On the Anisotropic Impact Behavior of an Additively Manufactured AlSi10Mg Alloy in Different Heat Treatment Conditions

The present work deals with the anisotropic high-strain rate behavior of laser-powder bed fusion (L-PBF) produced AlSi10Mg alloy in different heat treatment conditions. Impact specimens were produced with different orientations towards building platform and U-notch positions to assess the anisotropic properties. Besides the as-built material, several heat treatments were considered, including annealing, standard T6, hot isostatic pressing (HIP), HIP plus T6, and a recently proposed T6 at high pressure. The high-strain rate behavior was investigated by conducting Charpy impact tests, while material characterization was performed by scanning electron microscopy and x-ray diffraction. Results show that as-built and annealed alloys display significant anisotropic impact properties, whereas samples heat-treated at high temperatures generally have more consistent behavior. A coupled microstructural and fractographic investigation highlights that mitigation of anisotropy descends from the recovery of microstructural heterogeneity of the Si phase after heat treatment at high temperatures. This does not happen for both grain morphology or crystallographic structure, which are not significantly altered after the heat treatment. The present study aims to fill the gap in the literature regarding the anisotropic high-strain rate behavior of additively manufactured Al alloys and provide useful insights for mitigation of anisotropy by heat treatment.