Enhanced stretch formability at room temperature for Mg-Al-Zn/Mg-Y laminated composite via porthole die extrusion

In this work, Mg-3Al-1Zn/Mg-0.3Y (AZ31/W0) laminated composite sheet was successfully fabricated by porthole die extrusion. Herein, microstructures, textures and stretch formability at room temperature of the AZ31 sheet, the W0 sheet and AZ31/W0 laminated composite sheet were systematically investigated and compared. The results showed that a tiny diffusion zone of ~ 0.35 µm and crystallographic interface were observed in the AZ31/W0 interface, indicating that the AZ31/W0 laminated composite sheet had a well bonding interface. The stretch formability at room temperature of the AZ31/W0 laminated composite sheet was apparently improved by ~ 71% and ~ 20%, respectively, as compared with the AZ31 sheet and W0 sheet. The activation of more basal slip in the W0 layer of the AZ31/W0 laminated composite sheet and the formation of extensive tensile twins in the AZ31 layer, which could effectively accommodate through-thickness strain during stretch forming, were assumed to be the main contribution to the stretch formability enhancement. Therefore, the bimetal laminated composite sheet provided a new thought to achieve high stretch formability Mg alloys via the porthole die extrusion.