According to the current state of the art, additive manufacturing of high-strength aluminium alloys without hot cracks is challenging. As a prevention strategy for powder bed fusion of metals by a laser beam (PBF-LB/M), in which the aluminium alloy EN AW-7075 (7075) is processed, titanium carbide (TiC) nanoparticles are used for heterogenous nucleation provoking grain refinement. The modification of 7075 with TiC has already been elaborated for PBF-LB/M. Mechanical decoration via ball milling demonstrated successful grain refinement and cracking elimination in PBF-LB/M studies with the addition of 2.5 wt% TiC. In view of the latter experimental results, questions and prompts ascertain a closer examination of the dosage of TiC since the nanoparticles are agglomerated on the 7075 microparticle surface. Based on the reactive tendency to build up a passive oxide layer of 1-3 nm thickness at room temperature on the 7075 microparticle surface, a natural barrier can be assumed as an obstacle reducing the effectiveness of grain refinement by mechanical decoration. Moreover, the material costs of nanoparticles are crucial for industrial use and must be put into perspective.
To address the challenge of more efficient grain refinement in the PBF-LB/M process, a different modification route will be demonstrated in this study for TiC-modified 7075 powder material. Subsequent to the surface inoculation process step, here, the ball-milled TiC + 7075 powder is additionally extruded into rod material. Then, the extruded rods are atomised via ultrasonic oscillation. The main advantage of the novel process route can be identified in the encapsulation of TiC nanoparticles within the volume of 7075 microparticles during PBF-LB/M processing.