Friction spot extrusion welding-brazing of copper to aluminum alloy M. Paidar a,⇑ , S. Memon b,⇑ , V. Olegovich Samusenkov c , B. Babaei d , O.O. Ojo e a Department of Material Engineering, South Tehran Branch, Islamic Azad University, Tehran 1459853849, Iran b Department of Mechanical Engineering, Wichita State University, Wichita, United States c Sechenov First Moscow State Medical University, Department of Prosthetic Dentistry, Institute of Dentistry, Trubetskaya St., 8-2, Moscow 119991, Russian Federation d School of Mechanical and Manufacturing Engineering, University of New South Wales, Sydney, NSW 2052, Australia e Department of Industrial and Production Engineering, Federal University of Technology Akure, Nigeria article info Article history: Received 6 November 2020 Received in revised form 28 November 2020 Accepted 30 November 2020 Available online 3 December 2020 Keywords: Friction spot extrusion welding-brazing Interfaces Pure copper Brazed zone Tensile/shear strength Microstructure abstract Friction spot extrusion welding-brazing of pure copper to 5083 aluminum alloy sheet using pure Zn as interlayer has been elucidated. The effect of shoulder geometry on the microstructural characterizations and mechanical behavior of the joints was explored. Results indicated that changing the geometry of the shoulder from cylindrical to triangular not only enlarged the brazed zone from 14.98 lm to 19.65 lm, but also the tensile/shear strength had a rising trend and improved from 3268 N to 4398 N, which can be attributed to the larger brazed zone and complete filling of the pre-threaded hole in the joint produced by the triangular shoulder. Ó 2020 Elsevier B.V. All rights reserved. 1. Introduction The dissimilar welding of Al to Cu is increasing in various indus- tries ranging from automotive and electronics applications owing to their prominent benefits such as cost-effectiveness and heat conductivity [1–3]. The formation of a large number of brittle intermetallic compounds (IMCs) during the welding of these two metals is a challenging issue due to their different coefficient of thermal expansion, deformability, and heat conductivity [4]. Bou- cherit et al. [5] reported that the use of the Zn interlayer acts as a barrier and hampered the creation of undesirable brittle phases during the welding of the Al/Cu joint. A Friction Spot Extrusion Welding–Brazing (FSEW-B) process is a derivative of Friction Stir Spot Welding (FSSW) that establishes mechanical interlocks between overlapped sheets by employing the downward plunging action of a rotating pin-less tool to create an extrusion of the upper plate into a prefabricated (through) hole in the lower sheet. The schematic of the FSEW-B is shown in Fig. 1a and b. The interlayer reduces the reaction between the reactive base metals and further creates a brazed zone via a self-reacting mechanism to increase the joint’s bonded width during the welding process. Thus, in the pre- sent study, the novel FSEW-B process is employed to join Al to Cu with Zn interlayer in order to aid the suppression of detrimental phases. The impact of shoulder geometry (Cylindrical and Triangu- lar) as a crucial parameter during the welding process on microstructure, fracture mode, and tensile/shear strength of the joints is examined. 2. Materials and methods 2 mm and 1.5 mm thick sheets of pure Cu and 5083-H112 Al alloys were the materials used in this study. As obvious in Fig. 1a and b, the AA5083 alloy is placed on the top of the copper plate and 100 mm thick pure Zn, as interlayer, was added between the substrate materials. For the sake of remove dirt and contamination, the mating surfaces of the AA5083 and pure copper were ground to 1000 grit, before the FSEW-B process. After welding, the cross- section of the joints for microstructural examinations was ground by silicon carbide papers, and then polished and etched by Keller reagent. The FSEW-B process was conducted using a FP4MK milling machine at 1500 rpm tool rotational speed, 10 s dwell time, and 0.4 mm shoulder plunge depth. It is imperative to mention that two flat shoulder (probeless) tools made of H13 steel with cylindrical and triangular shapes (Cylindrical shoulder: CS and tri- angular shoulder: TS) were used for the generation of the welds, as indicated in Fig. 1c and d. Note that the shoulders diameter was 14 mm. To explore the phases generated at the interface of the https://doi.org/10.1016/j.matlet.2020.129160 0167-577X/Ó 2020 Elsevier B.V. All rights reserved. ⇑ Corresponding authors. E-mail addresses: m.paidar@srbiau.ac.ir (M. Paidar), sxmemon@shockers.wichi- ta.edu (S. Memon). Materials Letters 285 (2021) 129160 Contents lists available at ScienceDirect Materials Letters journal homepage: www.elsevier.com/locate/mlblue