The Evolution of Grain Microstructure in Friction Stir Welding of Dissimilar Al/Mg Alloys with Ultrasonic Assistance

Zhao, J and Zhao, B and Wu, C and Kumar, S (2024) The Evolution of Grain Microstructure in Friction Stir Welding of Dissimilar Al/Mg Alloys with Ultrasonic Assistance. In: Materials, 17 (13).

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Abstract

The process of grain refinement during welding significantly influences both the final microstructure and performance of the weld joint. In the present work, merits of acoustic addition in the conventional Frictions Stir Welding (FSW) process were evaluated for joining dissimilar Al/Mg alloys. To capture the near �in situ� structure around the exit hole, an �emergency stop� followed by rapid cooling using liquid nitrogen was employed. Electron Backscatter Diffraction analysis was utilized to characterize and examine the evolution of grain microstructure within the aluminum matrix as the material flowed around the exit hole. The findings reveal that two mechanisms, continuous dynamic recrystallization (CDRX) and geometric dynamic recrystallization (GDRX), jointly or alternatively influence the grain evolution process. In conventional FSW, CDRX initially governs grain evolution, transitioning to GDRX as material deformation strain and temperature increase. Subsequently, as material deposition commences, CDRX reasserts dominance. Conversely, in acoustic addition, ultrasonic vibration accelerates GDRX, promoting its predominance by enhancing material flow and dislocation movements. Even during the material deposition, GDRX remains the dominant mechanism. © 2024 by the authors.

Item Type:	Journal Article
Publication:	Materials
Publisher:	Multidisciplinary Digital Publishing Institute (MDPI)
Additional Information:	The copyright for this article belongs to authors.
Keywords:	Aluminum alloys; Deposition; Dynamic recrystallization; Friction; Grain refinement; Liquefied gases; Magnesium alloys; Microstructure; Research laboratories; Ultrasonic effects; Ultrasonic waves; Welds, AlMg alloy; Evolution of grain; Final microstructures; Friction-stir-welding; Grain evolution; Grain microstructure; Grains refinement; Material deposition; Ultrasonic assistance; Ultrasonic-vibration, Friction stir welding
Department/Centre:	Division of Mechanical Sciences > Mechanical Engineering
Date Deposited:	18 Dec 2024 04:51
Last Modified:	18 Dec 2024 04:51
URI:	http://eprints.iisc.ac.in/id/eprint/85832

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