Effect of double-extrusion following by stepwise-hot-rolling on microstructures and mechanical properties of Mg-Gd-Y-Zn-Zr alloy

Mg alloys with a combination of high strength and excellent ductility are increasingly required for structural applications. This study investigates the influence of advanced processing techniques on the mechanical properties and microstructural evolution of Mg-Gd-Y-Zn-Zr alloys. Utilizing a combination of double extrusion and stepwise hot rolling followed by aging treatments, significant enhancements in the mechanical performance of these alloys are demonstrated. The processing techniques applied lead to notable refinement in grain-size and modifications in the microstructure, including the transformation of LPSO phases from 18R to 24R and the dispersion of β phase particles. These microstructural transformations contribute to a substantial increase in yield-strength, ultimate-tensile-strength, and ductility. Furthermore, findings reveal that these improvements are also supported by alterations in material texture, which influence dislocation dynamics as indicated by changes in Kernel Average Misorientation (KAM) values. The combined effect of grain boundary (GB) strengthening, phase distribution, and texture modification elucidates the observed mechanical enhancements. This research provides valuable insights into the design and optimization of Mg-Gd-Y-Zn-Zr alloys for critical applications in aerospace and automotive industries where high strength and ductility are paramount.