Achieving synergistically enhanced corrosion resistance and hardness in nano-ZrB2/Al composites through friction stir based solid-state additive manufacturing

Aluminum matrix composites (AMCs) hold significant potential as lightweight structural materials for aerospace applications. However, achieving a simultaneous enhancement in both strength and corrosion resistance remains a longstanding challenge. In this work, nano-ZrB2 particle-reinforced AMCs were fabricated via solid-state additive friction stir deposition (AFSD), which enables uniform dispersion of nanoparticles through severe plastic deformation and mechanical stirring at low processing temperatures. With the incorporation of 6 vol% ZrB2, the composite exhibited a 35.62% increase in hardness and a 14.42% improvement in ultimate tensile strength compared to the unreinforced AFSD-processed alloy. The strengthening is attributed to the combined effects of high-hardness ZrB2 nanoparticles and a dual grain refinement mechanism: dynamic recrystallization induced by AFSD leads to fine equiaxed grains, while ZrB2 particles serve as heterogeneous nucleation sites and effectively pin grain boundaries, resulting in further microstructural refinement. More importantly, the 6% ZrB2-reinforced composite demonstrated optimal corrosion resistance, exhibiting a low corrosion current density of 0.29 μA/cm2. This improvement is ascribed to the redistribution of precipitates during the solid-state process: Mg-Si phases preferentially encapsulate ZrB2 particles to form a core-shell structure, while the fraction of cathodic Al-Fe-Si intermetallics is significantly reduced. Such microstructural modifications alleviate electrochemical heterogeneity and suppress micro-galvanic coupling, leading to significantly enhanced corrosion performance. This study provides an effective solid-state additive manufacturing strategy for tailoring microstructures and breaking the conventional strength-corrosion resistance trade-off in AMCs.