Utilization of Hot Deformation to Trigger Strain-Induced Boundary Migration, Particle-Stimulated Nucleation, and Influence of Nano-Precipitates on Mechanical Properties in High-Alloyed Al–Zn–Mg–Cu Alloys

The second phases, nano-sized precipitates, and mechanical properties of high-alloyed Al–2.9 Mg–10.8Zn–7.55Cu and Al–3.56 Mg–7.69Zn–10.25Cu aluminum (Al) alloys were analyzed using SEM, XRD, DSC, EBSD, TEM, and tensile tests. The second phases of as-cast Z1 and Z2 alloy were mainly Al₂Cu and Al₂MgCu. After hot deformation, the phases at grain boundary in Z1HR and Z2HR were mainly Al₂Cu, Al₂MgCu and Mg₂Al₅Cu₆. The nano-precipitates within grain are Al₂Cu, Al₂MgCu and Mg₂Al₅Cu₆ whose nano-precipitates are different from that in traditional Al alloy and there is a coarsening process of nano-precipitates. The recrystallization nucleation mechanisms of Z1HR and Z2HR Al alloys during hot deformation were strain-induced boundary migration (SIBM) and particle-stimulated nucleation (PSN), which are related to nano-Al₂Cu at grain boundaries and intergranular second phases, respectively. The Z1HR Al alloy showed good tensile strengths (\(\sim\) 500 MPa) and ductility \(\sim\) 0.068 after hot deformation. The better tensile properties of Z1HR than Z1, Z2 and Z2HR Al alloys can be ascribed to the precipitation strengthening effect. This study provides insights into novel precipitate structures that can be used in future alloy design.