Composite number

Materials science

Ultimate tensile strength

Ductility (Earth science)

Creep

Grain boundary

Toughening

Ball mill

Organic chemistry

Whiskers

Microstructure

Fracture toughness

Composite material

Strengthening mechanisms of materials

Chemistry

Nucleation

Toughness

Acta Materialia

Due to native deficiency of the interfacial mismatch between Al2O3 and Al-melt, as well as micron-Al2O3 segregation at matrix grain boundaries (GBs), achieving both high strength and fracture toughness has been the long-lasting challenge for Al-CuO composite fabricated by conventional casting. Herein, we report a novel manufacturing of Al-CuO composite via shift-speed ball-milling (SSBM) of Al-5 wt.% CuO powders and afterwards subjected to hot-pressing (HP) as well as heat treatment. Comprehensive characterization shows that in-situ generation of the two types of Al2O3 with intragranular distribution, including δ*-Al2O3 particles (~200 nm) and γ-Al2O3 whiskers (length of ~150 nm, thickness of ~20 nm), was governed by a diffusion-assisted nucleation-regime ascribing to the intense thermal effect of Al-CuO reaction. The size and spatial distribution of Al2O3 were emphasized to address their contribution to the high mechanical performance of the composite, which exhibits a tensile strength of ~481 MPa and fracture elongation of ~16.8 %. Meanwhile, the toughening mechanism of present Al-CuO composite was rationalized on basis of the "dislocation punched zone" and "plastic zone" affected by Al2O3. Both the theoretical analysis and fracture morphology support a reinforcements-matrix interface failure mechanism and the non-uniform distribution of Al2O3 consisting alternant "rich/poor zones" can markedly contribute to the high toughness. The present findings may provide a promising strategy to achieve an intragranular distribution of nano-sized reinforcements in Al-metal oxides composites, which enables increasing strength and ductility of the metal matrix.

Revealing the strengthening and toughening mechanisms of Al-CuO composite fabricated via in-situ solid-state reaction