Enhanced mechanical properties by eutectic cells in AlSi10Mg - A promising paradigm for strengthening aluminum in additive manufacturing

Abstract

AlSi10Mg, as-built by laser powder bed fusion, includes performance-enhancing refined eutectic cells invariably paired with performance-impairing melt pool boundaries, where the cell network coarsens and breaks down. Eliminating melt pool boundaries (and their associated anisotropy) is a motivation for conventional heat treatments but at the cost of removing the AM-specific eutectic cell strengthening. This work evaluates the advantages and disadvantages of retaining the AlSi10Mg cell network (with melt pool boundaries) via direct aging, in contrast to a conventional (T6) approach, which relies primarily upon precipitation strengthening. We compare both heat treatment approaches and their impacts on microstructure, tensile properties, fracture, strain-hardening, and thermal stability. Direct aging achieves superior thermal stability and performance by preserving the as-built cell network and its exceptional strain-hardening capacity, despite the retained melt pool boundaries. As-built eutectic cells (which closely depend on build parameters and do not require post-processing) offer unique promise as potential enablers of voxel-by-voxel AM property control.