AlSi10Mg hollow-strut lattice metamaterials by laser powder bed fusion

Abstract

Hollow-strut lattices (HSLs) with submillimetre-diameter hollow channels are emerging lightweight multifunctional metamaterials. High-strength aluminium alloys are highly attractive as hollow-strut materials due to their low density, cost efficiency, and corrosion resistance. However, their laser powder bed fusion (LPBF) is more challenging than commonly examined metal alloys like Ti–6Al–4V for three fundamental reasons. Aluminium alloys observe (i) large volume shrinkage from the high melt pool temperature to room temperature, (ii) high reflectivity and thermal conductivity necessitating higher laser energies, while also having a (iii) low liquidus temperature (557 °C) creating a dynamic melt pool. These factors imply that AlSi10Mg has a high likelihood of geometric defects and powder occlusion through the hollow channels. This work investigates the LPBF manufacturability of AlSi10Mg HSLs and their mechanical properties. High-fidelity LPBF-manufactured AlSi10Mg hollow-strut channel diameters, wall thicknesses, and scan strategy are identified. Compression testing reveals that as-fabricated AlSi10Mg HSLs reach the empirical upper limit of the Gibson–Ashby model for relative yield strength, while solid-strut lattices (SSLs) of Ti–6Al–4V, AlSi10Mg, and SS316L with comparable relative densities are normally below it. Furthermore, their absolute yield strengths are remarkably comparable to SSLs, even with much lower absolute densities. Finally, their failure modes are analysed and assisted with numerical simulations. AlSi10Mg HSLs are lightweight, cost-effective, and structurally efficient metamaterials.