Effect of composite on the early- and mid-stage precipitation hardening phenomena in Al-Mg-Si (Cu)

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Al-Mg-Si-(Cu), i.e. AA6xxx, alloys are commonly used as medium strength alloys for automotive, mass transportation, and structural applications. In particular, they are the light alloy of choice for automotive skin panels owing to their specific strength, corrosion resistance, surface appearance, and recyclability. The alloys acquire their desired strength through age hardening treatments, during which phase transformation processes involving a complex sequence of solute atom clustering and precipitation of nano-scale hardening particles take place. Previous studies have provided important information on the effect of alloy composition and/or heat treatment routes on the type of hardening precipitates or changes in precipitation processes. However, the underlying mechanisms for the effect of composition on phase transformations remain ambiguous or unverified. The goal of the proposed work is to use the state-of-the art atomic- and nano-scale characterization techniques, as well as macro-scale testing methods, to acquire a better understanding of the role of composition and aging history on the commercially-important precipitation hardening behaviour in Al-Mg-Si-(Cu) alloys.