Microstructure and micromechanical properties of microcellular AlSi10Mg produced by LPBF

In this work, the microstructure and micromechanical properties of a microcellular AlSi10Mg alloy produced by Laser Powder Bed Fusion (LPBF) are studied. Notably, the investigated material contains random distributions of cylindrical pores up to 20 % in volume, whose arrangement and geometry are generated numerically by a Random Sequential Absorption (RSA) algorithm prior to LPBF fabrication. In particular, the geometric pores have circular shape and their average size is around 400 µm. They are manufactured using a general contour-hatch strategy. The influence of the LPBF scanning process is thoroughly investigated in this study. In particular, the effect of the contour scanning on the resulting alloy microstructure is examined, using both scanning electron microscopy (SEM) (combined with EBSD analysis) and nanoindentation testing. It is shown that the different scanning sequences (i.e., contour and hatching) lead to different grain morphologies and crystallographic textures, and result in highly heterogeneous micromechanical properties (nano-hardness) Finally, the results of the microstructural analysis on the as-built AlSi10Mg microcellular alloy are compared against those obtained on the same alloy after conventional T6-like heat-treatment, highlighting the beneficial effect of heat-treatments in mitigating microstructural heterogeneity.