Unravelling the relation between Laser Powder Bed Fusion processing parameters and the mechanical behaviour of as built lattices in a novel Al–Cu–Mg–Ag–Ti–B alloy

Abstract

Laser Powder Bed Fusion (L-PBF) allows manufacturing of lattice structures whilst enabling their integration within a complex shaped solid component to design locally different properties depending on the desired part functionality. The recently developed aluminium A205 alloy offers high strength, good corrosion resistance, thermal and electrical conductivity, hence is promising for such multifunctional components. However, knowledge on the mechanical performance of lattices is currently lacking specifically for A205, while knowledge on geometrical accuracy of lattices in general is limitedly available. Both limit the practical use of lattices. Therefore, this paper presents novel L-PBF work on as built rhombic dodecahedron A205 lattices with relative lattice densities (RD) 10%, 20% and 30% achieving high geometrical accuracy and with detailed investigations of microstructure, fatigue and quasi-static properties. This step is critical to move forward to multifunctional components. An in-depth L-PBF parameter optimisation identifies the significant difference between optimal parameters for lattices and bulk, hence the general importance of a dedicated optimisation for metal lattice structures. The results show a high and repeatable geometrical accuracy and relative material densities above 99% for RD 10% and 20%. For RD 30%, lack of fusion porosities were present without significantly affecting mechanical properties, indicating surface quality dominates the mechanical behaviour. In a final step, a modified local stress-based fatigue analysis was applied and discussed. The results indicate predictable and stable fatigue behaviour which allows reducing the amount of samples necessary to define a representative SN curve for each RD for other unit cells in the future.