UC Irvine

Interest in additive manufacturing (AM) has grown exponentially in recent decades and is now being used in many different industries, such as the aerospace, automotive, and biomedical device industries. Unfortunately, the high cost of feedstock powder material, the need for high energy lasers, and a low rate of production have limited the use of this powerful technique on a large scale. Among all the parameters that are crucial in the quality of the parts, the relationship between starting feedstock powder and the quality of the part is not well explored. The common feedstock used in AM, gas atomized powder, requires a high amount of energy and inert gas to be produced. Therefore, gas atomized powder production is costly and not environmentally desirable. AM is believed to produce lower waste compared to the conventional manufacturing process due to minimal required post-processing; however, unless more sustainable starting materials and continuous powder reuse are implemented, the process is very wasteful. The primary focus of this dissertation is on understanding the role of the starting powder on the AM process sustainability in addition to the properties of additively manufactured parts. Powder size and morphology strongly influence powder flow and powder packing density, both of which are critical to successful AM processing. Therefore, the relationship between powder morphological features and flowability was explored and concluded that flowability of powders are heavily influenced by the particles size and shape. In order to reduce the amount of waste produced in laser directed energy deposition (L-DED) process, gas atomized powder was reused, and the reused powders and manufactured parts were characterized. The results indicate that although particles undergo severe changes as they are being reused in AM, the mechanical properties of the manufactured parts show minimal changes.

The production of powder from waste material for AM was explored. High energy milling and cryomilling were employed to recycle waste materials to be used as a starting material in AM. The results show that the size and morphology of the produced powder are significantly influenced by the production method, which was modified by tailoring the processing parameters. In addition, the feasibility of depositing aluminum matrix composites has been investigated as a way to improve the mechanical properties of parts manufactured with milled powder. The composite single tracks deposited in L-DED showed comparable morphologies to the single tracks deposited with gas atomized powder. Understanding the effects of using milled powder prepared as composite or recycled powder on the mechanical and microstructural properties of AM parts will be investigated in future work.