Effect of different heat-treatment routes on the impact properties of an additively manufactured AlSi10Mg alloy

This work aims at investigating the impact behavior of an additively manufactured AlSi10Mg alloy subjected to different heat-treatment conditions. The commonly used heat-treatment routes were compared with a novel route (HPT6), which combines hot isostatic pressing (HIP), gas quenching, and ageing at high pressures. The as-built and treated alloy was characterized by Charpy impact testing and several microstructural and fractographic techniques, such as scanning electron microscopy, transmission electron microscopy (TEM), and X-ray diffraction. The as-built material displayed a very fine non-equilibrium microstructure, which led to a high impact strength but limited absorbed energy. Low-temperature annealing severely modified the starting microstructure of the alloy and restored its equilibrium condition. Even though this alloy did not suffer from strength loss, its absorbed energy increased significantly, resulting in an excellent impact performance. HIP application inhibited the growth of gas-hosting pores in the alloy when treated at high temperatures, yielding a material with a final relative density higher than 99%. TEM demonstrated that the novel HPT6 route induced precipitation strengthening in the alloy, thus increasing its impact strength when compared to the HIP route. Moreover, the HPT6 alloy and the alloy subjected to standard heat-treatment exhibited comparable impact performance. This suggests that the novel route proposed in this study can possibly replace the standard heat-treatment protocol, which would reduce the processing duration and cost of production of the additively manufactured AlSi10Mg alloy.