Sub-micron particles induced microstructure modification to achieve exceptional mechanical and corrosion properties combination in additive manufactured TiB2/Al–Zn–Mg–Cu composites

The aluminum alloys processed by additive friction stir deposition (AFSD) typically exhibit dense microstructures with fine grains. However, these fine grains are prone to coarsen during subsequent heat treatment, limiting the application of AFSDed materials. In this study, sub-micron TiB2 particles with different contents (3.5 wt.% and 8 wt.%) were introduced to modify the microstructure and tailor the mechanical/corrosion properties of Al–Zn–Mg–Cu alloys. Compared with the typical 7055 aluminum alloy, the TiB2 particles led to great grain refinement by promotion of recrystallization and significantly enhanced the thermal stability of two TiB2/7055 composites during heat treatment. Meanwhile, the particles could alter the precipitation behavior during aging treatment, resulting in the formation of interface precipitates, a discontinuous distribution of grain boundary precipitates, and a narrower precipitate-free zone. An exceptional combination of mechanical and corrosion properties was achieved by particle addition, where 3.5 wt.% particle addition could enhance both strength and ductility of alloy, with a reduction in intergranular corrosion resistance, and 8 wt.% particle addition would enhance the strength and intergranular corrosion resistance, with a slight decrease in ductility. According to microstructure characterization, the underlying mechanism regarding the effects of sub-micron TiB2 particles on grain structure and its thermal stability was deeply revealed. The comprehensive effects of particle contents on the mechanical properties and corrosion behavior were discussed. This study offers a novel perspective on balancing the mechanical and corrosion properties in high-performance aluminum matrix composites.