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JMEPEG DOI: 10.1007/s11665-017-2772-x

Effect of Brass Interlayer Sheet on Microstructure and Joint Performance of Ultrasonic Spot-Welded Copper-Steel Joints Mantra Prasad Satpathy, Abhishek Kumar, and Susanta Kumar Sahoo (Submitted September 28, 2016; in revised form May 4, 2017) Solid-state ultrasonic spot welding (USW) inevitably offers a potential solution for joining dissimilar metal combination like copper (Cu) and steel (SS). In this study, the USW has been performed on Cu (UNS C10100) and SS (AISI 304) with brass interlayer by varying various welding parameters, aiming to identify the interfacial reaction, changes in microstructure and weld strength. The highest tensile shear and T-peel failure loads of 1277 and 174 N are achieved at the optimum conditions like 68 lm of vibration amplitude, 0.42 MPa of weld pressure and 1 s of weld time. The fractured surface analysis of brass interlayer and AISI 304 stainless steel samples reveals the features like swirls, voids and intermetallic compounds (IMCs). These IMCs are composed of CuZn and FeZn composite-like structures with 1.0 lm thickness. This confirms that the weld quality is specifically sensitive to the levels of input parameter combinations as well as the type of material present on the sonotrode side. Keywords

brass interlayer, intermetallic compounds, tensile shear strength, T-peel strength, ultrasonic metal welding, weld quality

1. Introduction During the past few years, there is a drastic increase in demand of dissimilar metal welding, especially in the automobile sector by providing lightweight solutions (Ref 1). Moreover, the welding of thin and dissimilar metal sheets is a robust and complicated process and it cannot be easily achieved by the fusion welding process. Because these sheets are readily get melted without proper fusion, producing a large heat-affected zone (HAZ). In addition to it, some predominant features like porosity, voids, distortion and intermetallic compounds (IMCs) are also formed, which are the primary causes for lowering the strength of the weld (Ref 2). However, with the advent of increasing other welding techniques like resistance spot welding (RSW), friction stir welding (FSW) and ultrasonic welding (USW), these difficulties can be avoided. Although RSW is most popular in this field, one primary concern is the consumption of energy during the welding process. It consumes almost 10% of more energy than USW (Ref 3). Likewise, the long welding cycle and severe working condition at joint limits the application of FSW (Ref 4). USW includes the rubbing of metal sheets with high-frequency vibration to break the oxide layer, and microwelds are formed due to localized heating at the interface (Ref 5). Thus, it is considered to be one of the emerging and popular techniques in the solid-state welding Mantra Prasad Satpathy, Department of Mechanical Engineering, ITS, IFHE, Hyderabad 501203, India; and Abhishek Kumar and Susanta Kumar Sahoo, Department of Mechanical Engineering, National Institute of Technology Rourkela, Odisha 769008, I