Uncovering the role of hierarchical and heterogeneous structures on strength anisotropy and strain localization of laser power bed fusion AlSi10Mg

Abstract

Hierarchical and heterogeneous microstructure covers a vague veil on deformation mechanisms and origins of mechanical anisotropy of laser powder bed fusion (LPBF) AlSi10Mg. The present work is devoted to unveil the correlation between microstructure features and mechanical behaviors via high fidelity melt pool models and crystal plasticity finite element simulations. Following careful validation with experimental results, dedicated simulations were conducted to assess the effects of Si-rich network, melt pool border and polycrystalline structures on the mechanical properties, with a particular focus on strength anisotropy and strain localization. The results show that the elongated Si-rich network plays a critical role in strength anisotropy, whereas the melt pool border and grain structure exhibit a negligible influence. Although the softer melt pool border promotes strain localization, its softening effect on global strength is found to be weakened due to deformation compatibility induced constraints, promoting an enhanced strength of this region. Additionally, it is demonstrated that appropriate grain orientation distribution perpendicular to the building direction can effectively reduce the strength anisotropy, without affecting the strain localization level. These findings offer new insights into the microstructure optimization of LPBF aluminum alloys, aiming to achieve mechanical isotropy.