Additively Manufactured Lightweight and Hard High-Entropy Alloys by Thermally Activated Solvent Extraction

We introduce a scalable thermally activated solvent extraction based additive manufacturing process to produce lightweight, yet high-hardness, multicomponent alloys. The cost-effective process involves layer-wise curing a slurry composed of AlCoCrFeNi high-entropy alloy powder and a transparent ultraviolet-sensitive photopolymer, by stereolithography 3D printing followed by sintering. The alloy pellets assume a density of 4.3 g/cm3 and hardness of 400 HV with a BCC/FCC multiphase microstructure. A broad distribution in the particle sizes of the alloy powder augments the manufacturing process because the smaller particles operate as fillers to weld the larger ones. The relatively higher surface energy of the smaller particles limits the activation energy required for the onset of particulate diffusion that instigates the necking. Microscopic characterization reveals passivating surface oxides on the powder particles fabricating an alloy part suitable for harsh environments.