How heterogeneous microstructure determines mechanical behavior of laser powder bed fusion AlSi10Mg

Laser powder bed fusion AlSi10Mg exhibits hierarchical and heterogeneous microstructure, which leads to anisotropic mechanical properties. The present work systematically investigated strength, ductility and their correlations to heterogeneous microstructure along different loading directions. Two AlSi10Mg samples presenting distinct features of Al-Si cellular structures and melt pool borders were analyzed, using combined tensile tests and digital image correlation measurements at both macro and micro scales. In addition, crystal plasticity modeling and simulation were conducted to reveal the deformation behavior and propensity to damage in the melt pool interiors and at the melt pool borders. Strain localizations are found in both the building direction and the perpendicular direction, due to weaker melt pool border and soft grain orientation, respectively. With the experimental and numerical results, it is demonstrated that the strength anisotropy mainly originates from the elongated Al-Si cellular structure, while the melt pool border plays a secondary role. Moreover, the ductility and its anisotropy appear to be determined by combined effects of strain localization, propensity to damage and constraints to crack formation. The findings of the present work unveil clearly how hierarchical and heterogeneous microstructure renders the macroscopic mechanical properties of additively manufactured Al alloys in different loading directions.