Microstructure and micromechanical properties of microcellular AlSi10Mg produced via LPBF

Laser Powder Bed Fusion (LPBF) is an advanced additive manufacturing (AM) process that allows for the fabrication of complex-shaped metallic materials — colloquially referred to as architected materials. While it offers high design flexibility, LPBF often produces architected materials that contain a variety of defects (e.g., geometric imperfections or internal matrix porosity) and feature complex microstructures, whose characteristics and origin are investigated in this study for one class of architected materials. In this work, extensive Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD) are combined with nanoindentation testing to investigate the microstructure and micromechanical properties of a microcellular AlSi10Mg alloy, produced by LPBF using a contour-hatch strategy. The alloy’s cellular architecture is generated algorithmically prior to fabrication and consists of randomly distributed cylindrical pores embedded within the matrix. The influence of the LPBF scanning strategy is thoroughly examined, and the focus is put on the effect of contour scanning on the resulting as-built microstructure of this class of microcellular AlSi10Mg. The findings indicate that different scanning sequences (i.e., contour and hatching) lead to variations in grain morphologies, crystallographic texture, and morphology of the secondary phase, resulting in highly heterogeneous micromechanical properties (i.e., nanohardness). The effect of T6-like heat treatment is also examined and the resulting microstructural features are compared with those of the as-built AlSi10Mg microcellular alloy. The comparison highlights the effectiveness of heat treatment strategies in mitigating the microstructural and micromechanical heterogeneities induced by the contour-hatch scanning.