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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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Dissertation
01 Aug 2017
TL;DR: In this paper, a defect-free electron beam welded 20 mm thick AISI 316L austenitic stainless steel has been investigated as a function of beam power, and the weld microstructure is characterised by a columnar and equiaxed dendritic ferrite in an austenite matrix.
Abstract: Through thickness microstructure and mechanical properties of defect-free electron beam welded 20 mm thick AISI 316L austenitic stainless steel has been investigated as a function of beam power. The weld microstructure is characterised by a columnar and equiaxed dendritic ferrite in an austenite matrix. The dendritic structure was finer at the bottom of the weld zone. A microstructural boundary called “Parting” was seen along the weld centreline. Tensile tests, using a digital image correlation technique, demonstrated that the highest strain was concentrated in the fusion zone. The bottom section of the weld metal exhibited a yield strength of about 14 – 52 MPa higher than the top section. The ultimate tensile strength in the bottom of the weld was also about 4% higher than the top. The final fracture was detected in the parting region. It was observed from the EBSD scan that the grains in the weld zone contained a weak orientation and showed a high Schmid factor intensity with interception between some strong grains and soft grains at the weld centreline boundary. This explains the high weld ductility and the failure to happen in the parting region. Dissimilar welding of 20 mm thick AISI 316L stainless steel to TiAl6V4 using electron beam welding process was carried out. A successful joint was possible through using of copper sheet with 1.5 mm thick as a transition layer between the two metals. Preheating the weld samples was performed to lower the heat input and reduce the residual stresses. A double pass welding technique was applied to achieve full weld penetration. The weld microstructure was studied by SEM, EDS and XRD. The sensitivity of the microstructure to cracking was evaluated by a microhardness test of the weld cross-section. The weld region near the stainless steel contained Fe and Cu in solid solution. While the weld area near the titanium alloy characterised by the copper solid solution with Cu-Ti and Cu-Fe- Ti intermetallic phases. Ti-Fe intermetallic compounds was suppressed and replaced by relatively soft Cu-Ti intermetallics, which significantly improved the joint toughness. However, the formation of Ti-Cu at the Ti/Cu interface makes this region still susceptible to cracking.

3 citations

Journal ArticleDOI
TL;DR: In this article , the authors compared the cold metal transfer (CMT), low spatter control (LSC) and pulsed synergic (PS) current deposition modes to evaluate the influence of energy input on geometrical and mechanical properties of the deposits.
Abstract: In this work, AISI H13 tool steel build-ups were produced through wire arc additive manufacturing (WAAM). The cold metal transfer (CMT), low spatter control (LSC) and pulsed synergic (PS) current deposition modes were compared. Similar deposition strategy was employed in order to attempt to evaluate the influence of energy input on geometrical and mechanical properties of the deposits. To evaluate the mechanical properties of the deposits, hardness and tensile tests were carried out. Microstructures were analysed in optical microscope. As a result of the intrinsic characteristics of each current waveform and adjustments of the heat source used to perform the deposits, the heat input value was similar for CMT and PS mode and lower for the LSC mode. The CMT deposit was the tallest and widest. Temperatures were higher using the PS deposition mode. The hardness values for all deposits were higher than the usual ones for this tool steel. The microstructure was composed by hard phases, and the precipitates at grain boundaries were responsible for the brittle fracture observed in tensile specimens.

3 citations

DissertationDOI
01 Jan 2019

3 citations

Journal ArticleDOI
TL;DR: In this article , the fracture mechanism of as-deposited Cr12MoV and the effect of deposition direction on its mechanical properties are studied, and the phase composition and microstructure of deposited and forged samples are studied by XRD and scanning electron microscope (SEM).
Abstract: The deposition samples of Cr12MoV with different scanning speeds are prepared by laser melting deposition technology. Compared with forged Cr12MoV, the mechanism of laser melting deposition technology to improve hardness and wear resistance is studied. The tensile specimens of as‐deposited Cr12MoV are prepared by using the optimal process parameters. The fracture mechanism of as‐deposited Cr12MoV and the effect of deposition direction on its mechanical properties are studied. The phase composition and microstructure of deposited and forged samples are studied by X‐Ray diffractometry (XRD) and scanning electron microscope (SEM). The results show that the martensite in the as‐deposited Cr12MoV sample increases and has a finer grain size, which achieves the effect of fine‐grain strengthening. The hardness and wear resistance of the deposited Cr12MoV samples at three laser scanning speeds (4, 8, and 12 mm s−1) are better than those of the forged samples. The tensile fracture mode of the deposited Cr12MoV sample is an intergranular brittle fracture, and the sample perpendicular to the laser scanning speed has higher tensile strength and more excellent elongation.

3 citations

Journal ArticleDOI
TL;DR: In this paper, various preheating treatment and cooling rates conditions were carried out in Tungsten Inert Gas welding to study mechanical behavior and microstructural evolution of AA5083-H321 aluminum alloy welded joints.
Abstract: Various preheating treatment and cooling rates conditions were carried out in Tungsten Inert Gas welding to study mechanical behavior and microstructural evolution of AA5083-H321 aluminum alloy welded joints. The microstructural analysis illustrated the diverse grain size during welding at different preheating and cooling rate. The highest preheat temperature caused to enlarge dendritic grains and during the fastest cooling rate formed the smaller grains. Also, the texture and grain size impressed on tensile behavior and hardness welds. Grain structure of the heat-affected zone, partially melted zone, and weld metal appeared to have a tangible relationship with preheating and cooling rate conditions. The microhardness of these regions increased by increasing the cooling rate and decreasing the preheating temperature. The high preheating had a negative effect on the hardness and width of different zones of welded joints. The results showed that the cooling rate has remarkable effects on the mechanical properties of the welded specimen.

3 citations

References
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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

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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

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