Homogenization-free fabrication of a high-strength ductile melt-impact-deposited 7055 Al alloy via extrusion-assisted defect healing and Al3Sc-based/η′ precipitation synergy

Melt-impact deposition is a promising rapid-solidification route for fabricating highly alloyed 7xxx aluminum (Al) alloys. However, as-deposited billets often contain shrinkage porosity and continuous brittle intergranular constituent networks, which can trigger premature failure. Mitigating solute segregation and dissolving non-equilibrium constituents typically require energy-intensive and time-consuming homogenization treatments, whereas porosity must be addressed by mechanical consolidation. Here, we propose a homogenization-free short-process route for a Sc-microalloyed 7055 Al alloy, in which conventional pre-extrusion homogenization is omitted and direct hot extrusion is followed by solution treatment and peak aging. Microstructural analyses reveal that hot extrusion substantially reduces the detectable porosity and fragments the continuous intergranular constituent networks. More importantly, trace Sc addition promotes the formation of thermally stable Al 3 Sc-based dispersoids, which exert Zener pinning and thereby help retain extrusion-induced substructures, including dislocations and low-angle/subgrain boundaries, during subsequent solution treatment. A linear superposition model was used to semi-quantitatively assess the synergistic strengthening mechanisms, demonstrating that dense nanoscale η′ precipitates provide the dominant strengthening contribution, estimated to be approximately 550 MPa, whereas the retained substructures and Al 3 Sc-based dispersoids provide additional strengthening contributions. Owing to this multiscale structural synergy, the estimated yield strength(YS) of approximately 749 MPa agrees well with the measured value of 752.6 MPa, and the peak-aged alloy achieves an ultimate tensile strength (UTS) of 797.1 MPa and an elongation to fracture of 13.3%. Moreover, this comprehensive microstructural optimization changes the dominant fracture behavior from premature intergranular decohesion to a mixed mode involving particle-assisted cracking and extensive microvoid coalescence. Overall, these findings demonstrate a scalable homogenization-free strategy for fabricating advanced 7xxx Al alloys with an excellent strength–ductility combination.