Strong 3D-printed aluminium reinforced with ductile-transformable eutectic nano-skeleton

Lightweight metals for additive manufacturing remain constrained by limited strength-ductility synergy, restricting their use in high-performance structural applications. Here we report a design strategy for additively manufactured alloys based on ductile-transformable eutectic nano-skeletons (DT-ENS) enabled by non-equilibrium solidification. In a near-eutectic Al-Er system, we develop an alloy family containing a deformable Al₃(Er,Mg) nano-skeleton as the primary strengthening architecture. Site-specific atomic substitution and long-range chemical ordering within the  Al₃(Er,Mg) skeleton are associated with deformation twinning and the strain-induced formation of 9R-type long-period stacking ordered structures, which enhance work-hardening of the skeleton and promote cooperative deformation with the α-Al matrix. Laser powder bed fusion yields Al-Er alloys with strengths of 600-700 MPa, together with good printability and useful ductility. These findings establish a new benchmark for structural additively manufactured aluminium alloys, provide a route for developing ductile intermetallics to overcome the strength-ductility trade-off in high-strength aluminium alloys, and demonstrate the role of additive manufacturing in uncovering new alloy systems and deformation mechanisms.