Study of the Marangoni effect by FEM and AFM on microstructure properties and morphology of laser-treated Al-Fe alloy

Significance 

Historically several authors have discussed the Marangoni effect. This effect is a phenomenon of interfacial turbulence provoked by surface tension gradients that might be induced by gradients in temperature, concentration and surface charge through the interface, still, it is known that this effect effectively enhances the rate of mass transfer across the interface. This phenomenon takes into consideration thermophysical and metallurgical properties of the remelting Al-alloy, laser beam parameters and boundary conditions of the process. As a result of heating the material, in the area of laser beam operation a weld pool was created, whose shape and size depends on convection caused by the Marangoni force. Numerical simulation, in general, is a powerful tool to obtain complete understanding of the physical phenomena and the underlying mechanisms of welding processes.

A 3D thermal FEM model has been built to calculate the temperature field and fluid flow field in the molten pool cross-section. Results of numerical simulation, experimental of the micrographs and morphologies were presented, discussed and checked. By FEM the fluid flow due to the Marangoni effect presents two symmetric vortices corresponding to the molten pool center line. The Marangoni effect can lead to mass transfer and interfacial turbulence, when this phenomenon is considered, maximum values of the flow velocity and as well as thermal gradient occur around on the workpiece surface, smaller velocity and thermal gradient occur in the melt pool-substrate interface, thus, the Marangoni effect was more noticeable in lower than in high laser beam velocities. This phenomenon influences and controls the quality, such as, properties of the microstructure, morphological characteristic and as well as quality of laser-treated workpiece tracks, therefore, at low laser beam velocities the morphology is higher and quality of track presents many defects than at high laser beam velocities. Simulation results were assessed with the experimental data, their results were fairly coherent. Numerical simulation is a powerful tool to obtain complete understanding of physical phenomena and underlying mechanisms of LSR-treated processes, therefore, to better use this innovative technology, for thorough physical understanding associated to molten pool phenomena.

Study of the Marangoni effect by FEM and AFM on microstructure properties and morphology of laser-treated Al-Fe alloy, Advances in Engineering
Figure 1. For v= 60 mm/s. (a) Temperature field on the workpiece surface in 3-D and (b) shows the calculated temperature field evolution in the workpiece cross-section

 

Study of the Marangoni effect by FEM and AFM on microstructure properties and morphology of laser-treated Al-Fe alloy, Advances in Engineering
Figure 2. Microstructure in the cross-section; SEM and FEM results of the Marangoni effect in LSR-treated alloy (60 mm/s): (a) an overall view, (b) magnification of the molten pool zone, (c) magnifications of the molten pool-substrate interface, (d) high magnification of transition zone, (e) fluid-velocity vector field; (f) fluid-velocity field, and (g) thermal gradient

 

Study of the Marangoni effect by FEM and AFM on microstructure properties and morphology of laser-treated Al-Fe alloy, Advances in Engineering
Figure 3. For v= 60mm/s of laser beam velocity and single track. (a) SEM exhibition of laser-treated workpiece microstructure and (b) AFM mapping pictures of morphology superficial at track middle

 

About the author

Moises Meza Pariona. Bachelor’s degree in physics and master’s degree in materials engineering from National Engineering University, Lima Peru. Ph.D. in materials engineering from Federal University of Rio Grande do Sul, postdoctoral degree in materials engineering from Federal Universities of Sao Carlos and State University of Campinas-SP, Brazil. Associate Professor at the State University of Ponta Grossa-PR, Brazil.

Area of research, laser refusion in Al-Fe alloy, spray forming in super duplex steel, using several techniques of characterization, FEG-EDS, X-rays, electrochemical methods and AF and numerical simulation using FEM technique. Reviewer of many journals.

Graduate Program in Engineering and Materials Science, State University of Ponta Grossa (UEPG), Ponta Grossa 84010-919, PR, Brazil
E-mail : [email protected]

Reference

Moises Meza Pariona, André Felipe Taques, Luciano Allan Woiciechowski. The Marangoni effect on microstructure properties and morphology of laser-treated Al-Fe alloy with single track by FEM: Varying the laser beam velocity. International Journal of Heat and Mass Transfer 119 (2018) 10–19

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