Microstructure and mechanical properties of twin-roll cast Mg-4.5Al-1.0Zn sheets processed by differential speed rolling

The microstructure and mechanical properties of the twin-roll cast (TRC) Mg-4.5Al-1.0Zn alloy sheets produced by differential speed rolling (DSR) were investigated by optical microscopy, transmission electron microscope and electron backscattered diffraction. The results are compared with those of the sheet processed by equal speed rolling (ESR). It is shown that twining played an important role at the initial stage of rolling. With the increase of the rolling reduction, the microstructures in the processed sheets become more homogeneous and they are more refined by DSR than by ESR. After annealing, the sheet processed by DSR shows a higher elongation and slightly lower yield strength than those of the ESR-processed sheet, which could be attributed to grain refinement and texture weakening. These results suggest that, in comparison with conventional casting and rolling, the combined technology of TRC and DSR is a more effective way to process magnesium sheets with enhanced formability after final annealing. (C) 2009 Elsevier Ltd. All rights reserved.