SUPPLEMENT TO THE WELDING JOURNAL, JUNE 2016 Sponsored by the American Welding Society and the Welding Research Council Effects of Ultrasonic Power on the Hardness of Aluminum 3003H18 Alloy A look at the correlation between ultrasonic power and hardness change during very highpower ultrasonic additive manufacturing BY K. SOJIPHAN, S. S. BABU, A. BENATAR, A. MANONUKUL, AND M. NORFOLK Introduction Ultrasonic additive manufacturing (UAM) is a solid-state joining process used for fabricating complex geometry parts from thin metal tapes or foils (Ref. 1). The process utilizes ultrasonic welding of 100–200-μm-thick foils by joining one layer on top of another layer with 20 kHz ultrasonic frequency, 14–28 μm vibration amplitude, 800–1500 N normal force, and 25–50 mm/s weld speed with optional heating element (65°–150°C) to facilitate better metallic bonding (Ref. 2). During UAM, the first layer of metal foil is added and bonded on top of a base plate or substrate, where the foil is pressed down by a roller-shaped sonotrode in the normal direction (ND). To form a metallic bond, the oxide layers are broken through scrubbing between sonotrode and top foil surface as well as between foil and WELDING RESEARCH substrate surface in the transverse direction (TD), resulting in the nascent metal-to-metal surface contacts (Refs. 1, 3). The process is repeated while bonding along the rolling direction (RD) one layer after another until final dimension of the part is reached. The UAM system is operated by a single ultrasonic transducer with a power capacity of 1.5–3.0 kW, which can produce good bonding in soft FCC materials such as aluminum and copper (Ref. 4). However, this amount of power is insufficient to produce a higher vibration amplitude and normal force necessary to achieve good metallic bonding in harder materials and thicker foils (Refs. 5, 6). While UAM of harder materials has been performed, no mechanical testing was reported to assess the actual strength of the UAM joint (Refs. 3, 7, 8). In addition, unbonded regions were scattered within the interfaces between layers in the UAM microstructure (Ref. 3). Therefore, the process parameters must be improved to minimize the unbonded regions and achieve better metallic bonding. This leads to the development of the new generation of UAM machine or very high-power ultrasonic additive manufacturing (VHP-UAM), which is currently commercialized by Fabrisonic (Ref. 9). The ultrasonic power level JUNE 2016 / WELDING JOURNAL 185-s ABSTRACT Ultrasonic additive manufacturing (UAM) is a solidstate joining process used to build up a solid part from thin metal foils. The major process parameters are vibration amplitude, normal force, and weld speed. In this study, the upgraded version of UAM, called very highpower ultrasonic additive manufacturing (VHPUAM), which has a higher power capability to produce a larger vibration amplitude and larger normal force than UAM, was used to fabricate samples from aluminum 3003H18 (Al3003H18) foils. A total of six VHPUAM samples were fabricated from a TestBed machine and SonicLayer7200 commercial VHPUAM systems. The effects of increasing vibration amplitude and normal force on the change in the bulk hardness of Al3003H18 foil were investigated. The results revealed that vibration amplitude played a more significant role in decreasing hardness or softening behavior in Al3003H18 foil when a larger vibration amplitude was applied. There was also a clear correlation between the bulk hardness of Al3003H18 foil and the average ultrasonic power used, where the hardness decreased with increasing ultrasonic power in samples fabricated from both VHPUAM machines. KEYWORDS • Ultrasonic Additive Manufacturing • Aluminum Alloy • Microhardness • SolidState Joining • Process Control/Monitoring K. SOJIPHAN (kittichais@kmutnb.ac.th) is with Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio, and National Metal and Materials Technology Center, National Science and Technology Development Agency, Khlong Luang, Pathum Thani, Thailand. S. S. BABU is with Department of Mechanical, Aerospace, and Biomedical Engineering, The University of Tennessee, Knoxville, Tenn. A. BENATAR is with Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio. A. MANONUKUL is with National Metal and Materials Technology Center, National Science and Technology Development Agency, Khlong Luang, Pathum Thani, Thailand. M. NORFOLK is with Fabrisonic, LLC, Columbus, Ohio.
Welding Journal | June 2016
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