Selective laser melted Al-7Si-0.6Mg alloy with in-situ precipitation via platform heating for residual strain removal

A series of complex post-build heat treatment procedures are usually inevitable for selective laser melted (SLMed) Al-Si-Mg alloys, aiming to remove significant process-induced residual strains. In this work, we propose a new method to avoid the post-build heat treatment without compromising the mechanical properties in SLMed Al alloy A357. By heating up the build platform (up to 90 °C) during SLM fabrication or applying post heat treatment after SLM, the evolution of microstructure and mechanical properties for Al-7Si-0.6Mg alloy are compared at different conditions. Characterisations using scanning electron microscopy (SEM), X-ray Diffraction (XRD), transmission electron microscopy (TEM), and hardness tests suggest heating up the build platform is more effective in alleviating residual strain and resulting in uniform precipitates in the Al matrix. Tensile properties imply that SLMed A357 fabricated with a heated substrate possesses improved mechanical properties compared to SLMed A357 build on room temperature platforms and even with post-build heat treatment. Keywords: Selective laser melting, Al-Si-Mg alloys, Heat treatment, Residual strains, Mechanical properties