Enhanced stiffness of Al–Zn–Mg–Cu alloys via heterogeneous structure of soft and hard microdomains

Here we present a novel thermomechanical processing for constructing heterogeneous microstructure of Al–Zn–Mg–Cu alloys. This induced a heterogeneous microstructure consisting of a cellular bi-modal grain structure with coarse grains surrounded by fine grains, resulting in the changed precipitation and deformation behaviors, and greatly improved stiffness, in comparison to the Al alloys with uniform microstructure. The great increase in stiffness is related to the synergy of hard and soft micro-domains corresponding to the fine and coarse grain micro-domains. The related mechanisms of forming heterogeneous structure and high stiffness were put forward, which provide an important guidance on designing high stiffness Al alloys for automotive applications.