Aluminium alloy EN AW-7075 respectively EN AW-Al Zn5.5MgCu (AA7075) is a befitting material for the aerospace industry due to its ultimate tensile strength combined with a comparable low density. According to the current state-of-the-art, additive manufacturing (AM) of high-strength aluminium alloys is challenging, since hot cracks likely occur in the metallic solid. To avoid hot cracks a grain refinement (GR) agent is blended with the AA7075 in form of nanoparticles (NPs) and acts as a catalyst to excite heterogeneous grain growth and simultaneously reduces the material-specific large solidification interval.

By adding a GR agent, the solidified AA7075 matrix should display a fine microstructure. The heterogeneous grain growth reduces the possibility of a transcrystalline separation process, correlating proportionally with the amount of NPs. The chemical composition of AA7075 is modified in compliance with DIN EN 573-3 within the permitted tolerance range. Miscellaneous contents of titanium carbide (TiC) NPs were inoculated on the AA7075 microparticle surface via mechanical ball milling. The alloy blends were deployed in the Laser Powder Bed Fusion of Metals (PBF-LB/M) process. Additional powder batches were fabricated via melt atomisation under an inert atmosphere to integrate NPs into the microparticle volume. This volume approach is based on the assumption, that the natural development of an aluminium oxide layer reduces the quantity efficiency of the NPs. Since the material costs of NPs are crucial, a minimum quantity of GR agents is of interest for industrial use.

Concerning the mechanical decoration of NPs, the experimental studies indicate, that a minimum quantity of NPs is required to potentially expect a low incidence of hot cracks in the AM specimens. The grain size correlates with the amount of NPs added but the mechanical properties remain volatile, which could be an excess of inclusions in the aluminium matrix. By reducing the GR agent, based on the volume inoculation, the approach is reviewed in terms of more efficient material use. To address the challenge, the production of powder via metal atomisation is a suitable approach to bypass the natural oxidation barrier and thereby enable the utilisation of AA7075 for PBF-LB/M without hot cracks.