Inhibiting of the negative natural aging effect in Al–Mg–Si alloys

Abstract

The negative natural aging effect is commonly observed in heat-treatable reinforced Al–Mg–Si alloys. It has been observed that when the Mg/Si mass ratio in the alloy approaches 0.68 (equivalent to an atomic ratio of 0.77), which closely aligns with the stoichiometric ratios of β″, it induces a modification in the precipitation pathway. Within this alloy, clusters formed during natural aging exhibit a progression from Si-rich to Mg-rich and eventually back to Si-rich as the natural aging duration extends. Remarkably, the Si-rich clusters that form in the latter stages of natural aging exhibit stability and can attain the critical nucleation size required for β″ formation. Subsequently, an abundance of uniformly distributed nuclei emerges, contributing to the development of numerous fine β″ precipitates at the peak artificial aging temperature. Consequently, this phenomenon effectively curtails the negative effect of natural aging.