Research Article Effect of Feed Rate in FSW on the Mechanical and Microstructural Properties of AA5754 Joints Magdy M. El Rayes , 1 Mahmoud S. Soliman , 1 Adel T. Abbas , 1 Danil Yu. Pimenov, 2 Ivan N. Erdakov, 3 and Mahmoud M. Abdel-mawla 1 1 Department of Mechanical Engineering, College of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia 2 Department of Automated Mechanical Engineering, South Ural State University, Lenin Prosp. 76, Chelaybinsk 454080, Russia 3 Foundry Department, South Ural State University, Lenin Prosp. 76, Chelaybinsk 454080, Russia Correspondence should be addressed to Magdy M. El Rayes; melrayes@ksu.edu.sa Received 7 January 2019; Revised 1 April 2019; Accepted 22 April 2019; Published 8 May 2019 Academic Editor: Jose M. Cabrera Copyright © 2019 Magdy M. El Rayes et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Friction stir welding is a solid-state welding process, which is successfully applied to aluminum alloys to replace fusion welding processes. In the present work, the inﬂuence of varying the feed rate at constant rotational speed on the mechanical and microstructural properties of friction stir welded AA5754 was investigated. FSW caused dynamic recrystallization leading to microstructural changes in diﬀerent zones. Electron backscattered diﬀraction conﬁrmed such changes via misorientation angle and subgrain size distributions. Energy dispersive spectroscopy determined the elements present in the matrix quantitatively and their distribution through mapping. Tensile and hardness tests showed slight enhancement compared to base metal. e strain hardening exponent was used to investigate the eﬀect of varying the feed rate on the behavior of the welded samples. 1. Introduction Friction stir welding (FSW) is a newly introduced solid-state welding process, which was intended to replace conventional fusion welding processes that are normally accompanied by diﬀerent welding defects. In the past two decades, numerous researches focused on this process since it is characterized by being energy eﬃcient, versatile, and no localized melting and shielding gas are required. In FSW, a nonconsumable ro- tating tool having a shoulder and a concentric pin is brought into the opposite edges of sheets to be welded and moves along the joint. e tool provides heat arising from friction at the thickness and the workpiece surface, and mechanical stirring mixes both sides of workpiece material. is heating softens the material underneath the shoulder and sur- rounding the pin and thus enhances its plastic deformation leading to severe plastic deformation (SPD) hence dynamic recrystallization and consequently microstructural grain reﬁnement [1]. Jamshidi Aval et al. [2] studied the inﬂuence of feed rate and rotational speed on the properties of AA5086 friction stir welded joints. ey found that in- creasing tool rotational speed at a constant feed rate in- creases the grain size of the dynamically recrystallized grains, whereas increasing the feed rate at a constant rotational speed reduces it. In the same fashion, Hirata et al. [3] in- vestigated the inﬂuence of the welding parameter on me- chanical properties and grain size in AA5083. Similar results were obtained regarding the rotational speed with grain size, and the SZ hardness was the highest among other weldment zones. However, the tensile strength at various welding conditions was almost the same. FSW parameters of AA5083 lap joints were studied by Bisadi et al. [4], where it was reported that the welded area increased with increasing tool rotational speed, while the feed rate did not aﬀect it. Nev- ertheless, it was concluded that, at lower rotational speeds, increasing feed rate enhanced the joint’s mechanical properties compared to that of decreasing feed rate at higher rotational speeds. Sato et al. [5] investigated the hardness in Hindawi Advances in Materials Science and Engineering Volume 2019, Article ID 4156176, 12 pages https://doi.org/10.1155/2019/4156176