The effect of Mg/Si ratio on the microstructure and tensile properties of twin-roll casting Al-Mg-Si alloys.

In this work, two types of Al-Mg-Si strips with different Mg/Si ratios were fabricated by vertical-type twin-roll casting (TRC), and the effect of the Mg/Si ratio on microstructure and tensile properties of the TRC strips was investigated. The TRC strips show the heterogeneous structure, composed of columnar dendrites near the surface of both sides and near-equiaxed grains in the central region. Serious central segregation of eutectic phases occurred in the TRC strips with Mg/Si = 0.5 (S0.5), while no obvious central segregation was found in the strips with Mg/Si = 2.9 (S2.9), which was ascribed to the different solidification path. The low Mg/Si ratio promoted precipitation during aging, which resulted in an increase of 85 MPa in yield strength compared to the S2.9 sample. However, intergranular fracture occurred in the S0.5 sample, lowering uniform elongation. • The Mg/Si ratio affects the solidification path of Al-Mg-Si alloy. • High Mg/Si ratio inhibits central segregation and grain growth. • Serious central segregation occurred in the TRC strips with a low Mg/Si ratio. • The sample with a higher Mg/Si ratio has the higher elongation. [ABSTRACT FROM AUTHOR]