The effect of oxygen on transitional Marangoni flow in laser spot welding

Zhao, Chunxiao; Kwakernaak, C.; Pan, Yaohua; Richardson, I.M.; Saldi, Zaki S.; Kenjereš, Saša; Kleijn, Chris R.

doi:10.1016/j.actamat.2010.07.056

Cited by 112 publications

(48 citation statements)

References 37 publications

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“…Small changes in oxygen composition (from 0.1 to 1.0 vol%) have been observed to lead to large changes in the shape of the weld pool as small quantities of oxide form on the surface of the melt, changing the surface tension and impacting Marangoni flow within the liquid phase [36][37][38]. Any change in melt pool dimensions would impact the heat transfer process illustrated in Fig.…”

Section: Spears and Goldmentioning

confidence: 99%

“…processes [36][37][38], though it has not been studied with respect to SLM. Small changes in oxygen composition (from 0.1 to 1.0 vol%) have been observed to lead to large changes in the shape of the weld pool as small quantities of oxide form on the surface of the melt, changing the surface tension and impacting Marangoni flow within the liquid phase [36][37][38].…”

Section: Spears and Goldmentioning

confidence: 99%

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In-process sensing in selective laser melting (SLM) additive manufacturing

Spears¹,

Gold²

2016

Integr Mater Manuf Innov

379

161

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Additive manufacturing and specifically metal selective laser melting (SLM) processes are rapidly being industrialized. In order for this technology to see more widespread use as a production modality, especially in heavily regulated industries such as aerospace and medical device manufacturing, there is a need for robust process monitoring and control capabilities to be developed that reduce process variation and ensure quality. The current state of the art of such process monitoring technology is reviewed in this paper. The SLM process itself presents significant challenges as over 50 different process input variables impact the characteristics of the finished part. Understanding the impact of feed powder characteristics remains a challenge. Though many powder characterization techniques have been developed, there is a need for standardization of methods most relevant to additive manufacturing. In-process sensing technologies have primarily focused on monitoring melt pool signatures, either from a Lagrangian reference frame that follows the focal point of the laser or from a fixed Eulerian reference frame. Correlations between process measurements, process parameter settings, and quality metrics to date have been primarily qualitative. Some simple, first-generation process control strategies have also been demonstrated based on these measures. There remains a need for connecting process measurements to process models to enable robust model-based control.

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Section: Spears and Goldmentioning

confidence: 99%

Section: Spears and Goldmentioning

confidence: 99%

In-process sensing in selective laser melting (SLM) additive manufacturing

Spears¹,

Gold²

2016

Integr Mater Manuf Innov

379

161

View full text Add to dashboard Cite

show abstract

“…Although many results have been reported for oxygen effect in low-energy-density welding process, few have touched that in high-energy-density laser welding [38][39][40], especially in the keyhole mode welding. As the most commonly encountered welding atmosphere, air and argon are used as welding atmosphere and compared in the present study.…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical study on laser keyhole welding of 42CrMo under air and argon atmosphere

et al. 2016

Int J Adv Manuf Technol

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Laser keyhole welding of 42CrMo in air and argon atmospheres has been studied both experimentally and numerically. Significant macroscale difference is observed for welding carried out under argon and air shielding. Fusion zone of welding under argon shielding has a "▽" shape, while it has a "U" shape for welding in air. The surface of the weldment is smoother for welding in argon when compared with that in air. Oxygen effect is proposed to account for the experimental results. A three-dimensional heat transfer model with a predefined keyhole is developed to study the heat transport and fluid flow in laser welding process. The variation of weld pool geometry and temperature history is investigated for different oxygen concentrations. It is found that a small amount of oxygen could significantly modify the weld pool dimension, while keeping the temperature history of materials, and thus the microstructure, in the fusion zone and heat-affected zone unchanged.

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“…Zhao reported the formation of a minor phase shell structure, which was caused by the heterogeneous nucleation of the minor phase and the transfer of a solute. 25 Moreover, other concurrent processes such as surface wetting, droplet driing, collision, coagulation, 26 and non-gravity-relevant Marangoni convection [27][28][29] contribute to the formation of these structures. However, the explanations mainly focused on the macroscopic solid structure that underwent a cooling process and emphasized the role of the thermal gradient in the formation of this phase-separated structure.…”

Section: 11mentioning

confidence: 99%

Molecular dynamics study on the formation of self-organized core/shell structures in the Pb alloy at the nanoscale

Wang

Duan

et al. 2017

RSC Adv.

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Herein, we report a self-organized core/shell (CS) structure consisting of an Al core and a Pb shell in the liquid Pb alloys at a constant temperature. This is contrary to a believed opinion that the thermal gradient acts as the only driving force for the formation of this kind of structure. The results show that its forming ability greatly depends on the composition and temperature. Importantly, when the alloys are placed in the confined space, a structure of Al-Pb-Al sandwich construction and a completely different CS structure composed of a Pb core and an Al shell are obtained; this suggests a new strategy for controlling the phase-separated structures at the nanoscale. More interestingly, an abnormal phenomenon in the low Pb alloys with the amorphous thin Pb shell and the crystal Al core is observed after solidification, which does not occur in the high Pb alloys that just possess a secondary wrapped structure that never appears in the liquid state. The result of this study may help to shed light on understanding the formation of this core/shell structure and controlling it at an atomic view that have a potential application in the fabrication of these structural materials through nanotechnology.

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The effect of oxygen on transitional Marangoni flow in laser spot welding

Cited by 112 publications

References 37 publications

In-process sensing in selective laser melting (SLM) additive manufacturing

In-process sensing in selective laser melting (SLM) additive manufacturing

Experimental and numerical study on laser keyhole welding of 42CrMo under air and argon atmosphere

Molecular dynamics study on the formation of self-organized core/shell structures in the Pb alloy at the nanoscale

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