Effect of Rotation Speed to Welding Speed Ratio on Microstructure and Mechanical Behavior of Friction Stir Welded Aluminum–Lithium Alloy Joints

Abstract

2198 Al-Li alloy welds were performed by friction stir welding (FSW) to investigate the influence of the ratio of rotation speed to welding speed (v/n) on joint microstructure, microhardness, and tensile properties. Transmission electron microscopy (TEM) was used to reveal the precipitate type across the weld cross-section. Results show that v/n has a little impact on both macroscopic morphology and microstructure of joints. Dissolution of precipitates has occurred in the weld nugget (WN). The density of T 1 phase and its size in the WN decrease remarkably. Changes to the T 1 phase are linked to a significant reduction in microhardness across the weld. With increasing v/n the microhardness of the joints decreases. The value of v/n also has impact on the fracture mode of the joints as well as the elongation.

Microstructure distribution in an AA2050 T34 friction stir weld and its evolution during post-welding heat treatment

“…Indeed, a large variety of precipitates can be observed in these alloys [13][14][15][16][17], from the Al-Li binary system (d 0 phase), from the binary Al-Cu system (GP zones, h 00 and h 0 phases), form the Al-Cu-Mg system for Mg-containing alloys (GPB zones, S 0 /S phases) and other phases from the Al-Cu-Li system (T 2 , T B ). Joining Al-Cu-Li alloys by friction stir welding has received some attention, both from the viewpoint of the resulting microstructure [18][19][20][21][22][23][24][25][26][27][28], mechanical properties [29][30][31][32][33] and corrosion behavior [34][35][36]. Most welded in the T8 temper, whose precipitate microstructure mainly consists of very thin platelets of T 1 particles and some h 0 as well as GP zones [9].…”

Fabrication of third generation Al–Li alloy by friction stir welding: a review

“…It has been concluded from previous studies that shoulder and tool pin are the key factor of heat generation, material mixing in the welding and determines the mechanical properties of welded joints [44][45][46][47][48][49]. It has been observed that flat, scroll and concave feature of shoulder and frustrum shapped (truncated cone) with threaded, tapered triflat, threaded and cylindrical pin were applied in the joining of Al-Li alloy [50][51][52][53][54][55][56] Pin-less tool is also applied in the joining of thin sheet of Al-Li alloys [57].…”

Friction stir lap joining of 2198 aluminum–lithium alloy with weaving and pulsing variants

“…These alloys have also paired well with FSW as a joining method to offer an intriguing combination for manufacturers to consider [17,18]. The research community has taken notice as well, with a perhaps telling amount of work being conducted on FSW of Al-Li alloys [19][20][21][22][23][24][25][26][27][28][29][30][31], with particular emphasis on 2198. Other Al-Li alloys receiving attention including 2199, viewed as a viable candidate for aircraft skin, and 2099 extrusions, which would be used to form internal structural members [32].…”