The Department of Defense (DOD) aims to increase the use of additive manufacturing (AM) in its supply chain to reduce the “dead time” of equipment by using 3D printers that can produce parts in a matter of hours instead of weeks. There is always a need for improved AM materials that can meet the mechanical property standards required for all end-use parts, especially in as-printed form. Dispersion strengthening is a common method used in metal alloys to improve their properties, but it is challenging to distribute additives into metal alloys. This research explores methods for dispersion and precipitation strengthening of aluminum alloys produced in situ during liquid metal jet printing. This was accomplished by using the Additec ElemX™ liquid metal jet printer (LMJP) system at Naval Postgraduate School (NPS), along with the aluminum alloys 4008 and 7075. In situ attempts to incorporate boron nitride into AA4008 using direct powder addition or ink application to the wire did not yield mixing due to its low density compared to molten Al. Zinc was introduced to AA7075 in the printer crucible to mimic AA7068 a stronger aviation-grade alloy of aluminum. Results suggest that AA7068 can be printed in the ElemX™ with superior material properties to AA7075, where a 10.10% increase in hardness and ultimate tensile strengths over 600 MPa were found. Methods for zinc addition are explored and optimized for future research to continue characterizing a higher-Zn AA7075 alloy.

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Ensign, United States Navy