Effects of Casting Speed on Microstructural and Tensile Properties of Al–Mg–Si Alloy Fabricated by Horizontal and Vertical Twin-Roll Casting

For the development of Al–Mg–Si strips with high mechanical performance via twin-roll casting (TRC) technology, it is necessary to understand through comparative analysis of traditional horizontal twin-roll casting (HTRC) and promising vertical twin-roll casting (VTRC) technologies. In this study, two types of Al–Mg–Si alloys (denoted as H-alloy and V-alloy) were fabricated by HTRC and VTRC using different casting speeds (0.69 and 20 m/min, respectively). The microstructural evolution and mechanical properties of the two alloys were comprehensively assessed and compared. To reveal the microstructural characteristics, various techniques including energy-dispersive X-ray spectroscopy (EDS), electron backscatter diffraction (EBSD), texture calculation and differential scanning calorimetry (DSC) were utilized. Center segregation occurred in H-alloy and V-alloy in the form of channel segregation and segregation bands, respectively. Moreover, the texture components of H-alloy showed rolling and shear textures, indicating continuous casting with hot-rolling during HTRC; however, those of V-alloy showed a random texture, indicating the absence of hot-rolling during VTRC. Therefore, the amount of plastic deformation in H-alloy was greater than that in V-alloy, which increased the yield strength through dislocation strengthening. Furthermore, solid-solution strengthening and precipitation strengthening primarily helped improve the strength of V-alloy, whereas pre-existing voids caused premature fracture. Our comparative analysis of the microstructural evolution and tensile properties realized by HTRC and VTRC is anticipated to broaden the understanding of twin-roll-cast strips.