Formation of banded intergranular segregation and control via micro-alloying in twin-roll casted Al–Zn–Mg–Cu alloy with high solidification interval

Abstract

For twin-roll casting (TRC) aluminum alloys, research on segregation defects has mainly focused on center segregation. However, intergranular segregation has been rarely investigated. In this study, we found that the banded intergranular segregation was a distinctive feature in TRC aluminum alloys. The formation and coarsening mechanism of this banded intergranular segregation in TRC Al–Zn–Mg–Cu alloys were revealed for the first time. The results showed that the banded intergranular segregation was contributed to the shear-induced dilation as the cast-rolling force was gradually applied to the crystals in the semi-solid region. Macroscopic inverse segregation along the dendrite channels occurred under the strong shear-induced dilation, which resulted in significant coarsening of the banded intergranular segregation. Furthermore, a new path controlling the center segregation and the banded intergranular segregation simultaneously by micro-alloying was proposed, which provides a strategy to develop TRC aluminum alloys with a high solidification interval.