Defects, microstructures and mechanical properties of Al-Ce-Si-Mg alloys fabricated via laser powder bed fusion

A comprehensive understanding of defect–microstructure–property relationships is essential for advancing additively manufactured aluminum alloys. In this study, an Al-9.5Ce-0.5Si-0.6 Mg alloy was fabricated by laser powder bed fusion (L-PBF). In-situ X-ray computed tomography (XCT), combined with multi-scale microstructural characterization, revealed distinct defect-dependent damage mechanisms. Irregular lack-of-fusion (LOF) pores generated severe localized stress concentrations and served as dominant crack initiation sites, whereas small spherical gas pores exhibited isolated volumetric growth with negligible contribution to catastrophic failure. By tailoring processing parameters, LOF porosity was effectively suppressed while promoting a microstructural transition from columnar to fine equiaxed grains, coupled with interconnected nanoscale α-Al + Al₁₁Ce₃ eutectic networks. In the absence of severe LOF defects, damage evolution is dictated by intrinsic microstructural heterogeneity, where coarser eutectic networks at melt pool boundaries (MPBs) drive pronounced strain localization and govern final failure. Benefiting from the synergy of LOF pore suppression and microstructural refinement, the optimized L-PBF Al-Ce-Si-Mg alloy achieves a superior strength-ductility balance, with a yield strength of ∼285 MPa, an ultimate tensile strength of ∼427 MPa, and an elongation to fracture of ∼7%, significantly outperforming most reported L-PBF Al-Ce alloys. These findings clarify the roles of porosity and microstructural heterogeneity in damage evolution and provide mechanistic guidance for the design of high-performance additively manufactured aluminum alloys.