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Khushbu Zope1 Dinesh Krishna Kumar Jayabal1 Denis Cormier1

1, Rochester Institute of Technology, Rochester, New York, United States

Metal additive manufacturing processes using powder bed fusion have made incredible advances over the past decade. Many of these advances have been motivated by the needs of the aerospace community. While powder bed approaches are perfect for small or medium size parts, the extremely high cost of metal powders is a significant concern when large scale aerospace components are needed. Consequently, there has been a surge in metal AM research involving processes that use less expensive wire feedstock materials. The magnetohydrodynamic (MHD) liquid metal jetting process developed by Vader Systems is one such process. In MHD droplet jetting, an electromagnetic coil surrounds a reservoir where commodity metal wire is fed in and melted. Pulsed electromagnetic fields from the coil induce Lorentz forces in the electrically conductive molten metal that result in jetting of discrete droplets through a nozzle. Jetting frequencies of 500-1000 Hz with droplet diameters of 500 microns are typical. Process parameters such as reservoir temperature, substrate temperature, droplet firing frequency, and droplet overlap distance significantly affect how droplets spread and solidify upon impact with previously deposited material. This paper will describe results of process models that simulate the impact, spreading, and solidification of 4043 aluminum droplets during MHD deposition under different process conditions. Simulated material behavior will be compared with experimental results captured using high speed video, and results will be used to make recommendations on suitable process parameter windows that lead to preferred microstructures subject to the requirement of high density deposits.

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