Strength–ductility balance of AFSD-processed 7075 aluminum alloy: Synergistic roles of AFSD-induced dispersion and TiC nanoparticle modification

The traditional particle modification can inhibit hot cracking in 7xxx series aluminum alloy, but particle agglomeration can easily lead to stress concentration. In this study, TiC nanoparticles reinforced 7075 aluminum alloy was prepared by additive friction stir deposition (AFSD) technology. The interaction between TiC nanoparticles and the AFSD process, and the effect of T6 heat treatment were systematically studied. The results demonstrate that severe plastic deformation during AFSD effectively eliminates nanoparticle agglomeration and significantly improves the uniformity of particle distribution. At the same time, dynamic recrystallization refined the grain size from 79.77 μm to 1.54 μm. The above microstructure optimization increased the tensile strength from 285.7 ± 4.7 MPa to 491.8 ± 13.8 MPa, and the elongation from 1.1 ± 0.1% to 18.1 ± 1.3%, thereby achieving the simultaneous improvement of strength and plasticity. However, after traditional T6 heat treatment, the tensile strength of the material increased to 563.4 ± 17.3 MPa, and the elongation decreased to 10.6 ± 0.4%, indicating an obvious imbalance between strength and plasticity. This study demonstrates that AFSD can effectively overcome particle agglomeration, but the traditional T6 process is not suitable for such composites. It is therefore necessary to develop a tailored heat treatment system to achieve the synergistic optimization of strength and plasticity.