Trans. Nonferrous Met. Soc. China 24(2014) 1323−1330 Effects of processing parameters on corrosion properties of dissimilar friction stir welds of aluminium and copper Esther T. AKINLABI 1 , Anthony ANDREWS 2 , Stephen A. AKINLABI 3 1. Department of Mechanical Engineering Science, University of Johannesburg, Auckland Park Kingsway Campus, Johannesburg, South Africa; 2. Department of Materials Engineering, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana; 3. School of Mechanical, Industrial and Aeronautical Engineering, University of Witwatersrand, Johannesburg, South Africa Received 6 September 2013; accepted 25 December 2013 Abstract: The influence of friction stir welding processing parameters on dissimilar joints conducted between aluminium alloy (AA5754) and commercially pure copper (C11000) was studied. The welds were produced by varying the rotational speed from 600 to 1200 r/min and the feed rate from 50 to 300 mm/min. The resulting microstructure and the corrosion properties of the welds produced were studied. It was found that the joint interfacial regions of the welds were characterized by interlayers of aluminium and copper. The corrosion tests revealed that the corrosion resistance of the welds was improved as the rotational speed was increased. The corrosion rates of the welds compared to the base metals were improved compared with Cu and decreased slightly compared with the aluminium alloy. The lowest corrosion rate was obtained at welds produced at rotational speed of 950 r/min and feed rate of 300 mm/min which corresponds to a weld produced at a low heat input. Key words: aluminium alloy; copper; corrosion; friction stir weld; processing parameters 1 Introduction It is estimated that corrosion destroys one quarter of the world’s annual steel production, which corresponds to about 150 million tons per year, or 5 tons per second [1]. Corrosion is not limited to steel but affects other materials used in various applications especially in welded joints. Corrosion is known to destroy a material or degrade its functional properties, rendering it unsuitable for the intended use [1]. Generally, the durability and the life time of welds, installations, machines and devices are critically dependent on their corrosion rate and wear resistance. Welded joints are specifically susceptible to corrosion when exposed to the environment and most especially dissimilar welds. Friction stir welding (FSW) process is a solid state welding technique invented by Dr W. THOMAS of The Welding Institute (TWI), United Kingdom in 1991 [2]. FSW is a continuous process that involves plunging a portion of a specially shaped rotating tool between the butting faces of the joint. A schematic of the process is presented in Fig. 1. The relative motion between the tool and the substrate generates frictional heat that creates a plasticized region around the immersed portion of the tool. The tool is moved relatively along the joint line, forcing the plasticized material to coalesce behind the tool to form a solid-phase joint [3]. The resulting microstructures of friction stir welds are described by the different zones as follows: 1) the base metal (BM), which is the material remote from the weld that has not been deformed, and is not affected by the heat in terms of microstructure or the mechanical properties; 2) the heat affected zone (HAZ) which is a region that lies closer to the weld centre and has experienced a thermal cycle that has modified the microstructure and/or the mechanical properties, however, no plastic deformation has occurred in this area; 3) the thermo mechanically affected zone (TMAZ) which is a region where the FSW tool has plastically deformed the material at the weld interface; and 4) the weld nugget (WN) which is the fully recrystallized area, Corresponding author: Anthony ANDREWS; Tel: +27-83-3168708; E-mail: anthonydrews@gmail.com DOI: 10.1016/S1003-6326(14)63195-2