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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TL;DR: In this paper, a 700-W pulsed Nd:YAG laser welding was employed to weld 5456 aluminum alloy plates with thickness of 5.5mm, and it was found that hot cracks can be avoided by pulsed laser in preheated status.
Abstract: A 700 W pulsed Nd:YAG laser welding was employed to weld 5456 aluminum alloy plates with thickness of 5 mm. The weld penetration and tendency of liquation cracking in the heat affected zone and solidification cracking in the weld metal are investigated. It is found that hot cracks can be avoided by pulsed laser in preheated status. Increasing the laser average power in fixed pulse frequency and pulse duration resulted in a significant reduction in hot cracking tendency in pulsed laser welding. Also, the hot cracking susceptibility is reduced with increasing pulse frequency up to 50 Hz in fixed average power and pulse duration. The hot cracking tendency can be decreased by pulse duration decrement to 6 ms in fixed average power and pulse frequency. The factors contributing to the prevention or reduction of hot cracks in laser welding of aluminum alloy 5456 are the reduction in cooling rate causing change in solidification mode from columnar to equiaxed grains, and backfilling of liquated grain boundaries. With a 0.4 mm beam diameter Nd:YAG pulsed laser at 300 W average power, 6 ms pulse duration, 20 Hz pulse frequency, 5 mm/s travel speed and 150 °C preheating temperature, hot crack-free weld cross sections were achieved.
41 citations
TL;DR: In this article, the current demand for vehicles with high fuel efficiency, improved safety and enhanced crashworthiness qualities is being met by making use of high strength components with tailored mechanical components.
Abstract: The current demand for vehicles with high fuel efficiency, improved safety and enhanced crashworthiness qualities is being met by making use of high strength components with tailored mechanical pro...
41 citations
TL;DR: In this paper, a controlled thermal severity test (CTS) was performed on mild steel plates bolted together, with anchor welds deposited on opposite sides, after cooling, bithermal and trithermal test welds were deposited one after the other.
Abstract: Residual stress constitutes an integral part of the total stress acting on any component in service. It is imperative to determine residual stress to estimate the life of critical engineering components, especially those that are welded. The stresses caused by non-uniform temperature distribution due to welding and the effect of these multiaxial stresses upon service performance are discussed. A controlled thermal severity test (CTS) was performed on mild steel plates bolted together, with anchor welds deposited on opposite sides. After cooling, bithermal and trithermal test welds were deposited one after the other. Varying welding stresses were deliberately introduced by using different thicknesses of both plates to change the thermal severity numbers (TSN). The main experimental technique used here to determine the magnitude and nature of residual stress is based on X-ray diffraction (XRD). It was utilised to develop and standardise other techniques. The XRD method is based on the peak shiftin t...
41 citations
TL;DR: In this article, the effect of energy input on the characteristics of H13 and D2 steels deposited by a direct metal tooling process based on the directed energy deposition (DED) process was investigated.
Abstract: Among the many additive manufacturing technologies, the directed energy deposition (DED) process has attracted significant attention because of the application of metal products. Metal deposited by the DED process has different properties than wrought metal because of the rapid solidification rate, the high thermal gradient between the deposited metal and substrate, etc. Additionally, many operating parameters, such as laser power, beam diameter, traverse speed, and powder mass flow rate, must be considered since the characteristics of the deposited metal are affected by the operating parameters. In the present study, the effect of energy input on the characteristics of H13 and D2 steels deposited by a direct metal tooling process based on the DED process was investigated. In particular, we report that the hardness of the deposited H13 and D2 steels decreased with increasing energy input, which we discuss by considering microstructural observations and thermodynamics.
41 citations
Cites background from "Welding Metallurgy of"
...It is well known that the chemical composition of parts fabricated by welding change with energy input, especially for elements that have an affinity with oxygen such as titanium, silicon, manganese, etc.([27]) Since the DMT process is similar to welding because it uses high energy, it is necessary to consider the change in the chemical composition with energy input....
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TL;DR: In this article, the effect of welding speed on the tensile and fatigue properties of fiber laser welded AZ31B-H24 Mg alloy with special attention to welding speed was investigated.
Abstract: This study was aimed at characterizing microstructural change and evaluating tensile and fatigue properties of fiber laser welded AZ31B-H24 Mg alloy with special attention to the effect of welding speed Laser welding led to the formation of equiaxed dendrites in the fusion zone and columnar dendrites near the fusion zone boundary along with divorced eutectic Mg17Al12 particles and recrystallized grains in the heat-affected zone The lowest hardness across the weld appeared in the fusion zone Although the yield strength, ductility, and fatigue life decreased, the hardening capacity increased after laser welding, with a joint efficiency reaching about 90 pct A higher welding speed resulted in a narrower fusion zone, smaller grain size, higher yield strength, and longer fatigue life, as well as a slightly lower strain-hardening capacity mainly because of the smaller grain sizes Tensile fracture occurred in the fusion zone, whereas fatigue failure appeared essentially in between the heat-affected zone and the fusion zone Fatigue cracks initiated from the near-surface welding defects and propagated by the formation of fatigue striations together with secondary cracks
40 citations
Cites background from "Welding Metallurgy of"
...The formation of columnar dendrites was caused by the presence of a larger 2136—VOLUME 43A, JUNE 2012 METALLURGICAL AND MATERIALS TRANSACTIONS A temperature gradient near the fusion boundary than in the weld pool center, as reported by Kou....
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...temperature gradient near the fusion boundary than in the weld pool center, as reported by Kou.([31]) In the HAZ, the originally elongated and partially deformed BM structure had become equiaxed grains in both welded joints (Figures 2(f) and 3(e)), suggesting that recrystallization and grain growth occurred in the HAZ where no divorced eutectic b-Mg17Al12 precipitates were present in contrast to the FZ microstructure....
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References
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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
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
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
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
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