Pre-precipitating promoted by microshear bands effectively circumvents strength-ductility trade-off of RT-rolled Al-6Zn-1Mg alloy

The aging precipitated phases are of great significance for the strengthening and toughening of Al-Zn-Mg alloys. In this work, pre-precipitating was realized through equal channel angular pressing (ECAP) immediately followed by solid solution treatment at 475 degrees C for 6 h. Its corresponding strengthening and toughening effect on the room temperature (RT)-rolled Al-6Zn-1Mg alloy was systematically studied. The results indicate that preprecipitating by ECAP can effectively improve the strength of the RT-rolled Al-6Zn-1Mg alloy and circumvent the strength-ductility trade-off. Microstructure characterization reveals that ECAP induces a large number of microshear bands, which can not only encourage recrystallization but also effectively promote the precipitation of the eta ' phase. The synergistic effect of precipitation strengthening and dislocation strengthening contributes to the high strength of Al-6Zn-1Mg alloy, with UTS and YS increasing to -522 MPa and -400 MPa, respectively. Meanwhile, the ductility remains almost unchanged mainly due to the coordinated grain boundary sliding and the uniform and finely dispersed second phase particles. As a result, the strength-ductility trade-off is effectively avoided. The findings shed some light on optimizing the traditional aging treatment.