Fast age-hardening response of Al–Mg–Si–Cu–Zn–Fe–Mn alloy via coupling control of quenching rate and pre-aging

The coupling control of quenching rate and pre-aging and its positive effect on the age-hardening response of Al–Mg–Si–Cu–Zn–Fe–Mn alloy was systematically investigated. The larger and more stable solute clusters can be formed in alloy with fast age-hardening response by using the lower quenching rate (5.3 °C/min) and an appropriate pre-aging, in which the deterioration of natural aging also can be obviously suppressed. Additionally, the highest bake hardening increment of the alloy can reach 145.2 MPa, which is much higher than those of traditional Al–Mg–Si–(Cu) alloys (such as, 6016 and 6111 alloys). Based on the detailed precipitation behavior characterization of alloys with different quenching rates and the same pre-aging, the quenching rate change can result in the significant differences in the size, number density of precipitates in the both paint baking and peak aging states, but the type of precipitates basically keeps the same, i.e., Mg–Si precipitates, and no Mg–Zn precipitates can be observed. Finally, the related mechanisms of coupling control of quenching rate and pre-aging were also discussed in this paper. The developed coupling control method shows great potential and could significantly increase applications of Al–Mg–Si–Cu–Zn–Fe–Mn alloys with a fast age-hardening response.