Preparation and mechanical properties of aluminum-matrix composites with layered architecture

Aluminum-matrix nanocomposites (AMCs) reinforced by SiC nanoparticles (SiCnp) were prepared by directional freezing combined with spark plasma sintering (SPS) and hot extrusion. The effect of SiCnp and layered structure on the microstructure and mechanical properties of SiCnp/Al nanocomposites was studied. The composite showed a layered structure consisting of SiCnp-rich and poor areas. With addition of 1 wt.% SiCnp with average diameter 50 nm, the composite showed the best strength and toughness matching, with ultimate tensile strength (UTS) 326.2 MPa (35.4% higher than that of homogeneous counterpart) and fracture elongation 8.6%. The enhanced UTS in the layered nanocomposite was mainly attributed to the hetero-structure-induced formation of high density geometrically necessary dislocation (GND) in the near SiC-Al interface areas, which accordingly created pronounced hetero-deformation-induced (HDI) stress and work hardening capacity. The creation of layered architecture by feasibly directional freezing can advance the development of biomimetic layered composites with enhanced strength and toughness.