Precipitation behavior during re-aging of Al-Mg-Si-Cu alloy

Nano-scaled L phase, β′′ phase, Q′ phase and their composite phases can effectively strengthen Al-Mg-Si-Cu alloys, and balance the mechanical properties and electrical conductivity. However, the re-precipitation behavior and atomic structure of these re-precipitates and the formation and evolution of L phase still need to be further revealed. In this study, the re-precipitation behavior of a representative Al-Mg-Si-Cu alloy at atomic scale is investigated. The alloy samples are successively treated by peak aging, cold deformation and re-aging. The microstructural changes of re-precipitates are found mainly induced by dislocations and Guinier Preston zones formed in the deformation treatment. The re-precipitation process is proved beneficial to simultaneously improve the electrical conductivity and mechanical property. A type of L precursor with sawtooth-like cross section is also discovered. These findings comprehensively reveal the re-precipitation behavior in Al-Mg-Si-Cu alloy and help us to understand the formation and evolution mechanism of L phase more in-depth.