Properties of Laser Metal Fused AlSi10Mg Alloy Processed Using Different Heat Treatments

The AlSi10Mg alloy was fabricated by Laser Metal Fusion (LMF) using different post processing conditions. Tensile and dilatometric specimens were obtained with longitudinal axis parallel to the building direction. A first set of samples was directly aged in the as-built state (AB), while a second batch underwent solubilization annealing (SA) at 540 °C for 60 min just before artificial ageing (AA) at 160 °C for 8 h. Solubilization caused the precipitation of Si particles, suppressed by the rapid solidification during SLM. Moreover, it caused partial recrystallization leading to a coarser microstructure. The ageing response was very different in the two cases, involving a higher starting hardness for the as-built material, showing a markedly higher hardness during the whole process. In the as-built material, isochronal ageing experiments carried out by differential scanning calorimetry showed the precipitation of Mg₂Si particles beneath Si, while the same transformations were much less intense in the solubilized sample, due to the lower Si supersaturation. The ageing process raised the yield strength of about 20% compared to the AB material, slightly reducing the fracture elongation. The same alloy after SA+AA showed a strength 25% lower than the AB+AA material, while ductility significantly increased.