Microstructure and Mechanical Properties of Cold Metal Transfer Welding Similar and Dissimilar Aluminum Alloys Ahmed Elrefaey • Nigel G. Ross Received: 28 March 2014 / Revised: 29 January 2015 / Published online: 10 April 2015 Ó The Chinese Society for Metals and Springer-Verlag Berlin Heidelberg 2015 Abstract Integrating structures made from aluminum alloys in automotive industry requires a large amount of joining. As a consequence, the properties of the joints have a significant influence on the overall performance of the whole structure. Robot cold metal transfer welding is a relatively new joining technique and has been used in this work to join 6082-T4 and 5182-O aluminum alloy sheets by using ER5356 and ER4043 filler metals. Microstructure characterization was performed by optical microscopy and energy dispersive X-ray spectroscopy, and the mechanical properties were measured by tensile and hardness tests. A correlation is made between welding variables, mechanical properties and the microstructure of welded joints. Results indicate that robot cold metal transfer welding provides good joint efficiency with high welding speed, good tensile strength, and ductility. Owing to the low heat input of robot cold metal transfer welding process, the heat affected zone microstructure was quite similar to base metals, and weld metal microstructure was the controlling factor of joint efficiency. The best performing were the 5182/5182 joints welded with ER5356 and these had mechanical property coefficients of 100%, 98%, and 85% for yield strength, ultimate tensile strength, and elongation, respectively. KEY WORDS: Aluminum; CMT; Welding; Microstructure; Tensile property 1 Introduction Transportation is one of the largest energy-consuming sectors, using about 19% of the world’s energy demand. Nowadays, 96% of the world’s transportation systems de- pend on petroleum-based fuels and products, with global transportation systems accounting for about 40% of the world’s oil consumption of nearly 75 million barrels of oil per day [1]. Use of aluminum helps to reduce the weight of cars, buses, trucks, planes, trains and boats. When the weight is reduced, energy consumption during transport is reduced. Thus, the extra energy and extra greenhouse gas emissions related to the production of aluminum compared to alternative materials may be paid back many times through the life cycle of the product. Additionally, the strength and corrosion-resistance of aluminum alloys guarantee durability, reliability and security, coupled with cost-effectiveness. Finally, its total recyclability allows the aluminum industry to fulfill its commitment to the princi- ples of sustainable development and its pledge to future generations. So, it is not surprising that the use of aluminum is increasing across the whole range of transport applica- tions. At present over 130 kg of aluminum goes into the average European car, and this is rising steadily [2, 3]. Of particular interest are the 5000-series alloys used for inner body panels, heat shields, and structural and weldable parts; and the 6000-series alloys for body components, outer and inner body panels, and structural and weldable parts [4–7]. A perpetual challenge to the designer is determining the joining process needed to create an assembly made from a variation of grades of dissimilar materials. Additionally, Available online at http://link.springer.com/journal/40195 A. Elrefaey (&)  N. G. Ross LKR Leichtmetallkompetenzzentrum Ranshofen GmbH, Austrian Institute of Technology, 5282 Ranshofen, Austria e-mail: ahmed.elrefaei@ait.ac.at 123 Acta Metall. Sin. (Engl. Lett.), 2015, 28(6), 715–724 DOI 10.1007/s40195-015-0252-6