article, the effects of augment strain, the number of thermal cycles and cold working (rolling) on the cracking susceptibility were investigated, and the total crack length was used to evaluate the hot cracking susceptibility.

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Abstract: The Spot Varestraint test was used to evaluate the hot cracking susceptibility of several aluminium alloys namely 6061-T6, 6061-T6 (H), 7075-T6, 7075-T6 (H). The effects of augment strain, the number of thermal cycles and cold working (rolling) on the cracking susceptibility were investigated, and the total crack length was used to evaluate the hot cracking susceptibility. The results indicate that the number of thermal cycles is irrelevant to the hot cracking susceptibility in the weld fusion zone, but does affect this susceptibility in the heat affected zone (HAZ). More thermal cycles correspond to larger hot cracks in the HAZ, especially in the weld metal HAZ. The hot cracking susceptibility of materials increased with augment strain in both the fusion zone and the HAZ. Cold working of the materials can reduce their hot cracking susceptibility. The hot cracking susceptibility of 7075-T6 aluminium alloys is higher than that of 6061-T6. There was significant Cu segregation in the HAZ of 7075-T6 a...

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30 citations

Journal Article•DOI•

Effect of martensite–austenite constituent on toughness of simulated inter-critically reheated coarse-grained heat-affected zone in X70 pipeline steel

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Xinjie Di¹, X. An¹, F. J. Cheng¹, Dongpo Wang¹, X.J. Guo, Z.K. Xue - Show less +2 more•Institutions (1)

Tianjin University¹

20 May 2016-Science and Technology of Welding and Joining

TL;DR: In this article, the volume fraction, size, shape and distribution of martensite-austenite (M-A) constituent were analyzed for the intercritically reheated coarse-grained heat-affected zone (ICCGHAZ) of X70 pipeline steel with different second peak temperature and heat input.

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Abstract: The inter-critically reheated coarse-grained heat-affected zone (ICCGHAZ) of X70 pipeline steel with different second peak temperature and heat input was simulated in this study by means of Gleeble3500 simulator. The volume fraction, size, shape and distribution of martensite–austenite (M–A) constituent were analysed. The toughness of ICCGHAZ and corresponding fractographs were examined. The results showed that the distribution of M–A was strongly influenced by second peak temperature, and M–A constituent with necklace structure at lower second peak temperature led to worse toughness. The volume fraction and size of M–A were strongly affected by heat input, the volume fraction of M–A constituent increased with the increase of heat input; the volume fraction and size of M–A were key factors of toughness deterioration; the interfacial energies and the initiation of crack were related to the shape of M–A constituent.

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30 citations

Journal Article•DOI•

Resistance spot weld fatigue behavior and dislocation substructures in two different heats of AZ31 magnesium alloy

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L. Xiao¹, Lei Liu¹, Daolun Chen², Shahrzad Esmaeili¹, Y. Zhou¹ - Show less +1 more•Institutions (2)

University of Waterloo¹, Ryerson University²

25 Nov 2011-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing

TL;DR: In this paper, the authors evaluated the fatigue life and dislocation substructure of two groups of AZ31 Mg alloy resistance spot welds (heats SA and SB respectively), which had similar chemical compositions but different fusion zone microstructures.

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Abstract: Fatigue life and dislocation substructure were evaluated in two groups of AZ31 Mg alloy resistance spot welds (heats SA and SB respectively, which had similar chemical compositions but different fusion zone microstructures). The results showed that the SA welds with a refined microstructure displayed a higher fatigue resistance than the SB welds when tested under conditions of higher cyclic load range causing interfacial failure across the fusion zone. TEM examinations revealed that typical dislocation configurations in the coarse-grained SB welds were parallel dislocation lines and parallelogram dislocation cells produced by basal slip, while elongated dislocation cells arising from basal and pyramidal multiple slips occurred in the SA welds. Twinning was observed to occur in both SA and SB welds, with more twins present in the SB welds. The strong slip incompatibilities between adjacent dendritic grains led to high local stress concentrations that activated twinning in the coarse-grained SB welds, while pyramidal slip together with twinning occurred in the fine-grained SA welds. This resulted in increased number and dispersion of slip systems which improved fatigue life in the SA welds.

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30 citations

Journal Article•

Visualization of Marangoni convection in simulated weld pools containing a surface-active agent

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Chaowalit Limmaneevichitr, S. Kou

01 Jan 2000-Welding Journal

TL;DR: In this article, a simulated transparent weld pool of NaNO 3 (10 mm in diameter) was heated with a defocused CO 2 laser beam to induce Marangoni convection, and C 2 H 5 COOK was used as a surface active agent to cause flow reversal.

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Abstract: The theory that a surface-active agent can cause weld pool Marangoni convection to reverse itself -to go inward along the pool surface and downward toward the pool bottom and result in deeper weld penetration - was proposed by Heiple and Roper in 1982 and studied worldwide since then. To actually observe such a flow pattern, a simulated transparent weld pool of NaNO 3 (10 mm in diameter) was heated with a defocused CO 2 laser beam to induce Marangoni convection, and C 2 H 5 COOK was used as a surface-active agent to cause flow reversal. A laser light-cut technique was used to reveal convection in the pool. With pure NaNO 3 , convection was outward along the free surface and downward along the pool wall. However, when C 2 H 5 COOK was present (e.g., at 0.5 and 1 mole-%), convection slowed down. When more C 2 H 5 COOK was present (e.g., at 1.5 and 2 mole-%), convection was reversed to go inward along the pool surface and downward along the pool axis. Since this is in the opposite direction of gravity-induced buoyancy convection, Marangoni convection clearly dominated in the pools. In stationary laser beam welding, NaNO, containing 1 mole-% C 2 H 5 COOK showed deeper weld pools and inward surface flow, while pure NaNO, showed shallower weld pools and outward surface flow. This is consistent with the reversal of Marangoni convection caused by C 2 H 5 COOK observed in the flow visualization.

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30 citations

Journal Article•DOI•

Effect of Different Chromium Additions on the Microstructure and Mechanical Properties of Multipass Weld Joint of Duplex Stainless Steel

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Dong Hoon Kang¹, Hae-Woo Lee¹•Institutions (1)

Dong-a University¹

01 Aug 2012-Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science

TL;DR: In this paper, the correlation between the mechanical properties and ferrite volume fraction (approximately 40, 50, and 60 Ferrite Number [FN]) in duplex stainless steel weld metals were investigated by changing the Cr content in filler wires with a flux-cored arc-welding (FCAW) process.

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Abstract: The correlation between the mechanical properties and ferrite volume fraction (approximately 40, 50, and 60 Ferrite Number [FN]) in duplex stainless steel weld metals were investigated by changing the Cr content in filler wires with a flux-cored arc-welding (FCAW) process. The interpass temperature was thoroughly maintained under a maximum of 423 K (150 °C), and the heat input was also sustained at a level under 15 KJ/cm in order to minimize defects. The microstructure examination demonstrated that the δ-ferrite volume fraction in the deposited metals increased as the Cr/Ni equivalent ratio increased, and consequently, chromium nitride (Cr2N) precipitation was prone to occur in the ferrite domains due to low solubility of nitrogen in this phase. Thus, more dislocations are pinned by the precipitates, thereby lowering the mobility of the dislocations. Not only can this lead to the strength improvement, but also it can accentuate embrittlement of the weld metal at subzero temperature. Additionally, the solid-solution strengthening by an increase of Cr and Mo content in austenite phase depending on the reduction of austenite proportion also made an impact on the increase of the tensile and yield strength. On the other hand, the impact test (at 293 K, 223 K, and 173 K [20 °C, –50 °C, and –100 °C]) showed that the specimen containing about 40 to 50 FN had the best result. The absorbed energy of about 40 to 50 J sufficiently satisfied the requirements for industrial applications at 223 K (–50 °C), while the ductile-to-brittle transition behavior exhibited in weldment containing 60 FN. As the test temperature decreased under 223 K (–50 °C), a narrow and deep dimple was transformed into a wide and shallow dimple, and a significant portion of the fracture surface was occupied by a flat cleavage facet with river patterns.

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30 citations