Towards a high strength aluminium alloy development methodology for selective laser melting

TLDR

Selective Laser Melting offers high design flexibility, yet conventional alloys yield mediocre mechanical properties because they are not tailored to the process’s rapid solidification dynamics. This study proposes an experimentally based alloy development methodology that uses wedge mould casting and laser remelting to predict the processability and properties of alloys for SLM. By mimicking SLM’s high solidification rate, the method incorporates unusually large solute amounts into the aluminium matrix. The resulting Al‑Mn‑Sc alloy achieved an as‑fabricated yield strength of ~430 MPa and 21 % ductility, increasing to ~570 MPa and 18 % after 5 h ageing at 300 °C.

Abstract

Selective Laser Melting (SLM) has received tremendous attentions due to its high degree of flexibility for the design and fabrication of geometrically complex parts. However, the majority of the currently applied metals for this advanced technology are still based on the traditional weldable and/or castable alloys, and the resulting mechanical properties of SLM fabricated samples are often mediocre. This is because the conventional alloys are not designed to accommodate the dynamic metallurgical characteristics of the SLM process and the benefits offered by SLM are not fully captured. In this study, an experimentally-based novel alloy development methodology utilising wedge mould casting and laser remelting is proposed, and the processability and properties of the developed alloys can be predicted for SLM. By mimicking the high solidification rate of the SLM process, unconventionally large amounts of solute were successfully placed into solution in the aluminium (Al) matrix. A high strength Al-Mn-Sc based alloy has been successfully developed and verified by SLM processing. The developed alloy possessed an average yield strength of about 430 MPa and a ductility of 21% in the as fabricated state, compared to approximately 570 MPa and 18% after direct ageing for 5 h at 300 °C, respectively.