Tailoring the Microstructure of an AA5754 Aluminum Alloy by Tuning the Combination of Heat Treatment, Friction Stir Welding, and Cold Rolling

Abstract

Friction stir welding (FSW) has now reached a technological impact and diffusion that makes it a common joining practice for several classes of metallic materials. These include light alloys (aluminum, titanium, magnesium), steels, and other metallic alloys. In addition, the combination of FSW with pre- or post-welding heat treatments or plastic deformation, such as cold rolling (CR), can favor minimal necessary plate thicknesses and induce effective alloy strengthening mechanisms that make the FSW joint lines as plate reinforcing zones. Process parameters, such as pin rotation and transverse speed, can be tuned to optimize the mechanical properties of the resulting joint. This work presents a microstructural study of the mechanical response of different sequences of heat treatment, FSW, and CR in a non-age hardened Al-Mg AA5754 alloy. By using polarized optical microscopy and microhardness tests, two FSW conditions were used to fabricate a joint; and were than subjected to different sequences of heat treatment and cold rolling. The results suggest that FSW conditions have a limited effect on the microstructure, while microhardness profiles show a higher variability of the different datasets related to the low welding speed investigated.