Processing and microstructure of a Cu-Al-Fe-Mn alloy via droplet-on-demand additive manufacturing

Control over the microstructure and properties of alloys produced via additive manufacturing (AM) is a key barrier that limits widespread industrial adoption. Herein we demonstrate that liquid metal jetting (LMJ), an emerging metal-AM technique, can address this need by controlling the microstructure evolution during printing of bronze alloy C95400 (Cu-Al-Fe-Mn). We probed several solid-state phase transformations upon cooling by printing single-tracks onto a heated baseplate ranging from 50°C-600°C surface temperature, which led to significant variation in the α-Cu and δ-Fe phase distribution, grain morphology, and chemical distribution within the deposited single-tracks. The printed microstructures exhibited as much as 80% difference in α-Cu grain size and nearly 30% difference in α-Cu phase fraction due to baseplate temperature variation, indicating a wide range of available microstructures and properties achievable. Greater than 92% dense multi-layer samples were fabricated with fine grain structure and 27-34% higher hardness values to the barstock in the as-printed condition, demonstrating the applicability of this printing approach for multi-layer part fabrication. Our results highlight a unique microstructure tailoring capability for metal-AM parts that can be leveraged by manufacturers and end-users of AM technologies.