Crack-free laser powder bed fusion processing and stress-assisted phase transformations during high-temperature creep of Al 85 Cu 5 Li 4 Mg 3 Zn 3 lightweight Al-based entropy alloy

The high-temperature creep resistance of rapidly solidified aluminum (Al) alloys depends on the evolution of their strengthening phases under sustained loading. Here, we map the crack-free laser powder bed fusion (L-PBF) processing window of an Al85Cu5Li4Mg3Zn3 lightweight Al-based entropy alloy (LAEA) and probe how thermally established phases evolve during high-temperature compressive creep. After thermal exposure at 300°C, continuous nano-sized cellular eutectic networks are retained together with S-Al2CuMg and TB-Al7Cu4Li phases, whereas exposure at 400°C decomposes the networks into coarse and dispersed σ-Al5Cu6Mg2 and R-Al5CuLi3 phases. The alloy exposed at 300°C exhibits the lowest minimum creep strain rate over the common stress range at 300°C, with effective threshold stresses of 80.2 and 69.6 MPa at 200 and 300°C, respectively. Retained cellular interfaces confine dislocation motion and promote the rearrangement of accumulated dislocations into regularly polygonal interfacial dislocation networks while allowing dynamic recovery. Local and incomplete TB-to-R and S-to-θ transformations are further observed after creep at both temperatures, supporting a role for creep-generated defects in solute redistribution and interface migration. These results link the retained nano-sized cellular eutectic networks to dislocation confinement and rearrangement during creep, while showing that creep-generated defects can further assist local phase transformations.