Investigation into the microstructure, tensile properties and bendability of Mg–Al–Zn/Mg-xGd laminated composite sheets extruded by porthole die

In this work, laminated composite sheets of Mg alloys AZ31 and Mg-xGd are fabricated through co-extrusion using a pothole die. The asymmetric deformation of the dissimilar Mg alloys during the extrusion is analyzed by combining the results of experiments and numerical simulations. The microstructure, tensile properties and bendability of the laminated composite sheets are comparatively investigated. The results show that the sheet AZ31/Mg-1.2Gd obtains a flat profile, uniform composite layers and high bonding strength of 131 MPa because of the relatively symmetric deformation of the Mg alloys AZ31 and Mg-1.2Gd during the co-extrusion. Compared with the sheet AZ31, the bendability of the laminated composite sheet AZ31/Mg-xGd is significantly improved. In addition, when the Mg-xGd alloys, instead of the AZ31 alloy, are placed in the outer layer of the specimens during bending experiments, the laminated composite sheets get higher bendability. With the actions of the weakened texture and activation of non-basal slip in the composite layer containing the Gd element, both the ductility and bendability of sheet AZ31/Mg-1.6Gd reach the highest levels among those of the laminated composite sheet, corresponding to the elongation of 29% and the ultimate bending angle of 101 °, respectively. The analysis of the asymmetric deformation of dissimilar Mg alloys during the extrusion and the discussion of the effects of Gd content on the microstructure, tensile properties, and bendability in this study provides a comprehensive insight into the fabrication of high-formability laminated composite sheets of Mg alloys.