Dynamic behavior of the 7075 high strength aluminum alloy produced by LPBF

High strength aluminum alloys of the 7000 series show unsurpassed strength-to-weight ratio and therefore attract much of the attention of the aerospace industry where lightweight design is paramount in material development. Despite successful addition of grain refiners and a systematic process parameters optimization, the industrial use of Laser Powder Bed Fusion (LPBF) high-strength aluminum remains very limited. Indeed, further characterization remains necessary. This is especially the case for the study of the dynamic mechanical properties, that is to say under high strain rate (ε ̇ > 100 s-1). Such studies are necessary to produce finite element models that can simulate high speed events simulation, such as crashworthiness of vehicles, explosive welding and ballistic protection. High strain rates can result in differences in strength, ductility, and toughness. Although Ti6Al4V is quite covered in the literature and AlSi10Mg -despite controversies- is being studied as well, the dynamic characterization of LPBFed high strength aluminum alloys is yet to be completed.Using Split Hopkinson Pressure Bars (SHPB), the objective of this study is to compare the mechanical dynamic behavior of the conventional wrought 7075 with the LPBFed 7075 from Zr-modified pre-alloyed powder, boosted in Zn and Mg to account for their vaporization during processing. Two prealloyed powder compositions are compared: one with 1wt% Zr and one with 2wt% Zr. Those two new alloys achieve a hardness above 200 HV0.3 after T6 heat treatment, promising even higher performances than wrought 7075. The build direction is also known to have an influence on the microstructure, resulting in anisotropic mechanical (quasi-static) properties. The dependence on build direction is then also considered at high strain rates. In addition, two different thermal states (as-fabricated and T6) are studied within the strain rate range of 500-2500 s-1, where strain rate hardening and thermal softening compete with each other.