High-proportion intragranular nano-Al2O3 induced high strength-ductility Al matrix nano-composites via additive friction extrusion deposition

Herein, a novel additive friction extrusion deposition (AFED) solid state additive manufacturing technique was employed to fabricate nano-Al2O3/2009Al composite. The severe plastic deformation introduced by AFED led to a uniform dispersion of nano-Al2O3 and a significant grain refinement to less than 500 nm in average grain size due to the pinning effect of the dispersed nano-Al2O3 particles. As high as 78 % nano-Al2O3 particles were observed within the refined grains, rather than along the grain boundaries as previously reported. The unique microstructure with high proportion of intragranular nano-Al2O3 particles accumulated dislocations in grain interior, induced pronounced work hardening, thereby achieving high strength-ductility and relatively low yield strength to tensile strength ratio of 0.78 in the AFED Al2O3/2009Al composite.