Behaviour of 3D Printed Al7075 Square Hollow Sections in Compression

Abstract

High strength Aluminium alloys feature low densities, high strength‐to‐stiffness ratio, large ductility range and high fracture toughness, all attractive features for applications in industries such as automotive, aerospace and construction. To date, little attention has been given to the performance of 3D‐printed high strength Aluminium alloys such as Al7075 due to the inherent challenges in the additive manufacturing process. In this context, the present study reports material (tensile) and stub column (compression) tests on additively manufactured (AM) Al7075 square hollow sections (SHS). Both material and SHS samples were manufactured by Direct Metal Laser Sintering (DMLS), a laser powder‐bed fusion (L‐PBF) sub‐technology that uses metal powder as feedstock and a laser to fuse the feedstock layer by layer. Three newly develop set of process parameters that had successfully led to crack free medium sized samples were employed in this study. The effect of post processing treatments on the mechanical properties of printed Al7075 samples is investigated through the application of two heat treatments and a Hot Isostatics Pressing (HIP) treatment. A total of 33 material samples were manufactured and tested in tension, 6 of which in their as built condition and 27 subject to the above post processing treatments. The tensile test results showed that the Al7075 samples manufactured using the new set of parameters used is unable to produce specimens which can then develop their full tensile resistance. Nine square hollow tubes were subsequently manufactured utilising a selected heat treatment and tested in compression. All tubes successfully develop good compression performance and primarily exhibit failure due to local buckling, which led to the formation of a yield‐line‐like pattern of cracks, ultimately resulting in the specimens' failure.