Precipitation strengthening of Al-Mg-Si alloy subjected to multiple accumulative roll bonding combined with a heat treatment

Abstract

Thermo-mechanical treatment is one of the most important tools in designing properties of aluminum alloys. Plastic deformation introduces defects to microstructure and provides work hardening while a proper heat treatment may induce precipitation processes which lead to additional strengthening. In this work, a complex procedure is investigated with intention to increase mechanical strength of Al-Mg-Si alloy beyond conventional levels. Accumulative roll bonding is used as plastic deformation technique but with intention to provide a new microstructural feature – interlayer boundaries, instead of grain refinement. Solution heat treatment and ageing procedures are designed in a way that healing of the microstructure with maintaining some deformation-related features is maintained. Depending on the placement of solution treatment in the whole procedure, precipitation processes are similar or different from ones observed in a conventional solutionizing-ageing sequence. Nevertheless, the final hardness is always increased when compared to a typical heat treatment. Transmission electron microscope observations are performed to study variances in nucleation and growth of strengthening phases.