Tailoring ceramic particle size and fraction to optimize aluminum powders for additive manufacturing

The use of ceramic nanoparticles as inoculants can promote equiaxed microstructures and reduce solidification cracking during Laser Powder Bed Fusion (L-PBF) of high-strength aluminum alloys. However, concerns about particle agglomeration and health risks have shifted interest toward larger particles, though their effectiveness and optimal size and concentration remain unclear. This study examines how inoculant particle size and fraction affect the physical and rheological properties of gas-atomized AA2017 powder and evaluates their impact on L-PBF samples. Titanium carbide (TiC) particles of three sizes (45 nm, <4 μm, and 44 μm) and three concentrations (1, 2, and 4 wt.%) were investigated. Smaller particles and higher concentrations reduced laser reflectance, enhancing energy absorption. Adding 1 wt.% TiC significantly improved flowability, whereas higher concentrations decreased both flow and apparent density due to agglomeration. Coarse TiC particles (44 μm) further improved flow, with 1 wt.% achieving a flow time of 16.0 ± 0.6 s for 50 g. TiC-functionalized powders also exhibited lower cohesion and required less shear to initiate flow. Under dynamic conditions, 1 wt.% TiC <4 μm required the least energy for spreading. Under static conditions, 2 wt.% TiC (45 nm or 44 μm) and 1 wt.% TiC (44 μm) showed the lowest compressibility. Overall, 1 wt.% TiC—regardless of particle size—enhanced flow behavior, packing density, and laser absorption, and effectively promoted equiaxed microstructure formation without solidification cracking in L-PBF. These findings advance understanding of inoculant particle effects on powder performance, supporting improved processability and microstructural control in additive manufacturing.