Influence of vortex effect on the central segregation defects of horizontal twin-roll casting Al–Mg–Mn–Zn–Cu–Cr alloy sheet

Abstract

In this paper, the formation mechanism of the vortex zone at different low cast-rolling speed was investigated elaborately with the aid of simulating flow field in cast-rolling zone. Additionally, the Influence of vortex effect on the central segregation defects of horizontal twin-roll casting (TRC) Al–Mg–Mn–Zn–Cu–Cr alloy sheet was analyzed in detail. The concrete results revealed that the area of the vortex zone shows an upward trend with decreasing cast-rolling speed, whereas the grain aspect ratio in the central area exhibits the reduction trend. The macro-segregation ratio of different elements at the vertex of the curve were also diminished when the cast-rolling speed decreases, due to the vortex effect can improve the nucleation rate and uniform the temperature field. More importantly, the presence of obvious valleys on both sides of the macro-segregation ratio curve, which fully proves the existence of vortex zones in the cast-rolling zone of the D2 and D3 cast-rolled sheets. Moreover, the values, uniformity and consistency of the hardness were significantly improved, mainly result from the vortex effect which enhances solid solubility of the alloy and improves the microstructural uniformity of sheet. While, the intensities of the shear textures and rolling texture of the cast-rolled sheet was notably enhanced with the gradual reduction of cast-rolling speed. Ultimately, the high alloying Al–Mg–Mn–Zn–Cu–Cr alloy cast-rolled sheet with excellent comprehensive properties was obtained.

Keywords

• Horizontal twin-roll casting
• High alloying Al–Mg–Mn–Zn–Cu–Cr alloy
• Central segregation defects
• Vortex effect
• Microstructure and mechanical properties