Multiscale deformation-induced surface pattern in 3D-printed AlSi10Mg under uniaxial compression

Surface roughening, which typically accompanies plastic deformation of metals, is often considered detrimental. Using small-size samples, this study focuses on deformation-induced roughening in 3D printed AlSi10Mg alloy, linking this phenomenon to the complex hierarchical microstructure. The structure-mechanical property relation in as-built AlSi10Mg was analysed under quasistatic compression via a combined experimental and modelling approach, which considers macroscale (melt pool pattern), grain scale, and microscale (dendritic cells). Opposite to typical deformation-induced surface patterns in polycrystalline materials, a free surface of as-built AlSi10Mg undergoes smaller-scale roughening at later stages in the deformation process than larger-scale undulations. The stress-plastic strain curve displays two distinct parts with different slopes: an initial linear segment up to 400 MPa with a high slope factor and a subsequent portion characterised by a smaller slope. During the first stage of plastic deformation, the material undergoes quasi-uniform contraction without meso- and macroscale strain localisation. In the second stage, the entire surface progressively becomes involved in roughening. Analysis identified two distinct deformation regions - the bulk of the melt pool and melt pool boundary - and revealed that melt pools function as individual microstructural elements, significantly influencing the deformation behaviour of AlSi10Mg. Pronounced stress concentrations were observed near the melt pool boundaries, adjacent to track overlapping regions. Intense plastic deformation was observed in the track overlapping regions of the melt pool boundaries, suggesting these areas as potential sites for crack initiation under further loading, which was confirmed experimentally.