Microstructural differences at different positions of Al-Mg-Si alloy twin-rolling casting plate and effects on plate properties

Al-Mg-Si alloy plate produced by traditional hot rolling has many defects such as complicated processes, long time and high cost, which seriously restricts the development of Al-Mg-Si alloy. Therefore, the Al-Mg-Si alloy plate produced by the twin-rolling casting process has attracted great attention in recent years. The twin-rolling casting process was used to prepare the Al-Mg-Si aluminum alloy plate, and the difference of microstructure at different positions of the plate and the influence on the performance were investigated. The results show that the grain morphology of the edge and the center of the plate is significantly different, the texture composition is complex, a large number of second phases are unevenly distributed along the grain boundary, and there is obvious element segregation inside the plate. According to the theoretical calculation, the contribution strength of texture strengthening at the edges of the twin-rolling casting plate is 10. 7 MPa and the contribution strength of grain boundary strengthening is 86. 8 MPa, while the contribution strength of texture strengthening in the center of the twin-rolling casting plate is 15. 1 MPa and the contribution strength of grain boundary strengthening is 82.4 MPa. The contribution of plate texture and random texture to the strength is limited, and the strength difference between edge and center mainly depends on the grain boundary strengthening. Different degrees of dislocation tangles exist at the edge and the center, and the dislocation density at the edge is higher than that at the center, which is consistent with the statistical results of low angle grain boundaries. According to the characteristics of microstructure inhomogeneity of the plate, the theoretical guidance for the subsequent heat treatment system of the plate is provided through thermodynamic calculation.