Tensile deformation and failure of AlSi10Mg random cellular metamaterials

Cellular metamaterials are an emerging class of porous materials, in which the topology of the solid is precisely-engineered to achieve attractive combinations of properties. This work specifically examines the tensile response of a novel type of cellular metamaterials, in which pores of arbitrary elliptical shape are randomly-dispersed into an aluminum alloy matrix. Their porous mesostructure is generated numerically via a random sequential absorption algorithm, and is fabricated by laser powder bed fusion from AlSi10Mg powders. The results – obtained by means of digital image correlation combined with X-Ray tomography - highlight the advantages offered by a random cellular topology. These are notably a low sensitivity to geometric imperfections (which result inevitably from manufacturing), coupled with the ability to delay long-wavelength strain localization (which is in turn responsible for failure). Structural disorder also leads to highly heterogeneous deformation patterns, which result from the interaction between geometric pores and promote void growth and coalescence during plastic straining. The presence of manufacturing defects, moreover, exacerbates void interaction and in turn promotes early plastic flow localization. Interestingly, experiments reveal that this class of porous solids effectively display features of the ductile fracture of metals, albeit at the mesoscale. For example, void-sheeting is observed with increasing pore aspect ratio and is accompanied by large geometric distortions of the voids upon coalescence. Measured data for the pore strains are, moreover, highly scattered and show a departure from McClintock’s model predictions for the voids within the fracture band. Collectively, this study highlights the potential offered by random porous metamaterials, which can be harnessed to revisit the complex mechanisms of ductile fracture at the mesoscale.