Mechanical characterisation of aluminium alloys manufactured by direct liquid metal deposition

Additive manufacturing technologies for metals use high power intensity sources such as lasers, electron beams, or wire arcs to melt and fuse metal powders or wires. This results in high energy consumption, especially for aluminium alloys, as they are highly reflective; and complex melt pool dynamics which lead to stochastic formation of defects. Direct Liquid Metal Deposition (DLMD) is being developed as an alternative additive manufacturing technology. DLMD uses a metallic wire which is fed into a heated nozzle wherein it is fully melted and then deposited on a moving build plate. Subsequent layers can then be deposited on top of each other building up the part. The aluminium oxide stabilises the flow of liquid metal allowing it to be deposited continuously on the build plate. In this talk, the design and the challenges of a DLMD apparatus and its application to the manufacturing of aluminum alloys will be presented. Walls of eutectic AlSi12 were manufactured using DLMD and characterised by tensile testing and microstructural analysis. In the build direction the average ultimate tensile stress of the printed parts was 171.5 ± 5 MPa and elongation was 17.0 ± 8 % and perpendicular to the build direction was 174.5 ± 7 MPa and elongation was 14.1 ± 8%. The mechanical properties are seemingly isotropic, implying that there is complete bonding between deposited layers, and that the impact of the intermediary oxide layer, which might drive brittle failure of the material along the build direction, is minimal. Fractography was then performed to highlight the damage mechanism and the influence of defects introduced during the process.