The control of as-cast structure of 2024 aluminum alloy with intensive melt shearing and its effect on microstructure and mechanical properties after T4 treatment

The newly developed technology of intensive melt shearing direct-chill casting (MS–DC) was used to control the as-cast structure of 2024 aluminum alloy and study its genetic effects in deformation and heat treatment processes. The melt temperature near the bottom of the shearing device (TS) during MS–DC process was proposed as the key parameter to control the as-cast structure. The results showed that the grain refining effect of intensive melt shearing greatly depends on TS. With the decrease of TS, the grain size became smaller, but the grain morphology also got changed. The fine equiaxed dendritic structure was obtained when the TS is slightly above the liquidus of the alloy. The ellipsoid grains was generated when TS was below the liquidus of the alloy. Further work demonstrated that compared with ellipsoid grains, the fine equiaxed dendritic as-cast structure resulted in more refined second phase, smaller size of recrystallized grains, higher mechanical properties and lower intensity recrystallization texture in the samples after cold rolling and T4 treatment.