Regulating microstructure of novel Al-Mg-Zn alloy for enhancing comprehensive performance through retrogression and thermo-mechanical treatment

Abstract

A new generation aluminum alloy strengthened by T-Mg32(AlZn)49 phase has been created in the last decade based on 5xxx series AlMg alloy modified with the idea of precipitation strengthening in 7xxx series alloys, promising to overcome the trade-off between corrosion performance and mechanical properties. Herein, a novel retrogression and thermo-mechanical treatment (RTMT) was designed to further enhance comprehensive properties of the T-phase strengthened alloy through combining strain-hardening and precipitation-hardening. By comparing with traditional peak-aging treatment, retrogression and re-aging treatment, and final thermo-mechanical treatment, RTMT achieves an increase in tensile and yield strength of the alloy to 587.9 MPa and 537.5 MPa, respectively, and a significant reduction in the maximum intergranular corrosion depth to 37.5 μm simultaneously. Microstructure observation indicates that the enhanced interaction between the regulated precipitates and dislocations introduced during deformation is the key to synergistic improvement of corrosion and mechanical properties. The processing technology can be extendable to other age-hardening alloy systems for further development and application.