| The interaction between particle reinforcement and matrix was evaluated from the characteristic change at the interfacial microstructure during underaging(UA) and overaging(OA) heat-treatment of SiC reinforced 6061 Al composites. The objective of this study is to correlate the change of the interfacial microstructure with the failure mode of the composites. The underaged material exhibited a pronounced enrichment of Mg at the interface. The width of the Mg-enriched layer was wider than the overaged material, owing to equilibrium and non-equilibrium segregation. The failure was initiated at the matrix alloy which contained lower Mg contents. The failure mode was interface decohesion, resulting in the increased fracture toughness value. In the overaged case, the Mg-enriched layer was narrowed by the migration of non-equilibrium(vacancy drag) segregation to the interface, forming precipitates at the interface. The precipitation at the interface increases the interface strength, which causes the increased load transfer to the SiC particles. The failure mode was particle fracture, resulting in the lower fracture toughness value. |
|
