Analysis of phase, microstructure, and mechanical characteristics of selective laser melted AlSi10Mg alloy after post-heat treatment

The current study focuses on the effect of a post-heat treatment such as solutionizing at 520 °C for 0.5–2.5 h followed by artificial ageing at 165 °C for 2–14 h (T6-like heat treatment) on the microstructure and mechanical properties of selective laser melted (SLM) AlSi10Mg alloy. XRD & DSC analysis shows the Al, Si, and Mg2Si phases present in as-built and heat-treated conditions, which are well correlated with the Thermo-Calc simulation results. The density of as-built AlSi10Mg was 2.66 g/cm3, and it decreased to 2.63 g/cm3 after solutionization, and after artificial ageing, it further decreased to 2.61 g/cm3 due to the lattice strains. As-built sample microstructure consists of fine α-Al cells containing ultra-fine Si particles surrounded by a eutectic Si network due to the high heating and cooling rates involved in SLM processes. After solutionizing, the eutectic Si network structure disappeared by the thermally activated diffusion process forming Si particles in the aluminium matrix. Vickers hardness for as-built condition was 126.6 HV, and after solutionization for 30 min, it decreased to 95.6 HV. However, after subsequent artificial ageing (for 12 h), the hardness value again increased to 119.7 HV. As-built condition showed absorbed impact energy of 8 J and it increased to 17.33 J during solutionization for 0.5 h and again decreased to 9.33 J after subsequent artificial ageing.