Material flow modeling for the DSFSW of magnesium alloy

Abstract

The Coupled Eulerian Lagrangian (CEL) method is utilized to model the double shoulder friction stir welding (DSFSW) of AZ91 magnesium alloy and then the model is verified by the experiments. The effects of tool rotational speed and sheet thickness on temperature and strain distributions as well as the material flow patterns are considered at different steps of the process. The material flow pattern around the tool pin is demonstrated properly and the shoulder driven and pin driven zones are predicted very well. Results show that, the material movement in shoulder driven and pin driven zones is different, while it is from the advancing side (AS) to the retreating side (RS) in the pin driven zone, it is inverse in the shoulder driven zone. Additionally, increase in rotational speed raises the maximum temperature and strain, improves the material movement, expands the SZ width and increases the depth of shoulder driven zone. Furthermore, increase in sheet thickness results in a decrease in maximum temperature and strain as well as the material movement. In the sheets with low thickness due to the effects of two shoulders, the pin driven zone is not distinguishable, however in thicker welding sheets the pin driven zone is obvious by significantly lower strains.

Effect of tool–pin offset on microstructure, mechanical properties, and corrosion behavior of friction stir welded AA2024-T3 and SS304 dissimilar joints

“…The shoulder-driven area is the first zone, where the peak flow of material is generated, whereas the second zone is the pin-driven area where the flow of the material is dominantly influenced by the stirring action of the tool-pin. 61,62 In dissimilar-material FSW, the microstructural evolution follows a similar pattern to that of similar-material FSW. The different zones generated in the cross-sections of the welded samples are primarily a result of pronounced variations in sharp strain gradient, strain rate, and temperatures extending from the BMs to the center of the weld.…”

“…This observation suggests that sample S2 achieved improved material movement during FSW due to proper plastic deformation resulting from sufficient heat input at a lower tool–pin offset. 61,66 Figure 6(i) shows an efficient material bonding between the dispatched SS fragment and the Al matrix. This indicates that the Al part has undergone enough plastic deformation to effectively bond with the SS fragments, which indicates tool–pin offset exhibits a significant influence on plastic deformation and material movement.…”

“…4,5 Friction stir welding (FSW) invented in 1991 by "The Welding Institute" UK has emerged as a promising solution and offers advantages over fusion welding techniques by providing lower heat input and thinner intermetallic compounds (IMCs) interface. [6][7][8][9][10] Lightweight aluminum (Al) and its alloys possess properties like a substantial strength-to-weight ratio, good heat transfer, and adequate formability. While as, stainless steel (SS) possesses promising properties like high strength, good corrosion resistance, high toughness, and creep strength.…”

On the role of input welding parameters on the microstructure and mechanical properties of Al6061-T6 alloy during the friction stir welding: Experimental and numerical investigation

“…In addition, through this special material flow, it can be concluded that the FSW process joins the materials via the combination of coalescence and mechanical banding. 54 The highest velocity under optimal welding parameters occurs at the shoulder while during welding without optimal parameters, the highest value occurs at the root of the pin and shoulder. This indicates more slip at the root of the pin and shoulder than the outer shoulder diameter.…”

Study on mechanical properties of 2219 aluminum alloy bobbin tool friction stir welding

“…Under the action of the welding heat cycle, the grains appear and grow. However, due to the low heat input of BT-FSW, the change of grain orientation is small [38,39].…”