Interface structure and mechanical properties of Al2O3/Al co-continuous composites with three-dimensional network structures

Abstract

The Al₂O₃/Al co-continuous composites with three-dimensional network structures were successfully prepared by extruding the aluminum alloy melt into the porous Al₂O₃ ceramic skeleton prepared by the foam replication method. The interface structure, mechanical properties, and strengthening and toughening mechanisms of the composites were investigated. SEM analyses confirmed that the aluminum matrix filled the hollow channels in the foam ceramic struts, and the ceramic was tightly bonded to the aluminum matrix without transition layers. TEM analyses revealed multiple crystallographic orientation relationships at the Al₂O₃/Al interface, where the two phases were combined in coherent and semicoherent relationships. The dominant mode of interfacial bonding was mechanical bonding, but diffusional bonding and reactive bonding occurred. The composites had excellent strength and toughness, with their flexural strength and fracture toughness values reaching 506 MPa and 16.1 MPa m^1/2, respectively. The high strengths of the composites resulted from the joint action of various strengthening mechanisms, such as three-dimensional network structure strengthening, load transfer strengthening, and dislocation strengthening. Through a combination of internal and external toughening mechanisms, such as crack deflection and bridging, the composites obtained high toughness values. A balance between the reinforcement phase continuity and matrix phase continuity was necessary to strengthen and toughen the composites.