Microstructure and mechanical properties of hot-extruded Al–Ce–Mg–Si alloy fabricated from degraded laser powder bed fusion powders

Upcycling degraded alloy powders from laser powder bed fusion (LPBF) through alternative solid-state processing routes is important for sustainable additive manufacturing. In this study, an Al–10.0Ce–0.68Mg–0.51Si (wt.%) alloy was fabricated from powders recovered from the overflow bin of an LPBF system through spark plasma sintering followed by hot extrusion. The alloy exhibits a deformed microstructure dominated by coarse fibrous grains containing a high density of retained substructures (dislocation walls and subgrain boundaries), along with a limited fraction of fine recrystallized grains. The retention of these substructures is associated with strong interactions between the high-volume-fraction intermetallic particles, dislocations, and subgrain boundaries. At room temperature, the alloy exhibits a yield strength (YS) of ∼133 MPa, an ultimate tensile strength of ∼230 MPa, and an elongation to fracture (EF) of ∼22%. The YS arises from the combined effects of grain-boundary and dislocation strengthening, with additional particle-related contributions, while the heterogeneous grain structure and retained substructures sustain strain hardening and delay strain localization. At 200 °C, the alloy retains ∼93% of its room-temperature YS, accompanied by an increase in EF to ∼50%. This elevated-temperature response is associated with particle-assisted boundary pinning, matrix softening, and coordinated deformation promoted by crystallographic reorientation. This work demonstrates an alternative solid-state route for upcycling recovered LPBF powders and clarifies the roles of intermetallic particles and deformation-induced substructures in regulating the microstructure and mechanical behavior of Al–Ce-based alloys.